fix(delivery): preserve bounded operator failure diagnostics

Keep immutable overwrite refusal as the default. Explicit previous fingerprints authorize a stopped-node directory switch with retained private history and resumable publication. Preserve all installed versions with a 65536-entry backup inventory under the existing byte and resource limits.

.github/workflows/engineering.yml

@@ -0,0 +1,203 @@
+name: Trusted engineering checks
+
+on:
+  push:
+    branches: [feat/single-node-delivery]
+
+permissions:
+  contents: read
+
+concurrency:
+  group: kf-onlinejudge-trusted-engineering
+  cancel-in-progress: false
+
+jobs:
+  check:
+    if: github.server_url == 'https://github.com' && github.repository == 'KiriAky107/KF-OnlineJudge'
+    runs-on: ubuntu-24.04
+    timeout-minutes: 30
+    defaults:
+      run:
+        shell: bash --noprofile --norc -euo pipefail {0}
+    env:
+      CI: "true"
+      RUSTUP_TOOLCHAIN: 1.99.0
+      CARGO_BUILD_JOBS: "2"
+      CARGO_NET_RETRY: "2"
+      UV_PYTHON: 3.13.16
+      UV_NO_PROGRESS: "1"
+      UV_HTTP_TIMEOUT: "30"
+      UV_HTTP_RETRIES: "2"
+    steps:
+      - name: Check out the pushed commit
+        uses: actions/checkout@d23441a48e516b6c34aea4fa41551a30e30af803 # v6
+        timeout-minutes: 2
+        with:
+          persist-credentials: false
+          fetch-depth: 1
+          fetch-tags: false
+          submodules: false
+          lfs: false
+
+      - name: Set up Node.js
+        uses: actions/setup-node@249970729cb0ef3589644e2896645e5dc5ba9c38 # v6
+        timeout-minutes: 3
+        with:
+          node-version: 26.11.1
+          check-latest: false
+          package-manager-cache: false
+
+      - name: Set up uv
+        uses: astral-sh/setup-uv@94527f2e458b27549849d47d273a16bec83a01e9 # v7
+        timeout-minutes: 3
+        with:
+          version: 0.12.24
+          python-version: 3.13.16
+          enable-cache: false
+
+      - name: Install locked toolchains and dependencies
+        timeout-minutes: 10
+        run: |
+          test "$GITHUB_SERVER_URL" = https://github.com
+          test "$GITHUB_REPOSITORY" = KiriAky107/KF-OnlineJudge
+          test "$GITHUB_EVENT_NAME" = push
+          test "$GITHUB_REF" = refs/heads/feat/single-node-delivery
+          test "$(git rev-parse HEAD)" = "$GITHUB_SHA"
+          uv python install 3.13.16
+          rustup toolchain install 1.99.0 --profile minimal --component rustfmt --component clippy
+          npm install --global --ignore-scripts pnpm@11.28.4
+          make install
+
+      - name: Check toolchain versions and CI inputs
+        timeout-minutes: 1
+        run: |
+          test "$(node --version)" = v26.11.1
+          test "$(pnpm --version)" = 11.28.4
+          test "$(rustc --version | cut -d ' ' -f 2)" = 1.99.0
+          test "$(uv --version | cut -d ' ' -f 2)" = 0.12.24
+          backend/.venv/bin/python - <<'PYCODE'
+          import os
+          import subprocess
+          import sys
+          assert sys.version_info[:3] == (3, 13, 16)
+          assert not any(name.startswith(('KF_', 'PGPASSWORD', 'PGSERVICE', 'DATABASE_URL', 'AMQP_URL'))
+                         for name in os.environ), 'CI must not carry node credentials or VM flags'
+          assert not subprocess.check_output(['git', 'ls-files', '--', 'docs/', '.localplan/'])
+          PYCODE
+
+      - name: Check architecture and generated contracts
+        timeout-minutes: 3
+        run: |
+          uv run --project backend --locked python scripts/check_architecture.py
+          make contracts
+          git diff --exit-code -- contracts frontend/src/api/generated/schema.d.ts
+
+      - name: Check Backend and run ordinary tests
+        timeout-minutes: 5
+        working-directory: backend
+        run: |
+          uv run --locked ruff check . ../scripts
+          uv run --locked ruff format --check . ../scripts
+          uv run --locked pytest \
+            tests/test_contracts.py \
+            tests/test_judging_contracts.py \
+            tests/test_judging_v2_contracts.py \
+            tests/test_submission_performance_contract.py \
+            tests/test_admin_import_contracts.py \
+            tests/test_availability.py \
+            tests/test_dependency_errors.py \
+            tests/test_production_logging.py \
+            tests/test_delivery.py \
+            tests/test_delivery_io.py \
+            tests/test_delivery_proxy_startup.py \
+            tests/test_delivery_validation_work.py \
+            tests/test_delivery_bytecode.py \
+            tests/test_delivery_backup.py \
+            tests/test_delivery_restore_io.py \
+            tests/test_restore_io_contracts.py \
+            tests/test_restore_native_transport.py \
+            tests/test_operator_diagnostics.py \
+            tests/test_operator_imports.py \
+            tests/test_health.py \
+            tests/test_identity.py \
+            tests/test_coordinator_control.py \
+            --junitxml="$RUNNER_TEMP/kf-engineering-backend.xml"
+          uv run --locked python -m kf_oj.contracts.export --check
+
+      - name: Check Rust and run library and contract tests
+        timeout-minutes: 8
+        working-directory: judge
+        run: |
+          cargo fmt --all -- --check
+          cargo clippy --workspace --all-targets --locked -- -D warnings
+          cargo test --workspace --lib --locked
+          cargo test --package kf-contracts --locked
+          cargo test --package kf-sandbox --bin kf-restore-io --locked
+
+      - name: Check and build Frontend
+        timeout-minutes: 5
+        run: make check-frontend
+
+      - name: Parse development Compose configuration
+        timeout-minutes: 1
+        run: make infra-config
+
+      - name: Collect public contracts and engineering report
+        timeout-minutes: 1
+        run: |
+          backend/.venv/bin/python - <<'PYCODE'
+          import hashlib
+          import json
+          import os
+          import subprocess
+          import xml.etree.ElementTree as ET
+          from pathlib import Path
+          source = subprocess.check_output(['git', 'rev-parse', 'HEAD'], text=True).strip()
+          assert source == os.environ['GITHUB_SHA']
+          destination = Path(os.environ['RUNNER_TEMP']) / 'kf-engineering-artifacts'
+          destination.mkdir(mode=0o700)
+          names = subprocess.check_output(['git', 'ls-files', '-z', '--',
+                                           'contracts/openapi/platform.v1.json',
+                                           'contracts/schemas/*.json']).decode().split('\0')[:-1]
+          assert 1 <= len(names) <= 64
+          files, total = [], 0
+          for name in names:
+              path = Path(name)
+              assert not any(part.is_symlink() for part in (path, *path.parents))
+              assert path.is_file() and path.stat().st_size <= 2 * 1024**2
+              data = path.read_bytes()
+              json.loads(data)
+              total += len(data)
+              assert total <= 8 * 1024**2
+              output = destination / name
+              output.parent.mkdir(parents=True, exist_ok=True)
+              output.write_bytes(data)
+              files.append({'path': name, 'bytes': len(data),
+                            'sha256': hashlib.sha256(data).hexdigest()})
+          junit = ET.parse(Path(os.environ['RUNNER_TEMP']) / 'kf-engineering-backend.xml')
+          suites = list(junit.getroot().iter('testsuite'))
+          backend = {name: sum(int(suite.attrib.get(name, 0)) for suite in suites)
+                     for name in ('tests', 'failures', 'errors', 'skipped')}
+          assert backend['failures'] == backend['errors'] == 0
+          report = {'schema_version': 1, 'source_sha': source,
+                    'scope': 'Trusted engineering checks only', 'backend': backend,
+                    'toolchains': {'python': '3.13.16', 'rust': '1.99.0',
+                                   'node': '26.11.1', 'pnpm': '11.28.4', 'uv': '0.12.24'},
+                    'files': files,
+                    'not_run': ['real PostgreSQL acceptance', 'independent VM cases',
+                                'user source execution', 'adverse archives and filesystem acceptance',
+                                'Linux isolation acceptance', 'deployment']}
+          (destination / 'engineering-report.json').write_text(json.dumps(report, indent=2)+'\n')
+          PYCODE
+
+      - name: Upload public contracts and engineering report
+        uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6
+        timeout-minutes: 2
+        with:
+          name: engineering-checks-${{ github.sha }}
+          path: ${{ runner.temp }}/kf-engineering-artifacts
+          if-no-files-found: error
+          include-hidden-files: false
+          overwrite: false
+          retention-days: 1
+          compression-level: 6

AGENTS.md

@@ -16,6 +16,7 @@
 - 沙箱未验证隔离前拒绝执行；不得用直接运行宿主命令作为临时判题实现。
 - 只建立当期需要的接口和实现；未实现能力明确报告，不提供模拟成绩或虚假任务成功状态。
 - 使用项目锁文件；新增依赖说明职责。凭据、私有代码和隐藏测试数据不进入仓库。
+- 测试备份不得积累：测试结束并保存必要验收证据后，及时删除不再使用的备份、虚拟机磁盘/快照及临时工件；当前任务仍依赖的资源须列明用途和清理条件，被替代后立即清理，不能以保留日志为由长期保留大体积副本。
 
 按变更运行 `make check-backend`、`make check-judge`、`make check-frontend` 和 `make architecture`。
 跨工程骨架或契约改动运行完整 `make check`，记录实际通过项和未验证的能力。

README.md

@@ -5,14 +5,24 @@
 
 当前版本为 **0.0.1**：沙箱已有受控隔离、C/C++ 编译及 native 执行；平台已实现真实身份、
 不可变题目、工件与幂等提交创建。事务 outbox、持久化 Coordinator、普通 Worker 和受控
-helper 工厂已接通 C/C++ 编译一次、多测试点评测；登录、题库、提交和个人成绩页面
+helper 工厂已接通 C17/C++20、固定 CPython 3.13 与 OpenJDK 21 的普通题评测；登录、题库、提交和个人成绩页面
 使用真实接口。训练、比赛、社区等扩展页面仍为开发预览。
 
+管理控制台使用同源 Cookie 和服务端维护权限，支持有界 ZIP 题包上传、候选预览、
+不可变版本发布、题目下架/恢复及维护审计。初次授权与恢复走独立运维身份的本地 CLI；
+导入 Worker 仅解析数据，不执行题包内容或学生代码。操作、限额和恢复步骤见
+[题目维护运维说明](deploy/admin-problems.md)。
+
+题目工作台支持当前版本的“本题我的提交”、右侧详情与完整个人详情。
+性能展示读取受验证最终 AC 的 CPU 总和与内存峰值，只比较同版本、语言、精确工具链、
+预算与可信测量环境的最近有效记录。缺测、旧环境无法验证或其他记录不足五条时明确显示
+不可比较；不会填入示例成绩。口径、查询边界和权限见[提交模块说明](backend/src/kf_oj/modules/submissions/README.md)。
+
 ## 工程划分
 
 | 目录 | 职责 |
 | --- | --- |
-| `backend/` | Python 模块化单体、平台 API、学习 Worker、待投递事件发布器及唯一数据库迁移入口 |
+| `backend/` | Python 模块化单体、平台 API、题包导入 Worker、待投递事件发布器及唯一数据库迁移入口 |
 | `judge/` | Rust workspace：协议、沙箱、判题编排、判题 Worker 和协调器 |
 | `frontend/` | 页面、路由、请求生命周期与生成的 API 类型 |
 | `contracts/` | 版本化 JSON Schema 与 OpenAPI 快照 |
@@ -27,12 +37,14 @@ Python 业务域分为 `identity`、`problems`、`submissions`、`community`、`
 
 Rust 分为 `kf-contracts`、`kf-sandbox`、`kf-engine`、`kf-worker`、`kf-coordinator` 五个 crate。
 协调器拥有执行状态写入权，判题 Worker 不直接写评测数据库。
+Sandbox 内的 `kf-restore-io` 仅在固定离线恢复单元中复制和核验固定数据域，
+通过共享有界协议接收文件记录；不启动程序、服务或写业务状态。
 沙箱执行入口每次核验隔离与限额，任何未验证配置继续拒绝执行。
 用户程序及隔离/超限验收只在独立、整体限额的无业务凭据测试 VM 内运行。
 
 ## 安装与检查
 
-工具链基线：Python 3.13.16 + uv、Rust 1.99.0、Node 26.10.0 + pnpm 11.28.4。
+工具链基线：Python 3.13.16 + uv、Rust 1.99.0、Node 26.11.1 + pnpm 11.28.4。
 Python 和 Rust 版本由工程配置固定，三套工程分别提交依赖锁文件。
 开发与构建使用 Linux 原生文件系统。
 

backend/migrations/README.md

@@ -9,6 +9,22 @@ upgrade head`，API 不在启动时创建表。迁移账号拥有该数据库对
 协调器组领取和更新评测、插入 attempt / 用例成绩及恢复通知，不能修改账号、题库或提交身份。
 Worker 没有数据库角色，也不需要数据库连接配置。
 
+后续迁移另建 `kf_oj_identity_operator` 与 `kf_oj_problem_import` 两个受限 `NOLOGIN`
+权限组。前者只通过固定账号授权函数维护管理员能力/启用状态，不能读取口令哈希、
+直接修改角色字段或绕过最后一名启用管理员保护；后者仅处理已授权导入、候选/工件与
+追加审计，不能写评测状态、attempt、终态或表现指标。判题 Worker 继续无数据库身份。
+平台写入权按列收敛；当前会话与授权版本在每次维护事务内重新核对。
+
+可信表现指标由 Coordinator 在有效最终报告事务中派生，平台、导入器和普通 Worker
+不得自行写入。候选与发布版本/用例不可变，成功维护回执及审计只追加；清理保留所有
+已发布版本、合法旧提交和未结束候选的工件引用。
+
+升级前停止新维护写入、备份专用数据库与私有工件，并用独立迁移账号执行升级和
+`uv run --locked alembic check`。既有登录角色继续绑定各自最小权限组，迁移账号不进入
+运行服务配置。降级不作为丢弃候选或回滚一次发布的手段；含新语言/已引用数据时的
+降级拒绝须先核对原因，不能清空历史来通过检查。账号 bootstrap/恢复步骤见
+[维护运维说明](../../deploy/admin-problems.md)。
+
 服务使用各自独立的普通 `LOGIN` 角色，分别加入对应权限组；登录角色不能拥有数据库/表、
 不能加入迁移账号或其他高权限组，且必须为 `NOSUPERUSER NOCREATEDB NOCREATEROLE NOBYPASSRLS`。
 初始迁移拒绝已有的高权限同名组和继承其他角色的同名组。应用启动时不运行 migration。

backend/migrations/env.py

@@ -10,6 +10,8 @@ from kf_oj.infra.db.base import Base
 from kf_oj.infra.db.session import build_engine
 from kf_oj.infra.messaging import models as messaging_models  # noqa: F401
 from kf_oj.modules.identity import models as identity_models  # noqa: F401
+from kf_oj.modules.operations import models as operations_models  # noqa: F401
+from kf_oj.modules.problems import import_models, maintenance_models  # noqa: F401
 from kf_oj.modules.problems import models as problem_models  # noqa: F401
 from kf_oj.modules.submissions import models as submission_models  # noqa: F401
 

backend/migrations/versions/0003_submission_performance.py

@@ -0,0 +1,119 @@
+"""Trusted final performance projection; no re-encoding or promotion of old reports."""
+
+import sqlalchemy as sa
+from alembic import op
+
+revision = "0003_submission_performance"
+down_revision = "0002_multi_runtime"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column("judge_attempts", sa.Column("measurement_epoch", sa.String(64), nullable=True))
+    op.create_check_constraint(
+        op.f("ck_judge_attempts_measurement_epoch"),
+        "judge_attempts",
+        "measurement_epoch IS NULL OR measurement_epoch ~ '^[0-9a-f]{64}$'",
+    )
+    op.create_table(
+        "evaluation_performance",
+        sa.Column("evaluation_id", sa.Uuid(), primary_key=True),
+        sa.Column("submission_id", sa.Uuid(), nullable=False, unique=True),
+        sa.Column("attempt_id", sa.Uuid(), nullable=False, unique=True),
+        sa.Column("problem_version_id", sa.Uuid(), nullable=False),
+        sa.Column("language", sa.String(16), nullable=False),
+        sa.Column("comparison_group", sa.String(64), nullable=False),
+        sa.Column("measurement_epoch", sa.String(64), nullable=False),
+        sa.Column("report_digest", sa.String(64), nullable=False),
+        sa.Column("finished_at", sa.DateTime(timezone=True), nullable=False),
+        sa.Column("cpu_time_us", sa.BigInteger(), nullable=True),
+        sa.Column("memory_peak_bytes", sa.BigInteger(), nullable=True),
+        sa.ForeignKeyConstraint(
+            ["evaluation_id", "problem_version_id"],
+            ["evaluations.id", "evaluations.problem_version_id"],
+        ),
+        sa.ForeignKeyConstraint(
+            ["submission_id", "problem_version_id"],
+            ["submissions.id", "submissions.problem_version_id"],
+        ),
+        sa.ForeignKeyConstraint(
+            ["attempt_id", "evaluation_id"], ["judge_attempts.id", "judge_attempts.evaluation_id"]
+        ),
+        sa.CheckConstraint("language IN ('c17','cpp20','python313','java21')", name="language"),
+        sa.CheckConstraint("comparison_group ~ '^[0-9a-f]{64}$'", name="comparison_group"),
+        sa.CheckConstraint("measurement_epoch ~ '^[0-9a-f]{64}$'", name="measurement_epoch"),
+        sa.CheckConstraint("report_digest ~ '^[0-9a-f]{64}$'", name="report_digest"),
+        sa.CheckConstraint("cpu_time_us IS NULL OR cpu_time_us >= 0", name="cpu"),
+        sa.CheckConstraint("memory_peak_bytes IS NULL OR memory_peak_bytes >= 0", name="memory"),
+    )
+    for metric in ("cpu_time_us", "memory_peak_bytes"):
+        op.create_index(
+            f"ix_performance_{metric}_cohort",
+            "evaluation_performance",
+            ["comparison_group", sa.text("finished_at DESC"), sa.text("evaluation_id DESC")],
+            postgresql_where=sa.text(f"{metric} IS NOT NULL"),
+        )
+    op.create_index(
+        "ix_submissions_owned_problem_history",
+        "submissions",
+        ["account_id", "problem_version_id", sa.text("created_at DESC"), sa.text("id DESC")],
+    )
+    op.execute("""
+        CREATE FUNCTION public.kf_trusted_performance() RETURNS trigger LANGUAGE plpgsql
+        SET search_path = pg_catalog, public AS $$
+        BEGIN
+            IF TG_OP != 'INSERT' THEN
+                RAISE EXCEPTION 'final performance is immutable' USING ERRCODE = '23514';
+            END IF;
+            IF NOT EXISTS (
+                SELECT 1 FROM public.evaluations e
+                JOIN public.judge_attempts a ON a.id=e.current_attempt_id AND a.evaluation_id=e.id
+                JOIN public.submissions s ON s.id=e.submission_id
+                WHERE e.id=NEW.evaluation_id AND e.state='finished' AND e.verdict='accepted'
+                  AND e.failure_code IS NULL AND a.cleanup_complete IS TRUE
+                  AND e.current_attempt_id=NEW.attempt_id AND s.id=NEW.submission_id
+                  AND s.problem_version_id=NEW.problem_version_id AND s.language=NEW.language
+                  AND a.measurement_epoch=NEW.measurement_epoch
+                  AND e.final_report_digest=NEW.report_digest AND a.report_digest=NEW.report_digest
+                  AND e.updated_at=NEW.finished_at
+                  AND e.final_report->>'cleanup_complete'='true'
+                  AND (e.final_report->>'run_cpu_time_us')::bigint
+                      IS NOT DISTINCT FROM NEW.cpu_time_us
+                  AND (e.final_report->>'run_memory_peak_bytes')::bigint
+                      IS NOT DISTINCT FROM NEW.memory_peak_bytes
+            ) THEN
+                RAISE EXCEPTION 'performance requires a bound trusted final AC'
+                    USING ERRCODE = '23514';
+            END IF;
+            RETURN NEW;
+        END $$
+    """)
+    op.execute("REVOKE ALL ON FUNCTION public.kf_trusted_performance() FROM PUBLIC")
+    op.execute("""
+        CREATE TRIGGER kf_trusted_performance BEFORE INSERT OR UPDATE OR DELETE
+        ON public.evaluation_performance FOR EACH ROW
+        EXECUTE FUNCTION public.kf_trusted_performance()
+    """)
+    op.execute("REVOKE ALL ON evaluation_performance FROM PUBLIC,kf_oj_platform,kf_oj_coordinator")
+    op.execute("GRANT SELECT ON evaluation_performance TO kf_oj_platform,kf_oj_coordinator")
+    op.execute("GRANT INSERT ON evaluation_performance TO kf_oj_coordinator")
+    # Existing attempt INSERT permission covers the new column. No UPDATE epoch permission:
+    # an unbound historical attempt must never be promoted by changing current configuration.
+
+
+def downgrade() -> None:
+    op.execute("""
+        DO $$ BEGIN
+            IF EXISTS(SELECT 1 FROM evaluation_performance) OR
+                EXISTS(SELECT 1 FROM judge_attempts WHERE measurement_epoch IS NOT NULL) THEN
+                RAISE EXCEPTION 'cannot discard trusted measurement bindings'
+                    USING ERRCODE = '23514';
+            END IF;
+        END $$
+    """)
+    op.drop_table("evaluation_performance")
+    op.execute("DROP FUNCTION public.kf_trusted_performance()")
+    op.drop_index("ix_submissions_owned_problem_history", table_name="submissions")
+    op.drop_constraint(op.f("ck_judge_attempts_measurement_epoch"), "judge_attempts", type_="check")
+    op.drop_column("judge_attempts", "measurement_epoch")

backend/migrations/versions/0004_performance_watermark.py

@@ -0,0 +1,21 @@
+"""Indexed group watermark for bounded aggregate cache invalidation."""
+
+import sqlalchemy as sa
+from alembic import op
+
+revision = "0004_performance_watermark"
+down_revision = "0003_submission_performance"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.create_index(
+        "ix_performance_group_watermark",
+        "evaluation_performance",
+        ["comparison_group", sa.text("finished_at DESC"), sa.text("evaluation_id DESC")],
+    )
+
+
+def downgrade() -> None:
+    op.drop_index("ix_performance_group_watermark", table_name="evaluation_performance")

backend/migrations/versions/0005_identity_authority.py

@@ -0,0 +1,150 @@
+"""Default-denied administrator authority and separate local operator/import roles."""
+
+import sqlalchemy as sa
+from alembic import op
+
+revision = "0005_identity_authority"
+down_revision = "0004_performance_watermark"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "accounts",
+        sa.Column("is_administrator", sa.Boolean(), server_default="false", nullable=False),
+    )
+    op.add_column(
+        "accounts",
+        sa.Column("authorization_version", sa.BigInteger(), server_default="1", nullable=False),
+    )
+    op.create_check_constraint(
+        op.f("ck_accounts_authorization_version"), "accounts", "authorization_version >= 1"
+    )
+    op.create_index(
+        "ix_accounts_active_administrators",
+        "accounts",
+        ["id"],
+        postgresql_where=sa.text("is_administrator AND enabled"),
+    )
+    # Logins and secrets are provisioned separately by an operator. Neither group
+    # may inherit an existing privileged role or quietly reuse a privileged login.
+    for role in ("kf_oj_identity_operator", "kf_oj_problem_import"):
+        op.execute(f"""
+            DO $$ BEGIN
+                IF NOT EXISTS (SELECT 1 FROM pg_roles WHERE rolname='{role}') THEN
+                    CREATE ROLE {role} NOLOGIN NOSUPERUSER NOCREATEDB NOCREATEROLE
+                        NOREPLICATION NOBYPASSRLS;
+                ELSIF EXISTS (SELECT 1 FROM pg_roles WHERE rolname='{role}' AND
+                    (rolcanlogin OR rolsuper OR rolcreatedb OR rolcreaterole
+                        OR rolreplication OR rolbypassrls))
+                    OR EXISTS (SELECT 1 FROM pg_auth_members m JOIN pg_roles r ON r.oid=m.member
+                        WHERE r.rolname='{role}') THEN
+                    RAISE EXCEPTION 'unsafe existing authority or import role';
+                END IF;
+            END $$
+        """)
+    op.execute(
+        "REVOKE ALL ON ALL TABLES IN SCHEMA public "
+        "FROM kf_oj_identity_operator,kf_oj_problem_import"
+    )
+    # Table REVOKE does not remove explicit column grants. Remove those too,
+    # including grants left by an earlier downgrade or manual role provisioning.
+    op.execute("""
+        DO $$ DECLARE t record; BEGIN
+            FOR t IN SELECT c.relname, string_agg(quote_ident(a.attname),',' ORDER BY a.attnum) cols
+                FROM pg_class c JOIN pg_namespace n ON n.oid=c.relnamespace
+                JOIN pg_attribute a ON a.attrelid=c.oid
+                WHERE n.nspname='public' AND c.relkind IN ('r','p','v','f')
+                    AND a.attnum>0 AND NOT a.attisdropped
+                GROUP BY c.oid,c.relname LOOP
+                EXECUTE format('REVOKE SELECT (%s),INSERT (%s),UPDATE (%s),REFERENCES (%s) '
+                    'ON TABLE public.%I FROM kf_oj_identity_operator,kf_oj_problem_import',
+                    t.cols,t.cols,t.cols,t.cols,t.relname);
+            END LOOP;
+        END $$
+    """)
+    op.execute("GRANT USAGE ON SCHEMA public TO kf_oj_identity_operator,kf_oj_problem_import")
+    op.execute("REVOKE INSERT,UPDATE,DELETE ON accounts FROM kf_oj_platform")
+    op.execute(
+        "REVOKE INSERT(id,username,password_hash,enabled,created_at,"
+        "is_administrator,authorization_version),"
+        "UPDATE(id,username,password_hash,enabled,created_at,"
+        "is_administrator,authorization_version) "
+        "ON accounts FROM kf_oj_platform"
+    )
+    op.execute(
+        "GRANT INSERT(id,username,password_hash,enabled,created_at) ON accounts TO kf_oj_platform"
+    )
+    op.execute("GRANT UPDATE(enabled) ON accounts TO kf_oj_platform")
+    op.execute("GRANT SELECT ON accounts,sessions TO kf_oj_identity_operator")
+    op.execute("GRANT UPDATE(is_administrator,enabled) ON accounts TO kf_oj_identity_operator")
+    op.execute("GRANT UPDATE(revoked_at) ON sessions TO kf_oj_identity_operator")
+    op.execute("REVOKE ALL ON accounts,sessions FROM kf_oj_coordinator,kf_oj_problem_import")
+    # No import queue exists yet. Its role deliberately has no table privileges
+    # until the import migration grants only the queue/staging tables it needs.
+    op.execute("""
+        CREATE FUNCTION public.kf_account_authority_version() RETURNS trigger LANGUAGE plpgsql
+        SET search_path = pg_catalog, public AS $$
+        BEGIN
+            IF NEW.authorization_version IS DISTINCT FROM OLD.authorization_version THEN
+                RAISE EXCEPTION 'authorization version is server derived' USING ERRCODE='23514';
+            END IF;
+            IF OLD.is_administrator AND NEW.enabled IS DISTINCT FROM OLD.enabled
+                AND NOT pg_has_role(current_user,'kf_oj_identity_operator','USAGE') THEN
+                RAISE EXCEPTION 'administrator enablement requires the local operator'
+                    USING ERRCODE='42501';
+            END IF;
+            IF NEW.is_administrator IS DISTINCT FROM OLD.is_administrator
+                OR NEW.enabled IS DISTINCT FROM OLD.enabled THEN
+                NEW.authorization_version := OLD.authorization_version + 1;
+            END IF;
+            RETURN NEW;
+        END $$
+    """)
+    op.execute("""
+        CREATE FUNCTION public.kf_revoke_authority_sessions() RETURNS trigger LANGUAGE plpgsql
+        SET search_path = pg_catalog, public AS $$
+        BEGIN
+            IF NEW.authorization_version != OLD.authorization_version THEN
+                UPDATE public.sessions SET revoked_at=coalesce(revoked_at,clock_timestamp())
+                    WHERE account_id=NEW.id AND revoked_at IS NULL;
+            END IF;
+            RETURN NEW;
+        END $$
+    """)
+    for function in ("kf_account_authority_version", "kf_revoke_authority_sessions"):
+        op.execute(f"REVOKE ALL ON FUNCTION public.{function}() FROM PUBLIC")
+    op.execute("""
+        CREATE TRIGGER kf_account_authority_version BEFORE UPDATE ON public.accounts
+        FOR EACH ROW EXECUTE FUNCTION public.kf_account_authority_version()
+    """)
+    op.execute("""
+        CREATE TRIGGER kf_revoke_authority_sessions AFTER UPDATE ON public.accounts
+        FOR EACH ROW EXECUTE FUNCTION public.kf_revoke_authority_sessions()
+    """)
+
+
+def downgrade() -> None:
+    op.execute("""
+        DO $$ BEGIN
+            IF EXISTS(SELECT 1 FROM accounts
+                WHERE is_administrator OR authorization_version != 1) THEN
+                RAISE EXCEPTION 'cannot discard authority or revocation history'
+                    USING ERRCODE='23514';
+            END IF;
+        END $$
+    """)
+    for name in ("kf_revoke_authority_sessions", "kf_account_authority_version"):
+        op.execute(f"DROP TRIGGER {name} ON public.accounts")
+        op.execute(f"DROP FUNCTION public.{name}()")
+    op.execute("REVOKE ALL ON accounts,sessions FROM kf_oj_identity_operator")
+    op.execute("REVOKE UPDATE(is_administrator,enabled) ON accounts FROM kf_oj_identity_operator")
+    op.execute("REVOKE UPDATE(revoked_at) ON sessions FROM kf_oj_identity_operator")
+    op.drop_index("ix_accounts_active_administrators", table_name="accounts")
+    op.drop_constraint(op.f("ck_accounts_authorization_version"), "accounts", type_="check")
+    op.drop_column("accounts", "authorization_version")
+    op.drop_column("accounts", "is_administrator")
+    op.execute("GRANT INSERT,UPDATE,DELETE ON accounts TO kf_oj_platform")
+    # Shared NOLOGIN groups survive downgrade, as in the foundation migration;
+    # removing a cluster role could break another database using the same groups.

backend/migrations/versions/0006_authority_operations.py

@@ -0,0 +1,226 @@
+"""Fixed local authority operations and serialized last-administrator protection."""
+
+import sqlalchemy as sa
+from alembic import op
+
+revision = "0006_authority_operations"
+down_revision = "0005_identity_authority"
+branch_labels = None
+depends_on = None
+
+OWNER = "kf_oj_identity_authority_owner"
+
+
+def upgrade() -> None:
+    op.execute(f"""
+        DO $$ BEGIN
+            IF NOT EXISTS (SELECT 1 FROM pg_roles WHERE rolname='{OWNER}') THEN
+                CREATE ROLE {OWNER} NOLOGIN NOSUPERUSER NOCREATEDB NOCREATEROLE
+                    NOREPLICATION NOBYPASSRLS;
+            ELSIF EXISTS (SELECT 1 FROM pg_roles WHERE rolname='{OWNER}' AND
+                (rolcanlogin OR rolsuper OR rolcreatedb OR rolcreaterole
+                    OR rolreplication OR rolbypassrls))
+                OR EXISTS (SELECT 1 FROM pg_auth_members m JOIN pg_roles r ON r.oid=m.member
+                    WHERE r.rolname='{OWNER}') THEN
+                RAISE EXCEPTION 'unsafe existing authority function owner';
+            END IF;
+        END $$
+    """)
+    op.create_table(
+        "identity_authority_guard",
+        sa.Column("id", sa.SmallInteger(), primary_key=True),
+        sa.Column("generation", sa.BigInteger(), nullable=False, server_default="0"),
+        sa.CheckConstraint("id = 1", name="singleton"),
+        sa.CheckConstraint("generation >= 0", name="generation"),
+    )
+    op.execute("INSERT INTO public.identity_authority_guard(id) VALUES(1)")
+    for role in (OWNER, "kf_oj_identity_operator"):
+        op.execute(f"REVOKE ALL ON ALL TABLES IN SCHEMA public FROM {role}")
+        op.execute(f"""
+            REVOKE SELECT(id,username,password_hash,enabled,created_at,
+                is_administrator,authorization_version),
+                UPDATE(id,username,password_hash,enabled,created_at,
+                is_administrator,authorization_version) ON public.accounts FROM {role}
+        """)
+        op.execute(f"""
+            REVOKE SELECT(token_hash,account_id,csrf_hash,expires_at,revoked_at,created_at),
+                UPDATE(token_hash,account_id,csrf_hash,expires_at,revoked_at,created_at)
+                ON public.sessions FROM {role}
+        """)
+    op.execute(f"GRANT USAGE ON SCHEMA public TO {OWNER}")
+    op.execute(f"""
+        GRANT SELECT(id,username,enabled,is_administrator,authorization_version),
+            UPDATE(enabled,is_administrator) ON public.accounts TO {OWNER}
+    """)
+    op.execute(f"GRANT SELECT(account_id,revoked_at),UPDATE(revoked_at) ON sessions TO {OWNER}")
+    op.execute(f"GRANT SELECT,UPDATE(generation) ON identity_authority_guard TO {OWNER}")
+    # Every account write obtains the guard BEFORE it can lock an account row.
+    # Updating (rather than merely locking) the singleton also makes an old
+    # REPEATABLE READ/SERIALIZABLE snapshot fail safely with a serialization error.
+    op.execute("""
+        CREATE FUNCTION public.kf_serialize_account_authority() RETURNS trigger
+        LANGUAGE plpgsql SECURITY DEFINER SET search_path = pg_catalog, pg_temp AS $$
+        BEGIN
+            UPDATE public.identity_authority_guard SET generation=generation+1 WHERE id=1;
+            IF NOT FOUND THEN
+                RAISE EXCEPTION 'authority guard unavailable' USING ERRCODE='23514';
+            END IF;
+            RETURN NULL;
+        END $$
+    """)
+    op.execute("""
+        CREATE FUNCTION public.kf_protect_last_administrator() RETURNS trigger
+        LANGUAGE plpgsql SECURITY DEFINER SET search_path = pg_catalog, pg_temp AS $$
+        BEGIN
+            IF OLD.is_administrator AND OLD.enabled AND
+                (TG_OP='DELETE' OR NOT (NEW.is_administrator AND NEW.enabled)) AND
+                (SELECT count(*) FROM public.accounts WHERE is_administrator AND enabled) <= 1
+            THEN
+                RAISE EXCEPTION 'last enabled administrator is protected' USING ERRCODE='23514';
+            END IF;
+            IF TG_OP='DELETE' THEN RETURN OLD; END IF;
+            RETURN NEW;
+        END $$
+    """)
+    op.execute("""
+        CREATE OR REPLACE FUNCTION public.kf_account_authority_version() RETURNS trigger
+        LANGUAGE plpgsql SET search_path = pg_catalog, public AS $$
+        BEGIN
+            IF NEW.authorization_version IS DISTINCT FROM OLD.authorization_version THEN
+                RAISE EXCEPTION 'authorization version is server derived' USING ERRCODE='23514';
+            END IF;
+            IF OLD.is_administrator AND NEW.enabled IS DISTINCT FROM OLD.enabled
+                AND current_user != 'kf_oj_identity_authority_owner'
+                AND NOT pg_has_role(current_user,'kf_oj_identity_operator','USAGE') THEN
+                RAISE EXCEPTION 'administrator enablement requires the local operator'
+                    USING ERRCODE='42501';
+            END IF;
+            IF NEW.is_administrator IS DISTINCT FROM OLD.is_administrator
+                OR NEW.enabled IS DISTINCT FROM OLD.enabled THEN
+                NEW.authorization_version := OLD.authorization_version + 1;
+            END IF;
+            RETURN NEW;
+        END $$
+    """)
+    op.execute("""
+        CREATE FUNCTION public.kf_manage_account_authority(p_username text,p_operation text)
+        RETURNS TABLE(account_id uuid,username text,enabled boolean,is_administrator boolean,
+            authorization_version bigint,changed boolean)
+        LANGUAGE plpgsql SECURITY DEFINER SET search_path = pg_catalog, pg_temp AS $$
+        DECLARE target record; desired_admin boolean; desired_enabled boolean; active bigint;
+        BEGIN
+            IF p_username IS NULL OR p_username !~ '^[a-z0-9_]{3,24}$' OR
+                p_operation IS NULL OR
+                p_operation NOT IN ('bootstrap','grant','revoke','enable','disable') THEN
+                RAISE EXCEPTION 'invalid authority operation' USING ERRCODE='22023';
+            END IF;
+            UPDATE public.identity_authority_guard g SET generation=g.generation+1 WHERE g.id=1;
+            IF NOT FOUND THEN
+                RAISE EXCEPTION 'authority guard unavailable' USING ERRCODE='23514';
+            END IF;
+            SELECT a.id,a.username,a.enabled,a.is_administrator,a.authorization_version
+                INTO target FROM public.accounts a WHERE a.username=p_username FOR UPDATE;
+            IF NOT FOUND THEN
+                RAISE EXCEPTION 'account not found' USING ERRCODE='P0002';
+            END IF;
+            desired_admin:=target.is_administrator; desired_enabled:=target.enabled;
+            SELECT count(*) INTO active FROM public.accounts a
+                WHERE a.is_administrator AND a.enabled;
+            IF p_operation='bootstrap' THEN
+                IF active>0 AND NOT (target.is_administrator AND target.enabled) THEN
+                    RAISE EXCEPTION 'bootstrap requires no enabled administrator'
+                        USING ERRCODE='23514';
+                END IF;
+                desired_admin:=true; desired_enabled:=true;
+            ELSIF p_operation='grant' THEN
+                IF active=0 THEN
+                    RAISE EXCEPTION 'first administrator requires explicit bootstrap'
+                        USING ERRCODE='23514';
+                END IF;
+                IF NOT target.enabled THEN
+                    RAISE EXCEPTION 'enable the account before granting authority'
+                        USING ERRCODE='23514';
+                END IF;
+                desired_admin:=true;
+            ELSIF p_operation='revoke' THEN desired_admin:=false;
+            ELSIF p_operation='enable' THEN desired_enabled:=true;
+            ELSE desired_enabled:=false;
+            END IF;
+            changed:=desired_admin IS DISTINCT FROM target.is_administrator OR
+                desired_enabled IS DISTINCT FROM target.enabled;
+            IF changed THEN
+                UPDATE public.accounts a SET enabled=desired_enabled,is_administrator=desired_admin
+                    WHERE a.id=target.id;
+            END IF;
+            RETURN QUERY SELECT a.id,a.username::text,a.enabled,a.is_administrator,
+                a.authorization_version,changed FROM public.accounts a WHERE a.id=target.id;
+        END $$
+    """)
+    # A narrow NOLOGIN owner holds only these column privileges. The operator
+    # receives EXECUTE, never table writes or access to password/session digests.
+    op.execute(f"GRANT CREATE ON SCHEMA public TO {OWNER}")
+    for signature in (
+        "kf_serialize_account_authority()",
+        "kf_protect_last_administrator()",
+        "kf_manage_account_authority(text,text)",
+    ):
+        op.execute(f"ALTER FUNCTION public.{signature} OWNER TO {OWNER}")
+        op.execute(f"REVOKE ALL ON FUNCTION public.{signature} FROM PUBLIC")
+    op.execute(f"REVOKE CREATE ON SCHEMA public FROM {OWNER}")
+    op.execute("""
+        GRANT EXECUTE ON FUNCTION public.kf_manage_account_authority(text,text)
+            TO kf_oj_identity_operator
+    """)
+    op.execute("""
+        CREATE TRIGGER kf_serialize_account_authority BEFORE INSERT OR UPDATE OR DELETE
+        ON public.accounts FOR EACH STATEMENT
+        EXECUTE FUNCTION public.kf_serialize_account_authority()
+    """)
+    op.execute("""
+        CREATE TRIGGER kf_protect_last_administrator BEFORE UPDATE OR DELETE
+        ON public.accounts FOR EACH ROW EXECUTE FUNCTION public.kf_protect_last_administrator()
+    """)
+
+
+def downgrade() -> None:
+    op.execute("""
+        DO $$ BEGIN
+            IF EXISTS(SELECT 1 FROM public.accounts WHERE is_administrator) THEN
+                RAISE EXCEPTION 'cannot remove active authority safeguards' USING ERRCODE='23514';
+            END IF;
+        END $$
+    """)
+    for name in ("kf_protect_last_administrator", "kf_serialize_account_authority"):
+        op.execute(f"DROP TRIGGER {name} ON public.accounts")
+        op.execute(f"DROP FUNCTION public.{name}()")
+    op.execute("DROP FUNCTION public.kf_manage_account_authority(text,text)")
+    op.drop_table("identity_authority_guard")
+    op.execute(f"REVOKE ALL ON accounts,sessions FROM {OWNER}")
+    op.execute(f"""
+        REVOKE SELECT(id,username,enabled,is_administrator,authorization_version),
+            UPDATE(enabled,is_administrator) ON accounts FROM {OWNER}
+    """)
+    op.execute(f"REVOKE SELECT(account_id,revoked_at),UPDATE(revoked_at) ON sessions FROM {OWNER}")
+    op.execute("GRANT SELECT ON accounts,sessions TO kf_oj_identity_operator")
+    op.execute("GRANT UPDATE(is_administrator,enabled) ON accounts TO kf_oj_identity_operator")
+    op.execute("GRANT UPDATE(revoked_at) ON sessions TO kf_oj_identity_operator")
+    # Preserve the v0005 trigger policy without referring to the function owner.
+    op.execute("""
+        CREATE OR REPLACE FUNCTION public.kf_account_authority_version() RETURNS trigger
+        LANGUAGE plpgsql SET search_path = pg_catalog, public AS $$
+        BEGIN
+            IF NEW.authorization_version IS DISTINCT FROM OLD.authorization_version THEN
+                RAISE EXCEPTION 'authorization version is server derived' USING ERRCODE='23514';
+            END IF;
+            IF OLD.is_administrator AND NEW.enabled IS DISTINCT FROM OLD.enabled
+                AND NOT pg_has_role(current_user,'kf_oj_identity_operator','USAGE') THEN
+                RAISE EXCEPTION 'administrator enablement requires the local operator'
+                    USING ERRCODE='42501';
+            END IF;
+            IF NEW.is_administrator IS DISTINCT FROM OLD.is_administrator
+                OR NEW.enabled IS DISTINCT FROM OLD.enabled THEN
+                NEW.authorization_version := OLD.authorization_version + 1;
+            END IF;
+            RETURN NEW;
+        END $$
+    """)

backend/migrations/versions/0007_problem_imports.py

@@ -0,0 +1,212 @@
+"""Durable imports/candidates, append-only events and accepted-authority worker port."""
+
+import sqlalchemy as sa
+from alembic import op
+
+from kf_oj.modules.operations.models import MaintenanceEvent
+from kf_oj.modules.problems.import_models import (
+    CandidateCase,
+    ImportPool,
+    ProblemCandidate,
+    ProblemImportOperation,
+)
+
+revision = "0007_problem_imports"
+down_revision = "0006_authority_operations"
+branch_labels = depends_on = None
+
+
+def sql(script):
+    # asyncpg prepares one statement at a time; dollar-quoted bodies stay intact.
+    buffer, quote, dollar, i = [], False, False, 0
+    while i < len(script):
+        if not quote and script[i : i + 2] == "$$":
+            dollar = not dollar
+            buffer.append("$$")
+            i += 2
+            continue
+        character = script[i]
+        if not dollar and character == "'":
+            if quote and script[i : i + 2] == "''":
+                buffer.append("''")
+                i += 2
+                continue
+            quote = not quote
+        if character == ";" and not dollar and not quote:
+            if "".join(buffer).strip():
+                op.execute("".join(buffer))
+            buffer = []
+        else:
+            buffer.append(character)
+        i += 1
+    if "".join(buffer).strip():
+        op.execute("".join(buffer))
+
+
+def upgrade():
+    connection = op.get_bind()
+    # Cyclic candidate/operation link is installed only after both tables exist.
+    for model in (
+        ImportPool,
+        ProblemImportOperation,
+        ProblemCandidate,
+        CandidateCase,
+    ):
+        model.__table__.create(connection)
+    # Freeze the historical shape. A later operations model must not cause a
+    # fresh database to skip ahead and conflict with a subsequent ALTER migration.
+    op.create_table(
+        "problem_maintenance_events",
+        sa.Column("id", sa.Uuid(), primary_key=True),
+        sa.Column(
+            "created_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()
+        ),
+        sa.Column("actor_id", sa.Uuid(), sa.ForeignKey("accounts.id"), nullable=False),
+        sa.Column("authorization_version", sa.BigInteger(), nullable=False),
+        sa.Column("operation_id", sa.Uuid(), nullable=False),
+        sa.Column("action", sa.String(24), nullable=False),
+        sa.Column("target_id", sa.Uuid()),
+        sa.CheckConstraint("authorization_version > 0", name="authority"),
+        sa.CheckConstraint(
+            "action IN ('upload_created','upload_received','import_ready','import_failed',"
+            "'import_discarded','import_expired','published','disabled','restored')",
+            name="action",
+        ),
+    )
+    op.create_index(
+        "ix_problem_maintenance_events_page", "problem_maintenance_events", ["created_at", "id"]
+    )
+    op.create_foreign_key(
+        "fk_problem_import_candidate",
+        "problem_import_operations",
+        "problem_candidates",
+        ["candidate_id"],
+        ["id"],
+    )
+    op.execute("INSERT INTO problem_import_pool(id,reserved_bytes) VALUES(1,0)")
+    sql("""
+      CREATE FUNCTION public.kf_lock_reserved_maintenance(actor uuid, epoch bigint)
+      RETURNS void LANGUAGE plpgsql SECURITY DEFINER SET search_path=pg_catalog,pg_temp AS $$
+      DECLARE permitted boolean;
+      BEGIN
+        SELECT enabled AND is_administrator AND authorization_version=epoch
+        INTO permitted FROM public.accounts WHERE id=actor FOR SHARE;
+        IF permitted IS DISTINCT FROM true THEN
+          RAISE EXCEPTION 'problem maintenance required' USING ERRCODE='42501';
+        END IF;
+      END $$;
+      GRANT CREATE ON SCHEMA public TO kf_oj_identity_authority_owner;
+      ALTER FUNCTION public.kf_lock_reserved_maintenance(uuid,bigint)
+        OWNER TO kf_oj_identity_authority_owner;
+      REVOKE CREATE ON SCHEMA public FROM kf_oj_identity_authority_owner;
+      REVOKE ALL ON FUNCTION public.kf_lock_reserved_maintenance(uuid,bigint) FROM PUBLIC;
+      GRANT EXECUTE ON FUNCTION public.kf_lock_reserved_maintenance(uuid,bigint)
+        TO kf_oj_problem_import;
+      GRANT SELECT,INSERT,UPDATE ON problem_import_operations TO kf_oj_platform;
+      GRANT SELECT,UPDATE ON problem_import_pool TO kf_oj_platform,kf_oj_problem_import;
+      GRANT SELECT ON problem_candidates,problem_candidate_cases TO kf_oj_platform;
+      GRANT SELECT ON problem_import_operations TO kf_oj_problem_import;
+      GRANT UPDATE(state,updated_at,lease_until,attempts,fence,
+        reserved_bytes,failure_code,candidate_id)
+        ON problem_import_operations TO kf_oj_problem_import;
+      GRANT SELECT,INSERT,DELETE ON problem_candidates,problem_candidate_cases
+        TO kf_oj_problem_import;
+      GRANT SELECT,INSERT ON artifacts TO kf_oj_problem_import;
+      GRANT INSERT ON problem_maintenance_events TO kf_oj_platform,kf_oj_problem_import;
+      GRANT SELECT ON problem_maintenance_events TO kf_oj_platform;
+    """)
+    sql("""
+      CREATE FUNCTION public.kf_immutable_import_candidate() RETURNS trigger
+      LANGUAGE plpgsql SET search_path=pg_catalog,pg_temp AS $$
+      DECLARE candidate uuid; current_state text;
+      BEGIN
+        IF TG_TABLE_NAME='problem_candidates' THEN candidate=OLD.id;
+        ELSE candidate=OLD.candidate_id; END IF;
+        SELECT o.state INTO current_state FROM public.problem_candidates c
+          JOIN public.problem_import_operations o ON o.id=c.operation_id WHERE c.id=candidate;
+        IF TG_OP='UPDATE' OR current_state NOT IN ('discarded','expired','failed') THEN
+          RAISE EXCEPTION 'immutable candidate' USING ERRCODE='23514';
+        END IF;
+        RETURN OLD;
+      END $$;
+      CREATE TRIGGER immutable_candidate BEFORE UPDATE OR DELETE ON problem_candidates
+        FOR EACH ROW EXECUTE FUNCTION public.kf_immutable_import_candidate();
+      CREATE TRIGGER immutable_candidate_case BEFORE UPDATE OR DELETE ON problem_candidate_cases
+        FOR EACH ROW EXECUTE FUNCTION public.kf_immutable_import_candidate();
+      CREATE FUNCTION public.kf_insert_import_candidate() RETURNS trigger
+      LANGUAGE plpgsql SET search_path=pg_catalog,pg_temp AS $$
+      DECLARE operation uuid; current_state text;
+      BEGIN
+        IF TG_TABLE_NAME='problem_candidates' THEN operation=NEW.operation_id;
+        ELSE SELECT operation_id INTO operation FROM public.problem_candidates
+          WHERE id=NEW.candidate_id; END IF;
+        SELECT state INTO current_state FROM public.problem_import_operations
+          WHERE id=operation FOR SHARE;
+        IF current_state IS DISTINCT FROM 'validating' THEN
+          RAISE EXCEPTION 'candidate is not being validated' USING ERRCODE='23514';
+        END IF; RETURN NEW;
+      END $$;
+      CREATE TRIGGER insert_candidate BEFORE INSERT ON problem_candidates
+        FOR EACH ROW EXECUTE FUNCTION public.kf_insert_import_candidate();
+      CREATE TRIGGER insert_candidate_case BEFORE INSERT ON problem_candidate_cases
+        FOR EACH ROW EXECUTE FUNCTION public.kf_insert_import_candidate();
+      CREATE FUNCTION public.kf_fixed_import_receipt() RETURNS trigger
+      LANGUAGE plpgsql SET search_path=pg_catalog,pg_temp AS $$ BEGIN
+        IF NEW.id IS DISTINCT FROM OLD.id OR NEW.owner_id IS DISTINCT FROM OLD.owner_id
+          OR NEW.authorization_version IS DISTINCT FROM OLD.authorization_version
+          OR NEW.archive_digest IS DISTINCT FROM OLD.archive_digest
+          OR NEW.archive_bytes IS DISTINCT FROM OLD.archive_bytes
+          OR NEW.created_at IS DISTINCT FROM OLD.created_at
+          OR NEW.expires_at IS DISTINCT FROM OLD.expires_at THEN
+          RAISE EXCEPTION 'immutable import receipt' USING ERRCODE='23514';
+        END IF;
+        IF OLD.state IN ('ready','published') AND NEW.state IN ('ready','published')
+          AND NEW.candidate_id IS DISTINCT FROM OLD.candidate_id THEN
+          RAISE EXCEPTION 'immutable completed candidate receipt' USING ERRCODE='23514';
+        END IF;
+        IF OLD.state='published' AND (NEW.state IS DISTINCT FROM OLD.state
+          OR NEW.published_version_id IS DISTINCT FROM OLD.published_version_id) THEN
+          RAISE EXCEPTION 'immutable published import receipt' USING ERRCODE='23514';
+        END IF;
+        IF NEW.state='ready' THEN
+          IF (OLD.state IS DISTINCT FROM 'ready' AND
+              (NOT pg_has_role(current_user,'kf_oj_problem_import','USAGE')
+                OR OLD.state!='validating')) OR NEW.candidate_id IS NULL
+            OR NOT EXISTS(SELECT 1 FROM public.problem_candidates c
+              WHERE c.id=NEW.candidate_id AND c.operation_id=NEW.id
+                AND c.case_count=(SELECT count(*) FROM public.problem_candidate_cases b
+                  WHERE b.candidate_id=c.id)
+                AND c.case_count-1=(SELECT max(position) FROM public.problem_candidate_cases b
+                  WHERE b.candidate_id=c.id)) THEN
+            RAISE EXCEPTION 'invalid candidate completion' USING ERRCODE='23514';
+          END IF;
+        END IF; RETURN NEW;
+      END $$;
+      CREATE TRIGGER fixed_import_receipt BEFORE UPDATE ON problem_import_operations
+        FOR EACH ROW EXECUTE FUNCTION public.kf_fixed_import_receipt();
+    """)
+
+
+def downgrade():
+    connection = op.get_bind()
+    if connection.exec_driver_sql(
+        "SELECT EXISTS(SELECT 1 FROM problem_import_operations)"
+    ).scalar():
+        raise RuntimeError("cannot discard durable import history")
+    op.execute("DROP FUNCTION public.kf_lock_reserved_maintenance(uuid,bigint)")
+    op.drop_constraint(
+        "fk_problem_import_candidate", "problem_import_operations", type_="foreignkey"
+    )
+    for model in (
+        MaintenanceEvent,
+        CandidateCase,
+        ProblemCandidate,
+        ProblemImportOperation,
+        ImportPool,
+    ):
+        model.__table__.drop(connection)
+    sql(
+        "DROP FUNCTION public.kf_immutable_import_candidate(); "
+        "DROP FUNCTION public.kf_fixed_import_receipt(); "
+        "DROP FUNCTION public.kf_insert_import_candidate()"
+    )

backend/migrations/versions/0008_problem_maintenance.py

@@ -0,0 +1,117 @@
+"""Immutable maintenance receipts, explicit operator audit and read-only history."""
+
+import sqlalchemy as sa
+from alembic import op
+
+from kf_oj.modules.problems.maintenance_models import ProblemMaintenanceOperation
+
+revision = "0008_problem_maintenance"
+down_revision = "0007_problem_imports"
+branch_labels = depends_on = None
+OWNER = "kf_oj_identity_authority_owner"
+
+
+def upgrade():
+    ProblemMaintenanceOperation.__table__.create(op.get_bind())
+    op.execute("GRANT SELECT,INSERT ON problem_maintenance_operations TO kf_oj_platform")
+    op.add_column(
+        "problem_maintenance_events",
+        sa.Column("actor_kind", sa.String(8), nullable=False, server_default=sa.text("'account'")),
+    )
+    op.add_column("problem_maintenance_events", sa.Column("operator_name", sa.String(63)))
+    op.alter_column("problem_maintenance_events", "actor_id", nullable=True)
+    op.drop_constraint(op.f("ck_problem_maintenance_events_action"), "problem_maintenance_events")
+    op.create_check_constraint(
+        "action",
+        "problem_maintenance_events",
+        "action IN ('upload_created','upload_received','import_ready','import_failed',"
+        "'import_discarded','import_expired','published','disabled','restored',"
+        "'authority_bootstrap','authority_grant','authority_revoke','authority_enable','authority_disable')",
+    )
+    op.create_check_constraint(
+        "actor",
+        "problem_maintenance_events",
+        "(actor_kind='account' AND actor_id IS NOT NULL AND operator_name IS NULL) OR "
+        "(actor_kind='operator' AND actor_id IS NULL AND operator_name IS NOT NULL)",
+    )
+    op.execute("""CREATE FUNCTION public.kf_append_only_maintenance() RETURNS trigger
+        LANGUAGE plpgsql SET search_path=pg_catalog,pg_temp AS $$ BEGIN
+        RAISE EXCEPTION 'append-only maintenance history' USING ERRCODE='23514'; END $$""")
+    for table in ("problem_maintenance_operations", "problem_maintenance_events"):
+        op.execute(f"""CREATE TRIGGER append_only_maintenance BEFORE UPDATE OR DELETE ON {table}
+                       FOR EACH ROW EXECUTE FUNCTION public.kf_append_only_maintenance()""")
+    # Preserve the already-verified authority implementation; its only entry
+    # point becomes a fixed audited wrapper owned by the same narrow NOLOGIN role.
+    op.execute(
+        "ALTER FUNCTION public.kf_manage_account_authority(text,text) "
+        "RENAME TO kf_manage_account_authority_unlogged"
+    )
+    op.execute(
+        "REVOKE ALL ON FUNCTION public.kf_manage_account_authority_unlogged(text,text) "
+        "FROM PUBLIC,kf_oj_identity_operator"
+    )
+    op.execute(f"GRANT INSERT ON problem_maintenance_events TO {OWNER}")
+    op.execute("""
+        CREATE FUNCTION public.kf_manage_account_authority(p_username text,p_operation text)
+        RETURNS TABLE(account_id uuid,username text,enabled boolean,is_administrator boolean,
+            authorization_version bigint,changed boolean)
+        LANGUAGE plpgsql SECURITY DEFINER SET search_path=pg_catalog,pg_temp AS $$
+        DECLARE result record; BEGIN
+            SELECT * INTO STRICT result FROM
+                public.kf_manage_account_authority_unlogged(p_username,p_operation);
+            IF result.changed THEN
+                INSERT INTO public.problem_maintenance_events
+                    (id,created_at,actor_id,actor_kind,operator_name,authorization_version,
+                     operation_id,action,target_id)
+                VALUES (gen_random_uuid(),clock_timestamp(),NULL,'operator',session_user,
+                        result.authorization_version,gen_random_uuid(),'authority_' || p_operation,
+                        result.account_id);
+            END IF;
+            RETURN QUERY SELECT result.account_id,result.username,result.enabled,
+                result.is_administrator,result.authorization_version,result.changed;
+        END $$""")
+    op.execute(f"GRANT CREATE ON SCHEMA public TO {OWNER}")
+    op.execute(f"ALTER FUNCTION public.kf_manage_account_authority(text,text) OWNER TO {OWNER}")
+    op.execute(f"REVOKE CREATE ON SCHEMA public FROM {OWNER}")
+    op.execute("REVOKE ALL ON FUNCTION public.kf_manage_account_authority(text,text) FROM PUBLIC")
+    op.execute(
+        "GRANT EXECUTE ON FUNCTION public.kf_manage_account_authority(text,text) "
+        "TO kf_oj_identity_operator"
+    )
+
+
+def downgrade():
+    if (
+        op.get_bind()
+        .exec_driver_sql(
+            "SELECT EXISTS(SELECT 1 FROM problem_maintenance_operations) OR "
+            "EXISTS(SELECT 1 FROM problem_maintenance_events WHERE actor_kind='operator')"
+        )
+        .scalar()
+    ):
+        raise RuntimeError("cannot discard committed maintenance history")
+    op.execute("DROP FUNCTION public.kf_manage_account_authority(text,text)")
+    op.execute(
+        "ALTER FUNCTION public.kf_manage_account_authority_unlogged(text,text) "
+        "RENAME TO kf_manage_account_authority"
+    )
+    op.execute(
+        "GRANT EXECUTE ON FUNCTION public.kf_manage_account_authority(text,text) "
+        "TO kf_oj_identity_operator"
+    )
+    op.execute(f"REVOKE INSERT ON problem_maintenance_events FROM {OWNER}")
+    for table in ("problem_maintenance_operations", "problem_maintenance_events"):
+        op.execute(f"DROP TRIGGER append_only_maintenance ON {table}")
+    op.execute("DROP FUNCTION public.kf_append_only_maintenance()")
+    ProblemMaintenanceOperation.__table__.drop(op.get_bind())
+    op.drop_constraint(op.f("ck_problem_maintenance_events_actor"), "problem_maintenance_events")
+    op.drop_constraint(op.f("ck_problem_maintenance_events_action"), "problem_maintenance_events")
+    op.create_check_constraint(
+        "action",
+        "problem_maintenance_events",
+        "action IN ('upload_created','upload_received','import_ready','import_failed',"
+        "'import_discarded','import_expired','published','disabled','restored')",
+    )
+    op.alter_column("problem_maintenance_events", "actor_id", nullable=False)
+    op.drop_column("problem_maintenance_events", "operator_name")
+    op.drop_column("problem_maintenance_events", "actor_kind")

backend/pyproject.toml

@@ -22,6 +22,7 @@ dependencies = [
 ]
 
 [project.scripts]
+ kf-problem-import-worker = "kf_oj.workers.problem_import:main"
 kf-accounts = "kf_oj.modules.identity.cli:main"
 kf-problems = "kf_oj.modules.problems.cli:main"
 kf-artifacts = "kf_oj.infra.artifacts.cli:main"

backend/src/kf_oj/api/admin_dependencies.py

@@ -0,0 +1,26 @@
+"""Uniform live session gates; domains still lock/recheck authority in write transactions."""
+
+from typing import Annotated
+
+from fastapi import Depends, HTTPException
+
+from kf_oj.api.dependencies import current_principal, unsafe_principal
+from kf_oj.modules.identity.public import Principal
+
+
+async def maintenance_reader(
+    principal: Annotated[Principal, Depends(current_principal)],
+) -> Principal:
+    if not principal.can_maintain_problems:
+        raise HTTPException(403, "problem maintenance required")
+    return principal
+
+
+async def maintenance_writer(
+    principal: Annotated[Principal, Depends(unsafe_principal)],
+) -> Principal:
+    # unsafe_principal already checks an explicit Origin and the live session's
+    # bound CSRF token. This capability check cannot replace the domain's port.
+    if not principal.can_maintain_problems:
+        raise HTTPException(403, "problem maintenance required")
+    return principal

backend/src/kf_oj/api/app.py

@@ -6,7 +6,11 @@ from fastapi.exceptions import RequestValidationError
 from starlette.responses import JSONResponse
 
 from kf_oj import __version__
+from kf_oj.api.availability import AvailabilityMiddleware
 from kf_oj.api.body_limits import BodyLimitMiddleware
+from kf_oj.api.dependency_errors import install_handlers
+from kf_oj.api.v1.admin_imports import router as import_router
+from kf_oj.api.v1.admin_problems import router as maintenance_router
 from kf_oj.api.v1.identity import router as identity_router
 from kf_oj.api.v1.problems import router as problems_router
 from kf_oj.api.v1.router import router
@@ -15,11 +19,17 @@ from kf_oj.api.v1.worker_artifacts import router as worker_router
 from kf_oj.core.logging import configure_logging
 from kf_oj.core.settings import Settings
 from kf_oj.infra.artifacts.repository import ArtifactRepository
+from kf_oj.infra.artifacts.staging import ImportStaging
 from kf_oj.infra.artifacts.store import ArtifactStore
 from kf_oj.infra.coordinator import CoordinatorControl
 from kf_oj.infra.db.session import build_engine, build_session_factory
 from kf_oj.modules.identity.service import IdentityService
+from kf_oj.modules.operations.queries import MaintenanceAuditQueries
+from kf_oj.modules.operations.service import MaintenanceAudit
+from kf_oj.modules.problems.imports import ProblemImports
+from kf_oj.modules.problems.maintenance import ProblemMaintenance
 from kf_oj.modules.problems.service import ProblemService
+from kf_oj.modules.submissions.performance import SubmissionPerformanceQueries
 from kf_oj.modules.submissions.queries import SubmissionQueries
 from kf_oj.modules.submissions.service import SubmissionService
 from kf_oj.modules.submissions.worker_access import WorkerAccess
@@ -30,11 +40,12 @@ def create_app(settings: Settings | None = None) -> FastAPI:
 
     @asynccontextmanager
     async def lifespan(_: FastAPI):
-        configure_logging(settings.log_level)
+        configure_logging(settings.log_level, production=settings.environment == "production")
         logger = logging.getLogger("kf_oj.api")
         logger.info("Platform API started")
         engine = None
         store = None
+        staging = None
         try:
             if settings.database_url is not None:
                 engine = build_engine(settings)
@@ -42,6 +53,7 @@ def create_app(settings: Settings | None = None) -> FastAPI:
                 app.state.identity = IdentityService(
                     app.state.sessions, lifetime_seconds=settings.session_lifetime_seconds
                 )
+                app.state.submission_performance = SubmissionPerformanceQueries(app.state.sessions)
                 artifacts = None
                 if settings.artifact_root is not None:
                     store = ArtifactStore(
@@ -50,6 +62,28 @@ def create_app(settings: Settings | None = None) -> FastAPI:
                         max_files=settings.artifact_max_files,
                     )
                     artifacts = ArtifactRepository(store)
+                    if (
+                        settings.import_staging_root is not None
+                        and settings.judge_admission is not None
+                    ):
+                        staging = ImportStaging(settings.import_staging_root)
+                        app.state.problem_imports = ProblemImports(
+                            app.state.sessions,
+                            staging,
+                            app.state.identity,
+                            MaintenanceAudit(),
+                            settings.judge_admission,
+                        )
+                app.state.problem_maintenance = ProblemMaintenance(
+                    app.state.sessions,
+                    app.state.identity,
+                    MaintenanceAudit(),
+                    artifacts,
+                    settings.judge_admission,
+                )
+                app.state.maintenance_audit = MaintenanceAuditQueries(
+                    app.state.sessions, app.state.identity
+                )
                 app.state.problems = ProblemService(
                     app.state.sessions, artifacts, settings.judge_admission
                 )
@@ -77,10 +111,16 @@ def create_app(settings: Settings | None = None) -> FastAPI:
             app.state.worker_access = None
             app.state.submissions = None
             app.state.submission_queries = None
+            app.state.submission_performance = None
+            app.state.problem_imports = None
+            app.state.problem_maintenance = None
+            app.state.maintenance_audit = None
             if engine is not None:
                 await engine.dispose()
             if store is not None:
                 store.close()
+            if staging is not None:
+                staging.close()
             logger.info("Platform API stopped")
 
     app = FastAPI(
@@ -94,11 +134,14 @@ def create_app(settings: Settings | None = None) -> FastAPI:
     )
     app.state.settings = settings
     app.add_middleware(BodyLimitMiddleware)
+    app.add_middleware(AvailabilityMiddleware, settings=settings)
 
     @app.middleware("http")
     async def private_responses(request, call_next):
         response = await call_next(request)
-        if request.url.path.startswith(("/api/v1/auth", "/api/v1/submissions", "/api/v1/internal")):
+        if request.url.path.startswith(
+            ("/api/v1/auth", "/api/v1/submissions", "/api/v1/internal", "/api/v1/admin")
+        ):
             response.headers["Cache-Control"] = "no-store"
         return response
 
@@ -106,9 +149,13 @@ def create_app(settings: Settings | None = None) -> FastAPI:
     async def invalid_request(_, __):
         return JSONResponse({"detail": "invalid request"}, status_code=422)
 
+    install_handlers(app)
+
     app.include_router(router, prefix="/api/v1")
     app.include_router(identity_router, prefix="/api/v1")
     app.include_router(problems_router, prefix="/api/v1")
     app.include_router(worker_router, prefix="/api/v1")
     app.include_router(submission_router, prefix="/api/v1")
+    app.include_router(import_router, prefix="/api/v1")
+    app.include_router(maintenance_router, prefix="/api/v1")
     return app

backend/src/kf_oj/api/availability.py

@@ -0,0 +1,50 @@
+"""Admission barrier while already accepted work retains its read/cancel paths."""
+
+import re
+
+from starlette.responses import JSONResponse
+
+from kf_oj.infra.availability import current
+
+
+def needs_open(method: str, path: str) -> bool:
+    if method in {"GET", "HEAD", "OPTIONS"}:
+        return False
+    if method == "POST" and path == "/api/v1/auth/logout":
+        return False
+    if method == "POST" and re.fullmatch(r"/api/v1/submissions/[0-9a-f-]{36}/cancel", path):
+        return False
+    if method == "PUT" and re.fullmatch(
+        r"/api/v1/admin/problem-imports/[0-9a-f-]{36}/archive", path
+    ):
+        # The domain route still requires a previously authorized immutable
+        # receipt. This cannot create a new upload or bypass its lease/epoch.
+        return False
+    return path.startswith("/api/v1/")
+
+
+class AvailabilityMiddleware:
+    def __init__(self, app, *, settings):
+        self.app, self.settings = app, settings
+
+    async def __call__(self, scope, receive, send):
+        if (
+            scope["type"] == "http"
+            and self.settings.environment == "production"
+            and needs_open(scope["method"], scope.get("path", ""))
+        ):
+            try:
+                state = current(
+                    self.settings.delivery_release_id, self.settings.delivery_configuration_id
+                )
+                allowed = state.state == "open"
+            except (OSError, ValueError, RecursionError):
+                allowed = False
+            if not allowed:
+                await JSONResponse(
+                    {"detail": "platform mutations unavailable"},
+                    status_code=503,
+                    headers={"Cache-Control": "no-store", "Retry-After": "10"},
+                )(scope, receive, send)
+                return
+        await self.app(scope, receive, send)

backend/src/kf_oj/api/body_limits.py

@@ -1,6 +1,7 @@
 """Bound request bytes and upload time before schema parsing can allocate large inputs."""
 
 import asyncio
+import re
 
 from starlette.responses import JSONResponse
 
@@ -13,6 +14,14 @@ class BodyLimitMiddleware:
         if scope["type"] != "http" or scope["method"] in {"GET", "HEAD", "OPTIONS"}:
             await self.app(scope, receive, send)
             return
+        if scope["method"] == "PUT" and re.fullmatch(
+            r"/api/v1/admin/problem-imports/[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}/archive",
+            scope["path"],
+        ):
+            # Only this exact endpoint can stream. Its live administrator gate runs
+            # before receive(), then its service enforces actual bytes/chunks/deadline.
+            await self.app(scope, receive, send)
+            return
         limit = 8192 if scope["path"] == "/api/v1/auth/login" else 1024 * 1024
         if scope["path"] == "/api/v1/submissions":
             # Max256KiB UTF-8 source, worst-case JSON escaping plus bounded metadata.

backend/src/kf_oj/api/dependency_errors.py

@@ -0,0 +1,42 @@
+"""Bounded, non-secret API responses for transient dependency/capacity failures."""
+
+import errno
+
+from asyncpg import CannotConnectNowError, PostgresConnectionError
+from fastapi import FastAPI
+from sqlalchemy.exc import OperationalError
+from sqlalchemy.exc import TimeoutError as PoolTimeoutError
+from starlette.responses import JSONResponse
+
+
+async def temporarily_unavailable(_, __):
+    # Write outcomes may be uncertain. Existing operation/submission UUIDs, not
+    # automatic server retries, own recovery from a lost response.
+    return JSONResponse(
+        {"detail": "service temporarily unavailable"},
+        status_code=503,
+        headers={"Cache-Control": "no-store", "Retry-After": "5"},
+    )
+
+
+async def filesystem_failure(_, error: OSError):
+    if error.errno in {errno.ENOSPC, errno.EDQUOT, errno.EMFILE, errno.ENFILE}:
+        return await temporarily_unavailable(_, error)
+    # Unrelated filesystem/programming failures retain server-error semantics.
+    # Never serialize path/source/query/credential text from an exception.
+    return JSONResponse(
+        {"detail": "internal server error"}, status_code=500, headers={"Cache-Control": "no-store"}
+    )
+
+
+def install_handlers(app: FastAPI) -> None:
+    for error in (
+        ConnectionError,
+        TimeoutError,
+        OperationalError,
+        PoolTimeoutError,
+        PostgresConnectionError,
+        CannotConnectNowError,
+    ):
+        app.add_exception_handler(error, temporarily_unavailable)
+    app.add_exception_handler(OSError, filesystem_failure)

backend/src/kf_oj/api/v1/admin_imports.py

@@ -0,0 +1,139 @@
+"""Administrator import contract; configured service availability is explicit."""
+
+from typing import Annotated
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, HTTPException, Query, Request
+from sqlalchemy.exc import DBAPIError
+from starlette.requests import ClientDisconnect
+
+from kf_oj.api.admin_dependencies import maintenance_reader, maintenance_writer
+from kf_oj.contracts.admin_problems import (
+    CreateProblemImport,
+    ProblemImportCapabilities,
+    ProblemImportDetail,
+    ProblemImportPage,
+    ProblemImportSummary,
+)
+from kf_oj.infra.artifacts.store import ArtifactError
+from kf_oj.modules.identity.public import MaintenanceDenied, Principal
+from kf_oj.modules.problems.imports import ImportConflict, ImportMissing, ImportUnavailable
+
+router = APIRouter(prefix="/admin/problem-imports", tags=["problem-maintenance"])
+
+
+@router.get("/capabilities", response_model=ProblemImportCapabilities)
+async def capabilities(
+    request: Request, _: Annotated[Principal, Depends(maintenance_reader)]
+) -> ProblemImportCapabilities:
+    service = getattr(request.app.state, "problem_imports", None)
+    if service is None:
+        return ProblemImportCapabilities(uploads_available=False, validation_available=False)
+    return await service.capabilities()
+
+
+def service(request):
+    result = getattr(request.app.state, "problem_imports", None)
+    if result is None:
+        raise HTTPException(503, "problem imports unavailable")
+    return result
+
+
+async def operation(awaitable):
+    try:
+        return await awaitable
+    except MaintenanceDenied:
+        raise HTTPException(403, "problem maintenance required") from None
+    except ImportConflict:
+        raise HTTPException(409, "import request conflict") from None
+    except ImportMissing:
+        raise HTTPException(404, "import unavailable") from None
+    except TimeoutError:
+        raise HTTPException(408, "upload deadline exceeded") from None
+    except (ImportUnavailable, ArtifactError, OSError, DBAPIError):
+        raise HTTPException(503, "problem imports unavailable") from None
+    except ClientDisconnect:
+        raise HTTPException(400, "upload interrupted") from None
+
+
+@router.post("", status_code=201, response_model=ProblemImportSummary)
+async def create(
+    body: CreateProblemImport,
+    request: Request,
+    principal: Annotated[Principal, Depends(maintenance_writer)],
+):
+    if request.headers.get("content-type", "").split(";", 1)[0] != "application/json":
+        raise HTTPException(415, "JSON request required")
+    return await operation(service(request).create(principal, body))
+
+
+@router.get("", response_model=ProblemImportPage)
+async def page(
+    request: Request,
+    principal: Annotated[Principal, Depends(maintenance_reader)],
+    after: UUID | None = None,
+    limit: Annotated[int, Query(ge=1, le=100)] = 20,
+):
+    return await operation(service(request).list(principal, after, limit))
+
+
+@router.get("/{operation_id}", response_model=ProblemImportDetail)
+async def detail(
+    operation_id: UUID,
+    request: Request,
+    principal: Annotated[Principal, Depends(maintenance_reader)],
+):
+    return await operation(service(request).detail(principal, operation_id))
+
+
+@router.put(
+    "/{operation_id}/archive",
+    response_model=ProblemImportSummary,
+    openapi_extra={
+        "requestBody": {
+            "required": True,
+            "content": {"application/zip": {"schema": {"type": "string", "format": "binary"}}},
+        }
+    },
+)
+async def upload(
+    operation_id: UUID,
+    request: Request,
+    principal: Annotated[Principal, Depends(maintenance_writer)],
+):
+    if request.url.path != f"/api/v1/admin/problem-imports/{operation_id}/archive":
+        raise HTTPException(422, "canonical operation UUID required")
+    if request.headers.get("content-type", "").split(";", 1)[0] != "application/zip":
+        raise HTTPException(415, "ZIP request required")
+    if request.headers.get("content-encoding") not in (None, "identity"):
+        raise HTTPException(415, "encoded upload unavailable")
+    length = request.headers.get("content-length")
+    if length is not None:
+        try:
+            if not length.isascii() or not length.isdecimal() or len(length) > 12:
+                raise ValueError
+            length = int(length)
+        except ValueError:
+            raise HTTPException(413, "invalid archive length") from None
+
+    async def chunks():
+        while True:
+            message = await request.receive()
+            if message["type"] == "http.disconnect":
+                raise ClientDisconnect()
+            if message["type"] != "http.request":
+                raise ImportConflict("invalid upload frame")
+            yield message.get("body", b"")
+            if not message.get("more_body", False):
+                return
+
+    return await operation(service(request).upload(principal, operation_id, chunks(), length))
+
+
+@router.post("/{operation_id}/discard", response_model=ProblemImportSummary)
+async def discard(
+    operation_id: UUID,
+    request: Request,
+    principal: Annotated[Principal, Depends(maintenance_writer)],
+):
+    return await operation(service(request).discard(principal, operation_id))

backend/src/kf_oj/api/v1/admin_problems.py

@@ -0,0 +1,150 @@
+"""Live administrator projections and actor-bound immutable mutations."""
+
+from typing import Annotated
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, HTTPException, Query, Request
+from sqlalchemy.exc import DBAPIError
+
+from kf_oj.api.admin_dependencies import maintenance_reader, maintenance_writer
+from kf_oj.contracts.problem_maintenance import (
+    AuditAction,
+    ChangeProblemAvailability,
+    MaintainedProblem,
+    MaintainedProblemPage,
+    MaintainedVersionPage,
+    MaintenanceAuditPage,
+    MaintenanceReceipt,
+    PublishCandidate,
+)
+from kf_oj.infra.artifacts.store import ArtifactError
+from kf_oj.modules.identity.public import MaintenanceDenied, Principal
+from kf_oj.modules.problems.imports import ImportConflict, ImportMissing, ImportUnavailable
+from kf_oj.modules.problems.public import ProblemUnavailable
+
+router = APIRouter(prefix="/admin", tags=["problem-maintenance"])
+
+
+def service(request, name="problem_maintenance"):
+    result = getattr(request.app.state, name, None)
+    if result is None:
+        raise HTTPException(503, "problem maintenance unavailable")
+    return result
+
+
+async def operation(awaitable):
+    try:
+        return await awaitable
+    except MaintenanceDenied:
+        raise HTTPException(403, "problem maintenance required") from None
+    except ImportConflict:
+        raise HTTPException(409, "maintenance precondition conflict") from None
+    except ImportMissing:
+        raise HTTPException(404, "maintenance object unavailable") from None
+    except (ImportUnavailable, ArtifactError, ProblemUnavailable, OSError, DBAPIError):
+        raise HTTPException(503, "problem maintenance unavailable") from None
+    except ValueError:
+        raise HTTPException(422, "invalid maintenance request") from None
+
+
+@router.get("/problems", response_model=MaintainedProblemPage)
+async def page(
+    request: Request,
+    principal: Annotated[Principal, Depends(maintenance_reader)],
+    after: Annotated[str | None, Query(pattern=r"^[a-z0-9][a-z0-9_.-]{0,63}$")] = None,
+    limit: Annotated[int, Query(ge=1, le=100)] = 20,
+    enabled: bool | None = None,
+):
+    return await operation(
+        service(request).page(principal, after=after, limit=limit, enabled=enabled)
+    )
+
+
+@router.get("/problem-slugs/{slug}", response_model=MaintainedProblem)
+async def by_slug(
+    slug: str, request: Request, principal: Annotated[Principal, Depends(maintenance_reader)]
+):
+    from pydantic import TypeAdapter
+
+    from kf_oj.contracts.judging import Label
+
+    try:
+        TypeAdapter(Label).validate_python(slug)
+    except ValueError:
+        raise HTTPException(422, "invalid problem slug") from None
+    return await operation(service(request).by_slug(principal, slug))
+
+
+@router.get("/problems/{problem_id}", response_model=MaintainedProblem)
+async def detail(
+    problem_id: UUID, request: Request, principal: Annotated[Principal, Depends(maintenance_reader)]
+):
+    return await operation(service(request).detail(principal, problem_id))
+
+
+@router.get("/problems/{problem_id}/versions", response_model=MaintainedVersionPage)
+async def versions(
+    problem_id: UUID,
+    request: Request,
+    principal: Annotated[Principal, Depends(maintenance_reader)],
+    before: Annotated[int | None, Query(ge=1)] = None,
+    limit: Annotated[int, Query(ge=1, le=100)] = 20,
+):
+    return await operation(
+        service(request).versions(principal, problem_id, before=before, limit=limit)
+    )
+
+
+@router.get("/problem-maintenance/{operation_id}", response_model=MaintenanceReceipt)
+async def receipt(
+    operation_id: UUID,
+    request: Request,
+    principal: Annotated[Principal, Depends(maintenance_reader)],
+):
+    return await operation(service(request).receipt(principal, operation_id))
+
+
+@router.post("/problem-publications", response_model=MaintenanceReceipt, status_code=201)
+async def publish(
+    body: PublishCandidate,
+    request: Request,
+    principal: Annotated[Principal, Depends(maintenance_writer)],
+):
+    return await operation(service(request).publish(principal, body))
+
+
+@router.post("/problems/{problem_id}/disable", response_model=MaintenanceReceipt)
+async def disable(
+    problem_id: UUID,
+    body: ChangeProblemAvailability,
+    request: Request,
+    principal: Annotated[Principal, Depends(maintenance_writer)],
+):
+    return await operation(
+        service(request).availability(principal, problem_id, body, enabled=False)
+    )
+
+
+@router.post("/problems/{problem_id}/restore", response_model=MaintenanceReceipt)
+async def restore(
+    problem_id: UUID,
+    body: ChangeProblemAvailability,
+    request: Request,
+    principal: Annotated[Principal, Depends(maintenance_writer)],
+):
+    return await operation(service(request).availability(principal, problem_id, body, enabled=True))
+
+
+@router.get("/maintenance-audit", response_model=MaintenanceAuditPage)
+async def audit(
+    request: Request,
+    principal: Annotated[Principal, Depends(maintenance_reader)],
+    before: Annotated[str | None, Query(max_length=100)] = None,
+    limit: Annotated[int, Query(ge=1, le=100)] = 20,
+    action: AuditAction | None = None,
+):
+    return await operation(
+        service(request, "maintenance_audit").page(
+            principal, before=before, limit=limit, action=action
+        )
+    )

backend/src/kf_oj/api/v1/identity.py

@@ -9,13 +9,24 @@ from kf_oj.api.dependencies import (
     trusted_origin,
     unsafe_principal,
 )
-from kf_oj.contracts.identity import CurrentUser, LoginRequest, LoginResponse
+from kf_oj.contracts.identity import AccountCapabilities, CurrentUser, LoginRequest, LoginResponse
 from kf_oj.modules.identity.public import AuthenticationFailed, LoginThrottled, Principal
 from kf_oj.modules.identity.service import IdentityService
 
 router = APIRouter(prefix="/auth", tags=["identity"])
 
 
+def current_user(principal: Principal) -> CurrentUser:
+    return CurrentUser(
+        id=principal.account_id,
+        username=principal.username,
+        capabilities=AccountCapabilities(
+            problem_maintenance=principal.can_maintain_problems,
+            authorization_version=str(principal.authorization_version),
+        ),
+    )
+
+
 @router.post("/login", response_model=LoginResponse, dependencies=[Depends(trusted_origin)])
 async def login(
     body: LoginRequest,
@@ -58,7 +69,7 @@ async def login(
     )
     response.headers["Cache-Control"] = "no-store"
     return LoginResponse(
-        user=CurrentUser(id=issued.principal.account_id, username=issued.principal.username),
+        user=current_user(issued.principal),
         expires_at=issued.expires_at,
         csrf_token=issued.csrf_token,
     )
@@ -67,7 +78,7 @@ async def login(
 @router.get("/me", response_model=CurrentUser)
 async def me(response: Response, principal: Annotated[Principal, Depends(current_principal)]):
     response.headers["Cache-Control"] = "no-store"
-    return CurrentUser(id=principal.account_id, username=principal.username)
+    return current_user(principal)
 
 
 @router.post("/logout", status_code=204, dependencies=[Depends(unsafe_principal)])

backend/src/kf_oj/api/v1/submissions.py

@@ -4,6 +4,8 @@ from uuid import UUID
 from fastapi import APIRouter, Depends, HTTPException, Query, Request, Response
 
 from kf_oj.api.dependencies import current_principal, unsafe_principal
+from kf_oj.contracts.judging_v2 import Language
+from kf_oj.contracts.submission_performance import SubmissionPerformance
 from kf_oj.contracts.submissions import (
     CancellationAccepted,
     CreateSubmission,
@@ -65,9 +67,11 @@ async def history(
     principal: Annotated[Principal, Depends(current_principal)],
     after: Annotated[str | None, Query(max_length=128)] = None,
     limit: Annotated[int, Query(ge=1, le=100)] = 20,
+    problem_version_id: UUID | None = None,
+    language: Language | None = None,
 ):
     try:
-        return await queries(request).page(principal, after, limit)
+        return await queries(request).page(principal, after, limit, problem_version_id, language)
     except ValueError:
         raise HTTPException(422, "invalid history request") from None
 
@@ -86,6 +90,23 @@ async def detail(
         raise HTTPException(503, "stored result unavailable") from None
 
 
+@router.get("/{submission_id}/performance", response_model=SubmissionPerformance)
+async def performance(
+    submission_id: UUID,
+    request: Request,
+    principal: Annotated[Principal, Depends(current_principal)],
+):
+    service = getattr(request.app.state, "submission_performance", None)
+    if service is None:
+        raise HTTPException(503, "performance service unavailable")
+    try:
+        return await service.detail(principal, submission_id)
+    except SubmissionUnavailable:
+        raise HTTPException(404, "submission unavailable") from None
+    except ValueError:
+        raise HTTPException(503, "performance unavailable") from None
+
+
 @router.get("/{submission_id}/source", response_model=SubmissionSource)
 async def source(
     submission_id: UUID,

backend/src/kf_oj/contracts/admin_problems.py

@@ -0,0 +1,180 @@
+"""Versioned problem-import DTOs; hidden bytes, paths and toolchain selection stay private."""
+
+from datetime import datetime
+from enum import StrEnum
+from typing import Annotated, Literal
+
+from pydantic import Field, StrictBool, model_validator
+
+from kf_oj.contracts.judging import Digest, Identifier, Label, RunLimits, Version, WireModel
+from kf_oj.contracts.judging_v2 import Language
+from kf_oj.contracts.problems import PublicLanguageConfiguration, PublicSample
+
+MAX_ARCHIVE_BYTES = 64 * 1024**2
+MAX_UNPACKED_BYTES = 64 * 1024**2
+MAX_ARCHIVE_FILES = 534
+MAX_ARCHIVE_NAME_BYTES = 128
+MAX_UPLOAD_CHUNKS = 4096
+MAX_UPLOAD_CHUNK_BYTES = 1024**2
+UPLOAD_DEADLINE_SECONDS = 30
+VALIDATION_DEADLINE_SECONDS = 60
+MAX_IMPORT_ATTEMPTS = 2
+IMPORT_LIFETIME_SECONDS = 86400
+MAX_OWNER_CANDIDATES = 10
+MAX_TOTAL_CANDIDATES = 32
+STAGING_MAX_BYTES = 256 * 1024**2
+STAGING_RESERVATION_BYTES = MAX_ARCHIVE_BYTES + MAX_UNPACKED_BYTES
+
+
+class ImportState(StrEnum):
+    UPLOADING = "uploading"
+    UPLOADED = "uploaded"
+    VALIDATING = "validating"
+    READY = "ready"
+    FAILED = "failed"
+    PUBLISHED = "published"
+    DISCARDED = "discarded"
+    EXPIRED = "expired"
+
+
+class ImportFailure(StrEnum):
+    INVALID_ARCHIVE = "invalid_archive"
+    INVALID_MANIFEST = "invalid_manifest"
+    INVALID_DATA = "invalid_data"
+    DIGEST_MISMATCH = "digest_mismatch"
+    POLICY_REJECTED = "policy_rejected"
+    UPLOAD_INTERRUPTED = "upload_interrupted"
+    UPLOAD_DEADLINE = "upload_deadline"
+    VALIDATION_DEADLINE = "validation_deadline"
+    VALIDATION_UNAVAILABLE = "validation_unavailable"
+    STORAGE_UNAVAILABLE = "storage_unavailable"
+    AUTHORITY_REVOKED = "authority_revoked"
+    EXPIRED = "expired"
+
+
+class ProblemImportLimits(WireModel):
+    schema_version: Version = 1
+    archive_format: Literal["single_level_zip"] = "single_level_zip"
+    manifest_name: Literal["problem.json"] = "problem.json"
+    manifest_schema_versions: tuple[Literal[1, 2], ...] = (1, 2)
+    languages: tuple[Language, ...] = tuple(Language)
+    archive_bytes: int = MAX_ARCHIVE_BYTES
+    unpacked_bytes: int = MAX_UNPACKED_BYTES
+    files: int = MAX_ARCHIVE_FILES
+    filename_ascii_bytes: int = MAX_ARCHIVE_NAME_BYTES
+    upload_chunks: int = MAX_UPLOAD_CHUNKS
+    chunk_bytes: int = MAX_UPLOAD_CHUNK_BYTES
+    upload_deadline_seconds: int = UPLOAD_DEADLINE_SECONDS
+    validation_deadline_seconds: int = VALIDATION_DEADLINE_SECONDS
+    global_concurrency: Literal[1] = 1
+    owner_concurrency: Literal[1] = 1
+    owner_candidates: int = MAX_OWNER_CANDIDATES
+    total_candidates: int = MAX_TOTAL_CANDIDATES
+    staging_bytes: int = STAGING_MAX_BYTES
+    candidate_lifetime_seconds: int = IMPORT_LIFETIME_SECONDS
+
+
+class ProblemImportCapabilities(WireModel):
+    schema_version: Version = 1
+    limits: ProblemImportLimits = ProblemImportLimits()
+    uploads_available: StrictBool
+    validation_available: StrictBool
+
+
+class CreateProblemImport(WireModel):
+    schema_version: Version = 1
+    operation_id: Identifier
+    archive_digest: Digest
+    archive_bytes: Annotated[int, Field(strict=True, ge=1, le=MAX_ARCHIVE_BYTES)]
+
+
+class LegacyImportBudget(WireModel):
+    compile_limits: RunLimits
+    run_limits: RunLimits
+    job_wall_time_us: Annotated[int, Field(strict=True, ge=1000, le=3600000000)]
+
+
+class CandidatePreview(WireModel):
+    candidate_id: Identifier
+    slug: Label
+    title: Annotated[str, Field(strict=True, min_length=1, max_length=160)]
+    statement: Annotated[str, Field(strict=True, min_length=1, max_length=262144)]
+    samples: Annotated[tuple[PublicSample, ...], Field(max_length=10)]
+    judging_schema_version: Annotated[int, Field(strict=True, ge=1, le=2)]
+    languages: Annotated[tuple[Language, ...], Field(min_length=1, max_length=4)]
+    legacy_budget: LegacyImportBudget | None
+    language_configurations: Annotated[
+        tuple[PublicLanguageConfiguration, ...], Field(max_length=4)
+    ] = ()
+    case_count: Annotated[int, Field(strict=True, ge=1, le=256)]
+
+    @model_validator(mode="after")
+    def bounded_text(self):
+        if len(self.statement.encode("utf-8")) > 262144 or "\x00" in self.statement + self.title:
+            raise ValueError("invalid public text")
+        languages = [c.language for c in self.language_configurations]
+        if len(set(languages)) != len(languages):
+            raise ValueError("duplicate language configuration")
+        if len(set(self.languages)) != len(self.languages):
+            raise ValueError("duplicate language")
+        if self.judging_schema_version == 1:
+            if (
+                self.language_configurations
+                or self.legacy_budget is None
+                or any(
+                    language not in (Language.C17, Language.CPP20) for language in self.languages
+                )
+            ):
+                raise ValueError("invalid legacy candidate")
+        elif tuple(languages) != self.languages or self.legacy_budget is not None:
+            raise ValueError("invalid multi-runtime candidate")
+        return self
+
+
+class ProblemImportSummary(WireModel):
+    schema_version: Version = 1
+    operation_id: Identifier
+    state: ImportState
+    expected_archive_digest: Digest
+    archive_bytes: Annotated[int, Field(strict=True, ge=1, le=MAX_ARCHIVE_BYTES)]
+    created_at: datetime
+    expires_at: datetime
+    updated_at: datetime
+    failure_code: ImportFailure | None
+    candidate_id: Identifier | None
+    published_version_id: Identifier | None
+
+    @model_validator(mode="after")
+    def consistent_state(self):
+        if self.expires_at <= self.created_at or self.updated_at < self.created_at:
+            raise ValueError("invalid import time range")
+        if (self.state in (ImportState.READY, ImportState.PUBLISHED)) != (
+            self.candidate_id is not None
+        ):
+            raise ValueError("candidate state mismatch")
+        if (self.state == ImportState.PUBLISHED) != (self.published_version_id is not None):
+            raise ValueError("published state mismatch")
+        if self.state in (ImportState.FAILED, ImportState.EXPIRED):
+            if self.failure_code is None:
+                raise ValueError("failure code required")
+        elif self.failure_code is not None:
+            raise ValueError("unexpected failure code")
+        return self
+
+
+class ProblemImportDetail(ProblemImportSummary):
+    candidate: CandidatePreview | None
+
+    @model_validator(mode="after")
+    def candidate_matches(self):
+        if (self.candidate_id is None) != (self.candidate is None):
+            raise ValueError("candidate preview missing")
+        if self.candidate and self.candidate.candidate_id != self.candidate_id:
+            raise ValueError("candidate preview mismatch")
+        return self
+
+
+class ProblemImportPage(WireModel):
+    schema_version: Version = 1
+    items: Annotated[tuple[ProblemImportSummary, ...], Field(max_length=100)]
+    next_after: Identifier | None

backend/src/kf_oj/contracts/availability.py

@@ -0,0 +1,18 @@
+"""Root-to-API availability binding; independent from immutable judging protocols."""
+
+from typing import Annotated, Literal
+
+from pydantic import BaseModel, BeforeValidator, ConfigDict, Field
+
+from kf_oj.contracts.judging import integer_version
+
+AVAILABILITY_PATH = "/etc/kf-admission/status.json"
+
+
+class AvailabilityRecord(BaseModel):
+    model_config = ConfigDict(extra="forbid", frozen=True, strict=True)
+
+    schema_version: Annotated[Literal[1], BeforeValidator(integer_version)]
+    release_id: Annotated[str, Field(pattern=r"^sd-[0-9a-f]{12}$")]
+    configuration_id: Annotated[str, Field(pattern=r"^cfg-[0-9a-f]{24}$")]
+    state: Literal["open", "draining", "quiescent"]

backend/src/kf_oj/contracts/export.py

@@ -5,9 +5,23 @@ import json
 from pathlib import Path
 
 from kf_oj.api.app import create_app
+from kf_oj.contracts.admin_problems import (
+    CreateProblemImport,
+    ProblemImportCapabilities,
+    ProblemImportDetail,
+)
+from kf_oj.contracts.availability import AvailabilityRecord
 from kf_oj.contracts.judge import JudgeTaskNotification
 from kf_oj.contracts.judging import WIRE_MODELS
 from kf_oj.contracts.judging_v2 import WIRE_MODELS as WIRE_MODELS_V2
+from kf_oj.contracts.problem_maintenance import (
+    ChangeProblemAvailability,
+    MaintenanceAuditPage,
+    MaintenanceReceipt,
+    PublishCandidate,
+)
+from kf_oj.contracts.restore_io import RestoreIOReply, RestoreIORequest
+from kf_oj.contracts.submission_performance import SubmissionPerformance
 from kf_oj.core.settings import Settings
 
 
@@ -34,6 +48,30 @@ def main() -> None:
             "budgets, result consistency, UUID canonical form and UTF-8 byte limits."
         )
         outputs[root / f"contracts/schemas/{name}.v1.schema.json"] = document
+    performance = SubmissionPerformance.model_json_schema()
+    performance["$schema"] = "https://json-schema.org/draft/2020-12/schema"
+    performance["$id"] = "urn:kf-oj:submission-performance:v1"
+    performance["$comment"] = (
+        "Anonymous bounded aggregates, decimal raw units and strict same-snapshot "
+        "counts; also run model validation and server-side ownership/environment checks."
+    )
+    outputs[root / "contracts/schemas/submission-performance.v1.schema.json"] = performance
+    for name, model in {
+        "delivery-availability": AvailabilityRecord,
+        "restore-io-request": RestoreIORequest,
+        "restore-io-reply": RestoreIOReply,
+        "problem-publish": PublishCandidate,
+        "problem-availability": ChangeProblemAvailability,
+        "problem-maintenance": MaintenanceReceipt,
+        "problem-maintenance-audit": MaintenanceAuditPage,
+        "problem-import-create": CreateProblemImport,
+        "problem-import": ProblemImportDetail,
+        "problem-import-capabilities": ProblemImportCapabilities,
+    }.items():
+        document = model.model_json_schema()
+        document["$schema"] = "https://json-schema.org/draft/2020-12/schema"
+        document["$id"] = f"urn:kf-oj:{name}:v1"
+        outputs[root / f"contracts/schemas/{name}.v1.schema.json"] = document
     for name, model in WIRE_MODELS_V2.items():
         document = model.model_json_schema()
         document["$schema"] = "https://json-schema.org/draft/2020-12/schema"

backend/src/kf_oj/contracts/identity.py

@@ -1,5 +1,5 @@
 from datetime import datetime
-from typing import Annotated
+from typing import Annotated, Literal
 
 from pydantic import Field, SecretStr
 
@@ -11,9 +11,16 @@ class LoginRequest(WireModel):
     password: Annotated[SecretStr, Field(min_length=12, max_length=128)]
 
 
+class AccountCapabilities(WireModel):
+    schema_version: Literal[1] = 1
+    problem_maintenance: bool = False
+    authorization_version: Annotated[str, Field(pattern=r"^[1-9][0-9]{0,18}$")] = "1"
+
+
 class CurrentUser(WireModel):
     id: Identifier
     username: str
+    capabilities: AccountCapabilities = Field(default_factory=AccountCapabilities)
 
 
 class LoginResponse(WireModel):

backend/src/kf_oj/contracts/problem_maintenance.py

@@ -0,0 +1,103 @@
+"""Bounded administrator projections and immutable operation receipts, separate from judging."""
+
+from datetime import datetime
+from typing import Annotated, Literal
+
+from pydantic import Field, StrictBool
+
+from kf_oj.contracts.admin_problems import CandidatePreview
+from kf_oj.contracts.judging import Identifier, Label, Version, WireModel
+from kf_oj.contracts.problems import ProblemSummary
+
+MaintenanceAction = Literal["publish", "disable", "restore"]
+AuditAction = Literal[
+    "upload_created",
+    "upload_received",
+    "import_ready",
+    "import_failed",
+    "import_discarded",
+    "import_expired",
+    "published",
+    "disabled",
+    "restored",
+    "authority_bootstrap",
+    "authority_grant",
+    "authority_revoke",
+    "authority_enable",
+    "authority_disable",
+]
+
+
+class MaintainedProblem(WireModel):
+    id: Identifier
+    slug: Label
+    enabled: StrictBool
+    active_version_id: Identifier | None
+    revision: Annotated[int, Field(strict=True, ge=0)]
+    title: Annotated[str | None, Field(max_length=160)]
+    created_at: datetime
+
+
+class MaintainedProblemPage(WireModel):
+    schema_version: Version = 1
+    items: Annotated[tuple[MaintainedProblem, ...], Field(max_length=100)]
+    next_after: Label | None
+
+
+class MaintainedVersion(ProblemSummary):
+    published_at: datetime
+    case_count: Annotated[int, Field(strict=True, ge=1, le=256)]
+
+
+class MaintainedVersionPage(WireModel):
+    schema_version: Version = 1
+    items: Annotated[tuple[MaintainedVersion, ...], Field(max_length=100)]
+    next_before: Annotated[int | None, Field(strict=True, ge=1)]
+
+
+class PublishCandidate(WireModel):
+    schema_version: Version = 1
+    operation_id: Identifier
+    import_operation_id: Identifier
+    candidate_id: Identifier
+    expected_active_version_id: Identifier | None
+
+
+class ChangeProblemAvailability(WireModel):
+    schema_version: Version = 1
+    operation_id: Identifier
+    expected_active_version_id: Identifier
+    expected_enabled: StrictBool
+
+
+class MaintenanceReceipt(WireModel):
+    schema_version: Version = 1
+    operation_id: Identifier
+    action: MaintenanceAction
+    completed_at: datetime
+    problem: MaintainedProblem
+    published_version_id: Identifier | None = None
+
+
+class MaintenanceAuditEvent(WireModel):
+    id: Identifier
+    created_at: datetime
+    actor_kind: Literal["account", "operator"]
+    actor_id: Identifier | None
+    operator_name: Annotated[str | None, Field(max_length=63)]
+    authorization_version: Annotated[str, Field(pattern=r"^[1-9][0-9]{0,18}$")]
+    operation_id: Identifier
+    action: AuditAction
+    target_id: Identifier | None
+    result: Literal["committed"] = "committed"
+
+
+class MaintenanceAuditPage(WireModel):
+    schema_version: Version = 1
+    items: Annotated[tuple[MaintenanceAuditEvent, ...], Field(max_length=100)]
+    next_before: Annotated[str | None, Field(max_length=100)]
+
+
+# This alias deliberately uses the existing sanitized candidate contract. No new
+# endpoint exposes the private manifest, artifact digest or hidden case names.
+PublicCandidate = CandidatePreview

backend/src/kf_oj/contracts/restore_io.py

@@ -0,0 +1,129 @@
+"""Private offline restore byte-copy protocol; conveys no execution authority."""
+
+import re
+from typing import Annotated, Literal
+
+from pydantic import (
+    BaseModel,
+    BeforeValidator,
+    ConfigDict,
+    Field,
+    RootModel,
+    StrictInt,
+    model_validator,
+)
+
+from kf_oj.contracts.judging import integer_version
+
+MAX_FILES = 98304
+MAX_LOGICAL_BYTES = 12 * 1024**3
+MAX_FILE_BYTES = 256 * 1024**2
+MAX_BATCH_BYTES = 64 * 1024**2
+DOMAINS = frozenset(
+    "postgres artifacts imports app-config judge-config factory operations releases "
+    "images dependencies proxy recovery".split()
+)
+Count = Annotated[StrictInt, Field(ge=0, le=MAX_FILES)]
+ByteCount = Annotated[StrictInt, Field(ge=0, le=MAX_LOGICAL_BYTES)]
+
+
+class Record(BaseModel):
+    model_config = ConfigDict(extra="forbid", frozen=True, strict=True)
+
+
+class RestoreFile(Record):
+    path: Annotated[str, Field(min_length=1, max_length=512)]
+    uid: Annotated[StrictInt, Field(ge=0, le=1205)]
+    gid: Annotated[StrictInt, Field(ge=0, le=1205)]
+    mode: StrictInt
+    bytes: Annotated[StrictInt, Field(ge=0, le=MAX_FILE_BYTES)]
+    sha256: Annotated[str, Field(pattern=r"^[0-9a-f]{64}$")]
+
+    @model_validator(mode="after")
+    def check_member(self) -> "RestoreFile":
+        parts = self.path.split("/")
+        if (
+            len(parts) < 2
+            or parts[0] not in DOMAINS
+            or any(
+                p in {"", ".", "..", ".git", ".ssh", ".localplan", "docs"}
+                or re.fullmatch(r"[A-Za-z0-9_.+@-]{1,255}", p) is None
+                for p in parts
+            )
+        ):
+            raise ValueError("restore file must be below a fixed backup domain")
+        if self.uid not in {0, 1200, 1201, 1202, 1203, 1204, 1205} or self.gid not in (
+            {0, 1203, 1204, 1205} if self.uid == 0 else {self.uid}
+        ):
+            raise ValueError("unsupported restore identity")
+        if self.mode not in {0o400, 0o444, 0o600, 0o640, 0o644, 0o555, 0o755}:
+            raise ValueError("unsupported restore file mode")
+        if self.sha256 in {"a" * 64, "0" * 64}:
+            raise ValueError("placeholder digest refused")
+        return self
+
+
+class Open(Record):
+    schema_version: Annotated[Literal[1], BeforeValidator(integer_version)]
+    kind: Literal["restore.io.open"]
+    backup_id: Annotated[str, Field(pattern=r"^bk-[0-9a-f]{32}$")]
+    recovery_id: Annotated[str, Field(pattern=r"^rr-[0-9a-f]{32}$")]
+    expected_files: Annotated[StrictInt, Field(ge=1, le=MAX_FILES)]
+    expected_logical_bytes: ByteCount
+    deadline_monotonic_ns: Annotated[StrictInt, Field(ge=1, le=2**63 - 1)]
+
+
+class Batch(Record):
+    schema_version: Annotated[Literal[1], BeforeValidator(integer_version)]
+    kind: Literal["restore.io.batch"]
+    batch_id: Annotated[StrictInt, Field(ge=1, le=MAX_FILES)]
+    files: Annotated[list[RestoreFile], Field(min_length=1, max_length=256)]
+
+    @model_validator(mode="after")
+    def check_batch(self) -> "Batch":
+        if len(self.files) > 1 and sum(f.bytes for f in self.files) > MAX_BATCH_BYTES:
+            raise ValueError("restore batch byte bound exceeded")
+        if len({f.path for f in self.files}) != len(self.files):
+            raise ValueError("duplicate restore batch member")
+        return self
+
+
+class Finish(Record):
+    schema_version: Annotated[Literal[1], BeforeValidator(integer_version)]
+    kind: Literal["restore.io.finish"]
+
+
+class RestoreIORequest(RootModel[Annotated[Open | Batch | Finish, Field(discriminator="kind")]]):
+    pass
+
+
+class RestoreIOReply(Record):
+    schema_version: Annotated[Literal[1], BeforeValidator(integer_version)]
+    kind: Literal["restore.io.reply"]
+    stage: Literal["opened", "verified", "finished", "refused"]
+    batch_id: Count
+    verified_files: Count
+    verified_logical_bytes: ByteCount
+    execution_verified: Annotated[
+        Literal[False],
+        BeforeValidator(lambda value: value if type(value) is bool else _bad_boolean()),
+    ]
+    error: Literal["none", "protocol", "guard", "deadline", "filesystem", "bytes", "identity"]
+
+    @model_validator(mode="after")
+    def check_reply(self) -> "RestoreIOReply":
+        if (self.stage == "refused") != (self.error != "none"):
+            raise ValueError("restore refusal state differs")
+        if self.stage == "opened" and (
+            self.batch_id or self.verified_files or self.verified_logical_bytes
+        ):
+            raise ValueError("restore open cannot claim verified data")
+        if self.stage in {"verified", "finished"} and not (
+            1 <= self.batch_id <= self.verified_files
+        ):
+            raise ValueError("restore completion has no verified batch")
+        return self
+
+
+def _bad_boolean() -> bool:
+    raise ValueError("execution verification must be a boolean false")

backend/src/kf_oj/contracts/submission_performance.py

@@ -0,0 +1,126 @@
+"""Bounded anonymous aggregates; raw measurements never pass through JS floats."""
+
+from datetime import datetime
+from typing import Annotated, Literal, Self
+
+from pydantic import AfterValidator, Field, StrictBool, model_validator
+
+from kf_oj.contracts.judging import I64_MAX, Digest, Identifier, Version, WireModel
+from kf_oj.contracts.judging_v2 import Language
+
+MAX_PERFORMANCE_SAMPLES = 10_000
+MIN_PERFORMANCE_SAMPLES = 5
+MAX_PERFORMANCE_BUCKETS = 64
+
+
+def bounded_decimal(value: str) -> str:
+    if int(value) > I64_MAX:
+        raise ValueError("measurement exceeds signed storage range")
+    return value
+
+
+DecimalMeasurement = Annotated[
+    str,
+    Field(strict=True, min_length=1, max_length=19, pattern=r"^(0|[1-9][0-9]*)$"),
+    AfterValidator(bounded_decimal),
+]
+SampleCount = Annotated[int, Field(strict=True, ge=0, le=MAX_PERFORMANCE_SAMPLES)]
+UnavailableReason = Literal[
+    "not_accepted", "measurement_missing", "environment_unverified", "insufficient_samples"
+]
+
+
+class PerformanceBucket(WireModel):
+    start: DecimalMeasurement
+    end: DecimalMeasurement
+    upper_inclusive: StrictBool
+    count: SampleCount
+
+    @model_validator(mode="after")
+    def interval(self) -> Self:
+        if int(self.end) <= int(self.start):
+            raise ValueError("empty or reversed interval")
+        return self
+
+
+class PerformanceMetric(WireModel):
+    unit: Literal["cpu_microseconds", "bytes"]
+    current: DecimalMeasurement | None
+    available: StrictBool
+    reason: UnavailableReason | None
+    sample_count: SampleCount
+    window_truncated: StrictBool
+    oldest_sample_at: datetime | None
+    # These counts are computed against the original integers, never rounded bins.
+    strictly_slower_count: SampleCount | None
+    tied_count: SampleCount | None
+    buckets: Annotated[tuple[PerformanceBucket, ...], Field(max_length=MAX_PERFORMANCE_BUCKETS)]
+
+    @model_validator(mode="after")
+    def aggregate(self) -> Self:
+        if self.oldest_sample_at is not None and self.oldest_sample_at.utcoffset() is None:
+            raise ValueError("sample timestamp must have a timezone")
+        if self.available:
+            if (
+                self.reason is not None
+                or self.current is None
+                or self.sample_count < MIN_PERFORMANCE_SAMPLES
+                or self.strictly_slower_count is None
+                or self.tied_count is None
+                or self.oldest_sample_at is None
+                or not self.buckets
+            ):
+                raise ValueError("incomplete available aggregate")
+            if self.strictly_slower_count + self.tied_count > self.sample_count:
+                raise ValueError("comparison counts exceed the cohort")
+            if sum(b.count for b in self.buckets) != self.sample_count:
+                raise ValueError("histogram loses samples")
+            if int(self.buckets[0].start) != 0:
+                raise ValueError("histogram must include zero")
+            for index, bucket in enumerate(self.buckets):
+                if bucket.upper_inclusive != (index == len(self.buckets) - 1):
+                    raise ValueError("only the last interval includes its upper endpoint")
+                if index and self.buckets[index - 1].end != bucket.start:
+                    raise ValueError("histogram intervals must be contiguous")
+        elif (
+            self.reason is None
+            or self.buckets
+            or self.strictly_slower_count is not None
+            or self.tied_count is not None
+        ):
+            raise ValueError("unavailable aggregate cannot expose comparison data")
+        if self.reason == "measurement_missing" and self.current is not None:
+            raise ValueError("missing measurement cannot claim a value")
+        if self.reason == "insufficient_samples" and (
+            self.sample_count >= MIN_PERFORMANCE_SAMPLES or self.current is None
+        ):
+            raise ValueError("inconsistent insufficient cohort")
+        return self
+
+
+class SubmissionPerformance(WireModel):
+    schema_version: Version = 1
+    kind: Literal["judge.performance"] = "judge.performance"
+    submission_id: Identifier
+    problem_version_id: Identifier
+    language: Language
+    as_of: datetime
+    # Opaque trusted comparison identity, not a worker name, path or credential.
+    comparison_group: Digest | None
+    window_limit: Literal[10_000] = MAX_PERFORMANCE_SAMPLES
+    minimum_samples: Literal[5] = MIN_PERFORMANCE_SAMPLES
+    cpu: PerformanceMetric
+    memory: PerformanceMetric
+
+    @model_validator(mode="after")
+    def snapshot(self) -> Self:
+        if self.as_of.utcoffset() is None:
+            raise ValueError("snapshot timestamp must have a timezone")
+        if self.cpu.unit != "cpu_microseconds" or self.memory.unit != "bytes":
+            raise ValueError("metric unit mismatch")
+        for metric in (self.cpu, self.memory):
+            if metric.available and self.comparison_group is None:
+                raise ValueError("comparison requires trusted environment binding")
+            if metric.oldest_sample_at is not None and metric.oldest_sample_at > self.as_of:
+                raise ValueError("sample is newer than the snapshot")
+        return self

backend/src/kf_oj/core/logging.py

@@ -16,7 +16,53 @@ class JsonFormatter(logging.Formatter):
         return json.dumps(payload, ensure_ascii=False)
 
 
-def configure_logging(level: str) -> None:
+class ProductionFormatter(logging.Formatter):
+    """Closed event vocabulary; arbitrary messages/arguments/tracebacks are private data."""
+
+    EVENTS = {
+        ("kf_oj.api", "Platform API started"): "api_started",
+        ("kf_oj.api", "Platform API stopped"): "api_stopped",
+        ("kf_oj.outbox", "outbox broker unavailable"): "outbox_broker_unavailable",
+        ("kf_oj.outbox", "outbox database unavailable"): "outbox_database_unavailable",
+    }
+    LOGGERS = {"kf_oj.api", "kf_oj.outbox", "uvicorn", "uvicorn.error", "uvicorn.access"}
+    LEVELS = {
+        logging.DEBUG: "DEBUG",
+        logging.INFO: "INFO",
+        logging.WARNING: "WARNING",
+        logging.ERROR: "ERROR",
+        logging.CRITICAL: "CRITICAL",
+    }
+
+    def format(self, record: logging.LogRecord) -> str:
+        # Do not call getMessage/formatException: library errors can contain
+        # connection URIs, query parameters, source or diagnostic body bytes.
+        event = "infrastructure_event"
+        if isinstance(record.msg, str) and not record.args:
+            event = self.EVENTS.get((record.name, record.msg), event)
+        return json.dumps(
+            {
+                "timestamp": datetime.fromtimestamp(record.created, UTC).isoformat(),
+                "level": self.LEVELS.get(record.levelno, "UNKNOWN"),
+                "logger": record.name if record.name in self.LOGGERS else "infrastructure",
+                "message": event,
+                "exception_present": record.exc_info is not None,
+            },
+            ensure_ascii=False,
+        )
+
+
+def configure_logging(level: str, *, production: bool = False) -> None:
     handler = logging.StreamHandler()
-    handler.setFormatter(JsonFormatter())
+    handler.setFormatter(ProductionFormatter() if production else JsonFormatter())
     logging.basicConfig(level=level, handlers=[handler], force=True)
+    if production:
+        # Uvicorn installs its own handlers before lifespan, which otherwise
+        # bypass the root formatter when reporting an unhandled application error.
+        for name in ("uvicorn", "uvicorn.error"):
+            logger = logging.getLogger(name)
+            logger.handlers.clear()
+            logger.propagate = True
+        access = logging.getLogger("uvicorn.access")
+        access.handlers.clear()
+        access.propagate = False

backend/src/kf_oj/core/settings.py

@@ -13,6 +13,7 @@ class Settings(BaseSettings):
     environment: Literal["development", "test", "production"] = "development"
     log_level: Literal["DEBUG", "INFO", "WARNING", "ERROR", "CRITICAL"] = "INFO"
     database_url: SecretStr | None = None
+    identity_operator_database_url: SecretStr | None = None
     amqp_url: SecretStr | None = None
     browser_origins: tuple[str, ...] = (
         "http://localhost:5173",
@@ -22,11 +23,15 @@ class Settings(BaseSettings):
     )
     session_lifetime_seconds: int = Field(default=43200, ge=300, le=86400)
     artifact_root: Path | None = None
+    import_staging_root: Path | None = None
+    import_worker_cgroup: Path | None = None
     artifact_max_bytes: int = Field(default=536870912, ge=1, le=16 * 1024**3)
     artifact_max_files: int = Field(default=4096, ge=1, le=65536)
     judge_admission: NodeAdmission | None = None
     coordinator_url: str | None = None
     coordinator_token: SecretStr | None = None
+    delivery_release_id: str | None = Field(default=None, pattern=r"^sd-[0-9a-f]{12}$")
+    delivery_configuration_id: str | None = Field(default=None, pattern=r"^cfg-[0-9a-f]{24}$")
 
     @model_validator(mode="after")
     def secure_origins(self):

backend/src/kf_oj/infra/artifacts/archive_reader.py

@@ -0,0 +1,340 @@
+"""Bounded single-level ZIP reader; no extractall, metadata restoration or content execution."""
+
+import binascii
+import hashlib
+import os
+import re
+import stat
+import struct
+import time
+import zlib
+from collections.abc import Iterator
+from dataclasses import dataclass
+
+from kf_oj.contracts.admin_problems import (
+    MAX_ARCHIVE_BYTES,
+    MAX_ARCHIVE_FILES,
+    MAX_UNPACKED_BYTES,
+)
+
+NAME = re.compile(rb"[a-zA-Z0-9][a-zA-Z0-9_.-]{0,127}\Z")
+CHUNK = 65536
+LOCAL = struct.Struct("<4s5H3I2H")
+CENTRAL = struct.Struct("<4s6H3I5H2I")
+END = struct.Struct("<4s4H2IH")
+
+
+class ArchiveError(ValueError):
+    """A fixed sanitized failure; never echo an archive name, data or local path."""
+
+
+@dataclass(frozen=True)
+class ArchiveMember:
+    name: str
+    method: int
+    crc32: int
+    compressed_bytes: int
+    bytes: int
+    offset: int
+    flags: int
+
+
+class ArchiveReader:
+    def __init__(self, descriptor: int, expected_bytes: int, *, deadline: float):
+        self.descriptor, self.deadline = descriptor, deadline
+        self.before = os.fstat(descriptor)
+        if (
+            not stat.S_ISREG(self.before.st_mode)
+            or self.before.st_uid != os.getuid()
+            or self.before.st_nlink != 1
+            or stat.S_IMODE(self.before.st_mode) != 0o600
+            or not 22 <= expected_bytes <= MAX_ARCHIVE_BYTES
+            or self.before.st_size != expected_bytes
+        ):
+            raise ArchiveError("invalid_archive")
+        self.size = expected_bytes
+        self.unpacked_bytes, self.steps = 0, 0
+        self.read_members: set[str] = set()
+        self.members = self._members()
+
+    def _tick(self) -> None:
+        self.steps += 1
+        if self.steps > 8192 or time.monotonic() >= self.deadline:
+            raise ArchiveError("archive_deadline")
+
+    def _read(self, offset: int, size: int) -> bytes:
+        self._tick()
+        if not 0 <= size <= 1024**2 or offset < 0 or offset + size > self.size:
+            raise ArchiveError("invalid_archive")
+        data = os.pread(self.descriptor, size, offset)
+        if len(data) != size:
+            raise ArchiveError("invalid_archive")
+        return data
+
+    @staticmethod
+    def _extra(data: bytes) -> None:
+        offset, fields = 0, 0
+        # These bounded timestamps/UID attributes are ignored, never restored.
+        # ZIP64, Unicode aliases and all other extension semantics are unsupported.
+        while offset < len(data):
+            if offset + 4 > len(data) or fields >= 32:
+                raise ArchiveError("invalid_archive")
+            kind, size = struct.unpack_from("<HH", data, offset)
+            offset += 4
+            if kind not in (0x5455, 0x7875, 0x5855, 0x7855, 0x000A) or offset + size > len(data):
+                raise ArchiveError("invalid_archive")
+            offset += size
+            fields += 1
+
+    def _members(self) -> tuple[ArchiveMember, ...]:
+        tail_offset = max(0, self.size - 1046)
+        tail = self._read(tail_offset, self.size - tail_offset)
+        position = tail.rfind(b"PK\x05\x06")
+        if position < 0 or position + END.size > len(tail):
+            raise ArchiveError("invalid_archive")
+        sig, disk, cd_disk, disk_count, count, cd_bytes, cd_offset, comment = END.unpack_from(
+            tail, position
+        )
+        end_offset = tail_offset + position
+        if (
+            sig != b"PK\x05\x06"
+            or disk != 0
+            or cd_disk != 0
+            or disk_count != count
+            or not 1 <= count <= MAX_ARCHIVE_FILES
+            or comment > 1024
+            or end_offset + END.size + comment != self.size
+            or not 46 <= cd_bytes <= 1024**2
+            or cd_offset + cd_bytes != end_offset
+        ):
+            raise ArchiveError("invalid_archive")
+        directory = self._read(cd_offset, cd_bytes)
+        offset, records, names = 0, [], set()
+        for _ in range(count):
+            if offset + CENTRAL.size > len(directory):
+                raise ArchiveError("invalid_archive")
+            values = CENTRAL.unpack_from(directory, offset)
+            (
+                sig,
+                _,
+                needed,
+                flags,
+                method,
+                _,
+                _,
+                crc,
+                compressed,
+                size,
+                name_size,
+                extra_size,
+                comment_size,
+                disk,
+                _,
+                attributes,
+                local_offset,
+            ) = values
+            allowed_flags = 0x0808 | (0x0006 if method == 8 else 0)
+            if (
+                sig != b"PK\x01\x02"
+                or needed not in (10, 20)
+                or method not in (0, 8)
+                or (method == 8 and needed != 20)
+                or flags & ~allowed_flags
+                or disk != 0
+                or not 1 <= name_size <= 128
+                or extra_size > 1024
+                or comment_size > 256
+                or size > MAX_UNPACKED_BYTES
+                or compressed > MAX_ARCHIVE_BYTES
+                or local_offset + LOCAL.size > cd_offset
+                or attributes & 0x10
+                or stat.S_IFMT(attributes >> 16) not in (0, stat.S_IFREG)
+            ):
+                raise ArchiveError("invalid_archive")
+            start = offset + CENTRAL.size
+            finish = start + name_size + extra_size + comment_size
+            if finish > len(directory):
+                raise ArchiveError("invalid_archive")
+            name_bytes = directory[start : start + name_size]
+            if not NAME.fullmatch(name_bytes):
+                raise ArchiveError("invalid_archive")
+            name = name_bytes.decode("ascii")
+            if name.lower() in names:
+                raise ArchiveError("invalid_archive")
+            names.add(name.lower())
+            self._extra(directory[start + name_size : start + name_size + extra_size])
+            records.append(ArchiveMember(name, method, crc, compressed, size, local_offset, flags))
+            offset = finish
+        if offset != len(directory) or sum(m.bytes for m in records) > MAX_UNPACKED_BYTES:
+            raise ArchiveError("invalid_archive")
+        cursor, members = 0, []
+        for member in sorted(records, key=lambda m: m.offset):
+            if member.offset != cursor:
+                raise ArchiveError("invalid_archive")
+            sig, needed, flags, method, _, _, crc, compressed, size, name_size, extra_size = (
+                LOCAL.unpack(self._read(cursor, LOCAL.size))
+            )
+            if (
+                sig != b"PK\x03\x04"
+                or needed not in (10, 20)
+                or flags != member.flags
+                or method != member.method
+                or (method == 8 and needed != 20)
+                or name_size != len(member.name)
+                or extra_size > 1024
+            ):
+                raise ArchiveError("invalid_archive")
+            metadata = self._read(cursor + LOCAL.size, name_size + extra_size)
+            if metadata[:name_size] != member.name.encode("ascii"):
+                raise ArchiveError("invalid_archive")
+            self._extra(metadata[name_size:])
+            data_offset = cursor + LOCAL.size + name_size + extra_size
+            cursor = data_offset + member.compressed_bytes
+            if cursor > cd_offset or (method == 0 and member.compressed_bytes != member.bytes):
+                raise ArchiveError("invalid_archive")
+            if flags & 8:
+                if (crc, compressed, size) not in (
+                    (0, 0, 0),
+                    (member.crc32, member.compressed_bytes, member.bytes),
+                ):
+                    raise ArchiveError("invalid_archive")
+                marker = self._read(cursor, 4)
+                descriptor_size = 16 if marker == b"PK\x07\x08" else 12
+                descriptor = self._read(cursor, descriptor_size)
+                described = struct.unpack("<III", descriptor[-12:])
+                if described != (member.crc32, member.compressed_bytes, member.bytes):
+                    raise ArchiveError("invalid_archive")
+                cursor += descriptor_size
+            elif (crc, compressed, size) != (member.crc32, member.compressed_bytes, member.bytes):
+                raise ArchiveError("invalid_archive")
+            members.append(
+                ArchiveMember(
+                    member.name,
+                    method,
+                    member.crc32,
+                    member.compressed_bytes,
+                    member.bytes,
+                    data_offset,
+                    flags,
+                )
+            )
+        if cursor != cd_offset:
+            raise ArchiveError("invalid_archive")
+        return tuple(members)
+
+    def verify_digest(self, expected: str) -> None:
+        digest = hashlib.sha256()
+        for offset in range(0, self.size, CHUNK):
+            digest.update(self._read(offset, min(CHUNK, self.size - offset)))
+        if digest.hexdigest() != expected:
+            raise ArchiveError("archive_digest_mismatch")
+
+    def verify_unchanged(self) -> None:
+        after = os.fstat(self.descriptor)
+        fields = (
+            "st_dev",
+            "st_ino",
+            "st_nlink",
+            "st_mode",
+            "st_uid",
+            "st_size",
+            "st_mtime_ns",
+            "st_ctime_ns",
+        )
+        if any(getattr(self.before, f) != getattr(after, f) for f in fields):
+            raise ArchiveError("archive_changed")
+
+    @staticmethod
+    def _nested(prefix: bytes) -> bool:
+        return prefix.startswith(
+            (
+                b"PK\x03\x04",
+                b"PK\x05\x06",
+                b"PK\x07\x08",
+                b"\x1f\x8b",
+                b"BZh",
+                b"\xfd7zXZ\x00",
+                b"Rar!\x1a\x07",
+                b"7z\xbc\xaf\x27\x1c",
+            )
+        ) or (len(prefix) >= 262 and prefix[257:262] == b"ustar")
+
+    def chunks(self, name: str, maximum: int) -> Iterator[bytes]:
+        member = next((m for m in self.members if m.name == name), None)
+        if member is None or name in self.read_members or member.bytes > maximum:
+            raise ArchiveError("invalid_archive")
+        self.read_members.add(name)
+        used, crc, prefix = 0, 0, bytearray()
+        inflater = zlib.decompressobj(-15) if member.method == 8 else None
+        try:
+            for offset in range(0, member.compressed_bytes, CHUNK):
+                pending = self._read(
+                    member.offset + offset, min(CHUNK, member.compressed_bytes - offset)
+                )
+                while pending:
+                    self._tick()
+                    if inflater:
+                        data = inflater.decompress(pending, min(CHUNK, member.bytes - used + 1))
+                        pending = inflater.unconsumed_tail
+                        if inflater.unused_data:
+                            raise ArchiveError("invalid_archive")
+                    else:
+                        data, pending = pending, b""
+                    used += len(data)
+                    self.unpacked_bytes += len(data)
+                    if (
+                        used > member.bytes
+                        or used > maximum
+                        or self.unpacked_bytes > MAX_UNPACKED_BYTES
+                    ):
+                        raise ArchiveError("invalid_archive")
+                    prefix.extend(data[: max(0, 512 - len(prefix))])
+                    if self._nested(bytes(prefix)):
+                        raise ArchiveError("invalid_archive")
+                    crc = binascii.crc32(data, crc)
+                    if data:
+                        yield data
+            if (inflater and not inflater.eof) or used != member.bytes or crc != member.crc32:
+                raise ArchiveError("invalid_archive")
+        except zlib.error:
+            raise ArchiveError("invalid_archive") from None
+
+    def read(self, name: str, maximum: int) -> bytes:
+        return b"".join(self.chunks(name, maximum))
+
+    def extract_remaining(self, directory: int) -> dict[str, tuple[str, int]]:
+        info = os.fstat(directory)
+        if (
+            not stat.S_ISDIR(info.st_mode)
+            or info.st_uid != os.getuid()
+            or stat.S_IMODE(info.st_mode) != 0o700
+        ):
+            raise ArchiveError("invalid_extraction_directory")
+        references = {}
+        for member in self.members:
+            if member.name in self.read_members:
+                continue
+            fd = os.open(
+                member.name,
+                os.O_WRONLY | os.O_CREAT | os.O_EXCL | os.O_NOFOLLOW | os.O_CLOEXEC,
+                0o600,
+                dir_fd=directory,
+            )
+            try:
+                digest, size = hashlib.sha256(), 0
+                for chunk in self.chunks(member.name, member.bytes):
+                    digest.update(chunk)
+                    size += len(chunk)
+                    remaining = memoryview(chunk)
+                    while remaining:
+                        written = os.write(fd, remaining)
+                        if written <= 0:
+                            raise ArchiveError("extraction_unavailable")
+                        remaining = remaining[written:]
+                os.fsync(fd)
+                references[member.name] = (digest.hexdigest(), size)
+            finally:
+                os.close(fd)
+        os.fsync(directory)
+        self.verify_unchanged()
+        return references

backend/src/kf_oj/infra/artifacts/backup.py

@@ -0,0 +1,126 @@
+"""Read-only private backup inventory, separate from garbage collection and grading."""
+
+import argparse
+import asyncio
+import hashlib
+import json
+import os
+import stat
+from pathlib import Path
+
+from sqlalchemy import select, text
+from sqlalchemy.exc import SQLAlchemyError
+
+from kf_oj.contracts.judging import ArtifactReference
+from kf_oj.core.settings import Settings
+from kf_oj.infra.artifacts.models import Artifact
+from kf_oj.infra.db.session import build_engine, build_session_factory
+
+MAX_REFERENCES = 65536
+
+
+def verify_existing(root: Path, reference: ArtifactReference) -> None:
+    """No mkdir, lock creation or writable descriptor, even for a missing store."""
+    root = root.absolute()
+    if root.resolve(strict=True) != root:
+        raise ValueError("backup storage path contains links")
+    directory = os.open(root, os.O_RDONLY | os.O_DIRECTORY | os.O_NOFOLLOW | os.O_CLOEXEC)
+    try:
+        info = os.fstat(directory)
+        if info.st_uid != os.getuid() or stat.S_IMODE(info.st_mode) != 0o700:
+            raise ValueError("backup storage root identity differs")
+        descriptor = os.open(
+            reference.digest,
+            os.O_RDONLY | os.O_NOFOLLOW | os.O_NONBLOCK | os.O_CLOEXEC,
+            dir_fd=directory,
+        )
+        with os.fdopen(descriptor, "rb") as source:
+            before = os.fstat(source.fileno())
+            if (
+                not stat.S_ISREG(before.st_mode)
+                or before.st_nlink != 1
+                or before.st_uid != os.getuid()
+                or stat.S_IMODE(before.st_mode) != 0o600
+                or before.st_size != reference.bytes
+            ):
+                raise ValueError("backup artifact identity or length differs")
+            digest = hashlib.sha256()
+            remaining = reference.bytes
+            while remaining:
+                block = source.read(min(65536, remaining))
+                if not block:
+                    raise ValueError("backup artifact truncated")
+                digest.update(block)
+                remaining -= len(block)
+            after = os.fstat(source.fileno())
+            if (
+                source.read(1)
+                or digest.hexdigest() != reference.digest
+                or any(
+                    getattr(before, key) != getattr(after, key)
+                    for key in ("st_dev", "st_ino", "st_size", "st_mtime_ns", "st_ctime_ns")
+                )
+            ):
+                raise ValueError("backup artifact changed or digest differs")
+    finally:
+        os.close(directory)
+
+
+async def inventory() -> dict:
+    """Every ready registry object covers all enforced ready-state foreign keys.
+
+    The operator separately proves a stopped-writing cut. This CLI neither
+    claims that cut nor reads domain ORM models or changes a lifecycle state.
+    """
+    settings = Settings()
+    if settings.artifact_root is None:
+        raise ValueError("artifact root required")
+    engine = build_engine(settings)
+    try:
+        sessions = build_session_factory(engine)
+        async with sessions.begin() as session:
+            await session.execute(text("SET TRANSACTION ISOLATION LEVEL REPEATABLE READ READ ONLY"))
+            rows = await session.execute(
+                select(Artifact.digest, Artifact.bytes)
+                .where(Artifact.state == "ready")
+                .order_by(Artifact.digest)
+                .limit(MAX_REFERENCES + 1)
+            )
+            objects = list(rows)
+            if len(objects) > MAX_REFERENCES:
+                raise ValueError("backup registry count exceeds bound")
+            references = []
+            for digest, size in objects:
+                reference = ArtifactReference(digest=digest, bytes=size)
+                # A 64-KiB buffer checks actual bytes without source/case output.
+                await asyncio.to_thread(verify_existing, settings.artifact_root, reference)
+                references.append(reference.model_dump(mode="json"))
+        return {
+            "schema_version": 1,
+            "kind": "kf.private.artifact-backup-inventory",
+            "read_only": True,
+            "quiescence_verified": False,
+            "boot_id": Path("/proc/sys/kernel/random/boot_id").read_text().strip(),
+            "storage_identity": {
+                "device": settings.artifact_root.stat().st_dev,
+                "inode": settings.artifact_root.stat().st_ino,
+                "uid": settings.artifact_root.stat().st_uid,
+            },
+            "objects": references,
+        }
+    finally:
+        await engine.dispose()
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description="Private read-only artifact backup inventory")
+    parser.parse_args()
+    try:
+        result = asyncio.run(asyncio.wait_for(inventory(), timeout=300))
+        print(json.dumps(result, separators=(",", ":"), sort_keys=True))
+    except (ValueError, OSError, SQLAlchemyError, TimeoutError):
+        parser.exit(1, "Backup artifact inventory refused; no metadata or grade was modified.\n")
+
+
+if __name__ == "__main__":
+    main()

backend/src/kf_oj/infra/artifacts/repository.py

@@ -50,6 +50,28 @@ class ArtifactRepository:
             raise ArtifactError("artifact metadata unavailable")
         return await asyncio.to_thread(self.store.read, reference)
 
+    async def put_file(
+        self, session: AsyncSession, descriptor: int, reference: ArtifactReference
+    ) -> ArtifactReference:
+        await lock_digest(session, reference.digest)
+        existing = await session.get(Artifact, reference.digest)
+        if existing is not None and (
+            existing.state != "ready" or existing.bytes != reference.bytes
+        ):
+            raise ArtifactError("artifact metadata unavailable")
+        task = asyncio.create_task(asyncio.to_thread(self.store.put_file, descriptor, reference))
+        try:
+            await asyncio.shield(task)
+        except BaseException:
+            await task
+            raise
+        await session.execute(
+            insert(Artifact)
+            .values(digest=reference.digest, bytes=reference.bytes)
+            .on_conflict_do_nothing(index_elements=[Artifact.digest])
+        )
+        return reference
+
     async def check_metadata(self, session: AsyncSession, reference: ArtifactReference) -> None:
         metadata = await session.get(Artifact, reference.digest)
         if metadata is None or metadata.state != "ready" or metadata.bytes != reference.bytes:

backend/src/kf_oj/infra/artifacts/staging.py

@@ -0,0 +1,208 @@
+"""Owned, private, bounded import staging. A kernel lock survives parent/child handoff."""
+
+import fcntl
+import os
+import stat
+from contextlib import contextmanager
+from pathlib import Path
+from uuid import UUID
+
+from kf_oj.contracts.admin_problems import MAX_ARCHIVE_FILES, STAGING_MAX_BYTES
+from kf_oj.infra.artifacts.store import ArtifactError
+
+
+class ImportStaging:
+    def __init__(self, root: Path):
+        root = root.absolute()
+        root.mkdir(parents=True, mode=0o700, exist_ok=True)
+        if root.resolve() != root:
+            raise ArtifactError("invalid staging root")
+        self.root = root
+        self.fd = os.open(root, os.O_RDONLY | os.O_DIRECTORY | os.O_NOFOLLOW | os.O_CLOEXEC)
+        self.directory(self.fd)
+
+    @staticmethod
+    def directory(fd):
+        s = os.fstat(fd)
+        if (
+            not stat.S_ISDIR(s.st_mode)
+            or s.st_uid != os.getuid()
+            or stat.S_IMODE(s.st_mode) != 0o700
+        ):
+            raise ArtifactError("invalid staging directory")
+
+    def close(self):
+        os.close(self.fd)
+
+    @staticmethod
+    def names(descriptor, maximum):
+        result = []
+        with os.scandir(descriptor) as entries:
+            for entry in entries:
+                if len(result) >= maximum:
+                    raise ArtifactError("staging file capacity exhausted")
+                result.append(entry.name)
+        return result
+
+    def operation_ids(self):
+        identifiers = []
+        for name in self.names(self.fd, 33):
+            if name == ".lock":
+                continue
+            try:
+                identifier = UUID(name)
+                if str(identifier) != name:
+                    raise ValueError
+            except ValueError:
+                raise ArtifactError("unexpected staging entry") from None
+            identifiers.append(identifier)
+        return identifiers
+
+    @contextmanager
+    def exclusive(self):
+        lock = os.open(
+            ".lock", os.O_RDWR | os.O_CREAT | os.O_NOFOLLOW | os.O_CLOEXEC, 0o600, dir_fd=self.fd
+        )
+        try:
+            from kf_oj.infra.artifacts.store import ArtifactStore
+
+            ArtifactStore._regular(os.fstat(lock))
+            try:
+                fcntl.flock(lock, fcntl.LOCK_EX | fcntl.LOCK_NB)
+            except BlockingIOError:
+                raise ArtifactError("import capacity busy") from None
+            yield lock
+        finally:
+            os.close(lock)
+
+    def usage(self):
+        total, count = 0, 0
+        for name in self.names(self.fd, 33):
+            if name == ".lock":
+                continue
+            try:
+                if str(UUID(name)) != name:
+                    raise ValueError
+            except ValueError:
+                raise ArtifactError("unexpected staging entry") from None
+            descriptor = self.operation(UUID(name))
+            try:
+                for entry in self.names(descriptor, 3):
+                    count += 1
+                    if count > 2 * (MAX_ARCHIVE_FILES + 2):
+                        raise ArtifactError("staging file capacity exhausted")
+                    if entry == "members":
+                        child = self.members(descriptor)
+                        try:
+                            for member in self.names(child, MAX_ARCHIVE_FILES):
+                                count += 1
+                                info = os.stat(member, dir_fd=child, follow_symlinks=False)
+                                from kf_oj.infra.artifacts.store import ArtifactStore
+
+                                ArtifactStore._regular(info)
+                                total += info.st_size
+                        finally:
+                            os.close(child)
+                    elif entry in ("archive", "validated.json"):
+                        info = os.stat(entry, dir_fd=descriptor, follow_symlinks=False)
+                        from kf_oj.infra.artifacts.store import ArtifactStore
+
+                        ArtifactStore._regular(info)
+                        total += info.st_size
+                    else:
+                        raise ArtifactError("unexpected staging entry")
+                    if count > 2 * (MAX_ARCHIVE_FILES + 2) or total > STAGING_MAX_BYTES:
+                        raise ArtifactError("staging capacity exhausted")
+            finally:
+                os.close(descriptor)
+        return total
+
+    def operation(self, operation_id: UUID, *, create=False):
+        name = str(operation_id)
+        if create:
+            try:
+                os.mkdir(name, 0o700, dir_fd=self.fd)
+            except FileExistsError:
+                pass
+        descriptor = os.open(
+            name, os.O_RDONLY | os.O_DIRECTORY | os.O_NOFOLLOW | os.O_CLOEXEC, dir_fd=self.fd
+        )
+        try:
+            self.directory(descriptor)
+        except Exception:
+            os.close(descriptor)
+            raise
+        return descriptor
+
+    @staticmethod
+    def members(operation, *, create=False):
+        if create:
+            os.mkdir("members", 0o700, dir_fd=operation)
+        descriptor = os.open(
+            "members", os.O_RDONLY | os.O_DIRECTORY | os.O_NOFOLLOW | os.O_CLOEXEC, dir_fd=operation
+        )
+        try:
+            ImportStaging.directory(descriptor)
+        except Exception:
+            os.close(descriptor)
+            raise
+        return descriptor
+
+    def remove(self, operation_id):
+        try:
+            descriptor = self.operation(operation_id)
+        except FileNotFoundError:
+            return
+        try:
+            names = self.names(descriptor, 3)
+            if len(names) > 3:
+                raise ArtifactError("unexpected staging entry")
+            for name in names:
+                if name == "members":
+                    child = self.members(descriptor)
+                    try:
+                        entries = self.names(child, MAX_ARCHIVE_FILES)
+                        if len(entries) > MAX_ARCHIVE_FILES:
+                            raise ArtifactError("unexpected staging entry")
+                        for member in entries:
+                            from kf_oj.infra.artifacts.store import ArtifactStore
+
+                            ArtifactStore._regular(
+                                os.stat(member, dir_fd=child, follow_symlinks=False)
+                            )
+                            os.unlink(member, dir_fd=child)
+                    finally:
+                        os.close(child)
+                    os.rmdir("members", dir_fd=descriptor)
+                elif name in ("archive", "validated.json"):
+                    from kf_oj.infra.artifacts.store import ArtifactStore
+
+                    ArtifactStore._regular(os.stat(name, dir_fd=descriptor, follow_symlinks=False))
+                    os.unlink(name, dir_fd=descriptor)
+                else:
+                    raise ArtifactError("unexpected staging entry")
+        finally:
+            os.close(descriptor)
+        os.rmdir(str(operation_id), dir_fd=self.fd)
+        os.fsync(self.fd)
+
+    def reset_validation(self, operation_id):
+        directory = self.operation(operation_id)
+        try:
+            names = self.names(directory, 3)
+            if "members" in names:
+                members = self.members(directory)
+                try:
+                    for name in self.names(members, MAX_ARCHIVE_FILES):
+                        from kf_oj.infra.artifacts.store import ArtifactStore
+
+                        ArtifactStore._regular(os.stat(name, dir_fd=members, follow_symlinks=False))
+                        os.unlink(name, dir_fd=members)
+                finally:
+                    os.close(members)
+                os.rmdir("members", dir_fd=directory)
+            if "validated.json" in names:
+                os.unlink("validated.json", dir_fd=directory)
+            os.fsync(directory)
+        finally:
+            os.close(directory)

backend/src/kf_oj/infra/artifacts/store.py

@@ -168,6 +168,135 @@ class ArtifactStore:
         with self.exclusive():
             return self._read(reference)
 
+    def verify(self, reference: ArtifactReference) -> None:
+        """Verify publication inputs with a 64 KiB buffer, without exposing hidden bytes."""
+        ArtifactReference.model_validate(reference)
+        with self.exclusive():
+            try:
+                descriptor = os.open(
+                    reference.digest,
+                    os.O_RDONLY | os.O_NOFOLLOW | os.O_NONBLOCK | os.O_CLOEXEC,
+                    dir_fd=self._directory,
+                )
+                with os.fdopen(descriptor, "rb") as source:
+                    before = os.fstat(source.fileno())
+                    self._regular(before)
+                    if before.st_size != reference.bytes:
+                        raise ArtifactError("artifact digest or length mismatch")
+                    digest = hashlib.sha256()
+                    remaining = reference.bytes
+                    while remaining:
+                        data = source.read(min(65536, remaining))
+                        if not data:
+                            raise ArtifactError("artifact digest or length mismatch")
+                        digest.update(data)
+                        remaining -= len(data)
+                    after = os.fstat(source.fileno())
+                    if (
+                        source.read(1)
+                        or digest.hexdigest() != reference.digest
+                        or any(
+                            getattr(before, k) != getattr(after, k)
+                            for k in (
+                                "st_dev",
+                                "st_ino",
+                                "st_nlink",
+                                "st_mode",
+                                "st_uid",
+                                "st_size",
+                                "st_mtime_ns",
+                                "st_ctime_ns",
+                            )
+                        )
+                    ):
+                        raise ArtifactError("artifact input changed")
+            except OSError:
+                raise ArtifactError("artifact unavailable") from None
+
+    def put_file(self, source: int, expected: ArtifactReference) -> ArtifactReference:
+        """Adopt a validated private FD without buffering a hidden testcase in memory."""
+        before = os.fstat(source)
+        self._regular(before)
+        if before.st_size != expected.bytes:
+            raise ArtifactError("artifact digest or length mismatch")
+
+        def unchanged(descriptor, original):
+            current = os.fstat(descriptor)
+            fields = (
+                "st_dev",
+                "st_ino",
+                "st_nlink",
+                "st_mode",
+                "st_uid",
+                "st_size",
+                "st_mtime_ns",
+                "st_ctime_ns",
+            )
+            if any(getattr(current, k) != getattr(original, k) for k in fields):
+                raise ArtifactError("artifact input changed")
+
+        def stream(descriptor, *, output=None):
+            digest = hashlib.sha256()
+            for offset in range(0, expected.bytes, 65536):
+                data = os.pread(descriptor, min(65536, expected.bytes - offset), offset)
+                if len(data) != min(65536, expected.bytes - offset):
+                    raise ArtifactError("artifact digest or length mismatch")
+                digest.update(data)
+                if output is not None:
+                    output.write(data)
+            if digest.hexdigest() != expected.digest:
+                raise ArtifactError("artifact digest or length mismatch")
+
+        with self.exclusive():
+            entries = self._entries()
+            if any(name == expected.digest for name, _ in entries):
+                existing = os.open(
+                    expected.digest,
+                    os.O_RDONLY | os.O_NOFOLLOW | os.O_NONBLOCK | os.O_CLOEXEC,
+                    dir_fd=self._directory,
+                )
+                try:
+                    self._regular(os.fstat(existing))
+                    if os.fstat(existing).st_size != expected.bytes:
+                        raise ArtifactError("artifact digest or length mismatch")
+                    stream(source)
+                    stream(existing)
+                finally:
+                    os.close(existing)
+            else:
+                if (
+                    len(entries) + 1 > self.max_files
+                    or sum(s.st_size for _, s in entries) + expected.bytes > self.max_bytes
+                ):
+                    raise ArtifactError("storage capacity exhausted")
+                temporary = ".tmp-" + uuid4().hex
+                descriptor = os.open(
+                    temporary,
+                    os.O_WRONLY | os.O_CREAT | os.O_EXCL | os.O_NOFOLLOW | os.O_CLOEXEC,
+                    0o600,
+                    dir_fd=self._directory,
+                )
+                try:
+                    with os.fdopen(descriptor, "wb") as out:
+                        stream(source, output=out)
+                        out.flush()
+                        os.fsync(out.fileno())
+                    unchanged(source, before)
+                    os.rename(
+                        temporary,
+                        expected.digest,
+                        src_dir_fd=self._directory,
+                        dst_dir_fd=self._directory,
+                    )
+                    os.fsync(self._directory)
+                finally:
+                    try:
+                        os.unlink(temporary, dir_fd=self._directory)
+                    except FileNotFoundError:
+                        pass
+        unchanged(source, before)
+        return expected
+
     def remove(self, digest: str) -> None:
         if not DIGEST.fullmatch(digest):
             raise ArtifactError("invalid artifact identifier")

backend/src/kf_oj/infra/availability.py

@@ -0,0 +1,52 @@
+"""Ordinary read-only view of the fixed protected Root admission record."""
+
+import json
+import os
+import stat
+from pathlib import Path
+
+from kf_oj.contracts.availability import AVAILABILITY_PATH, AvailabilityRecord
+
+GATE = Path(AVAILABILITY_PATH)
+
+
+def protected_record() -> AvailabilityRecord:
+    for path in GATE.parents:
+        info = path.lstat()
+        if not stat.S_ISDIR(info.st_mode) or info.st_uid != 0 or info.st_mode & 0o022:
+            raise ValueError("protected availability directory required")
+    fd = os.open(GATE, os.O_RDONLY | os.O_NOFOLLOW | os.O_CLOEXEC)
+    try:
+        info = os.fstat(fd)
+        if (
+            not stat.S_ISREG(info.st_mode)
+            or info.st_nlink != 1
+            or info.st_uid != 0
+            or info.st_gid != 0
+            or stat.S_IMODE(info.st_mode) != 0o644
+            or info.st_size > 4096
+        ):
+            raise ValueError("protected availability file required")
+        with os.fdopen(fd, "rb", closefd=False) as source:
+            contents = source.read(4097)
+        if len(contents) > 4096:
+            raise ValueError("availability size bound")
+    finally:
+        os.close(fd)
+
+    def unique(pairs):
+        value = {}
+        for key, item in pairs:
+            if key in value:
+                raise ValueError("duplicate availability field")
+            value[key] = item
+        return value
+
+    return AvailabilityRecord.model_validate(json.loads(contents, object_pairs_hook=unique))
+
+
+def current(release: str | None, batch: str | None) -> AvailabilityRecord:
+    value = protected_record()
+    if value.release_id != release or value.configuration_id != batch:
+        raise ValueError("availability is not this running API binding")
+    return value

backend/src/kf_oj/infra/db/session.py

@@ -13,6 +13,7 @@ def build_engine(settings: Settings) -> AsyncEngine:
         max_overflow=0,
         pool_timeout=5,
         connect_args={
+            "timeout": 5,
             "command_timeout": 10,
             "server_settings": {
                 "statement_timeout": "10000",

backend/src/kf_oj/infra/messaging/outbox_queries.py

@@ -0,0 +1,48 @@
+"""Read-only bounded outbox counts, without broker or delivery dependencies."""
+
+from sqlalchemy import text
+
+
+class OutboxQueries:
+    def __init__(self, sessions):
+        self.sessions = sessions
+
+    async def status(self):
+        async with self.sessions() as session, session.begin():
+            await session.execute(text("SET TRANSACTION READ ONLY"))
+            await session.execute(text("SET LOCAL statement_timeout='1500'"))
+            await session.execute(text("SET LOCAL lock_timeout='500'"))
+            safe = await session.scalar(
+                text("""
+                SELECT rolcanlogin AND NOT(rolsuper OR rolcreatedb OR rolcreaterole
+                  OR rolreplication OR rolbypassrls)
+                  AND pg_has_role(current_user,'kf_oj_platform','USAGE')
+                  AND NOT pg_has_role(current_user,'kf_oj_coordinator','MEMBER')
+                  AND NOT pg_has_role(current_user,'kf_oj_identity_authority_owner','MEMBER')
+                  AND NOT has_column_privilege(current_user,'evaluations','state','UPDATE')
+                FROM pg_roles WHERE rolname=session_user
+            """)
+            )
+            if safe is not True:
+                raise ValueError("dedicated outbox projection role required")
+            row = (
+                (
+                    await session.execute(
+                        text("""
+                SELECT
+                  (SELECT count(*) FROM (SELECT 1 FROM outbox
+                    WHERE delivered_at IS NULL LIMIT 129) p) pending,
+                  (SELECT count(*) FROM (SELECT 1 FROM outbox WHERE delivered_at IS NULL
+                    AND locked_until>clock_timestamp() LIMIT 129) l) locked
+            """)
+                    )
+                )
+                .mappings()
+                .one()
+            )
+            return {
+                "schema_version": 1,
+                "pending_capped": min(row["pending"], 128),
+                "locked_capped": min(row["locked"], 128),
+                "truncated": row["pending"] > 128 or row["locked"] > 128,
+            }

backend/src/kf_oj/infra/messaging/publisher.py

@@ -11,6 +11,7 @@ from sqlalchemy import text
 from kf_oj.contracts.judge import JudgeTaskNotification
 from kf_oj.core.settings import Settings
 from kf_oj.infra.db.session import build_engine, build_session_factory
+from kf_oj.infra.messaging.outbox_queries import OutboxQueries
 
 QUEUE = "kf.judge.evaluations.v1"
 QUEUE_ARGUMENTS = {
@@ -25,6 +26,9 @@ class OutboxRepository:
     def __init__(self, sessions):
         self.sessions = sessions
 
+    async def status(self):
+        return await OutboxQueries(self.sessions).status()
+
     async def claim(self):
         owner = uuid4()
         async with self.sessions.begin() as s:

backend/src/kf_oj/modules/identity/README.md

@@ -4,7 +4,7 @@
 `public.py` 提供已验证主体，`service.py` 管理账号和可撤销会话，`repository.py` 封装持久化。
 用户身份不能来自前端自报字段或模型参数。
 
-本地管理命令为 `uv run --locked kf-accounts create <username>` / `disable <username>`。
+本地管理命令为 `uv run --locked kf-accounts create <username>`。
 创建口令由隐藏终端提示读取和确认，不接受命令行参数、环境中的默认口令或自助注册。
 用户名为 3–24 个小写 ASCII 字母、数字或下划线；口令 12–128 字符，最多 512 UTF-8 字节。
 密码摘要由新增的 `argon2-cffi` 依赖提供 Argon2id，固定 19 MiB/2 次/1 并行度。
@@ -14,6 +14,39 @@
 登录接口为 `/api/v1/auth/login`，退出 `/logout`，当前主体 `/me`。会话使用随机 256-bit token，
 数据库只保存 token / CSRF 摘要；默认 12 小时有效，单账号保留至多 10 个有效会话。
 账号禁用立即拒绝登录和旧会话。请求只采用 ASGI 连接 peer，不读取客户端转发地址。
+
+`0005_identity_authority` 为旧账号保留普通用户默认值，并加入管理员标记与服务端派生的授权版本。
+启用状态或管理员标记实际变化时，同一事务递增授权版本并撤销旧会话；事务回滚也回滚撤销。
+平台账号仅可插入普通账号列、更新启用状态，不能写管理员标记或授权版本；管理员的启用状态
+需要独立本地运维身份。`kf_oj_identity_operator` 与 `kf_oj_problem_import` 为无登录的独立权限组，
+口令与登录身份由运维另行配置，平台不继承运维组。导入组目前没有表权限，后续导入迁移只授予
+队列与候选所需权限，不授予评测状态写入权。迁移不创建默认管理员。
+保留授权或撤销历史后拒绝回退这次迁移。
+
+`0006_authority_operations` 将运维组进一步收敛为固定函数的 EXECUTE 权限；不能直接读取
+口令/会话摘要或修改账号/会话。函数由独立 NOLOGIN 角色持有，仅有授权所需列权限，固定
+`search_path` 并逐项限定操作。所有账号写操作在行锁前更新同一个事务守卫；撤销/禁用/删除
+最后一名启用管理员由数据库拒绝。重复授予/撤销不递增授权版本，实际变更仍原子撤销会话。
+旧可重复读快照的并发变更产生序列化失败，调用方须结束整个事务后重新操作；不吞掉失败。
+并发语义参见[PostgreSQL事务隔离](https://www.postgresql.org/docs/18/transaction-iso.html)，
+固定函数的权限与搜索路径参见[CREATE FUNCTION](https://www.postgresql.org/docs/18/sql-createfunction.html)。
+
+在单独的本地运维环境配置 `KF_OJ_IDENTITY_OPERATOR_DATABASE_URL`，使用具有
+`kf_oj_identity_operator` 权限组的普通 LOGIN，禁止超级用户、建库/建角色/复制/绕过 RLS
+以及平台/协调器/导入组成员。API、Worker 和常规服务不配置此凭据，CLI 不回退平台身份。
+先显式创建普通账号，再运行 `uv run --locked kf-accounts bootstrap-admin <username>`。
+没有启用管理员时只有明确 bootstrap 可首次授权；不创建默认账号或口令。已有管理员后使用
+`grant-admin` / `revoke-admin` / `disable` / `enable`。恢复已禁用管理员使用 `enable`；恢复失去
+全部管理员的受控数据库备份时可再次显式 bootstrap。最后一名启用管理员不能被撤销或禁用，
+应先授予另一名账号。操作的锁等待最多 2 秒、SQL 最多 5 秒，CLI 只输出账号/能力/授权版本和
+是否变化；错误不输出连接串、SQL 参数或驱动诊断。网页管理 API 与题包导入仍待后续实现。
+
+当前主体与登录响应附带版本为 1 的 `capabilities`，其中维护能力和十进制授权版本来自当前
+有效会话关联的账号；浏览器只展示这些信息，不能提交它们来获得授权。模块公开端口
+`ProblemMaintenancePort.require_problem_maintenance` 在调用方写事务中重新检查账号、授权版本
+与实时会话，并按账号→会话的顺序持有 SHARE 锁直到提交/回滚，防止验证之后撤权的竞态。
+普通构造的 `Principal` 默认没有维护能力；会话摘要仅在服务端主体内传递，不进入 DTO 或 repr。
+
 受控启动使用 `--no-proxy-headers`，避免服务器中间件预先替换 peer；反向代理后的用户共享
 该连接预算，引入可信代理的独立限流策略之前不能直接打开客户端转发头信任。
 每 peer 至多 10 次登录/15 分钟，预算通过真实数据库串行更新，失败尝试也消耗预算。

backend/src/kf_oj/modules/identity/authority.py

@@ -0,0 +1,83 @@
+"""Local-only composition for fixed database authority operations."""
+
+from dataclasses import dataclass
+from typing import Literal
+from uuid import UUID
+
+from sqlalchemy import text
+from sqlalchemy.exc import DBAPIError
+from sqlalchemy.ext.asyncio import async_sessionmaker
+
+from kf_oj.modules.identity.passwords import USERNAME
+
+AuthorityOperation = Literal["bootstrap", "grant", "revoke", "enable", "disable"]
+
+
+@dataclass(frozen=True)
+class AuthorityResult:
+    account_id: UUID
+    username: str
+    enabled: bool
+    is_administrator: bool
+    authorization_version: int
+    changed: bool
+
+
+async def manage_authority(
+    sessions: async_sessionmaker, username: str, operation: AuthorityOperation
+) -> AuthorityResult:
+    if not USERNAME.fullmatch(username) or operation not in (
+        "bootstrap",
+        "grant",
+        "revoke",
+        "enable",
+        "disable",
+    ):
+        raise ValueError("invalid authority operation")
+    try:
+        async with sessions.begin() as session:
+            await session.execute(text("SET LOCAL statement_timeout='5s'"))
+            await session.execute(text("SET LOCAL lock_timeout='2s'"))
+            # The CLI must use a dedicated, unprivileged local operator login.
+            # Web/platform, import and coordinator credentials are never reused.
+            safe = await session.scalar(
+                text("""
+                SELECT NOT (rolsuper OR rolcreatedb OR rolcreaterole OR rolreplication
+                    OR rolbypassrls)
+                    AND rolcanlogin AND pg_has_role(current_user,'kf_oj_identity_operator','USAGE')
+                    AND NOT pg_has_role(current_user,'kf_oj_platform','MEMBER')
+                    AND NOT pg_has_role(current_user,'kf_oj_coordinator','MEMBER')
+                    AND NOT pg_has_role(current_user,'kf_oj_problem_import','MEMBER')
+                FROM pg_roles WHERE rolname=current_user
+            """)
+            )
+            if not safe:
+                raise ValueError("a dedicated unprivileged identity operator login is required")
+            row = (
+                (
+                    await session.execute(
+                        text(
+                            "SELECT * FROM public.kf_manage_account_authority(:username,:operation)"
+                        ),
+                        {"username": username, "operation": operation},
+                    )
+                )
+                .mappings()
+                .one()
+            )
+            return AuthorityResult(**row)
+    except DBAPIError as error:
+        code = getattr(error.orig, "sqlstate", None)
+        messages = {
+            "P0002": "account not found",
+            "23514": (
+                "authority change rejected; preserve an enabled administrator "
+                "and use explicit bootstrap"
+            ),
+            "40001": "concurrent authority change rejected; retry the whole operation",
+            "55P03": "authority operation busy; retry later",
+            "57014": "authority operation timed out; verify current state before retrying",
+            "42501": "identity operator permissions unavailable",
+        }
+        # Never print a connection URL, SQL bind values or driver diagnostics.
+        raise ValueError(messages.get(code, "authority database operation unavailable")) from None

backend/src/kf_oj/modules/identity/cli.py

@@ -8,28 +8,58 @@ from sqlalchemy.exc import IntegrityError
 
 from kf_oj.core.settings import Settings
 from kf_oj.infra.db.session import build_engine, build_session_factory
+from kf_oj.modules.identity.authority import manage_authority
 from kf_oj.modules.identity.service import IdentityService
 
 
 async def run(command: str, username: str, password: str | None = None) -> None:
-    engine = build_engine(Settings())
+    settings = Settings()
+    authority_commands = {
+        "bootstrap-admin": "bootstrap",
+        "grant-admin": "grant",
+        "revoke-admin": "revoke",
+        "enable": "enable",
+        "disable": "disable",
+    }
+    if command != "create" and command not in authority_commands:
+        raise ValueError("unknown account command")
+    # Ordinary account creation uses the platform identity; authority management
+    # always requires a separately configured login and never falls back to it.
+    if command in authority_commands:
+        if settings.identity_operator_database_url is None:
+            raise ValueError("KF_OJ_IDENTITY_OPERATOR_DATABASE_URL is required")
+        if settings.identity_operator_database_url == settings.database_url:
+            raise ValueError("operator and platform database identities must be separate")
+        settings = settings.model_copy(
+            update={"database_url": settings.identity_operator_database_url}
+        )
+    engine = build_engine(settings)
     try:
+        if command in authority_commands:
+            result = await manage_authority(
+                build_session_factory(engine), username, authority_commands[command]
+            )
+            print(
+                f"Account {result.username}: enabled={result.enabled}, "
+                f"administrator={result.is_administrator}, "
+                f"authorization_version={result.authorization_version}, changed={result.changed}."
+            )
+            return
         service = IdentityService(build_session_factory(engine))
         if command == "create":
             assert password is not None
             await service.create_account(username, password)
             print("Account created.")
-        else:
-            if not await service.disable_account(username):
-                raise ValueError("account not found")
-            print("Account disabled; sessions revoked.")
     finally:
         await engine.dispose()
 
 
 def main() -> None:
     parser = argparse.ArgumentParser(description="Manage local OJ accounts")
-    parser.add_argument("command", choices=("create", "disable"))
+    parser.add_argument(
+        "command",
+        choices=("create", "disable", "enable", "bootstrap-admin", "grant-admin", "revoke-admin"),
+    )
     parser.add_argument("username")
     args = parser.parse_args()
     password = None

backend/src/kf_oj/modules/identity/models.py

@@ -3,24 +3,56 @@
 from datetime import datetime
 from uuid import UUID
 
-from sqlalchemy import Boolean, CheckConstraint, DateTime, ForeignKey, Index, String, Text
+from sqlalchemy import (
+    BigInteger,
+    Boolean,
+    CheckConstraint,
+    DateTime,
+    ForeignKey,
+    Index,
+    SmallInteger,
+    String,
+    Text,
+    text,
+)
 from sqlalchemy.orm import Mapped, mapped_column
 
 from kf_oj.infra.db.base import Base
 from kf_oj.infra.db.columns import CreatedAt
 
 
+class AuthorityGuard(Base):
+    """Migration-owned singleton; runtime roles have no access."""
+
+    __tablename__ = "identity_authority_guard"
+    __table_args__ = (
+        CheckConstraint("id = 1", name="singleton"),
+        CheckConstraint("generation >= 0", name="generation"),
+    )
+
+    id: Mapped[int] = mapped_column(SmallInteger, primary_key=True)
+    generation: Mapped[int] = mapped_column(BigInteger, server_default="0")
+
+
 class Account(CreatedAt, Base):
     __tablename__ = "accounts"
     __table_args__ = (
         CheckConstraint("username ~ '^[a-z0-9_]{3,24}$'", name="canonical_username"),
         CheckConstraint("char_length(password_hash) BETWEEN 40 AND 256", name="password_hash_size"),
+        CheckConstraint("authorization_version >= 1", name="authorization_version"),
+        Index(
+            "ix_accounts_active_administrators",
+            "id",
+            postgresql_where=text("is_administrator AND enabled"),
+        ),
     )
 
     id: Mapped[UUID] = mapped_column(primary_key=True)
     username: Mapped[str] = mapped_column(String(24), unique=True)
     password_hash: Mapped[str] = mapped_column(Text)
     enabled: Mapped[bool] = mapped_column(Boolean, server_default="true")
+    is_administrator: Mapped[bool] = mapped_column(Boolean, server_default="false")
+    authorization_version: Mapped[int] = mapped_column(BigInteger, server_default="1")
 
 
 class Session(CreatedAt, Base):

backend/src/kf_oj/modules/identity/public.py

@@ -1,6 +1,7 @@
 """Only verified principals cross business module boundaries."""
 
-from dataclasses import dataclass
+from dataclasses import dataclass, field
+from typing import Protocol
 from uuid import UUID
 
 
@@ -8,11 +9,30 @@ from uuid import UUID
 class Principal:
     account_id: UUID
     username: str
+    can_maintain_problems: bool = False
+    authorization_version: int = 1
+    session_token_hash: str | None = field(default=None, repr=False, compare=False)
+
+
+class MaintenanceDenied(ValueError):
+    pass
+
+
+class ProblemMaintenancePort(Protocol):
+    async def require_problem_maintenance(self, session, principal: Principal) -> None:
+        """Recheck and lock live authority/session inside the caller's write transaction."""
+        ...
 
 
 class AuthenticationFailed(ValueError):
     pass
 
 
+class ReservedMaintenancePort(Protocol):
+    async def require_reserved_maintenance(self, session, actor_id: UUID, epoch: int) -> None:
+        """Recheck/lock an immutable accepted receipt, with no login/session secret access."""
+        ...
+
+
 class LoginThrottled(ValueError):
     pass

backend/src/kf_oj/modules/identity/repository.py

@@ -51,19 +51,31 @@ async def account_by_username(session: AsyncSession, username: str) -> Account |
     return await session.scalar(select(Account).where(Account.username == username))
 
 
-async def current_session(session: AsyncSession, token_hash: str):
-    return (
-        await session.execute(
-            select(Session, Account)
-            .join(Account)
-            .where(
-                Session.token_hash == token_hash,
-                Session.revoked_at.is_(None),
-                Session.expires_at > func.now(),
-                Account.enabled.is_(True),
-            )
+async def lock_authority(session: AsyncSession, account_id) -> Account | None:
+    return await session.scalar(
+        select(Account)
+        .where(Account.id == account_id)
+        .with_for_update(read=True)
+        .execution_options(populate_existing=True)
+    )
+
+
+async def current_session(session: AsyncSession, token_hash: str, *, lock_session: bool = False):
+    query = (
+        select(Session, Account)
+        .join(Account)
+        .where(
+            Session.token_hash == token_hash,
+            Session.revoked_at.is_(None),
+            Session.expires_at > func.clock_timestamp(),
+            Account.enabled.is_(True),
         )
-    ).one_or_none()
+    )
+    if lock_session:
+        query = query.with_for_update(read=True, of=Session).execution_options(
+            populate_existing=True
+        )
+    return (await session.execute(query)).one_or_none()
 
 
 async def prune_sessions(session: AsyncSession, account_id) -> None:

backend/src/kf_oj/modules/identity/service.py

@@ -7,7 +7,8 @@ from dataclasses import dataclass, field
 from datetime import datetime, timedelta
 from uuid import uuid4
 
-from sqlalchemy import func, select, update
+from sqlalchemy import func, select, text, update
+from sqlalchemy.exc import DBAPIError
 from sqlalchemy.ext.asyncio import async_sessionmaker
 
 from kf_oj.modules.identity import repository
@@ -18,7 +19,12 @@ from kf_oj.modules.identity.passwords import (
     validate_account,
     verify_password,
 )
-from kf_oj.modules.identity.public import AuthenticationFailed, LoginThrottled, Principal
+from kf_oj.modules.identity.public import (
+    AuthenticationFailed,
+    LoginThrottled,
+    MaintenanceDenied,
+    Principal,
+)
 
 TOKEN = re.compile(r"[0-9a-f]{64}\Z")
 
@@ -107,7 +113,7 @@ class IdentityService:
                         expires_at=expires,
                     )
                 )
-                principal = Principal(account.id, account.username)
+                principal = self._principal(account, token_digest(token))
             return IssuedSession(principal, expires, token, csrf)
 
     async def authenticate(self, token: str | None, *, csrf_token: str | None = None) -> Principal:
@@ -123,9 +129,62 @@ class IdentityService:
                     record.csrf_hash, token_digest(csrf_token)
                 ):
                     raise AuthenticationFailed("invalid request token")
-            return Principal(account.id, account.username)
+            return self._principal(account, record.token_hash)
+
+    @staticmethod
+    def _principal(account: Account, session_token_hash: str) -> Principal:
+        return Principal(
+            account.id,
+            account.username,
+            account.is_administrator,
+            account.authorization_version,
+            session_token_hash,
+        )
+
+    async def require_problem_maintenance(self, session, principal: Principal) -> None:
+        if not session.in_transaction():
+            raise ValueError("maintenance authorization requires an active write transaction")
+        if (
+            not principal.can_maintain_problems
+            or principal.session_token_hash is None
+            or not TOKEN.fullmatch(principal.session_token_hash)
+        ):
+            raise MaintenanceDenied("problem maintenance required")
+        # Account first, then session: authority changes use that same lock order.
+        # SHARE locks last until the caller commits/rolls back; a stale principal,
+        # explicit logout, revocation or expired session cannot authorize a write.
+        account = await repository.lock_authority(session, principal.account_id)
+        if (
+            account is None
+            or not account.enabled
+            or not account.is_administrator
+            or account.authorization_version != principal.authorization_version
+        ):
+            raise MaintenanceDenied("problem maintenance required")
+        row = await repository.current_session(
+            session, principal.session_token_hash, lock_session=True
+        )
+        if row is None or row[1].id != account.id:
+            raise MaintenanceDenied("problem maintenance required")
 
     async def logout(self, token: str, csrf_token: str) -> None:
         await self.authenticate(token, csrf_token=csrf_token)
         async with self.sessions.begin() as session:
             await repository.revoke(session, token_digest(token))
+
+
+class ReservedMaintenance:
+    """Import worker uses only the fixed, narrow SQL authority port."""
+
+    async def require_reserved_maintenance(self, session, actor_id, epoch):
+        if not session.in_transaction() or type(epoch) is not int or epoch < 1:
+            raise MaintenanceDenied("invalid maintenance receipt")
+        try:
+            await session.execute(
+                text("SELECT public.kf_lock_reserved_maintenance(:actor,:epoch)"),
+                {"actor": actor_id, "epoch": epoch},
+            )
+        except DBAPIError as error:
+            if getattr(error.orig, "sqlstate", None) == "42501":
+                raise MaintenanceDenied("problem maintenance revoked") from None
+            raise

backend/src/kf_oj/modules/operations/README.md

@@ -1,5 +1,17 @@
 # operations
 
-负责平台侧节点、任务积压、重试原因和审计查询的管理视图。
-对判题状态的操作必须调用协调器协议；观测模块不成为第二个状态写入入口。
-当前只有目录边界，节点登记、指标聚合和管理员接口待实现。
+维护审计通过 `public.py` 的追加端口写入调用方事务；本模块不成为评测状态的写入入口。
+上传、解析完成/失败、丢弃、发布、下架与恢复记录真实账号、授权版本、操作 UUID、对象与
+数据库时间。发布回执和审计同时提交；审计失败使整个业务事务回滚，不确认半发布。
+
+本机受控身份 CLI 使用已核验的窄权限数据库函数。授权变化由固定包装函数在同一事务
+追加审计，主体类型为 operator，操作者为数据库 `session_user`，对象为实际变更账号；
+不把授予/撤销冒充成该账号自己的操作。旧账号事件保留 account 主体类型。
+
+管理员 `/api/v1/admin/maintenance-audit` 按时间和 UUID 的复合游标递减读取，每页至多
+100项，可选择有限动作类型；只展示已提交事件。导入失败动作仍是失败，committed 表示
+审计事务提交。响应不含口令、会话令牌、工件引用、内部路径或任意诊断正文。
+
+应用数据库角色无审计 UPDATE/DELETE 权限，数据库触发器还阻止历史改写。
+导入 Worker 只有追加权限，不能读取整个维护审计；Coordinator 无审计写入权限。
+节点管理、部署控制及跨账号业务管理仍未开放。

backend/src/kf_oj/modules/operations/models.py

@@ -0,0 +1,39 @@
+"""Append-only bounded maintenance events, independent of evaluation state."""
+
+from uuid import UUID
+
+from sqlalchemy import BigInteger, CheckConstraint, ForeignKey, Index, String, text
+from sqlalchemy.orm import Mapped, mapped_column
+
+from kf_oj.infra.db.base import Base
+from kf_oj.infra.db.columns import CreatedAt
+
+
+class MaintenanceEvent(CreatedAt, Base):
+    __tablename__ = "problem_maintenance_events"
+    __table_args__ = (
+        CheckConstraint(
+            "action IN ('upload_created','upload_received','import_ready',"
+            "'import_failed','import_discarded','import_expired','published',"
+            "'disabled','restored','authority_bootstrap','authority_grant',"
+            "'authority_revoke','authority_enable','authority_disable')",
+            name="action",
+        ),
+        CheckConstraint("authorization_version > 0", name="authority"),
+        CheckConstraint(
+            "(actor_kind='account' AND actor_id IS NOT NULL AND operator_name IS NULL) "
+            "OR (actor_kind='operator' AND actor_id IS NULL AND operator_name IS NOT NULL)",
+            name="actor",
+        ),
+        Index("ix_problem_maintenance_events_page", "created_at", "id"),
+    )
+    id: Mapped[UUID] = mapped_column(primary_key=True)
+    actor_id: Mapped[UUID | None] = mapped_column(ForeignKey("accounts.id"))
+    actor_kind: Mapped[str] = mapped_column(
+        String(8), default="account", server_default=text("'account'")
+    )
+    operator_name: Mapped[str | None] = mapped_column(String(63))
+    authorization_version: Mapped[int] = mapped_column(BigInteger)
+    operation_id: Mapped[UUID] = mapped_column()
+    action: Mapped[str] = mapped_column(String(24))
+    target_id: Mapped[UUID | None] = mapped_column()

backend/src/kf_oj/modules/operations/public.py

@@ -0,0 +1,28 @@
+"""Accepted actor receipts and finite maintenance events; no private data/log text."""
+
+from typing import Literal, Protocol
+from uuid import UUID
+
+Action = Literal[
+    "upload_created",
+    "upload_received",
+    "import_ready",
+    "import_failed",
+    "import_discarded",
+    "import_expired",
+    "published",
+    "disabled",
+    "restored",
+]
+
+
+class MaintenanceAuditPort(Protocol):
+    async def record(
+        self,
+        session,
+        actor_id: UUID,
+        authorization_version: int,
+        operation_id: UUID,
+        action: Action,
+        target_id: UUID | None = None,
+    ) -> None: ...

backend/src/kf_oj/modules/operations/queries.py

@@ -0,0 +1,62 @@
+"""Only authorized administrators read bounded append-only maintenance projections."""
+
+from datetime import datetime
+from uuid import UUID
+
+from sqlalchemy import select, text, tuple_
+
+from kf_oj.contracts.problem_maintenance import MaintenanceAuditEvent, MaintenanceAuditPage
+from kf_oj.modules.identity.public import ProblemMaintenancePort
+from kf_oj.modules.operations.models import MaintenanceEvent
+
+
+class MaintenanceAuditQueries:
+    def __init__(self, sessions, identity: ProblemMaintenancePort):
+        self.sessions, self.identity = sessions, identity
+
+    async def page(self, principal, *, before=None, limit=20, action=None):
+        if not 1 <= limit <= 100:
+            raise ValueError("invalid page limit")
+        cursor = None
+        if before is not None:
+            stamp, identifier = before.split("|")
+            stamp = datetime.fromisoformat(stamp)
+            if stamp.tzinfo is None:
+                raise ValueError("invalid audit cursor")
+            cursor = stamp, UUID(identifier)
+        async with self.sessions.begin() as session:
+            await session.execute(text("SET LOCAL statement_timeout='5s'"))
+            await session.execute(text("SET LOCAL lock_timeout='2s'"))
+            await self.identity.require_problem_maintenance(session, principal)
+            q = select(MaintenanceEvent)
+            if cursor:
+                q = q.where(tuple_(MaintenanceEvent.created_at, MaintenanceEvent.id) < cursor)
+            if action:
+                q = q.where(MaintenanceEvent.action == action)
+            rows = list(
+                await session.scalars(
+                    q.order_by(
+                        MaintenanceEvent.created_at.desc(), MaintenanceEvent.id.desc()
+                    ).limit(limit + 1)
+                )
+            )
+            visible = rows[:limit]
+            return MaintenanceAuditPage(
+                items=tuple(
+                    MaintenanceAuditEvent(
+                        id=r.id,
+                        created_at=r.created_at,
+                        actor_kind=r.actor_kind,
+                        actor_id=r.actor_id,
+                        operator_name=r.operator_name,
+                        authorization_version=str(r.authorization_version),
+                        operation_id=r.operation_id,
+                        action=r.action,
+                        target_id=r.target_id,
+                    )
+                    for r in visible
+                ),
+                next_before=f"{visible[-1].created_at.isoformat()}|{visible[-1].id}"
+                if len(rows) > limit
+                else None,
+            )

backend/src/kf_oj/modules/operations/service.py

@@ -0,0 +1,27 @@
+from uuid import uuid4
+
+from sqlalchemy import func, select
+
+from kf_oj.modules.operations.models import MaintenanceEvent
+from kf_oj.modules.operations.public import Action
+
+
+class MaintenanceAudit:
+    async def record(
+        self, session, actor_id, authorization_version, operation_id, action: Action, target_id=None
+    ):
+        if not session.in_transaction():
+            raise ValueError("audit requires a write transaction")
+        # Supplying the trusted DB timestamp avoids ORM INSERT ... RETURNING:
+        # the ordinary importer has append-only authority and cannot SELECT this table.
+        session.add(
+            MaintenanceEvent(
+                id=uuid4(),
+                created_at=await session.scalar(select(func.clock_timestamp())),
+                actor_id=actor_id,
+                authorization_version=authorization_version,
+                operation_id=operation_id,
+                action=action,
+                target_id=target_id,
+            )
+        )

backend/src/kf_oj/modules/problems/README.md

@@ -31,3 +31,50 @@ v2 使用 `schema_version: 2` 与 `language_configurations`，每个配置包含
 导入同一 slug 的 v2 版本保持原 v1 版本与提交不变。已有提交按其保存的协议版本解析，
 不能重新序列化旧 canonical 数据来补入新字段。Java 使用 Main.java 与默认包 Main；
 Python 使用 main.py。每个新版本的语言集合独立，浏览器不得为旧版本补开新语言。
+
+
+Web题包导入是独立的待发布流程：`/api/v1/admin/problem-imports` 使用真实维护会话，
+写入还要求明确Origin与绑定CSRF。先以稳定操作UUID、ZIP摘要和精确字节数建立容量预约，
+再向该操作的 `/archive` 流式PUT；同键重试仍验证实际内容，不会确认异内容。
+列表、详情和丢弃只开放给该操作的管理员本人，响应仅含公开题面、样例、语言预算与有限错误。
+`ready` 尚未发布，不会加入学生题库，也不改变既有题目版本。
+
+Web格式固定单层ZIP的stored/deflate，清单名为`problem.json`；公开文件与隐藏用例文件
+必须显式分别声明且不得混用。文件名只接受有界ASCII单层普通名；未知成员、链接/设备、
+加密、嵌套归档、额外前缀/尾随内容、损坏CRC与虚假大小被拒。旧受控目录CLI格式保持原义。
+压缩与实际解压各64 MiB、最多534文件，上传最多4096帧/每帧1 MiB/30秒；
+解析期限60秒。staging总预约256 MiB，每次128 MiB，单全局上传/解析槽位，
+本人最多10个/全局32个活跃候选，操作24小时到期，解析死亡最多领取两次。
+真实限额由管理capabilities返回；缺少配置或新鲜Worker资源证明时明确不可用。
+
+`uv run --locked kf-problem-import-worker` 是普通用户、独立数据库登录的组合入口。
+配置`KF_OJ_IMPORT_STAGING_ROOT`、`KF_OJ_ARTIFACT_ROOT`、可信准入和
+`KF_OJ_IMPORT_WORKER_CGROUP`；staging与工件目录必须归服务用户所有且权限0700。
+服务不会sudo、执行上传内容/学生源码、联网安装依赖或读写评测状态。启动及每次解析
+读回128 MiB/swap0/PIDs16/CPU不超过一核及文件/FD/core上限，错误身份/无界环境拒绝服务。
+解析子进程继承同一个内核文件锁，父进程死亡不能让GC在存活子进程仍持有文件时释放容量。
+租约与fence防止旧结果写入；完整工件持久化、候选和引用原子落库后才返回ready。
+丢弃/失败/到期先清理私有暂存字节再释放预约，保留不可变操作记录与追加式有限审计。
+
+资源约束服务模板见`deploy/problem-import-worker.service.example`。API和Worker需可访问
+同一普通用户的私有目录；数据库采用各自最小角色，导入Worker只通过固定身份公开端口
+验证已受理的维护授权。PrivateNetwork模板要求Unix PostgreSQL socket；实际部署前由运维
+设置外部私有配置、专用登录与目录，不包含默认口令，也不代表本轮已经生产部署。
+
+管理员发布使用 `/api/v1/admin/problem-publications`，绑定独立操作 UUID、本人导入操作、
+候选 UUID 与预期活动版本（首次发布为 null）。`publication.py` 为 CLI 与 Web 共用的
+准入与不可变版本写入路径；Web 在事务内再次校验实时维护权限、候选摘要、工件实际字节
+和可信节点配置。CLI 保留本机受控入口与原有导入格式，不借用网页会话。
+
+成功维护回执只追加保存，UUID 同内容重试返回原快照，不重复创建 revision 或审计。
+UUID 绑定不同内容或活动版本变化返回409；前端应核对最新状态后建立新的操作凭据。
+题目状态写入同样要求预期活动版本及 enabled；下架不修改历史版本或删除任何提交。
+新提交持有逻辑题目的共享锁直到提交事务结束，下架/恢复持有排他锁，二者明确排序。
+
+管理列表按 slug、版本历史按递减 revision 分页，每页至多100条，仅返回公开元数据。
+候选仍通过本人导入操作读取；维护回执仅本人可读。隐藏测试字节、摘要和宿主路径不进入
+这些投影。所有管理读取也经实时维护权限检查，缺失发布配置明确503。
+
+`for_accepted_execution` 仅在 submissions 已核对有效租约、源码归属及不可变尝试快照后
+调用，读取已发布原版本时允许逻辑题目已下架。它没有外部 UUID 直读端点，不放宽未发布
+版本或无有效租约的访问。公开读取与新提交仍检查 enabled。

backend/src/kf_oj/modules/problems/candidate_validation.py

@@ -0,0 +1,74 @@
+"""Pure data validation shared by the bounded child and fenced candidate transaction."""
+
+import hashlib
+import json
+from dataclasses import dataclass
+from uuid import uuid5
+
+from kf_oj.contracts.admin_problems import CandidatePreview, LegacyImportBudget
+from kf_oj.contracts.judging import ArtifactReference, TestCase
+from kf_oj.contracts.problems import PublicLanguageConfiguration
+from kf_oj.modules.problems.import_format import ImportEnvelope, ProblemImport
+from kf_oj.modules.problems.publication import admit_version
+
+
+@dataclass(frozen=True)
+class ValidatedCandidate:
+    manifest: dict
+    preview: CandidatePreview
+    references: dict[str, ArtifactReference]
+
+    @property
+    def digest(self):
+        return hashlib.sha256(
+            json.dumps(
+                self.manifest, sort_keys=True, separators=(",", ":"), ensure_ascii=True
+            ).encode()
+        ).hexdigest()
+
+
+def validate_candidate(manifest_data, preview_data, references, policy) -> ValidatedCandidate:
+    manifest = ImportEnvelope.model_validate(manifest_data).root
+    preview = CandidatePreview.model_validate(preview_data)
+    refs = {k: ArtifactReference.model_validate(v) for k, v in references.items()}
+    legacy = isinstance(manifest, ProblemImport)
+    if (
+        preview.slug != manifest.slug
+        or preview.title != manifest.title
+        or preview.case_count != len(manifest.cases)
+        or preview.judging_schema_version != manifest.schema_version
+        or tuple(v.value for v in preview.languages) != tuple(v.value for v in manifest.languages)
+    ):
+        raise ValueError("invalid candidate projection")
+    expected_budget = (
+        LegacyImportBudget(
+            compile_limits=manifest.compile_limits,
+            run_limits=manifest.run_limits,
+            job_wall_time_us=manifest.job_wall_time_us,
+        )
+        if legacy
+        else None
+    )
+    configs = (
+        ()
+        if legacy
+        else tuple(
+            PublicLanguageConfiguration.from_configuration(c)
+            for c in manifest.language_configurations
+        )
+    )
+    if preview.legacy_budget != expected_budget or preview.language_configurations != configs:
+        raise ValueError("invalid candidate budget")
+    names = {name for c in manifest.cases for name in (c.input_file, c.expected_file)}
+    if set(refs) != names:
+        raise ValueError("invalid hidden references")
+    cases = tuple(
+        TestCase(
+            case_id=uuid5(preview.candidate_id, c.key),
+            input=refs[c.input_file],
+            expected=refs[c.expected_file],
+        )
+        for c in manifest.cases
+    )
+    admit_version(policy, manifest, preview.candidate_id, preview.candidate_id, cases)
+    return ValidatedCandidate(manifest.model_dump(mode="json"), preview, refs)

backend/src/kf_oj/modules/problems/import_models.py

@@ -0,0 +1,121 @@
+"""Private durable imports and immutable candidates; no grading-state write authority."""
+
+from datetime import datetime
+from uuid import UUID
+
+from sqlalchemy import (
+    BigInteger,
+    CheckConstraint,
+    Computed,
+    DateTime,
+    ForeignKey,
+    ForeignKeyConstraint,
+    Index,
+    Integer,
+    SmallInteger,
+    String,
+    UniqueConstraint,
+    text,
+)
+from sqlalchemy.dialects.postgresql import JSONB
+from sqlalchemy.orm import Mapped, mapped_column
+
+from kf_oj.infra.db.base import Base
+from kf_oj.infra.db.columns import CreatedAt
+from kf_oj.modules.problems.models import ProblemVersion
+
+
+class ImportPool(Base):
+    __tablename__ = "problem_import_pool"
+    __table_args__ = (
+        CheckConstraint("id = 1", name="singleton"),
+        CheckConstraint("reserved_bytes BETWEEN 0 AND 268435456", name="capacity"),
+    )
+    id: Mapped[int] = mapped_column(SmallInteger, primary_key=True)
+    reserved_bytes: Mapped[int] = mapped_column(BigInteger, server_default="0")
+    worker_ready_until: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
+    worker_policy_digest: Mapped[str | None] = mapped_column(String(64))
+
+
+class ProblemImportOperation(CreatedAt, Base):
+    __tablename__ = "problem_import_operations"
+    __table_args__ = (
+        CheckConstraint(
+            "state IN ('uploading','uploaded','validating','ready','failed',"
+            "'published','discarded','expired')",
+            name="state",
+        ),
+        CheckConstraint("archive_digest ~ '^[0-9a-f]{64}$'", name="digest"),
+        CheckConstraint("archive_bytes BETWEEN 1 AND 67108864", name="bytes"),
+        CheckConstraint("authorization_version > 0", name="authority"),
+        CheckConstraint("attempts BETWEEN 0 AND 2 AND fence >= 0", name="attempts"),
+        CheckConstraint("reserved_bytes IN (0,134217728)", name="reservation"),
+        CheckConstraint("expires_at > created_at AND updated_at >= created_at", name="times"),
+        Index("ix_problem_import_owner", "owner_id", "id"),
+        Index("ix_problem_import_queue", "state", "created_at"),
+        Index("ix_problem_import_expiry", "expires_at"),
+        Index("ix_problem_import_reservations", "id", postgresql_where=text("reserved_bytes>0")),
+    )
+    id: Mapped[UUID] = mapped_column(primary_key=True)
+    owner_id: Mapped[UUID] = mapped_column(ForeignKey("accounts.id"))
+    authorization_version: Mapped[int] = mapped_column(BigInteger)
+    archive_digest: Mapped[str] = mapped_column(String(64))
+    archive_bytes: Mapped[int] = mapped_column(BigInteger)
+    state: Mapped[str] = mapped_column(String(16), server_default="uploading")
+    expires_at: Mapped[datetime] = mapped_column(DateTime(timezone=True))
+    updated_at: Mapped[datetime] = mapped_column(DateTime(timezone=True))
+    lease_until: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
+    attempts: Mapped[int] = mapped_column(Integer, server_default="0")
+    fence: Mapped[int] = mapped_column(BigInteger, server_default="0")
+    reserved_bytes: Mapped[int] = mapped_column(BigInteger, server_default="134217728")
+    failure_code: Mapped[str | None] = mapped_column(String(32))
+    candidate_id: Mapped[UUID | None] = mapped_column(
+        ForeignKey("problem_candidates.id", use_alter=True, name="fk_problem_import_candidate")
+    )
+    published_version_id: Mapped[UUID | None] = mapped_column(ForeignKey(ProblemVersion.id))
+
+
+class ProblemCandidate(CreatedAt, Base):
+    __tablename__ = "problem_candidates"
+    __table_args__ = (
+        UniqueConstraint("operation_id"),
+        CheckConstraint("manifest_digest ~ '^[0-9a-f]{64}$'", name="digest"),
+        CheckConstraint("case_count BETWEEN 1 AND 256", name="cases"),
+        CheckConstraint("octet_length(preview::text) <= 4194304", name="preview"),
+        CheckConstraint("octet_length(manifest::text) <= 262144", name="manifest"),
+    )
+    id: Mapped[UUID] = mapped_column(primary_key=True)
+    operation_id: Mapped[UUID] = mapped_column(ForeignKey("problem_import_operations.id"))
+    manifest_digest: Mapped[str] = mapped_column(String(64))
+    manifest: Mapped[dict] = mapped_column(JSONB)
+    preview: Mapped[dict] = mapped_column(JSONB)
+    case_count: Mapped[int] = mapped_column(Integer)
+
+
+class CandidateCase(Base):
+    __tablename__ = "problem_candidate_cases"
+    __table_args__ = (
+        CheckConstraint("position BETWEEN 0 AND 255", name="position"),
+        CheckConstraint(
+            "input_bytes BETWEEN 0 AND 67108864 AND expected_bytes BETWEEN 0 AND 67108864",
+            name="bytes",
+        ),
+        ForeignKeyConstraint(
+            ["input_digest", "artifact_state"], ["artifacts.digest", "artifacts.state"]
+        ),
+        ForeignKeyConstraint(
+            ["expected_digest", "artifact_state"],
+            ["artifacts.digest", "artifacts.state"],
+            name="fk_candidate_cases_expected_artifacts",
+        ),
+    )
+    candidate_id: Mapped[UUID] = mapped_column(
+        ForeignKey("problem_candidates.id"), primary_key=True
+    )
+    position: Mapped[int] = mapped_column(Integer, primary_key=True)
+    key: Mapped[str] = mapped_column(String(64))
+    input_digest: Mapped[str] = mapped_column(String(64))
+    input_bytes: Mapped[int] = mapped_column(BigInteger)
+    expected_digest: Mapped[str] = mapped_column(String(64))
+    expected_bytes: Mapped[int] = mapped_column(BigInteger)
+    artifact_state: Mapped[str] = mapped_column(String(8), Computed("'ready'", persisted=True))

backend/src/kf_oj/modules/problems/import_policy.py

@@ -0,0 +1,11 @@
+"""Shared import availability error and exact policy identity; no lifecycle imports."""
+
+import hashlib
+
+
+class ImportUnavailable(ValueError):
+    pass
+
+
+def policy_digest(policy):
+    return hashlib.sha256(policy.model_dump_json().encode()).hexdigest()

backend/src/kf_oj/modules/problems/import_worker.py

@@ -0,0 +1,430 @@
+"""Fenced ordinary-user import consumption. No student execution or evaluation DB access."""
+
+import asyncio
+import json
+import os
+import resource
+import sys
+from datetime import timedelta
+from pathlib import Path
+from uuid import uuid4
+
+from sqlalchemy import delete, func, or_, select, text
+from sqlalchemy.exc import DBAPIError
+
+from kf_oj.contracts.admin_problems import MAX_IMPORT_ATTEMPTS, VALIDATION_DEADLINE_SECONDS
+from kf_oj.infra.artifacts.store import ArtifactError
+from kf_oj.modules.identity.public import MaintenanceDenied
+from kf_oj.modules.problems.candidate_validation import validate_candidate
+from kf_oj.modules.problems.import_models import (
+    CandidateCase,
+    ImportPool,
+    ProblemCandidate,
+)
+from kf_oj.modules.problems.import_models import (
+    ProblemImportOperation as Operation,
+)
+from kf_oj.modules.problems.imports import ACTIVE, ImportUnavailable, ProblemImports, policy_digest
+
+
+def verify_worker_limits(configured_group: Path):
+    if os.getuid() == 0:
+        raise ImportUnavailable("import worker must be ordinary")
+    actual = next(
+        line.split(":", 2)[2]
+        for line in Path("/proc/self/cgroup").read_text().splitlines()
+        if line.startswith("0::")
+    )
+    group = Path("/sys/fs/cgroup") / actual.lstrip("/")
+    if group.resolve() != configured_group.absolute().resolve():
+        raise ImportUnavailable("import worker cgroup mismatch")
+    caps = {
+        n: (group / n).read_text().strip()
+        for n in ("memory.max", "memory.swap.max", "pids.max", "cpu.max")
+    }
+    if (
+        caps["memory.max"] == "max"
+        or not 0 < int(caps["memory.max"]) <= 134217728
+        or caps["memory.swap.max"] != "0"
+        or caps["pids.max"] == "max"
+        or not 0 < int(caps["pids.max"]) <= 16
+    ):
+        raise ImportUnavailable("import worker resource limits unavailable")
+    quota, period = caps["cpu.max"].split()
+    if quota == "max" or int(quota) > int(period):
+        raise ImportUnavailable("import worker CPU limit unavailable")
+    for name, maximum in (
+        (resource.RLIMIT_FSIZE, 67108864),
+        (resource.RLIMIT_NOFILE, 64),
+        (resource.RLIMIT_CORE, 0),
+    ):
+        limits = resource.getrlimit(name)
+        if any(v == resource.RLIM_INFINITY or v > maximum for v in limits):
+            raise ImportUnavailable("import worker process limits unavailable")
+    return caps
+
+
+class ImportWorker:
+    def __init__(self, sessions, staging, artifacts, authority, audit, policy, cgroup):
+        (
+            self.sessions,
+            self.staging,
+            self.artifacts,
+            self.authority,
+            self.audit,
+            self.policy,
+            self.cgroup,
+        ) = sessions, staging, artifacts, authority, audit, policy, cgroup
+
+    async def heartbeat(self):
+        verify_worker_limits(self.cgroup)
+        async with self.sessions.begin() as session:
+            safe = await session.scalar(
+                text("""
+              SELECT rolcanlogin AND NOT(rolsuper OR rolcreatedb OR rolcreaterole
+                OR rolreplication OR rolbypassrls)
+                AND pg_has_role(current_user,'kf_oj_problem_import','USAGE')
+                AND NOT pg_has_role(current_user,'kf_oj_platform','MEMBER')
+                AND NOT pg_has_role(current_user,'kf_oj_coordinator','MEMBER')
+                AND NOT pg_has_role(current_user,'kf_oj_identity_operator','MEMBER')
+                AND NOT pg_has_role(current_user,'kf_oj_identity_authority_owner','MEMBER')
+              FROM pg_roles WHERE rolname=current_user
+            """)
+            )
+            if not safe:
+                raise ImportUnavailable("dedicated unprivileged import login required")
+            pool = await session.get(ImportPool, 1, with_for_update=True)
+            if pool is None:
+                raise ImportUnavailable("import pool unavailable")
+            pool.worker_ready_until = await session.scalar(
+                select(func.clock_timestamp())
+            ) + timedelta(seconds=90)
+            pool.worker_policy_digest = policy_digest(self.policy)
+
+    async def _release(self, operation_id):
+        await asyncio.to_thread(self.staging.remove, operation_id)
+        async with self.sessions.begin() as session:
+            pool = await ProblemImports.pool(session)
+            op = await session.get(Operation, operation_id, with_for_update=True)
+            pool.reserved_bytes -= op.reserved_bytes
+            op.reserved_bytes = 0
+            op.lease_until = None
+
+    async def collect(self):
+        # Caller owns the root flock, so a live upload/parser cannot be unlinked or
+        # have its reservation reused, even if its DB lease expired while suspended.
+        async with self.sessions() as session:
+            now = await session.scalar(select(func.clock_timestamp()))
+            names = list(
+                await session.scalars(
+                    select(Operation.id)
+                    .where(
+                        or_(
+                            Operation.reserved_bytes > 0,
+                            Operation.state.in_(ACTIVE) & (Operation.expires_at <= now),
+                        )
+                    )
+                    .order_by(Operation.updated_at, Operation.id)
+                    .limit(32)
+                )
+            )
+            garbage = list(
+                await session.scalars(
+                    select(ProblemCandidate.operation_id)
+                    .join(Operation, Operation.id == ProblemCandidate.operation_id)
+                    .where(Operation.state.in_(("discarded", "expired", "failed")))
+                    .limit(32)
+                )
+            )
+            names = list(dict.fromkeys(names + garbage))[:32]
+        for identifier in names:
+            async with self.sessions.begin() as session:
+                await ProblemImports.pool(session)
+                op = await session.get(Operation, identifier, with_for_update=True)
+                now = await session.scalar(select(func.clock_timestamp()))
+                if op.state in ACTIVE and op.expires_at <= now:
+                    op.state = "expired"
+                    op.failure_code = "expired"
+                    op.updated_at = now
+                    op.candidate_id = None
+                    op.fence += 1
+                    await self.audit.record(
+                        session, op.owner_id, op.authorization_version, op.id, "import_expired"
+                    )
+                elif op.state == "uploading" and op.lease_until and op.lease_until <= now:
+                    op.state = "failed"
+                    op.failure_code = "upload_interrupted"
+                    op.updated_at = now
+                    op.fence += 1
+                    await self.audit.record(
+                        session, op.owner_id, op.authorization_version, op.id, "import_failed"
+                    )
+                elif op.state == "validating" and op.lease_until and op.lease_until <= now:
+                    if op.attempts < MAX_IMPORT_ATTEMPTS:
+                        op.state = "uploaded"
+                        op.failure_code = None
+                        op.lease_until = None
+                        op.fence += 1
+                        op.updated_at = now
+                        await asyncio.to_thread(self.staging.reset_validation, op.id)
+                    else:
+                        op.state = "failed"
+                        op.failure_code = "validation_unavailable"
+                        op.updated_at = now
+                        op.fence += 1
+                        await self.audit.record(
+                            session, op.owner_id, op.authorization_version, op.id, "import_failed"
+                        )
+                if op.state in ("discarded", "expired", "failed"):
+                    op.candidate_id = None
+                    await session.flush()
+                    candidate = await session.scalar(
+                        select(ProblemCandidate).where(ProblemCandidate.operation_id == op.id)
+                    )
+                    if candidate:
+                        await session.execute(
+                            delete(CandidateCase).where(CandidateCase.candidate_id == candidate.id)
+                        )
+                        await session.delete(candidate)
+                release = (
+                    op.state in ("ready", "published", "discarded", "expired", "failed")
+                    and op.reserved_bytes > 0
+                )
+            if release:
+                await self._release(identifier)
+        # Uncommitted staging objects after a failed transaction are removed only under
+        # the same kernel lock and only from this service's private, bounded namespace.
+        for identifier in self.staging.operation_ids():
+            async with self.sessions() as session:
+                exists = await session.get(Operation, identifier)
+            if exists is None:
+                await asyncio.to_thread(self.staging.remove, identifier)
+
+    async def once(self):
+        await self.heartbeat()
+        try:
+            with self.staging.exclusive() as lock:
+                await self.collect()
+                async with self.sessions.begin() as session:
+                    await ProblemImports.pool(session)
+                    now = await session.scalar(select(func.clock_timestamp()))
+                    busy = await session.scalar(
+                        select(func.count())
+                        .select_from(Operation)
+                        .where(
+                            Operation.state.in_(("uploading", "validating")),
+                            Operation.lease_until > now,
+                        )
+                    )
+                    if busy:
+                        return False
+                    op = await session.scalar(
+                        select(Operation)
+                        .where(
+                            Operation.state == "uploaded",
+                            Operation.attempts < MAX_IMPORT_ATTEMPTS,
+                            Operation.expires_at > now,
+                        )
+                        .order_by(Operation.created_at, Operation.id)
+                        .limit(1)
+                        .with_for_update()
+                    )
+                    if op is None:
+                        return False
+                    op.attempts += 1
+                    op.fence += 1
+                    op.state = "validating"
+                    op.updated_at = now
+                    op.lease_until = now + timedelta(seconds=VALIDATION_DEADLINE_SECONDS + 15)
+                    identifier, fence, size, digest, actor, epoch = (
+                        op.id,
+                        op.fence,
+                        op.archive_bytes,
+                        op.archive_digest,
+                        op.owner_id,
+                        op.authorization_version,
+                    )
+                try:
+                    async with self.sessions.begin() as session:
+                        await self.authority.require_reserved_maintenance(session, actor, epoch)
+                    candidate_id = uuid4()
+                    result = await self.parse(identifier, size, digest, candidate_id, lock)
+                    if "failure_code" in result:
+                        await self.fail(identifier, fence, result["failure_code"])
+                        return True
+                    candidate = validate_candidate(
+                        result["manifest"], result["preview"], result["references"], self.policy
+                    )
+                    if (
+                        candidate.digest != result["manifest_digest"]
+                        or candidate.preview.candidate_id != candidate_id
+                    ):
+                        raise ValueError("invalid candidate receipt")
+                    directory = self.staging.operation(identifier)
+                    members = self.staging.members(directory)
+                    try:
+                        async with self.sessions.begin() as session:
+                            await self.authority.require_reserved_maintenance(session, actor, epoch)
+                            await ProblemImports.pool(session)
+                            op = await session.get(Operation, identifier, with_for_update=True)
+                            now = await session.scalar(select(func.clock_timestamp()))
+                            if (
+                                op.state != "validating"
+                                or op.fence != fence
+                                or op.lease_until <= now
+                                or op.expires_at <= now
+                            ):
+                                raise ValueError("stale candidate receipt")
+                            for name, reference in sorted(
+                                candidate.references.items(), key=lambda item: item[1].digest
+                            ):
+                                fd = os.open(
+                                    name,
+                                    os.O_RDONLY | os.O_NOFOLLOW | os.O_NONBLOCK | os.O_CLOEXEC,
+                                    dir_fd=members,
+                                )
+                                try:
+                                    await self.artifacts.put_file(session, fd, reference)
+                                finally:
+                                    os.close(fd)
+                            session.add(
+                                ProblemCandidate(
+                                    id=candidate_id,
+                                    operation_id=identifier,
+                                    manifest_digest=candidate.digest,
+                                    manifest=candidate.manifest,
+                                    preview=candidate.preview.model_dump(mode="json"),
+                                    case_count=candidate.preview.case_count,
+                                )
+                            )
+                            await session.flush()
+                            for position, case in enumerate(candidate.manifest["cases"]):
+                                input_ref, answer_ref = (
+                                    candidate.references[case["input_file"]],
+                                    candidate.references[case["expected_file"]],
+                                )
+                                session.add(
+                                    CandidateCase(
+                                        candidate_id=candidate_id,
+                                        position=position,
+                                        key=case["key"],
+                                        input_digest=input_ref.digest,
+                                        input_bytes=input_ref.bytes,
+                                        expected_digest=answer_ref.digest,
+                                        expected_bytes=answer_ref.bytes,
+                                    )
+                                )
+                            await session.flush()
+                            # Adoption must not turn an expired lease into a ready candidate.
+                            completed_at = await session.scalar(select(func.clock_timestamp()))
+                            if op.lease_until <= completed_at or op.expires_at <= completed_at:
+                                raise ValueError("candidate completion lease expired")
+                            op.state = "ready"
+                            op.candidate_id = candidate_id
+                            op.updated_at = completed_at
+                            op.lease_until = None
+                            await self.audit.record(
+                                session, actor, epoch, identifier, "import_ready", candidate_id
+                            )
+                    finally:
+                        os.close(members)
+                        os.close(directory)
+                    await self._release(identifier)
+                except MaintenanceDenied:
+                    await self.fail(identifier, fence, "authority_revoked")
+                except (ArtifactError, OSError):
+                    await self.fail(identifier, fence, "storage_unavailable")
+                except (ValueError, DBAPIError):
+                    await self.fail(identifier, fence, "validation_unavailable")
+                return True
+        except ArtifactError:
+            return False  # Another live writer holds the one global slot.
+
+    async def fail(self, identifier, fence, code):
+        from kf_oj.contracts.admin_problems import ImportFailure
+
+        code = ImportFailure(code).value
+        async with self.sessions.begin() as session:
+            await ProblemImports.pool(session)
+            op = await session.get(Operation, identifier, with_for_update=True)
+            if op.state != "validating" or op.fence != fence:
+                return
+            op.state = "failed"
+            op.failure_code = code
+            op.updated_at = await session.scalar(select(func.clock_timestamp()))
+            op.lease_until = None
+            await self.audit.record(
+                session, op.owner_id, op.authorization_version, op.id, "import_failed"
+            )
+        await self._release(identifier)
+
+    async def parse(self, identifier, size, digest, candidate, lock):
+        verify_worker_limits(self.cgroup)
+        directory = self.staging.operation(identifier)
+        archive = members = None
+        try:
+            archive = os.open(
+                "archive",
+                os.O_RDONLY | os.O_NOFOLLOW | os.O_NONBLOCK | os.O_CLOEXEC,
+                dir_fd=directory,
+            )
+            members = self.staging.members(directory, create=True)
+            # Preserve only the trusted runtime import roots, without inheriting DB/
+            # service credentials. Curated runtimes may keep dependencies outside site-packages.
+            env = {
+                "PATH": str(Path(sys.executable).parent),
+                "PYTHONPATH": os.pathsep.join(
+                    dict.fromkeys(
+                        [str(Path(__file__).parents[3])]
+                        + [p for p in os.environ.get("PYTHONPATH", "").split(os.pathsep) if p]
+                    )
+                ),
+                "PYTHONUNBUFFERED": "1",
+                "PYTHONDONTWRITEBYTECODE": "1",
+                "PYTHONNOUSERSITE": "1",
+                "LC_ALL": "C.UTF-8",
+            }
+            # Minimal environment may require the trusted dynamic-loader path in a curated VM.
+            if "LD_LIBRARY_PATH" in os.environ:
+                env["LD_LIBRARY_PATH"] = os.environ["LD_LIBRARY_PATH"]
+            child = await asyncio.create_subprocess_exec(
+                sys.executable,
+                "-m",
+                "kf_oj.workers._archive_child",
+                str(archive),
+                str(members),
+                str(lock),
+                str(size),
+                digest,
+                str(candidate),
+                self.policy.model_dump_json(),
+                env=env,
+                pass_fds=(archive, members, lock),
+                stdout=asyncio.subprocess.PIPE,
+                stderr=asyncio.subprocess.DEVNULL,
+            )
+            try:
+                async with asyncio.timeout(VALIDATION_DEADLINE_SECONDS + 5):
+                    output, _ = await child.communicate()
+            except BaseException:
+                child.kill()
+                await child.wait()
+                raise
+            if child.returncode != 0 or not 0 < len(output) <= 4 * 1024**2:
+                return {
+                    "failure_code": "validation_deadline"
+                    if child.returncode == -14
+                    else "validation_unavailable"
+                }
+            result = json.loads(output)
+            if not isinstance(result, dict):
+                raise ValueError("invalid child result")
+            return result
+        except TimeoutError:
+            return {"failure_code": "validation_deadline"}
+        finally:
+            if members is not None:
+                os.close(members)
+            if archive is not None:
+                os.close(archive)
+            os.close(directory)

backend/src/kf_oj/modules/problems/imports.py

@@ -0,0 +1,432 @@
+"""Authenticated durable import lifecycle; filesystem work remains behind private adapters."""
+
+import asyncio
+import hashlib
+import os
+from contextlib import asynccontextmanager
+from datetime import timedelta
+from uuid import UUID
+
+from sqlalchemy import func, select, text
+
+from kf_oj.contracts.admin_problems import (
+    IMPORT_LIFETIME_SECONDS,
+    MAX_OWNER_CANDIDATES,
+    MAX_TOTAL_CANDIDATES,
+    MAX_UPLOAD_CHUNK_BYTES,
+    MAX_UPLOAD_CHUNKS,
+    STAGING_MAX_BYTES,
+    STAGING_RESERVATION_BYTES,
+    UPLOAD_DEADLINE_SECONDS,
+    CandidatePreview,
+    CreateProblemImport,
+    ProblemImportCapabilities,
+    ProblemImportDetail,
+    ProblemImportPage,
+    ProblemImportSummary,
+)
+from kf_oj.infra.artifacts.staging import ImportStaging
+from kf_oj.infra.artifacts.store import ArtifactError
+from kf_oj.modules.identity.public import MaintenanceDenied, ProblemMaintenancePort
+from kf_oj.modules.operations.public import MaintenanceAuditPort
+from kf_oj.modules.problems.import_models import ImportPool, ProblemCandidate
+from kf_oj.modules.problems.import_models import ProblemImportOperation as Operation
+from kf_oj.modules.problems.import_policy import ImportUnavailable as ImportUnavailable
+from kf_oj.modules.problems.import_policy import policy_digest as policy_digest
+
+ACTIVE = ("uploading", "uploaded", "validating", "ready")
+
+
+class ImportConflict(ValueError):
+    pass
+
+
+class ImportBadDigest(ImportConflict):
+    pass
+
+
+class ImportMissing(ValueError):
+    pass
+
+
+def summary(operation) -> ProblemImportSummary:
+    return ProblemImportSummary(
+        operation_id=operation.id,
+        state=operation.state,
+        expected_archive_digest=operation.archive_digest,
+        archive_bytes=operation.archive_bytes,
+        created_at=operation.created_at,
+        expires_at=operation.expires_at,
+        updated_at=operation.updated_at,
+        failure_code=operation.failure_code,
+        candidate_id=operation.candidate_id,
+        published_version_id=operation.published_version_id,
+    )
+
+
+class ProblemImports:
+    def __init__(
+        self,
+        sessions,
+        staging: ImportStaging,
+        identity: ProblemMaintenancePort,
+        audit: MaintenanceAuditPort,
+        policy,
+    ):
+        self.sessions, self.staging, self.identity, self.audit, self.policy = (
+            sessions,
+            staging,
+            identity,
+            audit,
+            policy,
+        )
+
+    @asynccontextmanager
+    async def write(self, principal):
+        async with self.sessions.begin() as session:
+            await session.execute(text("SET LOCAL statement_timeout='5s'"))
+            await session.execute(text("SET LOCAL lock_timeout='2s'"))
+            await self.identity.require_problem_maintenance(session, principal)
+            yield session
+
+    @staticmethod
+    async def pool(session):
+        pool = await session.get(ImportPool, 1, with_for_update=True)
+        if pool is None:
+            raise ImportUnavailable("import capacity unavailable")
+        actual = await session.scalar(
+            select(func.coalesce(func.sum(Operation.reserved_bytes), 0)).where(
+                Operation.reserved_bytes > 0
+            )
+        )
+        if pool.reserved_bytes != actual:
+            raise ImportUnavailable("import capacity inconsistent")
+        return pool
+
+    async def capabilities(self):
+        async with self.sessions() as session:
+            pool = await session.get(ImportPool, 1)
+            now = await session.scalar(select(func.clock_timestamp()))
+            available = bool(
+                pool
+                and pool.worker_ready_until
+                and pool.worker_ready_until > now
+                and pool.worker_policy_digest == policy_digest(self.policy)
+            )
+        return ProblemImportCapabilities(
+            uploads_available=available, validation_available=available
+        )
+
+    async def create(self, principal, request: CreateProblemImport):
+        # Immutable receipt retries need no filesystem slot, including while a parser/GC
+        # owns the root lock. Missing receipts still enter the locked creation path below.
+        async with self.write(principal) as session:
+            existing = await session.get(Operation, request.operation_id)
+            if existing:
+                if (
+                    existing.owner_id != principal.account_id
+                    or existing.archive_digest != request.archive_digest
+                    or existing.archive_bytes != request.archive_bytes
+                ):
+                    raise ImportConflict("operation key already bound")
+                return summary(existing)
+        try:
+            with self.staging.exclusive():
+                await asyncio.to_thread(self.staging.usage)
+                async with self.write(principal) as session:
+                    pool = await self.pool(session)
+                    existing = await session.get(
+                        Operation, request.operation_id, with_for_update=True
+                    )
+                    if existing:
+                        if (
+                            existing.owner_id != principal.account_id
+                            or existing.archive_digest != request.archive_digest
+                            or existing.archive_bytes != request.archive_bytes
+                        ):
+                            raise ImportConflict("operation key already bound")
+                        return summary(existing)
+                    now = await session.scalar(select(func.clock_timestamp()))
+                    if (
+                        not pool.worker_ready_until
+                        or pool.worker_ready_until <= now
+                        or pool.worker_policy_digest != policy_digest(self.policy)
+                    ):
+                        raise ImportUnavailable("import validation unavailable")
+                    global_count = await session.scalar(
+                        select(func.count())
+                        .select_from(Operation)
+                        .where(Operation.state.in_(ACTIVE))
+                    )
+                    owner_count = await session.scalar(
+                        select(func.count())
+                        .select_from(Operation)
+                        .where(
+                            Operation.state.in_(ACTIVE), Operation.owner_id == principal.account_id
+                        )
+                    )
+                    busy = await session.scalar(
+                        select(func.count())
+                        .select_from(Operation)
+                        .where(
+                            Operation.state.in_(("uploading", "validating")),
+                            Operation.lease_until > now,
+                        )
+                    )
+                    if (
+                        global_count >= MAX_TOTAL_CANDIDATES
+                        or owner_count >= MAX_OWNER_CANDIDATES
+                        or busy
+                        or pool.reserved_bytes + STAGING_RESERVATION_BYTES > STAGING_MAX_BYTES
+                    ):
+                        raise ImportUnavailable("import capacity exhausted")
+                    operation = Operation(
+                        id=request.operation_id,
+                        owner_id=principal.account_id,
+                        authorization_version=principal.authorization_version,
+                        archive_digest=request.archive_digest,
+                        archive_bytes=request.archive_bytes,
+                        state="uploading",
+                        created_at=now,
+                        updated_at=now,
+                        expires_at=now + timedelta(seconds=IMPORT_LIFETIME_SECONDS),
+                        lease_until=now + timedelta(seconds=UPLOAD_DEADLINE_SECONDS + 15),
+                        attempts=0,
+                        fence=0,
+                        reserved_bytes=STAGING_RESERVATION_BYTES,
+                    )
+                    session.add(operation)
+                    pool.reserved_bytes += STAGING_RESERVATION_BYTES
+                    await self.audit.record(
+                        session,
+                        principal.account_id,
+                        principal.authorization_version,
+                        operation.id,
+                        "upload_created",
+                    )
+                    await session.flush()
+                    return summary(operation)
+        except ArtifactError:
+            raise ImportUnavailable("import storage unavailable") from None
+
+    async def detail(self, principal, operation_id):
+        # Recheck live authority even when a principal was injected by an internal caller.
+        async with self.write(principal) as session:
+            op = await session.get(Operation, operation_id)
+            if op is None or op.owner_id != principal.account_id:
+                raise ImportMissing("import unavailable")
+            candidate = (
+                await session.get(ProblemCandidate, op.candidate_id) if op.candidate_id else None
+            )
+            return ProblemImportDetail(
+                **summary(op).model_dump(),
+                candidate=CandidatePreview.model_validate(candidate.preview) if candidate else None,
+            )
+
+    async def list(self, principal, after=None, limit=20):
+        if not 1 <= limit <= 100:
+            raise ValueError("invalid page limit")
+        async with self.write(principal) as session:
+            query = select(Operation).where(Operation.owner_id == principal.account_id)
+            if after:
+                query = query.where(Operation.id > after)
+            rows = list(await session.scalars(query.order_by(Operation.id).limit(limit + 1)))
+            return ProblemImportPage(
+                items=tuple(summary(o) for o in rows[:limit]),
+                next_after=rows[limit - 1].id if len(rows) > limit else None,
+            )
+
+    async def upload(self, principal, operation_id: UUID, chunks, content_length: int | None):
+        # Reject missing/foreign receipts before consulting shared filesystem capacity.
+        # The locked transaction below still rechecks authority and ownership before writes.
+        async with self.write(principal) as session:
+            op = await session.get(Operation, operation_id)
+            if op is None or op.owner_id != principal.account_id:
+                raise ImportMissing("import unavailable")
+            if content_length is not None and content_length != op.archive_bytes:
+                raise ImportConflict("archive length mismatch")
+        descriptor = operation_fd = None
+        fence = None
+        received = 0
+        chunk_count = 0
+        digest = hashlib.sha256()
+        try:
+            with self.staging.exclusive():
+                async with self.write(principal) as session:
+                    await self.pool(session)
+                    op = await session.get(Operation, operation_id, with_for_update=True)
+                    if not op or op.owner_id != principal.account_id:
+                        raise ImportMissing("import unavailable")
+                    accepted = op.state in ("uploaded", "validating", "ready", "published")
+                    now = await session.scalar(select(func.clock_timestamp()))
+                    if (
+                        not accepted
+                        and (
+                            op.state != "uploading"
+                            or op.lease_until is None
+                            or op.lease_until <= now
+                        )
+                    ) or op.expires_at <= now:
+                        raise ImportConflict("upload no longer available")
+                    if content_length is not None and content_length != op.archive_bytes:
+                        raise ImportConflict("archive length mismatch")
+                    if not accepted:
+                        op.fence += 1
+                        fence = op.fence
+                        op.lease_until = now + timedelta(seconds=UPLOAD_DEADLINE_SECONDS + 15)
+                    expected_bytes, expected_digest = op.archive_bytes, op.archive_digest
+                if not accepted:
+                    operation_fd = self.staging.operation(operation_id, create=True)
+                    descriptor = os.open(
+                        "archive",
+                        os.O_WRONLY | os.O_CREAT | os.O_EXCL | os.O_NOFOLLOW | os.O_CLOEXEC,
+                        0o600,
+                        dir_fd=operation_fd,
+                    )
+                async with asyncio.timeout(UPLOAD_DEADLINE_SECONDS):
+                    async for chunk in chunks:
+                        chunk_count += 1
+                        received += len(chunk)
+                        if (
+                            type(chunk) is not bytes
+                            or len(chunk) > MAX_UPLOAD_CHUNK_BYTES
+                            or chunk_count > MAX_UPLOAD_CHUNKS
+                            or received > expected_bytes
+                        ):
+                            raise ImportConflict("archive bytes outside policy")
+                        digest.update(chunk)
+                        if accepted:
+                            continue
+                        # Cancellation waits for the finite writer outside the event loop.
+                        task = asyncio.create_task(asyncio.to_thread(write_all, descriptor, chunk))
+                        try:
+                            await asyncio.shield(task)
+                        except BaseException:
+                            await task
+                            raise
+                if received != expected_bytes or digest.hexdigest() != expected_digest:
+                    raise ImportBadDigest("archive digest or length mismatch")
+                if accepted:
+                    async with self.write(principal) as session:
+                        op = await session.get(Operation, operation_id)
+                        if not op or op.state not in (
+                            "uploaded",
+                            "validating",
+                            "ready",
+                            "published",
+                        ):
+                            raise ImportConflict("import receipt no longer available")
+                        return summary(op)
+                await asyncio.to_thread(os.fsync, descriptor)
+                os.close(descriptor)
+                descriptor = None
+                os.fsync(operation_fd)
+                async with self.write(principal) as session:
+                    await self.pool(session)
+                    op = await session.get(Operation, operation_id, with_for_update=True)
+                    now = await session.scalar(select(func.clock_timestamp()))
+                    if op.state != "uploading" or op.fence != fence or op.lease_until <= now:
+                        raise ImportConflict("upload receipt expired")
+                    op.state = "uploaded"
+                    op.lease_until = None
+                    op.updated_at = now
+                    await self.audit.record(
+                        session, op.owner_id, op.authorization_version, op.id, "upload_received"
+                    )
+                    result = summary(op)
+                return result
+        except BaseException as error:
+            # Failure bookkeeping cannot authorize a new business write. It only fences this
+            # accepted upload and releases capacity after physical bytes have been removed.
+            if descriptor is not None:
+                os.close(descriptor)
+                descriptor = None
+            if operation_fd is not None:
+                os.close(operation_fd)
+                operation_fd = None
+            if fence is not None:
+                try:
+                    with self.staging.exclusive():
+                        await asyncio.to_thread(self.staging.remove, operation_id)
+                        async with self.sessions.begin() as session:
+                            pool = await self.pool(session)
+                            op = await session.get(Operation, operation_id, with_for_update=True)
+                            if op and op.state == "uploading" and op.fence == fence:
+                                op.state = "failed"
+                                op.failure_code = (
+                                    "upload_deadline"
+                                    if isinstance(error, TimeoutError)
+                                    else "digest_mismatch"
+                                    if isinstance(error, ImportBadDigest)
+                                    else "authority_revoked"
+                                    if isinstance(error, MaintenanceDenied)
+                                    else "storage_unavailable"
+                                    if isinstance(error, OSError)
+                                    else "upload_interrupted"
+                                )
+                                op.updated_at = await session.scalar(select(func.clock_timestamp()))
+                                op.lease_until = None
+                                pool.reserved_bytes -= op.reserved_bytes
+                                op.reserved_bytes = 0
+                                await self.audit.record(
+                                    session,
+                                    op.owner_id,
+                                    op.authorization_version,
+                                    op.id,
+                                    "import_failed",
+                                )
+                except (ArtifactError, OSError):
+                    pass  # Durable reservation retained for fenced GC.
+            raise
+        finally:
+            if descriptor is not None:
+                os.close(descriptor)
+            if operation_fd is not None:
+                os.close(operation_fd)
+
+    async def discard(self, principal, operation_id):
+        async with self.write(principal) as session:
+            op = await session.get(Operation, operation_id)
+            if op is None or op.owner_id != principal.account_id:
+                raise ImportMissing("import unavailable")
+            if op.state == "discarded":
+                return summary(op)
+        try:
+            with self.staging.exclusive():
+                async with self.write(principal) as session:
+                    pool = await self.pool(session)
+                    op = await session.get(Operation, operation_id, with_for_update=True)
+                    if not op or op.owner_id != principal.account_id:
+                        raise ImportMissing("import unavailable")
+                    if op.state == "published":
+                        raise ImportConflict("published import cannot be discarded")
+                    if op.state == "discarded":
+                        return summary(op)
+                    await asyncio.to_thread(self.staging.remove, operation_id)
+                    op.state = "discarded"
+                    op.candidate_id = None
+                    op.failure_code = None
+                    op.lease_until = None
+                    op.fence += 1
+                    op.updated_at = await session.scalar(select(func.clock_timestamp()))
+                    pool.reserved_bytes -= op.reserved_bytes
+                    op.reserved_bytes = 0
+                    await self.audit.record(
+                        session,
+                        principal.account_id,
+                        principal.authorization_version,
+                        op.id,
+                        "import_discarded",
+                    )
+                    return summary(op)
+        except ArtifactError:
+            raise ImportUnavailable("import storage unavailable") from None
+
+
+def write_all(descriptor, data):
+    remaining = memoryview(data)
+    while remaining:
+        size = os.write(descriptor, remaining)
+        if size <= 0:
+            raise OSError("short staging write")
+        remaining = remaining[size:]

backend/src/kf_oj/modules/problems/maintenance.py

@@ -0,0 +1,324 @@
+"""Administrator transactions; no evaluation writes or private data in projections."""
+
+import asyncio
+import hashlib
+import json
+from contextlib import asynccontextmanager
+from uuid import uuid4, uuid5
+
+from sqlalchemy import func, select, text
+
+from kf_oj.contracts.admin_problems import CandidatePreview
+from kf_oj.contracts.judging import ArtifactReference, TestCase
+from kf_oj.contracts.problem_maintenance import (
+    MaintainedProblem,
+    MaintainedProblemPage,
+    MaintainedVersion,
+    MaintainedVersionPage,
+    MaintenanceReceipt,
+)
+from kf_oj.modules.identity.public import ProblemMaintenancePort
+from kf_oj.modules.operations.public import MaintenanceAuditPort
+from kf_oj.modules.problems import repository
+from kf_oj.modules.problems.candidate_validation import validate_candidate
+from kf_oj.modules.problems.import_format import ImportEnvelope
+from kf_oj.modules.problems.import_models import (
+    CandidateCase,
+    ProblemCandidate,
+    ProblemImportOperation,
+)
+from kf_oj.modules.problems.imports import ImportConflict, ImportMissing, ImportUnavailable
+from kf_oj.modules.problems.maintenance_models import ProblemMaintenanceOperation
+from kf_oj.modules.problems.models import Problem, ProblemCase, ProblemVersion
+from kf_oj.modules.problems.publication import admit_version, publish_version
+from kf_oj.modules.problems.service import ProblemService
+
+
+def project_problem(problem, version):
+    return MaintainedProblem(
+        id=problem.id,
+        slug=problem.slug,
+        enabled=problem.enabled,
+        active_version_id=problem.active_version_id,
+        revision=version.revision if version else 0,
+        title=version.title if version else None,
+        created_at=problem.created_at,
+    )
+
+
+class ProblemMaintenance:
+    def __init__(
+        self,
+        sessions,
+        identity: ProblemMaintenancePort,
+        audit: MaintenanceAuditPort,
+        artifacts=None,
+        policy=None,
+    ):
+        self.sessions, self.identity, self.audit = sessions, identity, audit
+        self.artifacts, self.policy = artifacts, policy
+        self._publishing = asyncio.Semaphore(2)
+
+    @asynccontextmanager
+    async def transaction(self, principal):
+        async with self.sessions.begin() as session:
+            await session.execute(text("SET LOCAL statement_timeout='5s'"))
+            await session.execute(text("SET LOCAL lock_timeout='2s'"))
+            await self.identity.require_problem_maintenance(session, principal)
+            yield session
+
+    async def page(self, principal, *, after=None, limit=20, enabled=None):
+        if not 1 <= limit <= 100:
+            raise ValueError("invalid page limit")
+        async with self.transaction(principal) as session:
+            q = select(Problem, ProblemVersion).outerjoin(
+                ProblemVersion, Problem.active_version_id == ProblemVersion.id
+            )
+            if after is not None:
+                q = q.where(Problem.slug > after)
+            if enabled is not None:
+                q = q.where(Problem.enabled == enabled)
+            rows = list(await session.execute(q.order_by(Problem.slug).limit(limit + 1)))
+            return MaintainedProblemPage(
+                items=tuple(project_problem(*r) for r in rows[:limit]),
+                next_after=rows[limit - 1][0].slug if len(rows) > limit else None,
+            )
+
+    async def by_slug(self, principal, slug):
+        async with self.transaction(principal) as session:
+            row = (
+                await session.execute(
+                    select(Problem, ProblemVersion)
+                    .outerjoin(ProblemVersion, Problem.active_version_id == ProblemVersion.id)
+                    .where(Problem.slug == slug)
+                )
+            ).one_or_none()
+            if row is None:
+                raise ImportMissing("problem unavailable")
+            return project_problem(*row)
+
+    async def detail(self, principal, problem_id):
+        async with self.transaction(principal) as session:
+            problem = await session.get(Problem, problem_id)
+            if problem is None:
+                raise ImportMissing("problem unavailable")
+            version = (
+                await session.get(ProblemVersion, problem.active_version_id)
+                if problem.active_version_id
+                else None
+            )
+            return project_problem(problem, version)
+
+    async def versions(self, principal, problem_id, *, before=None, limit=20):
+        if not 1 <= limit <= 100 or (before is not None and before < 1):
+            raise ValueError("invalid page limit")
+        async with self.transaction(principal) as session:
+            problem = await session.get(Problem, problem_id)
+            if problem is None:
+                raise ImportMissing("problem unavailable")
+            count = (
+                select(func.count())
+                .where(ProblemCase.version_id == ProblemVersion.id)
+                .scalar_subquery()
+            )
+            q = select(ProblemVersion, count).where(
+                ProblemVersion.problem_id == problem_id, ProblemVersion.published_at.is_not(None)
+            )
+            if before is not None:
+                q = q.where(ProblemVersion.revision < before)
+            rows = list(
+                await session.execute(q.order_by(ProblemVersion.revision.desc()).limit(limit + 1))
+            )
+            return MaintainedVersionPage(
+                items=tuple(
+                    MaintainedVersion(
+                        **ProblemService._summary(problem, v).model_dump(),
+                        published_at=v.published_at,
+                        case_count=n,
+                    )
+                    for v, n in rows[:limit]
+                ),
+                next_before=rows[limit - 1][0].revision if len(rows) > limit else None,
+            )
+
+    async def receipt(self, principal, operation_id):
+        async with self.transaction(principal) as session:
+            row = await session.get(ProblemMaintenanceOperation, operation_id)
+            if row is None or row.owner_id != principal.account_id:
+                raise ImportMissing("operation unavailable")
+            return MaintenanceReceipt.model_validate(row.receipt)
+
+    async def _replay(self, session, principal, action, body, target):
+        digest = hashlib.sha256(
+            json.dumps(
+                {"action": action, "target": str(target), "request": body.model_dump(mode="json")},
+                sort_keys=True,
+                separators=(",", ":"),
+            ).encode()
+        ).hexdigest()
+        key = int.from_bytes(hashlib.sha256(body.operation_id.bytes).digest()[:4], signed=True)
+        await session.execute(text("SELECT pg_advisory_xact_lock(1262907470,:key)"), {"key": key})
+        row = await session.get(ProblemMaintenanceOperation, body.operation_id)
+        if row is not None:
+            if row.owner_id != principal.account_id:
+                raise ImportMissing("operation unavailable")
+            if row.action != action or row.request_digest != digest:
+                raise ImportConflict("operation UUID already bound")
+            return digest, MaintenanceReceipt.model_validate(row.receipt)
+        return digest, None
+
+    async def _record(
+        self, session, principal, request, action, digest, problem, version, published=None
+    ):
+        receipt = MaintenanceReceipt(
+            operation_id=request.operation_id,
+            action=action,
+            completed_at=await session.scalar(select(func.clock_timestamp())),
+            problem=project_problem(problem, version),
+            published_version_id=published,
+        )
+        session.add(
+            ProblemMaintenanceOperation(
+                id=request.operation_id,
+                owner_id=principal.account_id,
+                authorization_version=principal.authorization_version,
+                action=action,
+                request_digest=digest,
+                receipt=receipt.model_dump(mode="json"),
+            )
+        )
+        await self.audit.record(
+            session,
+            principal.account_id,
+            principal.authorization_version,
+            request.operation_id,
+            {"publish": "published", "disable": "disabled", "restore": "restored"}[action],
+            published if action == "publish" else problem.id,
+        )
+        await session.flush()
+        return receipt
+
+    async def publish(self, principal, request):
+        if self.artifacts is None or self.policy is None or self._publishing.locked():
+            raise ImportUnavailable("publication unavailable")
+        async with self._publishing:
+            async with self.transaction(principal) as session:
+                digest, replay = await self._replay(
+                    session, principal, "publish", request, request.import_operation_id
+                )
+                if replay:
+                    return replay
+                op = await session.get(
+                    ProblemImportOperation, request.import_operation_id, with_for_update=True
+                )
+                if op is None or op.owner_id != principal.account_id:
+                    raise ImportMissing("candidate unavailable")
+                if (
+                    op.state != "ready"
+                    or op.candidate_id != request.candidate_id
+                    or op.authorization_version != principal.authorization_version
+                    or op.expires_at <= await session.scalar(select(func.clock_timestamp()))
+                ):
+                    raise ImportConflict("candidate no longer publishable")
+                candidate = await session.get(ProblemCandidate, op.candidate_id)
+                if candidate is None or candidate.operation_id != op.id:
+                    raise ImportUnavailable("candidate unavailable")
+                manifest = ImportEnvelope.model_validate(candidate.manifest).root
+                preview = CandidatePreview.model_validate(candidate.preview)
+                rows = list(
+                    await session.scalars(
+                        select(CandidateCase)
+                        .where(CandidateCase.candidate_id == candidate.id)
+                        .order_by(CandidateCase.position)
+                    )
+                )
+                if len(rows) != len(manifest.cases) or len(rows) != candidate.case_count:
+                    raise ImportUnavailable("candidate references unavailable")
+                refs = {}
+                for position, (row, c) in enumerate(zip(rows, manifest.cases, strict=True)):
+                    if row.position != position or row.key != c.key:
+                        raise ImportUnavailable("candidate references unavailable")
+                    for name, ref in (
+                        (
+                            c.input_file,
+                            ArtifactReference(digest=row.input_digest, bytes=row.input_bytes),
+                        ),
+                        (
+                            c.expected_file,
+                            ArtifactReference(digest=row.expected_digest, bytes=row.expected_bytes),
+                        ),
+                    ):
+                        if name in refs and refs[name] != ref:
+                            raise ImportUnavailable("candidate references unavailable")
+                        refs[name] = ref
+                validated = validate_candidate(
+                    candidate.manifest, candidate.preview, refs, self.policy
+                )
+                if (
+                    validated.digest != candidate.manifest_digest
+                    or preview.candidate_id != candidate.id
+                ):
+                    raise ImportUnavailable("candidate integrity unavailable")
+                await repository.lock_slug(session, manifest.slug)
+                problem = await repository.lock_problem(session, manifest.slug)
+                actual = problem.active_version_id if problem else None
+                if actual != request.expected_active_version_id or (
+                    problem and not problem.enabled
+                ):
+                    raise ImportConflict("active version or availability changed")
+                if problem is None:
+                    problem = Problem(id=uuid4(), slug=manifest.slug)
+                    session.add(problem)
+                    await session.flush()
+                version_id = uuid4()
+                cases = tuple(
+                    TestCase(
+                        case_id=uuid5(version_id, c.key),
+                        input=refs[c.input_file],
+                        expected=refs[c.expected_file],
+                    )
+                    for c in manifest.cases
+                )
+                admit_version(self.policy, manifest, version_id, problem.id, cases)
+                # Candidate FKs protect all referenced ready metadata from GC. The
+                # private adapter additionally re-hashes disk bytes without buffering them.
+                for ref in sorted(
+                    {r.digest: r for r in refs.values()}.values(), key=lambda r: r.digest
+                ):
+                    await self.artifacts.check_metadata(session, ref)
+                    task = asyncio.create_task(asyncio.to_thread(self.artifacts.store.verify, ref))
+                    try:
+                        await asyncio.shield(task)
+                    except BaseException:
+                        await task
+                        raise
+                version = await publish_version(
+                    session, problem, manifest, preview, version_id, cases
+                )
+                op.state, op.published_version_id = "published", version.id
+                op.updated_at = await session.scalar(select(func.clock_timestamp()))
+                return await self._record(
+                    session, principal, request, "publish", digest, problem, version, version.id
+                )
+
+    async def availability(self, principal, problem_id, request, *, enabled):
+        action = "restore" if enabled else "disable"
+        async with self.transaction(principal) as session:
+            digest, replay = await self._replay(session, principal, action, request, problem_id)
+            if replay:
+                return replay
+            problem = await session.get(Problem, problem_id, with_for_update=True)
+            if problem is None:
+                raise ImportMissing("problem unavailable")
+            if (
+                problem.active_version_id != request.expected_active_version_id
+                or problem.enabled != request.expected_enabled
+                or problem.enabled == enabled
+            ):
+                raise ImportConflict("active version or availability changed")
+            version = await session.get(ProblemVersion, problem.active_version_id)
+            if version is None or version.published_at is None:
+                raise ImportUnavailable("published version unavailable")
+            problem.enabled = enabled
+            await session.flush()
+            return await self._record(session, principal, request, action, digest, problem, version)

backend/src/kf_oj/modules/problems/maintenance_models.py

@@ -0,0 +1,26 @@
+"""Append-only actor-bound receipts; replay never re-applies a published operation."""
+
+from uuid import UUID
+
+from sqlalchemy import BigInteger, CheckConstraint, ForeignKey, String
+from sqlalchemy.dialects.postgresql import JSONB
+from sqlalchemy.orm import Mapped, mapped_column
+
+from kf_oj.infra.db.base import Base
+from kf_oj.infra.db.columns import CreatedAt
+
+
+class ProblemMaintenanceOperation(CreatedAt, Base):
+    __tablename__ = "problem_maintenance_operations"
+    __table_args__ = (
+        CheckConstraint("action IN ('publish','disable','restore')", name="action"),
+        CheckConstraint("request_digest ~ '^[0-9a-f]{64}$'", name="digest"),
+        CheckConstraint("authorization_version > 0", name="authority"),
+        CheckConstraint("octet_length(receipt::text) <= 4096", name="receipt"),
+    )
+    id: Mapped[UUID] = mapped_column(primary_key=True)
+    owner_id: Mapped[UUID] = mapped_column(ForeignKey("accounts.id"))
+    authorization_version: Mapped[int] = mapped_column(BigInteger)
+    action: Mapped[str] = mapped_column(String(16))
+    request_digest: Mapped[str] = mapped_column(String(64))
+    receipt: Mapped[dict] = mapped_column(JSONB)

backend/src/kf_oj/modules/problems/operations.py

@@ -0,0 +1,64 @@
+"""Read-only import projection for the ordinary operator CLI; no private archive data."""
+
+from sqlalchemy import text
+
+from kf_oj.modules.problems.import_models import ImportPool
+from kf_oj.modules.problems.import_policy import ImportUnavailable, policy_digest
+
+
+class ImportOperationQueries:
+    def __init__(self, sessions, policy):
+        self.sessions, self.policy = sessions, policy
+
+    async def status(self) -> dict:
+        async with self.sessions() as session, session.begin():
+            await session.execute(text("SET TRANSACTION READ ONLY"))
+            await session.execute(text("SET LOCAL statement_timeout='1500'"))
+            await session.execute(text("SET LOCAL lock_timeout='500'"))
+            authorized = await session.scalar(
+                text("""
+                SELECT rolcanlogin AND NOT(rolsuper OR rolcreatedb OR rolcreaterole
+                  OR rolreplication OR rolbypassrls)
+                  AND pg_has_role(current_user,'kf_oj_problem_import','USAGE')
+                  AND NOT pg_has_role(current_user,'kf_oj_platform','MEMBER')
+                  AND NOT pg_has_role(current_user,'kf_oj_coordinator','MEMBER')
+                  AND NOT pg_has_role(current_user,'kf_oj_identity_operator','MEMBER')
+                  AND NOT pg_has_role(current_user,'kf_oj_identity_authority_owner','MEMBER')
+                FROM pg_roles WHERE rolname=session_user
+            """)
+            )
+            if authorized is not True:
+                raise ImportUnavailable("dedicated import observation role required")
+            pool = await session.get(ImportPool, 1)
+            row = (
+                (
+                    await session.execute(
+                        text("""
+                SELECT clock_timestamp() now,
+                  (SELECT count(*) FROM (SELECT 1 FROM problem_import_operations
+                    WHERE state='uploaded' LIMIT 129) q) uploaded,
+                  (SELECT count(*) FROM (SELECT 1 FROM problem_import_operations
+                    WHERE state='validating' LIMIT 129) q) validating,
+                  (SELECT coalesce(sum(reserved_bytes),0) FROM (
+                    SELECT reserved_bytes FROM problem_import_operations
+                    WHERE reserved_bytes>0 LIMIT 129) q) actual_reserved
+            """)
+                    )
+                )
+                .mappings()
+                .one()
+            )
+            if pool is None or pool.reserved_bytes != row["actual_reserved"]:
+                raise ImportUnavailable("import reservation consistency unknown")
+            return {
+                "schema_version": 1,
+                "worker_ready": bool(
+                    pool.worker_ready_until
+                    and pool.worker_ready_until > row["now"]
+                    and pool.worker_policy_digest == policy_digest(self.policy)
+                ),
+                "reserved_bytes": pool.reserved_bytes,
+                "uploaded_capped": min(row["uploaded"], 128),
+                "validating_capped": min(row["validating"], 128),
+                "truncated": row["uploaded"] > 128 or row["validating"] > 128,
+            }

backend/src/kf_oj/modules/problems/public.py

@@ -78,3 +78,7 @@ class JudgingVersion:
 
 class ProblemPort(Protocol):
     async def for_submission(self, session, version_id: UUID) -> JudgingVersion: ...
+
+    async def for_accepted_execution(self, session, version_id: UUID) -> JudgingVersion:
+        """Require an already-validated live execution lease; allow a disabled published version."""
+        ...

backend/src/kf_oj/modules/problems/publication.py

@@ -0,0 +1,82 @@
+"""One admission and immutable publication path for local and web imports."""
+
+from uuid import uuid4
+
+from sqlalchemy import func, select
+
+from kf_oj.contracts import judging_v2 as v2
+from kf_oj.contracts.judging import MAX_SOURCE_BYTES, ArtifactReference
+from kf_oj.modules.problems import repository
+from kf_oj.modules.problems.import_format import ProblemImport
+from kf_oj.modules.problems.models import ProblemCase, ProblemVersion
+from kf_oj.modules.problems.public import JudgingVersion, ProblemUnavailable
+
+
+def admit_version(policy, manifest, version_id, problem_id, cases):
+    legacy = isinstance(manifest, ProblemImport)
+    projection = JudgingVersion(
+        version_id,
+        problem_id,
+        manifest.languages,
+        manifest.toolchain if legacy else None,
+        manifest.compile_limits if legacy else None,
+        manifest.run_limits if legacy else None,
+        manifest.job_wall_time_us if legacy else None,
+        cases,
+        manifest.schema_version,
+        () if legacy else manifest.language_configurations,
+    )
+    for language in manifest.languages:
+        v2.admit_manifest(
+            policy,
+            projection.manifest(
+                uuid4(),
+                uuid4(),
+                language,
+                ArtifactReference(digest="0" * 64, bytes=MAX_SOURCE_BYTES),
+            ),
+            1,
+        )
+    return projection
+
+
+async def publish_version(session, problem, manifest, preview, version_id, cases):
+    """Caller holds the logical slug/row locks and has made all artifacts durable."""
+    if not problem.enabled:
+        raise ProblemUnavailable("problem disabled")
+    legacy = isinstance(manifest, ProblemImport)
+    version = ProblemVersion(
+        id=version_id,
+        problem_id=problem.id,
+        revision=await repository.next_revision(session, problem.id),
+        title=manifest.title,
+        statement=preview.statement,
+        languages=[lang.value for lang in manifest.languages],
+        judging_schema_version=manifest.schema_version,
+        language_configurations=None
+        if legacy
+        else [c.model_dump(mode="json") for c in manifest.language_configurations],
+        toolchain=manifest.toolchain.model_dump(mode="json") if legacy else None,
+        compile_limits=manifest.compile_limits.model_dump(mode="json") if legacy else None,
+        run_limits=manifest.run_limits.model_dump(mode="json") if legacy else None,
+        job_wall_time_us=manifest.job_wall_time_us if legacy else None,
+        comparison=manifest.comparison,
+        public_samples=[s.model_dump(mode="json") for s in preview.samples],
+    )
+    session.add(version)
+    await session.flush()
+    for position, case in enumerate(cases):
+        session.add(
+            ProblemCase(
+                id=case.case_id,
+                version_id=version_id,
+                position=position,
+                input_digest=case.input.digest,
+                expected_digest=case.expected.digest,
+            )
+        )
+    await session.flush()
+    version.published_at = await session.scalar(select(func.now()))
+    problem.active_version_id = version_id
+    await session.flush()
+    return version

backend/src/kf_oj/modules/problems/repository.py

@@ -24,7 +24,22 @@ async def next_revision(session: AsyncSession, problem_id: UUID) -> int:
     return (latest or 0) + 1
 
 
-async def public_version(session: AsyncSession, version_id: UUID):
+async def published_version(session: AsyncSession, version_id: UUID, *, admission=False):
+    query = (
+        select(ProblemVersion, Problem)
+        .join(Problem, Problem.id == ProblemVersion.problem_id)
+        .where(ProblemVersion.id == version_id, ProblemVersion.published_at.is_not(None))
+    )
+    if admission:
+        # A new submission commits while this shared problem lock is held. A
+        # concurrent disable either precedes admission or follows that commit.
+        query = query.where(Problem.enabled.is_(True)).with_for_update(read=True, of=Problem)
+    return (await session.execute(query)).one_or_none()
+
+
+async def public_version(session: AsyncSession, version_id: UUID, *, admission=False):
+    if admission:
+        return await published_version(session, version_id, admission=True)
     return (
         await session.execute(
             select(ProblemVersion, Problem)

backend/src/kf_oj/modules/problems/service.py

@@ -1,8 +1,9 @@
 import base64
 from pathlib import Path
+from types import SimpleNamespace
 from uuid import UUID, uuid4, uuid5
 
-from sqlalchemy import func, select
+from sqlalchemy import select
 from sqlalchemy.ext.asyncio import async_sessionmaker
 
 from kf_oj.contracts import judging_v2 as v2
@@ -28,8 +29,9 @@ from kf_oj.infra.artifacts.repository import ArtifactRepository
 from kf_oj.modules.problems import repository
 from kf_oj.modules.problems.import_format import ImportEnvelope, ProblemImport
 from kf_oj.modules.problems.local_files import LocalImportFiles
-from kf_oj.modules.problems.models import Problem, ProblemCase, ProblemVersion
+from kf_oj.modules.problems.models import Problem
 from kf_oj.modules.problems.public import JudgingVersion, ProblemUnavailable
+from kf_oj.modules.problems.publication import admit_version, publish_version
 
 
 class ProblemService:
@@ -83,27 +85,7 @@ class ProblemService:
             )
             for case, (data, answer) in zip(manifest.cases, payloads, strict=True)
         )
-        legacy = isinstance(manifest, ProblemImport)
-        projection = JudgingVersion(
-            version_id,
-            uuid4(),
-            manifest.languages,
-            manifest.toolchain if legacy else None,
-            manifest.compile_limits if legacy else None,
-            manifest.run_limits if legacy else None,
-            manifest.job_wall_time_us if legacy else None,
-            cases,
-            manifest.schema_version,
-            () if legacy else manifest.language_configurations,
-        )
-        for language in manifest.languages:
-            check = projection.manifest(
-                uuid4(),
-                uuid4(),
-                language,
-                ArtifactReference(digest="0" * 64, bytes=MAX_SOURCE_BYTES),
-            )
-            v2.admit_manifest(self.policy, check, 1)
+        admit_version(self.policy, manifest, version_id, uuid4(), cases)
         async with self.sessions.begin() as session:
             # Lock existing and not-yet-existing logical slugs before assigning revisions.
             await repository.lock_slug(session, manifest.slug)
@@ -114,32 +96,6 @@ class ProblemService:
                 await session.flush()
             if not problem.enabled:
                 raise ProblemUnavailable("problem disabled")
-            revision = await repository.next_revision(session, problem.id)
-            session.add(
-                ProblemVersion(
-                    id=version_id,
-                    problem_id=problem.id,
-                    revision=revision,
-                    title=manifest.title,
-                    statement=statement,
-                    languages=[lang.value for lang in manifest.languages],
-                    judging_schema_version=manifest.schema_version,
-                    language_configurations=(
-                        None
-                        if legacy
-                        else [c.model_dump(mode="json") for c in manifest.language_configurations]
-                    ),
-                    toolchain=manifest.toolchain.model_dump(mode="json") if legacy else None,
-                    compile_limits=manifest.compile_limits.model_dump(mode="json")
-                    if legacy
-                    else None,
-                    run_limits=manifest.run_limits.model_dump(mode="json") if legacy else None,
-                    job_wall_time_us=manifest.job_wall_time_us if legacy else None,
-                    comparison=manifest.comparison,
-                    public_samples=[s.model_dump() for s in samples],
-                )
-            )
-            await session.flush()
             # Consistent digest lock order avoids deadlocks between overlapping imports/jobs.
             unique = {
                 ref.digest: (data, ref)
@@ -149,20 +105,14 @@ class ProblemService:
             for digest in sorted(unique):
                 data, reference = unique[digest]
                 await self.artifacts.put(session, data, reference)
-            for position, case in enumerate(cases):
-                session.add(
-                    ProblemCase(
-                        id=case.case_id,
-                        version_id=version_id,
-                        position=position,
-                        input_digest=case.input.digest,
-                        expected_digest=case.expected.digest,
-                    )
-                )
-            await session.flush()
-            version = await session.get(ProblemVersion, version_id)
-            version.published_at = await session.scalar(select(func.now()))
-            problem.active_version_id = version_id
+            await publish_version(
+                session,
+                problem,
+                manifest,
+                SimpleNamespace(statement=statement, samples=samples),
+                version_id,
+                cases,
+            )
         return version_id
 
     @staticmethod
@@ -213,7 +163,16 @@ class ProblemService:
     async def for_submission(self, session, version_id: UUID) -> JudgingVersion:
         if self.artifacts is None:
             raise ProblemUnavailable("artifact service unavailable")
-        row = await repository.public_version(session, version_id)
+        row = await repository.public_version(session, version_id, admission=True)
+        return await self._judging_version(session, row)
+
+    async def for_accepted_execution(self, session, version_id: UUID) -> JudgingVersion:
+        # Only WorkerAccess calls this after validating the current lease and its
+        # immutable submission/attempt binding; this is never a public UUID lookup.
+        row = await repository.published_version(session, version_id)
+        return await self._judging_version(session, row)
+
+    async def _judging_version(self, session, row):
         if row is None:
             raise ProblemUnavailable("problem version unavailable")
         version, problem = row

backend/src/kf_oj/modules/problems/web_format.py

@@ -0,0 +1,31 @@
+"""Stricter Web package declarations; the accepted local CLI format remains unchanged."""
+
+from dataclasses import dataclass
+
+from kf_oj.contracts.judging import decode_wire
+from kf_oj.modules.problems.import_format import ImportEnvelope, ProblemImport, ProblemImportV2
+
+ARCHIVE_SUFFIXES = (".zip", ".jar", ".war", ".tar", ".tgz", ".gz", ".bz2", ".xz", ".7z", ".rar")
+
+
+@dataclass(frozen=True)
+class WebDeclaration:
+    manifest: ProblemImport | ProblemImportV2
+    members: frozenset[str]
+
+
+def decode_web_declaration(data: bytes) -> WebDeclaration:
+    # decode_wire rejects duplicate JSON keys, unknown fields and noncanonical
+    # protocol values before either local paths or node policy can be considered.
+    manifest = decode_wire(ImportEnvelope, data).root
+    hidden = {name for c in manifest.cases for name in (c.input_file, c.expected_file)}
+    samples = {name for s in manifest.samples for name in (s.input_file, s.output_file)}
+    metadata = {"problem.json", manifest.statement_file}
+    if len(metadata) != 2 or hidden & (samples | metadata) or samples & metadata:
+        raise ValueError("public and hidden package declarations must be separate")
+    members = frozenset(metadata | hidden | samples)
+    if len({name.lower() for name in members}) != len(members):
+        raise ValueError("package names must be case-insensitively unique")
+    if any(name.lower().endswith(ARCHIVE_SUFFIXES) for name in members):
+        raise ValueError("nested archive declarations are unsupported")
+    return WebDeclaration(manifest, members)

backend/src/kf_oj/modules/submissions/README.md

@@ -23,3 +23,28 @@ submission、queued evaluation 和 outbox；同键同内容复用既有提交，
 Coordinator 通过正式 claim 创建短期领取权，Worker 不写业务数据库。
 真实服务链与安全条件必须在独立 VM 验收；数据库 fixture 的租约或合成报告只能
 验证控制规则、授权和投影，不能作为真实程序执行/停止证明。
+
+`performance.py` 提供本人提交的只读匿名聚合。Coordinator 在受验证最终 AC 的同一事务
+写入不可变 `evaluation_performance`；平台只有 SELECT 权限。比较组绑定不可变版本、
+语言、精确镜像/工具链、编译与运行预算，以及运维核验后配置的测量环境纪元。
+没有原纪元的旧尝试不会通过当前配置被补造可信性，仍保留个人历史与正常成绩。
+单条受控回填与纪元变更规则见[协调器说明](../../../../../judge/crates/coordinator/README.md)。
+
+历史可按 `problem_version_id` 与可选 wire `language` 过滤，始终带当前账号条件。
+`GET /api/v1/submissions/{submission_id}/performance` 每次先检查会话和所有权；
+匿名拒绝、其他主体与不存在记录同为不可用，私有响应为 `no-store`。
+缓存命中仍查归属。每进程最多一个聚合查询，不排等待队列；SQL 期限两秒、请求总期限
+三秒、锁等待至多半秒。聚合 DTO 缓存三十秒且最多128项，新 AC 的索引水位改变即失效。
+缓存不保存逐条样本数组，不向浏览器发送其他账号的身份、源码或逐条用量。
+
+每指标在同一个只读可重复读快照内，排除当前提交，取最近最多10,000条非缺测的其他
+有效 AC，响应带快照、最早样本及截断标志。少于五条时仅显示本次真实用量。
+CPU 为测试点运行 CPU 微秒之和，内存为测试点运行峰值字节的最大值，不包括编译。
+用量与桶边界以十进制字符串传输；零合法、缺测不补零。严格优于数按原整数的 `>`
+计算，同值独立计数。响应至多24个连续桶，只有最后上界包含端点；浏览器仅格式化单位
+和绘制坐标，比例以服务端严格计数除以样本数，不按人数统计。
+
+下架只阻止新提交与公开题目读取。Worker 的版本读取通过 `ProblemPort.for_accepted_execution`，
+在本模块验证当前 Coordinator 租约/尝试/源码绑定之后才调用；生成并比较原 canonical
+快照，再次核对租约后才释放字节。无有效租约、外来工件、未发布版本和其他提交仍拒绝。
+本人历史和源码读取保留所有权检查，不依赖题目当前 enabled 状态。

backend/src/kf_oj/modules/submissions/models.py

@@ -15,6 +15,7 @@ from sqlalchemy import (
     String,
     UniqueConstraint,
     func,
+    text,
 )
 from sqlalchemy.dialects.postgresql import JSONB
 from sqlalchemy.orm import Mapped, mapped_column
@@ -38,6 +39,13 @@ class Submission(CreatedAt, Base):
             ["source_digest", "artifact_state"], ["artifacts.digest", "artifacts.state"]
         ),
         Index("ix_submissions_account_history", "account_id", "created_at", "id"),
+        Index(
+            "ix_submissions_owned_problem_history",
+            "account_id",
+            "problem_version_id",
+            text("created_at DESC"),
+            text("id DESC"),
+        ),
     )
 
     id: Mapped[UUID] = mapped_column(primary_key=True)
@@ -112,6 +120,10 @@ class JudgeAttempt(CreatedAt, Base):
         CheckConstraint("fencing_version > 0", name="fence"),
         CheckConstraint("lease_token_hash ~ '^[0-9a-f]{64}$'", name="token_digest"),
         CheckConstraint("manifest_digest ~ '^[0-9a-f]{64}$'", name="manifest_digest"),
+        CheckConstraint(
+            "measurement_epoch IS NULL OR measurement_epoch ~ '^[0-9a-f]{64}$'",
+            name="measurement_epoch",
+        ),
         CheckConstraint("sequence >= 0", name="sequence"),
         Index("ix_judge_attempts_expiry", "expires_at", "evaluation_id"),
     )
@@ -132,6 +144,64 @@ class JudgeAttempt(CreatedAt, Base):
     report: Mapped[dict | None] = mapped_column(JSONB)
     report_digest: Mapped[str | None] = mapped_column(String(64))
     cleanup_complete: Mapped[bool | None] = mapped_column(Boolean)
+    measurement_epoch: Mapped[str | None] = mapped_column(String(64))
+
+
+class EvaluationPerformance(Base):
+    """Coordinator-only immutable final projection; the platform only reads it."""
+
+    __tablename__ = "evaluation_performance"
+    __table_args__ = (
+        ForeignKeyConstraint(
+            ["evaluation_id", "problem_version_id"],
+            ["evaluations.id", "evaluations.problem_version_id"],
+        ),
+        ForeignKeyConstraint(
+            ["submission_id", "problem_version_id"],
+            ["submissions.id", "submissions.problem_version_id"],
+        ),
+        ForeignKeyConstraint(
+            ["attempt_id", "evaluation_id"], ["judge_attempts.id", "judge_attempts.evaluation_id"]
+        ),
+        CheckConstraint("language IN ('c17','cpp20','python313','java21')", name="language"),
+        CheckConstraint("comparison_group ~ '^[0-9a-f]{64}$'", name="comparison_group"),
+        CheckConstraint("measurement_epoch ~ '^[0-9a-f]{64}$'", name="measurement_epoch"),
+        CheckConstraint("report_digest ~ '^[0-9a-f]{64}$'", name="report_digest"),
+        CheckConstraint("cpu_time_us IS NULL OR cpu_time_us >= 0", name="cpu"),
+        CheckConstraint("memory_peak_bytes IS NULL OR memory_peak_bytes >= 0", name="memory"),
+        Index(
+            "ix_performance_group_watermark",
+            "comparison_group",
+            text("finished_at DESC"),
+            text("evaluation_id DESC"),
+        ),
+        Index(
+            "ix_performance_cpu_time_us_cohort",
+            "comparison_group",
+            text("finished_at DESC"),
+            text("evaluation_id DESC"),
+            postgresql_where=text("cpu_time_us IS NOT NULL"),
+        ),
+        Index(
+            "ix_performance_memory_peak_bytes_cohort",
+            "comparison_group",
+            text("finished_at DESC"),
+            text("evaluation_id DESC"),
+            postgresql_where=text("memory_peak_bytes IS NOT NULL"),
+        ),
+    )
+
+    evaluation_id: Mapped[UUID] = mapped_column(primary_key=True)
+    submission_id: Mapped[UUID] = mapped_column(unique=True)
+    attempt_id: Mapped[UUID] = mapped_column(unique=True)
+    problem_version_id: Mapped[UUID]
+    language: Mapped[str] = mapped_column(String(16))
+    comparison_group: Mapped[str] = mapped_column(String(64))
+    measurement_epoch: Mapped[str] = mapped_column(String(64))
+    report_digest: Mapped[str] = mapped_column(String(64))
+    finished_at: Mapped[datetime] = mapped_column(DateTime(timezone=True))
+    cpu_time_us: Mapped[int | None] = mapped_column(BigInteger)
+    memory_peak_bytes: Mapped[int | None] = mapped_column(BigInteger)
 
 
 class CaseResult(Base):

backend/src/kf_oj/modules/submissions/performance.py

@@ -0,0 +1,217 @@
+"""Read-only, bounded anonymous cohorts from Coordinator's immutable projection."""
+
+import asyncio
+import json
+import time
+from collections import OrderedDict
+from uuid import UUID
+
+from sqlalchemy import select, text
+from sqlalchemy.exc import SQLAlchemyError
+from sqlalchemy.ext.asyncio import async_sessionmaker
+
+from kf_oj.contracts.judging import I64_MAX
+from kf_oj.contracts.judging_versions import decode_report
+from kf_oj.contracts.submission_performance import (
+    MAX_PERFORMANCE_SAMPLES,
+    MIN_PERFORMANCE_SAMPLES,
+    PerformanceBucket,
+    PerformanceMetric,
+    SubmissionPerformance,
+)
+from kf_oj.modules.identity.public import Principal
+from kf_oj.modules.submissions.models import Evaluation, EvaluationPerformance, Submission
+from kf_oj.modules.submissions.public import SubmissionUnavailable
+
+CACHE_TTL_SECONDS = 30
+CACHE_CAPACITY = 128
+HISTOGRAM_BUCKETS = 24
+
+
+def metric(unit, current, rows=(), *, reason=None) -> PerformanceMetric:
+    """Integer arithmetic throughout; conversion for display belongs to the client."""
+    truncated = len(rows) > MAX_PERFORMANCE_SAMPLES
+    rows = rows[:MAX_PERFORMANCE_SAMPLES]
+    count = len(rows)
+    base = dict(
+        unit=unit,
+        current=None if current is None else str(current),
+        sample_count=count,
+        window_truncated=truncated,
+        oldest_sample_at=rows[-1][1] if rows else None,
+    )
+    if reason is None:
+        reason = (
+            "measurement_missing"
+            if current is None
+            else ("insufficient_samples" if count < MIN_PERFORMANCE_SAMPLES else None)
+        )
+    if reason is not None:
+        return PerformanceMetric(
+            **base,
+            available=False,
+            reason=reason,
+            strictly_slower_count=None,
+            tied_count=None,
+            buckets=(),
+        )
+    values = [row[0] for row in rows]
+    end = max(1, current, max(values))
+    step = (end + HISTOGRAM_BUCKETS - 1) // HISTOGRAM_BUCKETS
+    # Last upper bound includes the maximum, including I64_MAX. No overflow/padding.
+    boundaries = list(range(0, end, step)) + [end]
+    counts = [0] * (len(boundaries) - 1)
+    for value in values:
+        counts[min(value // step, len(counts) - 1)] += 1
+    return PerformanceMetric(
+        **base,
+        available=True,
+        reason=None,
+        strictly_slower_count=sum(value > current for value in values),
+        tied_count=sum(value == current for value in values),
+        buckets=tuple(
+            PerformanceBucket(
+                start=str(start),
+                end=str(stop),
+                upper_inclusive=index == len(counts) - 1,
+                count=counts[index],
+            )
+            for index, (start, stop) in enumerate(zip(boundaries, boundaries[1:], strict=False))
+        ),
+    )
+
+
+class SubmissionPerformanceQueries:
+    def __init__(self, sessions: async_sessionmaker):
+        self.sessions = sessions
+        # No queued aggregate workload. At most one bounded in-memory row cohort per process.
+        self._slot = asyncio.Lock()
+        # Cache contains small immutable aggregate DTOs, never 10,000-row arrays.
+        self._cache: OrderedDict[tuple, tuple[float, SubmissionPerformance]] = OrderedDict()
+
+    async def detail(self, principal: Principal, submission_id: UUID) -> SubmissionPerformance:
+        if self._slot.locked():
+            raise ValueError("performance query capacity unavailable")
+        async with self._slot:
+            try:
+                async with asyncio.timeout(3), self.sessions() as session, session.begin():
+                    await session.execute(
+                        text("SET TRANSACTION ISOLATION LEVEL REPEATABLE READ READ ONLY")
+                    )
+                    await session.execute(text("SET LOCAL statement_timeout='2s'"))
+                    await session.execute(text("SET LOCAL lock_timeout='500ms'"))
+                    # Ownership checked even on a cache hit. Session authentication is upstream.
+                    row = (
+                        await session.execute(
+                            select(Submission, Evaluation, EvaluationPerformance)
+                            .join(Evaluation, Evaluation.submission_id == Submission.id)
+                            .outerjoin(
+                                EvaluationPerformance,
+                                EvaluationPerformance.evaluation_id == Evaluation.id,
+                            )
+                            .where(
+                                Submission.id == submission_id,
+                                Submission.account_id == principal.account_id,
+                            )
+                        )
+                    ).one_or_none()
+                    if row is None:
+                        raise SubmissionUnavailable("submission unavailable")
+                    submission, evaluation, projection = row
+                    as_of = await session.scalar(text("SELECT clock_timestamp()"))
+                    accepted = (
+                        evaluation.state == "finished"
+                        and evaluation.verdict == "accepted"
+                        and evaluation.failure_code is None
+                    )
+                    if projection is not None and (
+                        not accepted
+                        or projection.attempt_id != evaluation.current_attempt_id
+                        or projection.report_digest != evaluation.final_report_digest
+                    ):
+                        raise ValueError("stored performance binding invalid")
+                    cpu = memory = None
+                    reason = None if accepted else "not_accepted"
+                    if projection is not None:
+                        cpu, memory = projection.cpu_time_us, projection.memory_peak_bytes
+                    elif accepted:
+                        # A single owned legacy report, never a full-table JSON scan or promotion.
+                        report = decode_report(
+                            json.dumps(evaluation.final_report, ensure_ascii=False).encode()
+                        )
+                        if (
+                            report.binding.evaluation_id != evaluation.id
+                            or report.binding.attempt_id != evaluation.current_attempt_id
+                            or report.verdict.value != "accepted"
+                            or not report.cleanup_complete
+                        ):
+                            raise ValueError("stored result binding invalid")
+                        cpu, memory = report.run_cpu_time_us, report.run_memory_peak_bytes
+                        reason = "environment_unverified"
+                    if any(v is not None and not 0 <= v <= I64_MAX for v in (cpu, memory)):
+                        raise ValueError("stored measurement out of range")
+                    base = dict(
+                        submission_id=submission.id,
+                        problem_version_id=submission.problem_version_id,
+                        language=submission.language,
+                        as_of=as_of,
+                        comparison_group=None
+                        if projection is None
+                        else projection.comparison_group,
+                    )
+                    if projection is None:
+                        return SubmissionPerformance(
+                            **base,
+                            cpu=metric("cpu_microseconds", cpu, reason=reason),
+                            memory=metric("bytes", memory, reason=reason),
+                        )
+                    group = projection.comparison_group
+                    watermark = (
+                        await session.execute(
+                            select(
+                                EvaluationPerformance.finished_at,
+                                EvaluationPerformance.evaluation_id,
+                            )
+                            .where(EvaluationPerformance.comparison_group == group)
+                            .order_by(
+                                EvaluationPerformance.finished_at.desc(),
+                                EvaluationPerformance.evaluation_id.desc(),
+                            )
+                            .limit(1)
+                        )
+                    ).one()
+                    key = (submission.id, projection.report_digest, group, tuple(watermark))
+                    cached = self._cache.get(key)
+                    now = time.monotonic()
+                    if cached is not None and now - cached[0] < CACHE_TTL_SECONDS:
+                        self._cache.move_to_end(key)
+                        return cached[1]
+                    metrics = []
+                    for column, unit, current in [
+                        (EvaluationPerformance.cpu_time_us, "cpu_microseconds", cpu),
+                        (EvaluationPerformance.memory_peak_bytes, "bytes", memory),
+                    ]:
+                        rows = (
+                            await session.execute(
+                                select(column, EvaluationPerformance.finished_at)
+                                .where(
+                                    EvaluationPerformance.comparison_group == group,
+                                    EvaluationPerformance.evaluation_id != evaluation.id,
+                                    column.is_not(None),
+                                )
+                                .order_by(
+                                    EvaluationPerformance.finished_at.desc(),
+                                    EvaluationPerformance.evaluation_id.desc(),
+                                )
+                                .limit(MAX_PERFORMANCE_SAMPLES + 1)
+                            )
+                        ).all()
+                        metrics.append(metric(unit, current, rows))
+                    result = SubmissionPerformance(**base, cpu=metrics[0], memory=metrics[1])
+                    self._cache[key] = (now, result)
+                    self._cache.move_to_end(key)
+                    while len(self._cache) > CACHE_CAPACITY:
+                        self._cache.popitem(last=False)
+                    return result
+            except (SQLAlchemyError, TimeoutError) as error:
+                raise ValueError("performance database unavailable") from error

backend/src/kf_oj/modules/submissions/queries.py

@@ -88,7 +88,14 @@ class SubmissionQueries:
             .where(Submission.id == submission_id, Submission.account_id == principal.account_id)
         )
 
-    async def page(self, principal: Principal, after: str | None, limit: int) -> SubmissionPage:
+    async def page(
+        self,
+        principal: Principal,
+        after: str | None,
+        limit: int,
+        problem_version_id: UUID | None = None,
+        language: str | None = None,
+    ) -> SubmissionPage:
         if not 1 <= limit <= 100:
             raise ValueError("invalid history limit")
         query = (
@@ -98,6 +105,10 @@ class SubmissionQueries:
             .order_by(Submission.created_at.desc(), Submission.id.desc())
             .limit(limit + 1)
         )
+        if problem_version_id is not None:
+            query = query.where(Submission.problem_version_id == problem_version_id)
+        if language is not None:
+            query = query.where(Submission.language == language)
         if after is not None:
             query = query.where(tuple_(Submission.created_at, Submission.id) < cursor_decode(after))
         async with self.sessions() as session:

backend/src/kf_oj/modules/submissions/worker_access.py

@@ -62,7 +62,9 @@ class WorkerAccess:
                 )
             ):
                 raise WorkerAccessDenied("worker snapshot rejected")
-            version = await self.problems.for_submission(session, manifest.problem_version_id)
+            version = await self.problems.for_accepted_execution(
+                session, manifest.problem_version_id
+            )
             await self.artifacts.check_metadata(session, manifest.source)
             expected = version.manifest(
                 manifest.evaluation_id, manifest.submission_id, manifest.language, manifest.source

backend/src/kf_oj/workers/_archive_child.py

@@ -0,0 +1,116 @@
+"""Fixed data-only child. It inherits no DB credentials and executes no uploaded contents."""
+
+import base64
+import json
+import os
+import resource
+import signal
+import sys
+import time
+from uuid import UUID
+
+from pydantic import TypeAdapter
+
+from kf_oj.contracts.admin_problems import (
+    VALIDATION_DEADLINE_SECONDS,
+    CandidatePreview,
+    LegacyImportBudget,
+)
+from kf_oj.contracts.judging_v2 import NodeAdmission
+from kf_oj.contracts.problems import PublicLanguageConfiguration, PublicSample
+from kf_oj.infra.artifacts.archive_reader import ArchiveError, ArchiveReader
+from kf_oj.modules.problems.candidate_validation import validate_candidate
+from kf_oj.modules.problems.import_format import ProblemImport
+from kf_oj.modules.problems.web_format import decode_web_declaration
+
+
+def main():
+    # These are ordinary downward-only process limits, independent of the parent's life.
+    resource.setrlimit(resource.RLIMIT_AS, (128 * 1024**2, 128 * 1024**2))
+    resource.setrlimit(resource.RLIMIT_CPU, (60, 60))
+    resource.setrlimit(resource.RLIMIT_FSIZE, (64 * 1024**2, 64 * 1024**2))
+    resource.setrlimit(resource.RLIMIT_NOFILE, (64, 64))
+    resource.setrlimit(resource.RLIMIT_CORE, (0, 0))
+    signal.alarm(VALIDATION_DEADLINE_SECONDS)
+    archive, directory, lock, size, digest, candidate, policy_json = sys.argv[1:]
+    archive, directory, lock = int(archive), int(directory), int(lock)
+    os.fstat(lock)  # Held inherited flock prevents GC releasing capacity while any child lives.
+    deadline = time.monotonic() + VALIDATION_DEADLINE_SECONDS
+    result = {"failure_code": "invalid_archive"}
+    try:
+        reader = ArchiveReader(archive, int(size), deadline=deadline)
+        reader.verify_digest(digest)
+        result["failure_code"] = "invalid_manifest"
+        declared = decode_web_declaration(reader.read("problem.json", 256 * 1024))
+        if {m.name for m in reader.members} != set(declared.members):
+            raise ValueError("unexpected package members")
+        manifest = declared.manifest
+        result["failure_code"] = "invalid_data"
+        statement = reader.read(manifest.statement_file, 256 * 1024).decode("utf-8")
+        sample_data = {
+            name: reader.read(name, 65536)
+            for name in sorted({n for s in manifest.samples for n in (s.input_file, s.output_file)})
+        }
+        samples = tuple(
+            PublicSample(
+                input=base64.b64encode(sample_data[s.input_file]).decode("ascii"),
+                output=base64.b64encode(sample_data[s.output_file]).decode("ascii"),
+            )
+            for s in manifest.samples
+        )
+        references = reader.extract_remaining(directory)
+        reader.verify_unchanged()
+        legacy = isinstance(manifest, ProblemImport)
+        preview = CandidatePreview(
+            candidate_id=UUID(candidate),
+            slug=manifest.slug,
+            title=manifest.title,
+            statement=statement,
+            samples=samples,
+            judging_schema_version=manifest.schema_version,
+            languages=manifest.languages,
+            legacy_budget=LegacyImportBudget(
+                compile_limits=manifest.compile_limits,
+                run_limits=manifest.run_limits,
+                job_wall_time_us=manifest.job_wall_time_us,
+            )
+            if legacy
+            else None,
+            language_configurations=()
+            if legacy
+            else tuple(
+                PublicLanguageConfiguration.from_configuration(c)
+                for c in manifest.language_configurations
+            ),
+            case_count=len(manifest.cases),
+        )
+        result["failure_code"] = "policy_rejected"
+        validated = validate_candidate(
+            manifest.model_dump(mode="json"),
+            preview.model_dump(mode="json"),
+            {k: {"digest": v[0], "bytes": v[1]} for k, v in references.items()},
+            TypeAdapter(NodeAdmission).validate_json(policy_json),
+        )
+        result = {
+            "manifest": validated.manifest,
+            "preview": validated.preview.model_dump(mode="json"),
+            "references": {k: v.model_dump(mode="json") for k, v in validated.references.items()},
+            "manifest_digest": validated.digest,
+        }
+    except ArchiveError as error:
+        result = {
+            "failure_code": "digest_mismatch"
+            if str(error) == "archive_digest_mismatch"
+            else "invalid_archive"
+        }
+    except (ValueError, OSError, MemoryError):
+        result = {"failure_code": result["failure_code"]}
+    payload = json.dumps(result, separators=(",", ":"), ensure_ascii=True).encode()
+    if len(payload) > 4 * 1024**2:
+        payload = b'{"failure_code":"invalid_data"}'
+    sys.stdout.buffer.write(payload)
+    sys.stdout.buffer.flush()
+
+
+if __name__ == "__main__":
+    main()

backend/src/kf_oj/workers/outbox_status.py

@@ -0,0 +1,27 @@
+"""Read only publisher-owned counts; never claim, publish or acknowledge a task."""
+
+import asyncio
+import json
+
+from kf_oj.core.settings import Settings
+from kf_oj.infra.db.session import build_engine, build_session_factory
+from kf_oj.infra.messaging.outbox_queries import OutboxQueries
+
+
+async def run() -> dict:
+    engine = build_engine(Settings())
+    try:
+        return await OutboxQueries(build_session_factory(engine)).status()
+    finally:
+        await engine.dispose()
+
+
+def main() -> None:
+    try:
+        print(json.dumps(asyncio.run(asyncio.wait_for(run(), timeout=6)), sort_keys=True))
+    except Exception:
+        raise SystemExit("outbox status unavailable") from None
+
+
+if __name__ == "__main__":
+    main()

backend/src/kf_oj/workers/problem_import.py

@@ -0,0 +1,74 @@
+"""Ordinary import service composition. Provision its dedicated DB role and cgroup separately."""
+
+import asyncio
+import signal
+import sys
+
+from sqlalchemy.exc import DBAPIError
+
+from kf_oj.core.settings import Settings
+from kf_oj.infra.artifacts.repository import ArtifactRepository
+from kf_oj.infra.artifacts.staging import ImportStaging
+from kf_oj.infra.artifacts.store import ArtifactStore
+from kf_oj.infra.db.session import build_engine, build_session_factory
+from kf_oj.modules.identity.service import ReservedMaintenance
+from kf_oj.modules.operations.service import MaintenanceAudit
+from kf_oj.modules.problems.import_worker import ImportWorker, verify_worker_limits
+
+
+async def run():
+    stop = asyncio.Event()
+    loop = asyncio.get_running_loop()
+    for event in (signal.SIGTERM, signal.SIGINT):
+        loop.add_signal_handler(event, stop.set)
+    settings = Settings()
+    if (
+        settings.import_staging_root is None
+        or settings.artifact_root is None
+        or settings.judge_admission is None
+        or settings.import_worker_cgroup is None
+    ):
+        raise ValueError("import service configuration required")
+    verify_worker_limits(settings.import_worker_cgroup)
+    engine = build_engine(settings)
+    store = ArtifactStore(
+        settings.artifact_root,
+        max_bytes=settings.artifact_max_bytes,
+        max_files=settings.artifact_max_files,
+    )
+    staging = ImportStaging(settings.import_staging_root)
+    try:
+        worker = ImportWorker(
+            build_session_factory(engine),
+            staging,
+            ArtifactRepository(store),
+            ReservedMaintenance(),
+            MaintenanceAudit(),
+            settings.judge_admission,
+            settings.import_worker_cgroup,
+        )
+        while not stop.is_set():
+            if not await worker.once():
+                try:
+                    await asyncio.wait_for(stop.wait(), timeout=1)
+                except TimeoutError:
+                    pass
+    finally:
+        staging.close()
+        store.close()
+        await engine.dispose()
+
+
+def main():
+    try:
+        asyncio.run(run())
+    except (ValueError, OSError, DBAPIError):
+        print(
+            "import service unavailable; check trusted configuration and resource limits",
+            file=sys.stderr,
+        )
+        raise SystemExit(1) from None
+
+
+if __name__ == "__main__":
+    main()

backend/src/kf_oj/workers/problem_status.py

@@ -0,0 +1,33 @@
+"""Ordinary import-only read status; no parser, staging mutation or judging writes."""
+
+import asyncio
+import json
+
+from kf_oj.core.settings import Settings
+from kf_oj.infra.db.session import build_engine, build_session_factory
+from kf_oj.modules.problems.operations import ImportOperationQueries
+
+
+async def run() -> dict:
+    settings = Settings()
+    if settings.judge_admission is None:
+        raise ValueError("import admission required")
+    engine = build_engine(settings)
+    try:
+        return await ImportOperationQueries(
+            build_session_factory(engine), settings.judge_admission
+        ).status()
+    finally:
+        await engine.dispose()
+
+
+def main() -> None:
+    try:
+        result = asyncio.run(asyncio.wait_for(run(), timeout=6))
+        print(json.dumps(result, sort_keys=True))
+    except Exception:
+        raise SystemExit("import status unavailable") from None
+
+
+if __name__ == "__main__":
+    main()

backend/tests/conftest.py

@@ -2,7 +2,9 @@
 
 import asyncio
 import os
+import re
 import subprocess
+import sys
 from pathlib import Path
 from uuid import uuid4
 
@@ -39,14 +41,20 @@ def postgres_url():
 
 
 def migrate(url: str, command: str, target: str | None = None) -> None:
-    subprocess.run(
-        [str(Path(__file__).resolve().parents[1] / ".venv/bin/alembic"), command]
-        + ([target] if target else []),
-        cwd=Path(__file__).resolve().parents[1],
-        env=os.environ | {"KF_OJ_DATABASE_URL": url},
-        check=True,
-        capture_output=True,
-    )
+    try:
+        subprocess.run(
+            [sys.executable, "-m", "alembic", command] + ([target] if target else []),
+            cwd=Path(__file__).resolve().parents[1],
+            env=os.environ | {"KF_OJ_DATABASE_URL": url},
+            check=True,
+            capture_output=True,
+        )
+    except subprocess.CalledProcessError as error:
+        diagnostic = ((error.stdout or b"") + (error.stderr or b"")).decode(errors="replace")[
+            -8192:
+        ]
+        diagnostic = re.sub(r"postgresql(?:\+asyncpg)?://[^\s]+", "[test database URL]", diagnostic)
+        raise AssertionError(f"test migration {command} failed: " + diagnostic) from None
 
 
 async def connect(url: str):

backend/tests/test_admin_archive_vm.py

@@ -0,0 +1,180 @@
+"""Finite adverse archive/private-storage acceptance: independent capped VM only."""
+
+import hashlib
+import io
+import json
+import os
+import stat
+import struct
+import time
+import zipfile
+from pathlib import Path
+from uuid import uuid4
+
+import pytest
+from test_admin_import_vm import independent_import_vm as independent_import_vm
+from test_admin_import_vm import package
+
+from kf_oj.contracts.judging_v2 import AdmissionRegistry
+from kf_oj.infra.artifacts.archive_reader import ArchiveError, ArchiveReader
+from kf_oj.infra.artifacts.staging import ImportStaging
+from kf_oj.infra.artifacts.store import ArtifactError, ArtifactStore
+
+ROOT = Path(__file__).resolve().parents[2]
+
+
+def policy():
+    return AdmissionRegistry.model_validate_json(
+        (ROOT / "tests/fixtures/contracts-v2/judge-registry.valid.json").read_bytes()
+    )
+
+
+def proof(name, value):
+    print(
+        "KF_FINAL_ACCEPTANCE " + json.dumps({"name": name, "result": value}, default=str),
+        flush=True,
+    )
+
+
+def test_adverse_zip_and_private_storage_boundaries(independent_import_vm, tmp_path):
+    outside = tmp_path / "outside-sentinel"
+    outside.write_bytes(b"unchanged synthetic sentinel")
+    original = hashlib.sha256(outside.read_bytes()).hexdigest()
+    good, _ = package(policy())
+    cases = {}
+    for name in ("../outside-sentinel", "/outside-sentinel", "a/b", r"a\b", "a:b"):
+        cases["path-" + repr(name)] = package(
+            policy(), payload_mutation=lambda p, n=name: p.update({n: b"bad"})
+        )[0]
+    for kind in (
+        stat.S_IFLNK,
+        stat.S_IFCHR,
+        stat.S_IFBLK,
+        stat.S_IFIFO,
+        stat.S_IFSOCK,
+        stat.S_IFDIR,
+    ):
+        out = io.BytesIO()
+        with zipfile.ZipFile(out, "w") as archive:
+            entry = zipfile.ZipInfo("unsafe")
+            entry.create_system = 3
+            entry.external_attr = (kind | 0o600) << 16
+            archive.writestr(entry, b"synthetic")
+        cases[f"type-{kind}"] = out.getvalue()
+    for duplicate in ("statement.md", "STATEMENT.MD"):
+        out = io.BytesIO(good)
+        with zipfile.ZipFile(out, "a") as archive:
+            archive.writestr(duplicate, b"different")
+        cases["duplicate-" + duplicate] = out.getvalue()
+    for signature in (
+        b"PK\x03\x04",
+        b"\x1f\x8b",
+        b"BZh",
+        b"\xfd7zXZ\x00",
+        b"Rar!\x1a\x07",
+        b"7z\xbc\xaf\x27\x1c",
+        b"X" * 257 + b"ustar",
+    ):
+        cases["nested-" + signature[:6].hex()] = package(
+            policy(),
+            payload_mutation=lambda p, s=signature: p.update({"hidden.in": s + b"synthetic"}),
+        )[0]
+    central = good.index(b"PK\x01\x02")
+    for label, local_offset, central_offset, value, fmt in (
+        ("encrypted", 6, 8, 1, "<H"),
+        ("unsupported", 8, 10, 99, "<H"),
+        ("declared-size", 22, 24, 67108865, "<I"),
+        ("crc", 14, 16, 1, "<I"),
+    ):
+        blob = bytearray(good)
+        struct.pack_into(fmt, blob, local_offset, value)
+        struct.pack_into(fmt, blob, central + central_offset, value)
+        cases[label] = bytes(blob)
+    for label, extra in (("zip64", b"\x01\x00\x00\x00"), ("unknown-extra", b"\x99\x99\x00\x00")):
+        out = io.BytesIO()
+        with zipfile.ZipFile(out, "w") as archive:
+            entry = zipfile.ZipInfo("data")
+            entry.extra = extra
+            archive.writestr(entry, b"synthetic")
+        cases[label] = out.getvalue()
+    out = io.BytesIO()
+    with zipfile.ZipFile(out, "w") as archive:
+        for i in range(535):
+            archive.writestr(f"f{i}", b"")
+    cases["file-count"] = out.getvalue()
+    # Actual bounded inflation exceeds the forged declared size. The 65 MiB stream
+    # is produced in chunks under the VM cap; no 65 MiB object is allocated.
+    out = io.BytesIO()
+    with zipfile.ZipFile(out, "w", compression=zipfile.ZIP_DEFLATED) as archive:
+        with archive.open("inflate", "w") as member:
+            for _ in range(1040):
+                member.write(b"A" * 65536)
+    blob = bytearray(out.getvalue())
+    center = blob.index(b"PK\x01\x02")
+    struct.pack_into("<I", blob, 22, 67108864)
+    struct.pack_into("<I", blob, center + 24, 67108864)
+    cases["actual-inflate-over-64MiB"] = bytes(blob)
+    refused = []
+    for index, (label, blob) in enumerate(cases.items()):
+        file = tmp_path / f"archive-{index}"
+        file.write_bytes(blob)
+        file.chmod(0o600)
+        fd = os.open(file, os.O_RDONLY)
+        try:
+            with pytest.raises(ArchiveError) as error:
+                reader = ArchiveReader(fd, len(blob), deadline=time.monotonic() + 60)
+                for member in reader.members:
+                    for _ in reader.chunks(member.name, 67108864):
+                        pass
+            assert str(error.value) in ("invalid_archive", "archive_deadline")
+            refused.append(label)
+        finally:
+            os.close(fd)
+            file.unlink()
+    file = tmp_path / "mutable"
+    file.write_bytes(good)
+    file.chmod(0o600)
+    fd = os.open(file, os.O_RDONLY)
+    try:
+        reader = ArchiveReader(fd, len(good), deadline=time.monotonic() + 60)
+        with file.open("r+b") as writer:
+            writer.write(b"X")
+        with pytest.raises(ArchiveError, match="archive_changed"):
+            reader.verify_unchanged()
+    finally:
+        os.close(fd)
+    store = ArtifactStore(tmp_path / "objects", max_bytes=4, max_files=2)
+    try:
+        ref = store.put(b"1234")
+        with pytest.raises(ArtifactError, match="capacity"):
+            store.put(b"5")
+        assert store.read(ref) == b"1234"
+        store.remove(ref.digest)
+        recovered = store.put(b"5")
+        assert store.read(recovered) == b"5"
+    finally:
+        store.close()
+    link_root = tmp_path / "linked-store"
+    link_root.symlink_to(tmp_path / "objects", target_is_directory=True)
+    with pytest.raises((ArtifactError, OSError)):
+        ArtifactStore(link_root)
+    staging = ImportStaging(tmp_path / "staging")
+    operation_id = uuid4()
+    (tmp_path / "staging" / str(operation_id)).symlink_to(tmp_path, target_is_directory=True)
+    try:
+        with pytest.raises((ArtifactError, OSError)):
+            staging.operation(operation_id)
+    finally:
+        staging.close()
+    assert hashlib.sha256(outside.read_bytes()).hexdigest() == original
+    proof(
+        "archive_and_storage",
+        {
+            "refused": refused,
+            "outside_unchanged": True,
+            "content_never_executed": True,
+            "changed_descriptor_rejected": True,
+            "quota_recovered": True,
+            "symlink_roots_rejected": True,
+        },
+    )

backend/tests/test_admin_capacity_vm.py

@@ -0,0 +1,319 @@
+"""Upgrade, adverse storage and cross-process admission: capped independent VM only."""
+
+import asyncio
+import json
+import os
+import resource
+import subprocess
+import sys
+import time
+from pathlib import Path
+from uuid import uuid4
+
+import httpx
+from conftest import connect
+from sqlalchemy.engine import make_url
+from test_admin_import_vm import independent_import_vm as independent_import_vm
+
+from kf_oj.contracts.judging_v2 import AdmissionRegistry
+from kf_oj.modules.identity.passwords import hash_password
+
+ROOT = Path(__file__).resolve().parents[2]
+
+
+def policy():
+    return AdmissionRegistry.model_validate_json(
+        (ROOT / "tests/fixtures/contracts-v2/judge-registry.valid.json").read_bytes()
+    )
+
+
+def proof(name, value):
+    print(
+        "KF_FINAL_ACCEPTANCE " + json.dumps({"name": name, "result": value}, default=str),
+        flush=True,
+    )
+
+
+def test_cross_process_admission_and_worker_identity(independent_import_vm, postgres_url, tmp_path):
+    groups = independent_import_vm
+    roles = {name: "final_" + name + "_" + uuid4().hex for name in ("api", "worker")}
+    users = {f"capacity_admin_{i}": uuid4() for i in range(5)}
+    password = "Synthetic capacity acceptance only 2026!"
+    artifact, staging = tmp_path / "artifacts", tmp_path / "staging"
+    artifact.mkdir(mode=0o700)
+    staging.mkdir(mode=0o700)
+    processes, logs = {}, {}
+    base = {
+        k: v
+        for k, v in os.environ.items()
+        if k
+        in (
+            "PATH",
+            "PYTHONPATH",
+            "LD_LIBRARY_PATH",
+            "LC_ALL",
+            "PYTHONUNBUFFERED",
+            "PYTHONDONTWRITEBYTECODE",
+        )
+    }
+
+    def enter(group):
+        def apply():
+            (group / "cgroup.procs").write_text(str(os.getpid()))
+            resource.setrlimit(resource.RLIMIT_FSIZE, (67108864, 67108864))
+            resource.setrlimit(resource.RLIMIT_NOFILE, (64, 64))
+            resource.setrlimit(resource.RLIMIT_CORE, (0, 0))
+
+        return apply
+
+    def start(name, *, bad_identity=False, bad_group=False):
+        worker = name == "worker"
+        group = groups["import-worker" if worker else "api"]
+        env = base | {
+            "KF_OJ_DATABASE_URL": make_url(postgres_url)
+            .set(username=roles["api" if bad_identity or not worker else "worker"])
+            .render_as_string(hide_password=False),
+            "KF_OJ_ENVIRONMENT": "test",
+            "KF_OJ_ARTIFACT_ROOT": str(artifact),
+            "KF_OJ_IMPORT_STAGING_ROOT": str(staging),
+            "KF_OJ_JUDGE_ADMISSION": policy().model_dump_json(),
+            "KF_OJ_BROWSER_ORIGINS": '["http://127.0.0.1:58000"]',
+        }
+        if worker:
+            env["KF_OJ_IMPORT_WORKER_CGROUP"] = str(groups["api"] if bad_group else group)
+            command = [sys.executable, "-m", "kf_oj.workers.problem_import"]
+        else:
+            command = [
+                sys.executable,
+                "-m",
+                "uvicorn",
+                "kf_oj.api.app:create_app",
+                "--factory",
+                "--host",
+                "127.0.0.1",
+                "--port",
+                "58000" if name == "api0" else "58001",
+                "--no-proxy-headers",
+                "--limit-concurrency",
+                "4",
+                "--backlog",
+                "16",
+            ]
+        log = (tmp_path / (name + ".log")).open("a")
+        logs[name] = log
+        processes[name] = subprocess.Popen(
+            command, env=env, stdout=log, stderr=log, preexec_fn=enter(group)
+        )
+
+    def stop(name):
+        process = processes.pop(name, None)
+        if process and process.poll() is None:
+            process.terminate()
+            try:
+                process.wait(timeout=20)
+            except subprocess.TimeoutExpired:
+                process.kill()
+                process.wait(timeout=10)
+        if name in logs:
+            logs.pop(name).close()
+
+    async def run():
+        connection = await connect(postgres_url)
+        try:
+            for name, membership in (("api", "kf_oj_platform"), ("worker", "kf_oj_problem_import")):
+                await connection.execute(
+                    f"CREATE ROLE {roles[name]} LOGIN NOSUPERUSER "
+                    "NOCREATEDB NOCREATEROLE NOREPLICATION NOBYPASSRLS"
+                )
+                await connection.execute(f"GRANT {membership} TO {roles[name]}")
+            for name, identifier in users.items():
+                await connection.execute(
+                    "INSERT INTO accounts(id,username,password_hash) VALUES($1,$2,$3)",
+                    identifier,
+                    name,
+                    hash_password(name, password),
+                )
+                await connection.execute(
+                    "SELECT * FROM kf_manage_account_authority($1,$2)",
+                    name,
+                    "bootstrap" if name.endswith("_0") else "grant",
+                )
+            for wrong in ("identity", "cgroup"):
+                start("worker", bad_identity=wrong == "identity", bad_group=wrong == "cgroup")
+                assert await asyncio.to_thread(processes["worker"].wait, 120) != 0
+                assert not await connection.fetchval(
+                    "SELECT worker_ready_until>clock_timestamp() "
+                    "FROM problem_import_pool WHERE id=1"
+                )
+                stop("worker")
+            start("worker")
+            deadline = time.monotonic() + 180
+            while not await connection.fetchval(
+                "SELECT worker_ready_until>clock_timestamp() FROM problem_import_pool WHERE id=1"
+            ):
+                assert time.monotonic() < deadline and processes["worker"].poll() is None
+                await asyncio.sleep(0.1)
+            # Quiesce consumption. The actual verified heartbeat is retained for
+            # finite admission checks; synthetic capacity rows cannot be parsed.
+            stop("worker")
+            start("api0")
+            start("api1")
+            prefix = "/api/v1/admin/problem-imports"
+            async with (
+                httpx.AsyncClient(base_url="http://127.0.0.1:58000", timeout=30) as first,
+                httpx.AsyncClient(base_url="http://127.0.0.1:58001", timeout=30) as second,
+            ):
+                for client in (first, second):
+                    deadline = time.monotonic() + 300
+                    while True:
+                        try:
+                            if (await client.get("/api/v1/health/live")).status_code == 200:
+                                break
+                        except httpx.ConnectError:
+                            pass
+                        assert time.monotonic() < deadline
+                        await asyncio.sleep(0.1)
+                    result = await client.post(
+                        "/api/v1/auth/login",
+                        json={
+                            "username": "capacity_admin_0",
+                            "password": password,
+                        },
+                        headers={"Origin": "http://127.0.0.1:58000"},
+                    )
+                    assert result.status_code == 200, result.text
+
+                def headers(client):
+                    return {
+                        "Origin": "http://127.0.0.1:58000",
+                        "X-CSRF-Token": client.cookies["kf_csrf"],
+                    }
+
+                def body(key=None):
+                    return {
+                        "operation_id": str(key or uuid4()),
+                        "archive_digest": "a" * 64,
+                        "archive_bytes": 100,
+                    }
+
+                async def refresh_worker():
+                    previous = await connection.fetchval(
+                        "SELECT worker_ready_until FROM problem_import_pool WHERE id=1"
+                    )
+                    start("worker")
+                    deadline = time.monotonic() + 120
+                    while True:
+                        current = await connection.fetchval(
+                            "SELECT worker_ready_until FROM problem_import_pool WHERE id=1"
+                        )
+                        if current and (previous is None or current > previous):
+                            break
+                        assert time.monotonic() < deadline
+                        assert processes["worker"].poll() is None
+                        await asyncio.sleep(0.1)
+                    stop("worker")
+
+                await refresh_worker()
+                request = body()
+                replies = await asyncio.gather(
+                    *(
+                        client.post(prefix, json=request, headers=headers(client))
+                        for client in (first, second)
+                    )
+                )
+                # Identical UUIDs converge across independent API processes. A
+                # transient root-lock refusal is retried once after the winner.
+                assert 201 in [r.status_code for r in replies]
+                retry = await second.post(prefix, json=request, headers=headers(second))
+                assert retry.status_code == 201
+                assert (
+                    await connection.fetchval("SELECT count(*) FROM problem_import_operations") == 1
+                )
+                assert (
+                    await connection.fetchval("SELECT reserved_bytes FROM problem_import_pool")
+                    == 134217728
+                )
+                other = await first.post(prefix, json=body(), headers=headers(first))
+                assert other.status_code == 503
+                discarded = await first.post(
+                    prefix + "/" + request["operation_id"] + "/discard", headers=headers(first)
+                )
+                assert discarded.status_code == 200, discarded.text
+                assert (
+                    await connection.fetchval("SELECT reserved_bytes FROM problem_import_pool") == 0
+                )
+
+                async def capacity_rows(count):
+                    # Explicit unmeasured database fixtures exercise owner/global
+                    # admission boundaries; no ready candidate or grading is forged.
+                    await connection.execute(
+                        "DELETE FROM problem_import_operations WHERE state='uploaded'"
+                    )
+                    identifiers = list(users.values())
+                    for i in range(count):
+                        await connection.execute(
+                            """
+                          INSERT INTO problem_import_operations(id,owner_id,authorization_version,
+                          archive_digest,archive_bytes,state,reserved_bytes,expires_at,updated_at)
+                          VALUES($1,$2,2,$3,100,'uploaded',0,
+                            clock_timestamp()+interval '1 hour',clock_timestamp())
+                        """,
+                            uuid4(),
+                            identifiers[0] if count == 10 else identifiers[1 + i % 4],
+                            "b" * 64,
+                        )
+
+                results = {}
+                for label, count in (("owner_limit", 10), ("global_limit", 32)):
+                    await capacity_rows(0)
+                    await refresh_worker()
+                    await capacity_rows(count)
+                    before = await connection.fetchval(
+                        "SELECT count(*) FROM problem_import_operations"
+                    )
+                    response = await second.post(prefix, json=body(), headers=headers(second))
+                    assert response.status_code == 503
+                    assert (
+                        await connection.fetchval("SELECT count(*) FROM problem_import_operations")
+                        == before
+                    )
+                    results[label] = {
+                        "fixture_count": count,
+                        "actual_http_status": 503,
+                        "no_new_receipt": True,
+                    }
+                await capacity_rows(0)
+                await refresh_worker()
+                resumed = body()
+                result = await second.post(prefix, json=resumed, headers=headers(second))
+                assert result.status_code == 201, result.text
+                assert (
+                    await first.post(
+                        prefix + "/" + resumed["operation_id"] + "/discard", headers=headers(first)
+                    )
+                ).status_code == 200
+                assert (
+                    await connection.fetchval("SELECT reserved_bytes FROM problem_import_pool") == 0
+                )
+                proof(
+                    "cross_process_admission",
+                    results
+                    | {
+                        "two_actual_api_processes": True,
+                        "identical_uuid_one_receipt": True,
+                        "single_slot_http_status": 503,
+                        "wrong_worker_identity_and_group_exit_nonzero": True,
+                        "ordinary_worker_heartbeat_verified": True,
+                        "recovery_new_operation_201": True,
+                        "remaining_reserved_bytes": 0,
+                    },
+                )
+        finally:
+            for name in list(processes):
+                stop(name)
+            for role in roles.values():
+                await connection.execute(f"DROP OWNED BY {role}")
+                await connection.execute(f"DROP ROLE {role}")
+            await connection.close()
+
+    asyncio.run(run())

backend/tests/test_admin_import_contracts.py

@@ -0,0 +1,156 @@
+"""Contract checks only; upload/parser/security evidence requires the independent VM."""
+
+import copy
+import json
+from datetime import UTC, datetime, timedelta
+from pathlib import Path
+from uuid import uuid4
+
+import pytest
+from pydantic import ValidationError
+
+from kf_oj.contracts.admin_problems import (
+    CandidatePreview,
+    CreateProblemImport,
+    LegacyImportBudget,
+    ProblemImportCapabilities,
+    ProblemImportDetail,
+)
+from kf_oj.contracts.judging import AdmissionPolicy
+from kf_oj.modules.problems.import_format import ImportEnvelope
+from kf_oj.modules.problems.web_format import decode_web_declaration
+
+ROOT = Path(__file__).resolve().parents[2]
+
+
+def legacy_manifest():
+    policy = AdmissionPolicy.model_validate_json(
+        (ROOT / "tests/fixtures/contracts/judge-admission.valid.json").read_bytes()
+    )
+    return {
+        "schema_version": 1,
+        "slug": "web-fixture",
+        "title": "Public",
+        "statement_file": "statement.md",
+        "languages": ["c17", "cpp20"],
+        "toolchain": policy.toolchain.model_dump(mode="json"),
+        "comparison": "exact_bytes",
+        "compile_limits": policy.compile_ceiling.model_dump(),
+        "run_limits": policy.run_ceiling.model_dump(),
+        "job_wall_time_us": 60000000,
+        "cases": [{"key": "binary", "input_file": "hidden.in", "expected_file": "hidden.out"}],
+        "samples": [{"input_file": "sample.in", "output_file": "sample.out"}],
+    }
+
+
+def test_web_declaration_separates_public_data_and_preserves_local_format():
+    source = legacy_manifest()
+    original = copy.deepcopy(source)
+    declared = decode_web_declaration(json.dumps(source).encode())
+    assert declared.members == frozenset(
+        ("problem.json", "statement.md", "hidden.in", "hidden.out", "sample.in", "sample.out")
+    )
+    assert declared.manifest.model_dump(mode="json") == original
+    assert ImportEnvelope.model_validate(source).root == declared.manifest
+    for mutation in (
+        lambda x: x["samples"][0].update(input_file="hidden.in"),
+        lambda x: x.update(statement_file="problem.json"),
+        lambda x: x["cases"][0].update(input_file="Statement.md"),
+        lambda x: x["cases"][0].update(input_file="hidden.zip"),
+        lambda x: x.update(languages=["rust"]),
+        lambda x: x.update(download_url="https://example.invalid/private"),
+    ):
+        value = copy.deepcopy(source)
+        mutation(value)
+        with pytest.raises(ValueError):
+            decode_web_declaration(json.dumps(value).encode())
+    with pytest.raises(ValueError):
+        decode_web_declaration(
+            json.dumps(source)
+            .replace('"schema_version": 1', '"schema_version": 1, "schema_version": 1')
+            .encode()
+        )
+
+
+def test_import_operation_key_and_preview_have_no_private_payload_fields():
+    operation = {
+        "schema_version": 1,
+        "operation_id": str(uuid4()),
+        "archive_digest": "a" * 64,
+        "archive_bytes": 64 * 1024**2,
+    }
+    assert CreateProblemImport.model_validate(operation).archive_bytes == 64 * 1024**2
+    for field, value in (
+        ("archive_bytes", True),
+        ("archive_bytes", 64 * 1024**2 + 1),
+        ("url", "https://example.invalid"),
+        ("role", "admin"),
+    ):
+        with pytest.raises(ValidationError):
+            CreateProblemImport.model_validate(operation | {field: value})
+    manifest = ImportEnvelope.model_validate(legacy_manifest()).root
+    preview = CandidatePreview(
+        candidate_id=uuid4(),
+        slug=manifest.slug,
+        title=manifest.title,
+        statement="Public only",
+        samples=(),
+        judging_schema_version=1,
+        languages=manifest.languages,
+        legacy_budget=LegacyImportBudget(
+            compile_limits=manifest.compile_limits,
+            run_limits=manifest.run_limits,
+            job_wall_time_us=manifest.job_wall_time_us,
+        ),
+        case_count=1,
+    )
+    now = datetime.now(UTC)
+    response = ProblemImportDetail(
+        operation_id=uuid4(),
+        state="ready",
+        expected_archive_digest="a" * 64,
+        archive_bytes=100,
+        created_at=now,
+        updated_at=now,
+        expires_at=now + timedelta(days=1),
+        failure_code=None,
+        candidate_id=preview.candidate_id,
+        published_version_id=None,
+        candidate=preview,
+    )
+    assert set(response.candidate.model_dump()) == {
+        "candidate_id",
+        "slug",
+        "title",
+        "statement",
+        "samples",
+        "judging_schema_version",
+        "languages",
+        "legacy_budget",
+        "language_configurations",
+        "case_count",
+    }
+    with pytest.raises(ValidationError):
+        CandidatePreview.model_validate(preview.model_dump() | {"input_digest": "a" * 64})
+    capabilities = ProblemImportCapabilities(uploads_available=False, validation_available=False)
+    assert (
+        capabilities.limits.global_concurrency == 1 and capabilities.limits.owner_candidates == 10
+    )
+
+
+def test_standalone_import_worker_resolves_all_referenced_metadata():
+    # A separate trusted interpreter avoids accidental model registration by API test imports.
+    import subprocess
+    import sys
+
+    script = """
+import kf_oj.workers.problem_import
+from kf_oj.infra.db.base import Base
+for table in Base.metadata.tables.values():
+ for foreign in table.foreign_keys:
+  assert foreign.column.table is not None
+"""
+    result = subprocess.run(
+        [sys.executable, "-c", script], capture_output=True, text=True, timeout=15
+    )
+    assert result.returncode == 0, result.stderr

backend/tests/test_admin_upgrade_vm.py

@@ -0,0 +1,223 @@
+"""Approved baseline upgrade/retention: actual PostgreSQL in an independent capped VM."""
+
+import asyncio
+import hashlib
+import json
+import os
+import subprocess
+import sys
+from pathlib import Path
+from uuid import uuid4
+
+from conftest import connect, migrate
+from sqlalchemy.engine import make_url
+from test_admin_import_vm import independent_import_vm as independent_import_vm
+from test_admin_import_vm import package
+
+from kf_oj.contracts.judging_v2 import AdmissionRegistry
+
+ROOT = Path(__file__).resolve().parents[2]
+
+
+def policy():
+    return AdmissionRegistry.model_validate_json(
+        (ROOT / "tests/fixtures/contracts-v2/judge-registry.valid.json").read_bytes()
+    )
+
+
+def proof(name, value):
+    print(
+        "KF_FINAL_ACCEPTANCE " + json.dumps({"name": name, "result": value}, default=str),
+        flush=True,
+    )
+
+
+def test_baseline_upgrade_preserves_existing_data(independent_import_vm, postgres_url, tmp_path):
+    baseline = Path("/kf/baseline-platform")
+    assert baseline.is_dir(), "curated approved baseline required"
+    url = make_url(postgres_url).set(database="kf_oj_test_upgrade_" + uuid4().hex)
+    rendered = url.render_as_string(hide_password=False)
+
+    async def manage(command):
+        connection = await connect(postgres_url)
+        try:
+            await connection.execute(command)
+        finally:
+            await connection.close()
+
+    def old_run(args):
+        result = subprocess.run(
+            [sys.executable, *args],
+            cwd=baseline,
+            env=os.environ
+            | {
+                "PYTHONPATH": "/kf/baseline-platform/src:/kf/site",
+                "KF_OJ_DATABASE_URL": rendered,
+                "KF_BASELINE_FIXTURES": str(tmp_path),
+            },
+            capture_output=True,
+            timeout=300,
+        )
+        assert result.returncode == 0, (result.stdout + result.stderr).decode(errors="replace")[
+            -2000:
+        ]
+        return result
+
+    # Real old-schema data is created through the old public services. No student
+    # source executes here; historical report fixtures are explicitly unmeasured.
+    for multi in (False, True):
+        directory = tmp_path / ("v2" if multi else "v1")
+        directory.mkdir(mode=0o700)
+        _, payload = package(policy(), multi=multi)
+        for name, data in payload.items():
+            (directory / name).write_bytes(data)
+            (directory / name).chmod(0o600)
+    seed = """
+import asyncio,hashlib,json,os,secrets
+from datetime import datetime,timedelta,timezone
+from pathlib import Path
+from uuid import uuid4
+from sqlalchemy import text,update
+from kf_oj.api.app import create_app
+from kf_oj.core.settings import Settings
+from kf_oj.contracts.judging import ArtifactReference
+from kf_oj.contracts.judging_v2 import AdmissionRegistry
+from kf_oj.contracts.judging_versions import manifest_bytes
+from kf_oj.contracts.submissions import CreateSubmission
+from kf_oj.modules.submissions.models import Evaluation,JudgeAttempt
+async def main():
+ root=Path(os.environ['KF_BASELINE_FIXTURES'])
+ fixture=Path('/kf/tests/fixtures/contracts-v2/judge-registry.valid.json')
+ policy=AdmissionRegistry.model_validate_json(fixture.read_bytes())
+ database=os.environ['KF_OJ_DATABASE_URL']
+ app=create_app(Settings(_env_file=None,database_url=database,
+                         artifact_root=root/'objects',judge_admission=policy))
+ async with app.router.lifespan_context(app):
+  password='Synthetic upgrade acceptance only 2026!'
+  user=await app.state.identity.create_account('upgrade_student',password)
+  for name in ('v1','v2'):
+   version=await app.state.problems.import_directory(root/name)
+   request=CreateSubmission(problem_version_id=version,language='c17',
+                            idempotency_key=uuid4(),source='int main(void){return 0;}')
+   created=await app.state.submissions.create(user,request)
+   # Controlled, unmeasured historical database fixtures prove preservation of
+   # reports and their digests. They never claim execution or trusted performance.
+   async with app.state.sessions.begin() as session:
+    projected=await app.state.problems.for_submission(session,version)
+    source=ArtifactReference(digest=hashlib.sha256(request.source.encode()).hexdigest(),
+                             bytes=len(request.source.encode()))
+    manifest=projected.manifest(created.evaluation_id,created.submission_id,'c17',source)
+    md=hashlib.sha256(manifest_bytes(manifest)).hexdigest()
+    aid,wid=uuid4(),uuid4()
+    template=('contracts' if name=='v1' else 'contracts-v2')
+    file=('judge-result.valid.json' if name=='v1' else 'judge-result.valid-c17.json')
+    report=json.loads((Path('/kf/tests/fixtures')/template/file).read_text())
+    report['binding']={'evaluation_id':str(created.evaluation_id),'attempt_id':str(aid),
+                       'worker_id':str(wid),'fencing_version':1}
+    report['manifest_digest']=md
+    report['cases']=[{'case_id':str(case.case_id),'verdict':'accepted',
+                      'cpu_time_us':100,'memory_peak_bytes':262144}
+                     for case in manifest.cases]
+    report['run_cpu_time_us']=100*len(manifest.cases)
+    report['run_memory_peak_bytes']=262144
+    digest=hashlib.sha256(json.dumps(report,sort_keys=True,separators=(',',':'),
+                                    ensure_ascii=False).encode()).hexdigest()
+    await session.execute(text('SET LOCAL ROLE kf_oj_coordinator'))
+    session.add(JudgeAttempt(id=aid,evaluation_id=created.evaluation_id,worker_id=wid,
+                number=1,fencing_version=1,lease_token_hash=hashlib.sha256(
+                 secrets.token_hex(32).encode()).hexdigest(),
+                expires_at=datetime.now(timezone.utc)+timedelta(minutes=10),
+                manifest=manifest.model_dump(mode='json'),manifest_digest=md,
+                report=report,report_digest=digest,cleanup_complete=True))
+    await session.flush()
+    await session.execute(update(Evaluation).where(Evaluation.id==created.evaluation_id)
+                .values(current_attempt_id=aid,state='finished',attempts_count=1,
+                        fencing_version=1,verdict='accepted',final_report=report,
+                        final_report_digest=digest))
+asyncio.run(main())
+"""
+    asyncio.run(manage(f'CREATE DATABASE "{url.database}"'))
+    try:
+        old_run(["-m", "alembic", "upgrade", "head"])
+        old_run(["-c", seed])
+
+        async def snapshot(columns=None):
+            connection = await connect(rendered)
+            try:
+                if columns is None:
+                    rows = await connection.fetch("""
+                        SELECT table_name,column_name FROM information_schema.columns
+                        WHERE table_schema='public' AND table_name<>'alembic_version'
+                        ORDER BY table_name,ordinal_position
+                    """)
+                    columns = {}
+                    for row in rows:
+                        columns.setdefault(row["table_name"], []).append(row["column_name"])
+                data = {}
+                for table, names in columns.items():
+                    query = (
+                        "SELECT " + ",".join('"' + n + '"' for n in names) + ' FROM "' + table + '"'
+                    )
+                    records = sorted(
+                        json.dumps(dict(r), sort_keys=True, default=str)
+                        for r in await connection.fetch(query)
+                    )
+                    data[table] = {
+                        "rows": len(records),
+                        "sha256": hashlib.sha256("\n".join(records).encode()).hexdigest(),
+                    }
+                return columns, data
+            finally:
+                await connection.close()
+
+        columns, before = asyncio.run(snapshot())
+        assert before["accounts"]["rows"] == 1 and before["problem_versions"]["rows"] == 2
+        assert before["submissions"]["rows"] == 2
+        assert before["judge_attempts"]["rows"] == 2
+        migrate(rendered, "upgrade", "head")
+        _, after = asyncio.run(snapshot(columns))
+        assert after == before
+        migrate(rendered, "check")
+
+        async def defaults():
+            connection = await connect(rendered)
+            try:
+                account = await connection.fetchrow(
+                    "SELECT is_administrator,authorization_version FROM accounts"
+                )
+                assert not account["is_administrator"] and account["authorization_version"] == 1
+                assert await connection.fetchval("SELECT count(*) FROM evaluation_performance") == 0
+                assert (
+                    await connection.fetchval("SELECT count(*) FROM problem_maintenance_events")
+                    == 0
+                )
+                for role in ("kf_oj_identity_operator", "kf_oj_problem_import"):
+                    row = await connection.fetchrow("SELECT * FROM pg_roles WHERE rolname=$1", role)
+                    assert not any(
+                        row[k]
+                        for k in (
+                            "rolcanlogin",
+                            "rolsuper",
+                            "rolcreatedb",
+                            "rolcreaterole",
+                            "rolreplication",
+                            "rolbypassrls",
+                        )
+                    )
+            finally:
+                await connection.close()
+
+        asyncio.run(defaults())
+        proof(
+            "baseline_upgrade",
+            {
+                "baseline": "5df3c370aab0b12a1c3f8670a0c066f8b77a4078",
+                "retained_tables": before,
+                "old_v1_v2_manifests_and_source_bytes": "exact",
+                "historical_report_retention_fixture_unmeasured": True,
+                "fixture_reports_not_student_execution_or_performance_acceptance": True,
+                "fresh_current_database": postgres_url.split("/")[-1].split("?")[0],
+            },
+        )
+    finally:
+        asyncio.run(manage(f'DROP DATABASE "{url.database}"'))

backend/tests/test_administrator_storage.py

@@ -0,0 +1,244 @@
+"""Actual temporary PG migration and authority storage; API/CLI acceptance is separate."""
+
+import asyncio
+import subprocess
+from datetime import timedelta
+from uuid import uuid4
+
+import asyncpg
+import pytest
+from conftest import connect, migrate
+from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine
+from test_database_foundation import fixture_rows
+
+from kf_oj.modules.identity.public import AuthenticationFailed, Principal
+from kf_oj.modules.identity.service import IdentityService, token_digest
+
+
+class RollBackAuthorityChange(Exception):
+    """Abort the test transaction before any authority change commits."""
+
+
+async def submission_snapshot(connection):
+    # Synthetic queued metadata only; this does not claim real program execution.
+    return {
+        table: list(
+            await connection.fetch(
+                f"SELECT to_jsonb(t)::text FROM {table} t ORDER BY to_jsonb(t)::text"
+            )
+        )
+        for table in (
+            "artifacts",
+            "problems",
+            "problem_versions",
+            "problem_cases",
+            "submissions",
+            "evaluations",
+            "outbox",
+        )
+    }
+
+
+async def account_and_session(connection):
+    account = uuid4()
+    token, csrf = uuid4().hex * 2, uuid4().hex * 2
+    await connection.execute(
+        "INSERT INTO accounts(id,username,password_hash) VALUES($1,'storage_user',$2)",
+        account,
+        "synthetic-irreversible-placeholder-hash-" * 2,
+    )
+    now = await connection.fetchval("SELECT clock_timestamp()")
+    await connection.execute(
+        "INSERT INTO sessions(token_hash,csrf_hash,account_id,expires_at) VALUES($1,$2,$3,$4)",
+        token_digest(token),
+        token_digest(csrf),
+        account,
+        now + timedelta(hours=1),
+    )
+    return account, token, csrf
+
+
+def test_upgrade_preserves_ordinary_account_and_current_session(postgres_url):
+    migrate(postgres_url, "downgrade", "0004_performance_watermark")
+
+    async def seed():
+        connection = await connect(postgres_url)
+        try:
+            account, token, csrf = await account_and_session(connection)
+            await fixture_rows(connection)
+            return account, token, csrf, await submission_snapshot(connection)
+        finally:
+            await connection.close()
+
+    account, token, csrf, before = asyncio.run(seed())
+    migrate(postgres_url, "upgrade", "head")
+    migrate(postgres_url, "check")
+
+    async def inspect():
+        connection = await connect(postgres_url)
+        engine = create_async_engine(postgres_url)
+        try:
+            row = await connection.fetchrow("SELECT * FROM accounts WHERE id=$1", account)
+            assert row["enabled"] and not row["is_administrator"]
+            assert row["authorization_version"] == 1
+            assert await submission_snapshot(connection) == before
+            service = IdentityService(async_sessionmaker(engine, expire_on_commit=False))
+            assert await service.authenticate(token, csrf_token=csrf) == Principal(
+                account, "storage_user"
+            )
+        finally:
+            await connection.close()
+            await engine.dispose()
+
+    asyncio.run(inspect())
+
+
+def test_authority_columns_and_import_role_are_not_runtime_write_permissions(postgres_url):
+    async def inspect():
+        connection = await connect(postgres_url)
+        try:
+            for role in ("kf_oj_platform", "kf_oj_coordinator", "kf_oj_problem_import"):
+                for column in ("is_administrator", "authorization_version"):
+                    assert not await connection.fetchval(
+                        "SELECT has_column_privilege($1,'accounts',$2,'UPDATE')", role, column
+                    )
+                    assert not await connection.fetchval(
+                        "SELECT has_column_privilege($1,'accounts',$2,'INSERT')", role, column
+                    )
+            for table in (
+                "evaluations",
+                "judge_attempts",
+                "case_results",
+                "evaluation_performance",
+            ):
+                for privilege in ("SELECT", "INSERT", "UPDATE", "DELETE"):
+                    assert not await connection.fetchval(
+                        "SELECT has_table_privilege('kf_oj_problem_import',$1,$2)", table, privilege
+                    )
+            assert await connection.fetchval(
+                "SELECT has_column_privilege('kf_oj_platform','accounts','enabled','UPDATE')"
+            )
+            assert not await connection.fetchval(
+                "SELECT has_column_privilege('kf_oj_identity_operator',"
+                "'accounts','is_administrator','UPDATE')"
+            )
+            assert not await connection.fetchval(
+                "SELECT has_column_privilege('kf_oj_identity_operator',"
+                "'accounts','authorization_version','UPDATE')"
+            )
+            assert not await connection.fetchval(
+                "SELECT pg_has_role('kf_oj_platform','kf_oj_identity_operator','USAGE')"
+            )
+        finally:
+            await connection.close()
+
+    asyncio.run(inspect())
+
+
+def test_authority_change_derives_version_and_revokes_old_session_atomically(postgres_url):
+    async def inspect():
+        connection = await connect(postgres_url)
+        engine = create_async_engine(postgres_url)
+        try:
+            account, token, csrf = await account_and_session(connection)
+            service = IdentityService(async_sessionmaker(engine, expire_on_commit=False))
+            await service.authenticate(token, csrf_token=csrf)
+            async with connection.transaction():
+                await connection.execute("SET LOCAL ROLE kf_oj_identity_operator")
+                await connection.execute(
+                    "SELECT * FROM public.kf_manage_account_authority('storage_user','bootstrap')"
+                )
+            assert (
+                await connection.fetchval(
+                    "SELECT authorization_version FROM accounts WHERE id=$1", account
+                )
+                == 2
+            )
+            with pytest.raises(AuthenticationFailed):
+                await service.authenticate(token, csrf_token=csrf)
+            async with connection.transaction():
+                await connection.execute("SET LOCAL ROLE kf_oj_identity_operator")
+                await connection.execute(
+                    "SELECT * FROM public.kf_manage_account_authority('storage_user','bootstrap')"
+                )
+            assert (
+                await connection.fetchval(
+                    "SELECT authorization_version FROM accounts WHERE id=$1", account
+                )
+                == 2
+            )
+            fresh_token, fresh_csrf = uuid4().hex * 2, uuid4().hex * 2
+            await connection.execute(
+                "INSERT INTO sessions(token_hash,csrf_hash,account_id,expires_at) "
+                "VALUES($1,$2,$3,clock_timestamp()+interval '1 hour')",
+                token_digest(fresh_token),
+                token_digest(fresh_csrf),
+                account,
+            )
+            await connection.execute(
+                "INSERT INTO accounts(id,username,password_hash) "
+                "VALUES(gen_random_uuid(),'storage_recovery',repeat('synthetic-only-',5))"
+            )
+            async with connection.transaction():
+                await connection.execute("SET LOCAL ROLE kf_oj_identity_operator")
+                await connection.execute(
+                    "SELECT * FROM public.kf_manage_account_authority('storage_recovery','grant')"
+                )
+            with pytest.raises(RollBackAuthorityChange):
+                async with connection.transaction():
+                    await connection.execute(
+                        "SELECT * FROM public.kf_manage_account_authority('storage_user','revoke')"
+                    )
+                    assert (
+                        await connection.fetchval(
+                            "SELECT authorization_version FROM accounts WHERE id=$1", account
+                        )
+                        == 3
+                    )
+                    raise RollBackAuthorityChange
+            assert await connection.fetchval(
+                "SELECT is_administrator FROM accounts WHERE id=$1", account
+            )
+            assert (
+                await connection.fetchval(
+                    "SELECT authorization_version FROM accounts WHERE id=$1", account
+                )
+                == 2
+            )
+            await service.authenticate(fresh_token, csrf_token=fresh_csrf)
+            async with connection.transaction():
+                await connection.execute("SET LOCAL ROLE kf_oj_identity_operator")
+                await connection.execute(
+                    "SELECT * FROM public.kf_manage_account_authority('storage_user','revoke')"
+                )
+            assert (
+                await connection.fetchval(
+                    "SELECT authorization_version FROM accounts WHERE id=$1", account
+                )
+                == 3
+            )
+            with pytest.raises(AuthenticationFailed):
+                await service.authenticate(fresh_token, csrf_token=fresh_csrf)
+        finally:
+            await connection.close()
+            await engine.dispose()
+
+    asyncio.run(inspect())
+
+
+def test_authority_history_cannot_be_erased_by_downgrade(postgres_url):
+    async def change():
+        connection = await connect(postgres_url)
+        try:
+            account, _, _ = await account_and_session(connection)
+            await connection.execute("UPDATE accounts SET enabled=false WHERE id=$1", account)
+            with pytest.raises(asyncpg.CheckViolationError):
+                await connection.execute(
+                    "UPDATE accounts SET authorization_version=1 WHERE id=$1", account
+                )
+        finally:
+            await connection.close()
+
+    asyncio.run(change())
+    with pytest.raises(subprocess.CalledProcessError):
+        migrate(postgres_url, "downgrade", "0004_performance_watermark")

backend/tests/test_artifact_backup.py

@@ -0,0 +1,24 @@
+"""Trusted adapter checks; real cold PG/role/permission tests remain VM-only."""
+
+import hashlib
+
+from kf_oj.contracts.judging import ArtifactReference
+from kf_oj.infra.artifacts.backup import verify_existing
+
+
+def test_backup_verifies_binary_and_empty_objects_without_creating_storage_entries(tmp_path):
+    tmp_path.chmod(0o700)
+    values = [b"", b"\0\xff\n" * 50000]
+    expected = {}
+    for value in values:
+        digest = hashlib.sha256(value).hexdigest()
+        path = tmp_path / digest
+        path.write_bytes(value)
+        path.chmod(0o600)
+        expected[digest] = value
+    before = {p.name: (p.read_bytes(), p.stat().st_mtime_ns) for p in tmp_path.iterdir()}
+    for digest, value in expected.items():
+        verify_existing(tmp_path, ArtifactReference(digest=digest, bytes=len(value)))
+    after = {p.name: (p.read_bytes(), p.stat().st_mtime_ns) for p in tmp_path.iterdir()}
+    assert after == before
+    assert not (tmp_path / ".lock").exists()

backend/tests/test_authority_operations.py

@@ -0,0 +1,219 @@
+"""Real local authority/CLI transactions; run privilege faults in the independent VM."""
+
+import asyncio
+import os
+import subprocess
+import sys
+import time
+from pathlib import Path
+from uuid import uuid4
+
+import asyncpg
+import pytest
+from conftest import connect
+from sqlalchemy.engine import make_url
+
+from kf_oj.modules.identity.authority import manage_authority
+
+
+async def seed(connection, *usernames):
+    for name in usernames:
+        await connection.execute(
+            "INSERT INTO accounts(id,username,password_hash) VALUES($1,$2,repeat('synthetic-',6))",
+            uuid4(),
+            name,
+        )
+
+
+async def authority(connection, username, operation):
+    async with connection.transaction():
+        await connection.execute("SET LOCAL ROLE kf_oj_identity_operator")
+        return await connection.fetchrow(
+            "SELECT * FROM public.kf_manage_account_authority($1,$2)", username, operation
+        )
+
+
+def test_explicit_bootstrap_repeated_grants_recovery_and_last_administrator(postgres_url):
+    async def run():
+        c = await connect(postgres_url)
+        try:
+            await seed(c, "first_admin", "second_admin")
+            assert await c.fetchval("SELECT count(*) FROM accounts WHERE is_administrator") == 0
+            with pytest.raises(asyncpg.CheckViolationError):
+                await authority(c, "first_admin", "grant")
+            first = await authority(c, "first_admin", "bootstrap")
+            assert first["changed"] and first["authorization_version"] == 2
+            assert not (await authority(c, "first_admin", "bootstrap"))["changed"]
+            assert not (await authority(c, "first_admin", "grant"))["changed"]
+            with pytest.raises(asyncpg.CheckViolationError):
+                await authority(c, "second_admin", "bootstrap")
+            for operation in ("disable", "revoke"):
+                with pytest.raises(asyncpg.CheckViolationError):
+                    await authority(c, "first_admin", operation)
+            await authority(c, "second_admin", "grant")
+            disabled = await authority(c, "first_admin", "disable")
+            assert not disabled["enabled"] and disabled["is_administrator"]
+            assert disabled["authorization_version"] == 3
+            assert not (await authority(c, "first_admin", "disable"))["changed"]
+            restored = await authority(c, "first_admin", "enable")
+            assert restored["enabled"] and restored["authorization_version"] == 4
+            revoked = await authority(c, "first_admin", "revoke")
+            assert not revoked["is_administrator"] and revoked["authorization_version"] == 5
+            assert not (await authority(c, "first_admin", "revoke"))["changed"]
+            await authority(c, "first_admin", "grant")
+            with pytest.raises(asyncpg.NoDataFoundError):
+                await authority(c, "absent_user", "grant")
+            for role in ("kf_oj_platform", "kf_oj_coordinator", "kf_oj_problem_import"):
+                assert not await c.fetchval(
+                    "SELECT has_function_privilege($1,"
+                    "'kf_manage_account_authority(text,text)','EXECUTE')",
+                    role,
+                )
+            for column in ("password_hash", "is_administrator", "enabled"):
+                assert not await c.fetchval(
+                    "SELECT has_column_privilege('kf_oj_identity_operator','accounts',$1,'SELECT')",
+                    column,
+                )
+            async with c.transaction():
+                await c.execute("SET LOCAL ROLE kf_oj_identity_operator")
+                for sql in (
+                    "SELECT password_hash FROM accounts",
+                    "UPDATE accounts SET is_administrator=false",
+                    "SELECT token_hash FROM sessions",
+                ):
+                    with pytest.raises(asyncpg.InsufficientPrivilegeError):
+                        async with c.transaction():
+                            await c.execute(sql)
+        finally:
+            await c.close()
+
+    asyncio.run(run())
+
+
+@pytest.mark.parametrize("isolation", ("read_committed", "repeatable_read", "serializable"))
+def test_concurrent_different_account_revocations_preserve_one_admin(postgres_url, isolation):
+    async def serialized_run():
+        c, other = await connect(postgres_url), await connect(postgres_url)
+        first_tx = second_tx = pending = None
+        try:
+            await seed(c, "first_admin", "second_admin")
+            await authority(c, "first_admin", "bootstrap")
+            await authority(c, "second_admin", "grant")
+            first_tx, second_tx = (
+                c.transaction(isolation=isolation),
+                other.transaction(isolation=isolation),
+            )
+            await first_tx.start()
+            await second_tx.start()
+            assert (
+                await other.fetchval(
+                    "SELECT count(*) FROM accounts WHERE is_administrator AND enabled"
+                )
+                == 2
+            )
+            await authority(c, "first_admin", "revoke")
+            pending = asyncio.create_task(authority(other, "second_admin", "revoke"))
+            deadline = time.monotonic() + 5
+            while time.monotonic() < deadline:
+                if await c.fetchval(
+                    "SELECT EXISTS(SELECT 1 FROM pg_locks WHERE pid=$1 AND NOT granted)",
+                    other.get_server_pid(),
+                ):
+                    break
+                await asyncio.sleep(0.01)
+            else:
+                raise AssertionError("second authority operation never blocked on PG lock")
+            assert not pending.done()
+            await first_tx.commit()
+            first_tx = None
+            with pytest.raises((asyncpg.CheckViolationError, asyncpg.SerializationError)):
+                await asyncio.wait_for(pending, 5)
+            await second_tx.rollback()
+            second_tx = None
+            assert (
+                await c.fetchval("SELECT count(*) FROM accounts WHERE is_administrator AND enabled")
+                == 1
+            )
+            assert await c.fetchval(
+                "SELECT is_administrator FROM accounts WHERE username='second_admin'"
+            )
+        finally:
+            if pending is not None and not pending.done():
+                pending.cancel()
+                await asyncio.gather(pending, return_exceptions=True)
+            if first_tx is not None:
+                await first_tx.rollback()
+            if second_tx is not None:
+                await second_tx.rollback()
+            await c.close()
+            await other.close()
+
+    asyncio.run(serialized_run())
+
+
+def test_real_cli_uses_dedicated_login_and_never_prints_database_secret(postgres_url):
+    role = "authority_test_" + uuid4().hex
+
+    async def setup():
+        c = await connect(postgres_url)
+        try:
+            await seed(c, "cli_admin", "cli_backup")
+            await c.execute(
+                f"CREATE ROLE {role} LOGIN NOSUPERUSER NOCREATEDB NOCREATEROLE "
+                "NOREPLICATION NOBYPASSRLS"
+            )
+            await c.execute(f"GRANT kf_oj_identity_operator TO {role}")
+        finally:
+            await c.close()
+
+    asyncio.run(setup())
+    url = make_url(postgres_url).set(username=role).render_as_string(hide_password=False)
+    env = os.environ | {
+        "KF_OJ_DATABASE_URL": postgres_url,
+        "KF_OJ_IDENTITY_OPERATOR_DATABASE_URL": url,
+    }
+    cwd = Path(__file__).resolve().parents[1]
+
+    def invoke(command, username, expected=0):
+        result = subprocess.run(
+            [sys.executable, "-m", "kf_oj.modules.identity.cli", command, username],
+            cwd=cwd,
+            env=env,
+            capture_output=True,
+            text=True,
+            timeout=120,
+        )
+        assert result.returncode == expected, result.stderr
+        assert url not in result.stdout + result.stderr
+        assert "Traceback" not in result.stderr
+        return result.stdout
+
+    try:
+        assert "changed=True" in invoke("bootstrap-admin", "cli_admin")
+        assert "changed=False" in invoke("bootstrap-admin", "cli_admin")
+        invoke("revoke-admin", "cli_admin", 1)
+        invoke("grant-admin", "cli_backup")
+        invoke("disable", "cli_admin")
+        invoke("enable", "cli_admin")
+        invoke("revoke-admin", "cli_admin")
+        invoke("grant-admin", "cli_admin")
+    finally:
+
+        async def cleanup():
+            c = await connect(postgres_url)
+            try:
+                await c.execute(f"REVOKE kf_oj_identity_operator FROM {role}")
+                await c.execute(f"DROP ROLE {role}")
+            finally:
+                await c.close()
+
+        asyncio.run(cleanup())
+
+
+def test_bad_cli_operation_rejected_without_connecting():
+    async def run():
+        for username, operation in (("invalid name", "grant"), ("valid_name", "unknown")):
+            with pytest.raises(ValueError):
+                await manage_authority(None, username, operation)
+
+    asyncio.run(run())

backend/tests/test_availability.py

@@ -0,0 +1,88 @@
+"""Contract/admission-route tests; Root file/atomicity and drain acceptance are VM-only."""
+
+import asyncio
+import json
+from pathlib import Path
+from types import SimpleNamespace
+
+import pytest
+from jsonschema import Draft202012Validator
+
+from kf_oj.api.availability import AvailabilityMiddleware, needs_open
+from kf_oj.contracts.availability import AvailabilityRecord
+
+
+@pytest.mark.parametrize("state", ["open", "draining", "quiescent"])
+def test_availability_is_exactly_bound_to_a_known_version_and_state(state):
+    path = (
+        Path(__file__).resolve().parents[2]
+        / "tests/fixtures/contracts/delivery-availability.valid.json"
+    )
+    value = json.loads(path.read_text())
+    value["state"] = state
+    assert AvailabilityRecord.model_validate(value).state == state
+    schema = path.parents[3] / "contracts/schemas/delivery-availability.v1.schema.json"
+    Draft202012Validator(json.loads(schema.read_text())).validate(value)
+    for key, replacement in (
+        ("schema_version", True),
+        ("release_id", "../release"),
+        ("state", "always_allow"),
+    ):
+        with pytest.raises(ValueError):
+            AvailabilityRecord.model_validate({**value, key: replacement})
+
+
+@pytest.mark.parametrize(
+    "method,path,blocked",
+    [
+        ("POST", "/api/v1/submissions", True),
+        ("POST", "/api/v1/admin/problem-imports", True),
+        ("POST", "/api/v1/admin/problems/publish", True),
+        ("POST", "/api/v1/auth/login", True),
+        ("GET", "/api/v1/internal/evaluations/artifacts", False),
+        ("POST", "/api/v1/auth/logout", False),
+        ("POST", "/api/v1/submissions/11111111-1111-4111-8111-111111111111/cancel", False),
+        (
+            "PUT",
+            "/api/v1/admin/problem-imports/11111111-1111-4111-8111-111111111111/archive",
+            False,
+        ),
+    ],
+)
+def test_drain_blocks_new_mutations_without_cutting_accepted_reads_and_cancel(
+    method, path, blocked
+):
+    assert needs_open(method, path) is blocked
+
+
+def test_missing_admission_record_rejects_before_body_or_domain_execution(monkeypatch):
+    # Transport policy only: this stub does not verify Root ownership or Linux file safety.
+    calls = []
+    messages = []
+
+    def missing(*_):
+        raise FileNotFoundError("record missing")
+
+    monkeypatch.setattr("kf_oj.api.availability.current", missing)
+
+    async def receive():
+        calls.append("body")
+        return {"type": "http.request", "body": b""}
+
+    async def domain(*_):
+        calls.append("domain")
+
+    async def send(message):
+        messages.append(message)
+
+    settings = SimpleNamespace(
+        environment="production", delivery_release_id=None, delivery_configuration_id=None
+    )
+    asyncio.run(
+        AvailabilityMiddleware(domain, settings=settings)(
+            {"type": "http", "method": "POST", "path": "/api/v1/submissions"}, receive, send
+        )
+    )
+    assert calls == []
+    assert messages[0]["status"] == 503
+    assert (b"cache-control", b"no-store") in messages[0]["headers"]

backend/tests/test_coordinator.py

@@ -28,7 +28,13 @@ ROOT = Path(__file__).resolve().parents[2]
 
 @asynccontextmanager
 async def fixture(
-    postgres_url, tmp_path, monkeypatch, *, import_builder=import_fixture, node_policy=None
+    postgres_url,
+    tmp_path,
+    monkeypatch,
+    *,
+    import_builder=import_fixture,
+    node_policy=None,
+    measurement_epochs=None,
 ):
     _, policy = import_builder(tmp_path / "import")
     engine = create_async_engine(postgres_url)
@@ -59,6 +65,9 @@ async def fixture(
         reserved.bind(("127.0.0.1", 0))
         port = reserved.getsockname()[1]
     workers = [dict(id=str(uuid4()), token=secrets.token_hex(32)) for _ in range(2)]
+    if measurement_epochs is not None:
+        for worker, epoch in zip(workers, measurement_epochs, strict=True):
+            worker["measurement_epoch"] = epoch
     platform = secrets.token_hex(32)
     config = tmp_path / "coordinator.json"
     config.write_text(
@@ -152,6 +161,7 @@ async def fixture(
                 client.fixture_version = version
                 client.coordinator_unit = unit
                 client.coordinator_role = role
+                client.coordinator_config = config
                 yield client, c, workers, platform, create
     finally:
         subprocess.run(["systemctl", "--user", "stop", unit], check=True, capture_output=True)

backend/tests/test_database_foundation.py

@@ -1,5 +1,6 @@
 import asyncio
 import json
+import subprocess
 from uuid import uuid4
 
 import asyncpg
@@ -12,9 +13,15 @@ def test_migration_roundtrip_and_role_safety(postgres_url):
         c = await connect(postgres_url)
         try:
             tables = set(await c.fetch("SELECT tablename FROM pg_tables WHERE schemaname='public'"))
-            assert len(tables) == 13  # Twelve business tables and Alembic history.
+            assert len(tables) == 21  # Twenty domain/control tables and Alembic history.
             roles = await c.fetch("SELECT * FROM pg_roles WHERE rolname LIKE 'kf_oj_%'")
-            assert {row["rolname"] for row in roles} == {"kf_oj_platform", "kf_oj_coordinator"}
+            assert {row["rolname"] for row in roles} == {
+                "kf_oj_platform",
+                "kf_oj_coordinator",
+                "kf_oj_identity_operator",
+                "kf_oj_problem_import",
+                "kf_oj_identity_authority_owner",
+            }
             assert all(
                 not any(
                     r[k]
@@ -38,7 +45,14 @@ def test_migration_roundtrip_and_role_safety(postgres_url):
     asyncio.run(inspect())
     migrate(postgres_url, "downgrade", "base")
     migrate(postgres_url, "upgrade", "head")
-    migrate(postgres_url, "check")
+    try:
+        migrate(postgres_url, "check")
+    except subprocess.CalledProcessError as error:
+        raise AssertionError(
+            "migration model consistency failed: "
+            + (error.stdout or b"").decode(errors="replace")[-8192:]
+            + (error.stderr or b"").decode(errors="replace")[-8192:]
+        ) from None
     asyncio.run(inspect())
 
 

backend/tests/test_delivery_backup.py

@@ -0,0 +1,349 @@
+"""Trusted byte fixtures only; no privileged backup, recovery or RTO acceptance."""
+
+import hashlib
+import importlib
+import os
+import sys
+import time
+from pathlib import Path
+
+import pytest
+
+ROOT = Path(__file__).resolve().parents[2]
+sys.path.insert(0, str(ROOT))
+backup_manifest = importlib.import_module("scripts.release.backup_manifest")
+backup_objects = importlib.import_module("scripts.release.backup_objects")
+policy = importlib.import_module("scripts.release.policy")
+
+
+def empty_drain_projection():
+    return {
+        "execution": {
+            "database_clock_unix_ms": 1791830000000,
+            **{
+                name: {"count_capped": 0, "truncated": False}
+                for name in ("queued", "in_flight", "cleanup_unconfirmed")
+            },
+        },
+        "outbox": {
+            "schema_version": 1,
+            "pending_capped": 0,
+            "locked_capped": 0,
+            "truncated": False,
+        },
+        "imports": {
+            "schema_version": 1,
+            "worker_ready": True,
+            "reserved_bytes": 0,
+            "uploaded_capped": 0,
+            "validating_capped": 0,
+            "truncated": False,
+        },
+        "broker": {
+            "schema_version": 1,
+            "metadata_verified": True,
+            "messages_ready": 0,
+            "messages_unacknowledged": 0,
+            "message_bytes": 0,
+            "consumers": 1,
+        },
+        "factory": {
+            "schema_version": 1,
+            "configuration_sha256": "b" * 64,
+            "supervisor_authorized": True,
+            "execution_gate": "required_per_execution",
+            "isolation_verified": False,
+            "max_concurrent_runs": 1,
+            "active_helpers": 0,
+            "cleanup_complete": True,
+            "remaining_requests": 4096,
+            "remaining_lifetime_seconds": 3600,
+        },
+    }
+
+
+@pytest.fixture
+def snapshot():
+    data = b"trusted repeated bytes\n"
+    digest = hashlib.sha256(data).hexdigest()
+    files = [
+        {
+            "path": path,
+            "uid": uid,
+            "gid": uid,
+            "mode": mode,
+            "bytes": len(data),
+            "sha256": digest,
+        }
+        for path, uid, mode in [
+            ("postgres/PG_VERSION", 1203, 0o600),
+            ("postgres/global/pg_control", 1203, 0o600),
+            ("releases/first", 0, 0o444),
+            ("releases/second", 0, 0o555),
+        ]
+    ]
+    boot = "12345678-1234-1234-1234-123456789abc"
+    selected = {
+        "schema_version": 1,
+        "release_id": "sd-" + "c" * 12,
+        "manifest_sha256": "b" * 64,
+        "configuration_id": "cfg-" + "d" * 24,
+        "receipt_sha256": "e" * 64,
+    }
+    return {
+        "schema_version": 3,
+        "format": backup_manifest.FORMAT,
+        "backup_id": "bk-" + "2" * 32,
+        "source_sha": "c" * 40,
+        "manifest_sha256": selected["manifest_sha256"],
+        "configuration_id": selected["configuration_id"],
+        "created_unix_seconds": 1793070000,
+        "expires_unix_seconds": 1793070000 + 7 * 86400,
+        "selected": selected,
+        "consistent_cut": {
+            "schema_version": 1,
+            "source_sha": "c" * 40,
+            "configuration_id": selected["configuration_id"],
+            "action": "stop",
+            "phase": "complete",
+            "success": True,
+            "events": [],
+            "root_cleanup_confirmed": True,
+            "boot_id": boot,
+            "drain_projection": empty_drain_projection(),
+        },
+        "artifact_references": {
+            "schema_version": 1,
+            "kind": "kf.private.artifact-backup-inventory",
+            "read_only": True,
+            "quiescence_verified": False,
+            "boot_id": boot,
+            "storage_identity": {"device": 1, "inode": 2, "uid": 1200},
+            "objects": [],
+        },
+        "broker_cookie_sha256": "b" * 64,
+        "database_bootstrap_sha256": "e" * 64,
+        "images": {
+            key: {
+                "toolchain_id": key,
+                "image_kind": key,
+                "runtime_version": "1",
+                "image_revision": 1,
+                "image_digest": "f" * 64,
+            }
+            for key in ("gnu", "python313", "java21")
+        },
+        "directories": [
+            {"path": path, "uid": 0, "gid": 0, "mode": 0o700}
+            for path in sorted(backup_manifest.DOMAINS | {"postgres/global"})
+        ],
+        "files": files,
+        "payload_bytes": len(data) * len(files),
+        "restored": False,
+        "execution_verified": False,
+    }
+
+
+def object_format(value):
+    return {
+        **value,
+        "schema_version": 4,
+        "format": backup_manifest.OBJECT_FORMAT,
+        "logical_bytes": value["payload_bytes"],
+        "payload_bytes": value["files"][0]["bytes"],
+    }
+
+
+def test_v3_reader_and_v4_logical_permissions_survive_content_deduplication(snapshot, tmp_path):
+    old = backup_manifest.validate(snapshot)
+    new = backup_manifest.validate(object_format(snapshot))
+    assert len(backup_manifest.physical_files(old)) == 4
+    assert len(backup_manifest.physical_files(new)) == 1
+    assert backup_manifest.logical_bytes(old) == backup_manifest.logical_bytes(new)
+    assert new["payload_bytes"] * 4 == new["logical_bytes"]
+    assert new["files"][2]["mode"] != new["files"][3]["mode"]
+    for item in new["files"]:
+        assert backup_manifest.member_path(tmp_path, new, item) == (
+            tmp_path / "objects" / item["sha256"]
+        )
+        assert backup_manifest.named_member(tmp_path, old, item["path"]) == (
+            tmp_path / "payload" / item["path"]
+        )
+
+
+@pytest.mark.parametrize(
+    "field,change",
+    [
+        ("payload_bytes", 1),
+        ("logical_bytes", 1),
+        ("schema_version", True),
+        ("format", backup_manifest.FORMAT),
+    ],
+)
+def test_v4_cannot_confuse_stored_bytes_with_restored_bytes(snapshot, field, change):
+    value = object_format(snapshot)
+    value[field] = change
+    with pytest.raises(policy.DeliveryError):
+        backup_manifest.validate(value)
+
+
+def test_v4_preserves_logical_versions_above_v3_limit_without_raising_physical_limit(snapshot):
+    value = object_format(snapshot)
+    size = backup_manifest.MAX_FILE_BYTES
+    value["files"] = [
+        {**value["files"][0], "path": "releases/version-" + str(index), "bytes": size}
+        for index in range(32)
+    ] + [{**item, "bytes": size} for item in snapshot["files"][:2]]
+    value["logical_bytes"] = len(value["files"]) * size
+    value["payload_bytes"] = size
+    backup_manifest.validate(value)
+    assert value["logical_bytes"] > backup_manifest.MAX_BYTES
+    old = {
+        **value,
+        "schema_version": 3,
+        "format": backup_manifest.FORMAT,
+        "payload_bytes": value["logical_bytes"],
+    }
+    old.pop("logical_bytes")
+    with pytest.raises(policy.DeliveryError):
+        backup_manifest.validate(old)
+    # Distinct object digests still consume the unchanged physical budget.
+    for index, item in enumerate(value["files"]):
+        item["sha256"] = hashlib.sha256(str(index).encode()).hexdigest()
+    value["payload_bytes"] = value["logical_bytes"]
+    with pytest.raises(policy.DeliveryError):
+        backup_manifest.validate(value)
+
+
+def test_store_reads_each_source_but_writes_one_single_link_object(tmp_path, monkeypatch):
+    source, repeated, objects = tmp_path / "source", tmp_path / "repeated", tmp_path / "objects"
+    objects.mkdir(mode=0o700)
+    data = b"trusted source\n" * 2000
+    source.write_bytes(data)
+    repeated.write_bytes(data)
+    repeated.chmod(0o444)
+    original = backup_objects.read_stream
+    observed = []
+
+    def read(incoming, before, deadline, outgoing=None):
+        observed.append((before.st_ino, outgoing is not None))
+        return original(incoming, before, deadline, outgoing)
+
+    monkeypatch.setattr(backup_objects, "read_stream", read)
+    seen = {}
+    first, added = backup_objects.store(
+        source, source.stat(), objects, seen, time.monotonic() + 10, remaining_bytes=len(data)
+    )
+    second, repeated_bytes = backup_objects.store(
+        repeated, repeated.stat(), objects, seen, time.monotonic() + 10, remaining_bytes=0
+    )
+    assert first == second == hashlib.sha256(data).hexdigest()
+    assert (added, repeated_bytes) == (len(data), 0)
+    assert observed == [
+        (source.stat().st_ino, False),
+        (source.stat().st_ino, True),
+        (repeated.stat().st_ino, False),
+    ]
+    assert list(objects.iterdir()) == [objects / first]
+    assert (objects / first).read_bytes() == data
+    assert (objects / first).stat().st_nlink == 1
+    assert (objects / first).stat().st_mode & 0o777 == 0o600
+
+
+def test_failed_second_source_read_retains_incomplete_private_copy(tmp_path, monkeypatch):
+    source, objects = tmp_path / "source", tmp_path / "objects"
+    source.write_bytes(b"trusted fixture")
+    objects.mkdir(mode=0o700)
+    original = backup_objects.read_stream
+
+    def read(incoming, before, deadline, outgoing=None):
+        if outgoing is not None:
+            raise OSError("fixture write failure")
+        return original(incoming, before, deadline)
+
+    monkeypatch.setattr(backup_objects, "read_stream", read)
+    seen = {}
+    with pytest.raises(OSError):
+        backup_objects.store(
+            source, source.stat(), objects, seen, time.monotonic() + 10, remaining_bytes=100
+        )
+    assert seen == {}
+    assert list(objects.iterdir()) == [objects / ".pending"]
+    assert not (tmp_path / "manifest.json").exists()
+
+
+def test_restore_expands_repeated_content_into_independent_files_with_own_modes(tmp_path):
+    restore = importlib.import_module("scripts.release.restore")
+    content = tmp_path / "object"
+    data = b"trusted restoration fixture\n"
+    content.write_bytes(data)
+    row = {"bytes": len(data), "sha256": hashlib.sha256(data).hexdigest()}
+    first, second = tmp_path / "first", tmp_path / "second"
+    for path, mode in ((first, 0o600), (second, 0o444)):
+        witness = restore.write_file(
+            content, path, row, os.getuid(), os.getgid(), mode, time.monotonic() + 10
+        )
+        restore.unchanged_file(path, witness, os.getuid(), os.getgid(), mode)
+        assert path.read_bytes() == data
+        assert path.stat().st_mode & 0o777 == mode
+        assert path.stat().st_nlink == 1
+    assert len({path.stat().st_ino for path in (content, first, second)}) == 3
+
+
+def test_delayed_filesystem_write_error_is_not_success(tmp_path, monkeypatch):
+    class SyncFailure:
+        def __call__(self, descriptor):
+            assert os.fstat(descriptor).st_ino == tmp_path.stat().st_ino
+            return -1
+
+    class Library:
+        syncfs = SyncFailure()
+
+    monkeypatch.setattr(backup_objects.ctypes, "CDLL", lambda *_, **__: Library())
+    with pytest.raises(policy.DeliveryError, match="filesystem synchronization failed"):
+        backup_objects.sync_filesystem(tmp_path, time.monotonic() + 10)
+
+
+@pytest.mark.parametrize("missing", ["releases/older", "releases/older/nested"])
+def test_every_directory_ancestor_is_required_even_when_file_parent_exists(snapshot, missing):
+    value = object_format(snapshot)
+    value["directories"] = value["directories"] + [
+        {"path": path, "uid": 0, "gid": 0, "mode": 0o700}
+        for path in ("releases/older", "releases/older/nested")
+        if path != missing
+    ]
+    value["files"] = [
+        {**row, "path": "releases/older/nested/file"} if row["path"] == "releases/first" else row
+        for row in value["files"]
+    ]
+    with pytest.raises(policy.DeliveryError, match="private backup parent missing"):
+        backup_manifest.validate(value)
+
+
+def test_v4_complete_version_inventory_keeps_an_explicit_logical_entry_bound(snapshot):
+    value = object_format(snapshot)
+    count = backup_manifest.MAX_LOGICAL_ENTRIES - len(value["directories"])
+    template = {**value["files"][0], "bytes": 1, "sha256": hashlib.sha256(b"x").hexdigest()}
+    value["files"] = [{**template, "path": row["path"]} for row in value["files"][:2]] + [
+        {**template, "path": "releases/item-" + str(i)} for i in range(count - 2)
+    ]
+    value.update(logical_bytes=count, payload_bytes=1)
+    backup_manifest.validate(value)
+    assert len(value["files"]) + len(value["directories"]) == 98304
+    assert backup_manifest.MAX_BYTES == 7 * 1024**3
+    assert backup_manifest.MAX_LOGICAL_BYTES == 12 * 1024**3
+    old = {**value, "schema_version": 3, "format": backup_manifest.FORMAT, "payload_bytes": count}
+    old.pop("logical_bytes")
+    with pytest.raises(policy.DeliveryError, match="inventory count exceeds bound"):
+        backup_manifest.validate(old)
+    value["files"].append({**template, "path": "releases/one-too-many"})
+    value["logical_bytes"] += 1
+    with pytest.raises(policy.DeliveryError, match="inventory count exceeds bound"):
+        backup_manifest.validate(value)
+
+
+def test_private_metadata_rejects_a_file_above_the_explicit_byte_limit(tmp_path):
+    path = tmp_path / "metadata.json"
+    path.write_bytes(b" " * (backup_manifest.MAX_METADATA_BYTES + 1))
+    with pytest.raises(policy.DeliveryError, match="metadata byte limit"):
+        backup_manifest.read_metadata(path)

backend/tests/test_delivery_bytecode.py

@@ -0,0 +1,114 @@
+"""Ordinary owned source/cache checks; no service, isolation or recovery claims."""
+
+import importlib
+import os
+import subprocess
+import sys
+from pathlib import Path
+
+import pytest
+
+ROOT = Path(__file__).resolve().parents[2]
+sys.path.insert(0, str(ROOT))
+bytecode = importlib.import_module("scripts.release.bytecode")
+manifest = importlib.import_module("scripts.release.manifest")
+policy = importlib.import_module("scripts.release.policy")
+
+
+@pytest.fixture
+def compiled(tmp_path):
+    source = tmp_path / "site/toy.py"
+    source.parent.mkdir()
+    source.write_text("VALUE = (17, 'ordinary trusted fixture')\n")
+    source.chmod(0o444)
+    assert bytecode.compile_payload(tmp_path, "sd-" + "b" * 12) == 1
+    cache = source.parent / "__pycache__/toy.cpython-313.pyc"
+    return tmp_path, source, cache
+
+
+def test_complete_cache_inventory_and_actual_import_without_source_compilation(compiled):
+    payload, source, cache = compiled
+    records = manifest.inventory(payload)
+    assert {r["path"] for r in records} == {
+        "site/toy.py",
+        "site/__pycache__/toy.cpython-313.pyc",
+    }
+    assert all(r["mode"] == "0444" for r in records)
+    # Only this tiny trusted fixture executes. An attempted source compilation
+    # fails, so success demonstrates CPython actually consumes the checked cache.
+    code = """import builtins,sys
+sys.path.insert(0,sys.argv[1])
+def refuse(*args,**kwargs): raise AssertionError('unexpected source compilation')
+builtins.compile=refuse
+import toy
+assert toy.VALUE==(17,'ordinary trusted fixture')
+"""
+    before = {p: bytecode._stamp(p.lstat()) for p in (source, cache)}
+    result = subprocess.run(
+        [sys.executable, "-I", "-B", "-c", code, str(source.parent)],
+        capture_output=True,
+        timeout=15,
+    )
+    assert result.returncode == 0, result.stderr
+    assert {p: bytecode._stamp(p.lstat()) for p in before} == before
+
+
+def test_source_change_cannot_reuse_cache_even_with_restored_mtime(compiled):
+    payload, source, _ = compiled
+    before = source.stat()
+    source.chmod(0o600)
+    source.write_text("VALUE = (18, 'ordinary trusted fixture')\n")
+    source.chmod(0o444)
+    os.utime(source, ns=(before.st_atime_ns, before.st_mtime_ns))
+    with pytest.raises(policy.DeliveryError, match="bytecode source hash differs"):
+        manifest.inventory(payload)
+
+
+@pytest.mark.parametrize("offset,value", [(0, 0), (4, 0), (4, 1), (4, 2)])
+def test_wrong_magic_timestamp_and_unchecked_hash_caches_are_refused(compiled, offset, value):
+    payload, _, cache = compiled
+    data = bytearray(cache.read_bytes())
+    data[offset] = value
+    cache.chmod(0o600)
+    cache.write_bytes(data)
+    cache.chmod(0o444)
+    with pytest.raises(policy.DeliveryError, match="only pinned checked-hash"):
+        manifest.inventory(payload)
+
+
+def test_builder_refuses_inherited_cache_and_does_not_write_to_external_prefix(
+    compiled, monkeypatch
+):
+    payload, _, cache = compiled
+    before = cache.read_bytes()
+    monkeypatch.setattr(sys, "pycache_prefix", str(payload / "outside"))
+    with pytest.raises(policy.DeliveryError, match="inherited bytecode cache"):
+        bytecode.compile_payload(payload, "sd-" + "b" * 12)
+    assert cache.read_bytes() == before and not (payload / "outside").exists()
+
+
+@pytest.mark.parametrize(
+    "name",
+    [
+        "site/toy.pyc",
+        "site/__pycache__/toy.cpython-314.pyc",
+        "site/__pycache__/toy.cpython-313.opt-1.pyc",
+        "site/__pycache__/toy.py",
+        "site/__pycache__/nested/__pycache__/toy.cpython-313.pyc",
+        "site/../__pycache__/toy.cpython-313.pyc",
+        "images/python313/__pycache__/toy.cpython-313.pyc",
+        "frontend/__pycache__/toy.cpython-313.pyc",
+    ],
+)
+def test_cache_allowlist_keeps_wrong_versions_domains_and_paths_closed(name):
+    with pytest.raises(policy.DeliveryError):
+        policy.relative_name(name)
+
+
+@pytest.mark.parametrize("prefix", policy.BYTECODE_ROOTS)
+def test_only_source_adjacent_pinned_cache_paths_are_allowed(prefix):
+    name = prefix + "package/__pycache__/toy.cpython-313.pyc"
+    assert policy.relative_name(name) == name
+    assert policy.bytecode_source(name) == prefix + "package/toy.py"
+    directory = prefix + "package/__pycache__/.__directory__"
+    assert policy.relative_name(directory) == directory

backend/tests/test_delivery_proxy_startup.py

@@ -0,0 +1,140 @@
+"""Ordinary modeled lifecycle checks; actual HTTPS and service gates require the VM."""
+
+import importlib
+import ssl
+import sys
+from pathlib import Path
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).resolve().parents[2]))
+lifecycle = importlib.import_module("scripts.release.lifecycle")
+proxy_health = importlib.import_module("scripts.release.proxy_health")
+DeliveryError = importlib.import_module("scripts.release.policy").DeliveryError
+READY = {
+    "reachable": True,
+    "pinned_certificate_and_hostname_verified": True,
+    "public_browser_trust_verified": False,
+}
+
+
+def setup_maintenance(monkeypatch, *, active=False):
+    maintenance = object.__new__(lifecycle.Maintenance)
+    maintenance.selected = {"release_id": "sd-123456789abc", "configuration_id": "cfg-" + "1" * 24}
+    maintenance.record = {"events": []}
+    clock = [100.0]
+    state = {"active": active}
+    saves = []
+    monkeypatch.setattr(lifecycle.time, "monotonic", lambda: clock[0])
+    monkeypatch.setattr(
+        lifecycle.time, "sleep", lambda value: clock.__setitem__(0, clock[0] + value)
+    )
+    monkeypatch.setattr(lifecycle.install, "selection", lambda **_: maintenance.selected.copy())
+    monkeypatch.setattr(lifecycle.node_health, "inspect_unit", lambda *_: None)
+    monkeypatch.setattr(lifecycle.proxy_install, "check_binding", lambda *_: None)
+    monkeypatch.setattr(
+        maintenance,
+        "unit",
+        lambda _: {
+            "ActiveState": "active" if state["active"] else "inactive",
+            "SubState": "running",
+            "MainPID": "42" if state["active"] else "0",
+        },
+    )
+    monkeypatch.setattr(
+        maintenance,
+        "save",
+        lambda phase: saves.append((phase, [x.copy() for x in maintenance.record["events"]])),
+    )
+
+    def systemctl(*args):
+        assert args == ("--no-block", "start", "kf-proxy.service")
+        state["active"] = True
+        return ""
+
+    monkeypatch.setattr(lifecycle.service_install, "systemctl", systemctl)
+    return maintenance, clock, saves
+
+
+@pytest.mark.parametrize(
+    "group,active", [(True, False), (False, False), (True, True), (False, True)]
+)
+def test_proxy_process_is_not_confirmed_until_actual_https_probe_succeeds(
+    monkeypatch, group, active
+):
+    maintenance, clock, saves = setup_maintenance(monkeypatch, active=active)
+    probes = []
+
+    def probe(selected, *, timeout):
+        assert all(not x["confirmed"] for x in maintenance.record["events"])
+        probes.append(timeout)
+        if len(probes) == 1:
+            raise proxy_health.HTTPSNotReady("launcher has not served HTTPS yet")
+        return READY.copy()
+
+    monkeypatch.setattr(proxy_health, "observe", probe)
+    if group:
+        maintenance.start_group(("proxy",))
+    else:
+        maintenance.change("proxy", "start")
+    assert probes == [5.0, 5.0] and clock[0] == 100.5
+    if not active:
+        assert saves[0][1][0]["confirmed"] is False
+        assert saves[-1][1][0]["confirmed"] is True
+
+
+@pytest.mark.parametrize(
+    "error", [ssl.SSLCertVerificationError("bad certificate"), DeliveryError("changed TLS binding")]
+)
+def test_proxy_security_failure_is_fatal_without_wait_or_confirmation(monkeypatch, error):
+    maintenance, clock, _ = setup_maintenance(monkeypatch)
+    calls = []
+
+    def probe(*_, **__):
+        calls.append(1)
+        raise error
+
+    monkeypatch.setattr(proxy_health, "observe", probe)
+    with pytest.raises(type(error)):
+        maintenance.start_group(("proxy",))
+    assert calls == [1] and clock[0] == 100
+    assert maintenance.record["events"] == [
+        {"unit": "proxy", "operation": "start", "confirmed": False}
+    ]
+
+
+@pytest.mark.parametrize("late_ready", [False, True])
+def test_proxy_wait_cannot_restart_or_succeed_after_original_deadline(monkeypatch, late_ready):
+    maintenance, clock, _ = setup_maintenance(monkeypatch)
+    probes = []
+
+    def unavailable(*_, timeout):
+        probes.append(timeout)
+        clock[0] += 131
+        if late_ready:
+            return READY.copy()
+        raise proxy_health.HTTPSNotReady("still unavailable")
+
+    monkeypatch.setattr(proxy_health, "observe", unavailable)
+    with pytest.raises(DeliveryError, match="bounded HTTPS startup unconfirmed"):
+        maintenance.start_group(("proxy",))
+    assert probes == [5.0]
+    assert maintenance.record["events"][0]["confirmed"] is False
+
+
+@pytest.mark.parametrize(
+    "error", [ConnectionRefusedError("not listening"), TimeoutError("not ready")]
+)
+def test_proxy_probe_labels_only_transient_transport_failure(monkeypatch, error):
+    def unavailable(*_, **__):
+        raise error
+
+    monkeypatch.setattr(proxy_health, "_observe", unavailable)
+    with pytest.raises(proxy_health.HTTPSNotReady):
+        proxy_health.observe({})
+
+
+@pytest.mark.parametrize("timeout", [0, -1, 5.01, True, float("nan")])
+def test_proxy_probe_rejects_unbounded_timeout(timeout):
+    with pytest.raises(DeliveryError, match="timeout exceeds bound"):
+        proxy_health.observe({}, timeout=timeout)

backend/tests/test_delivery_restore_io.py

@@ -0,0 +1,537 @@
+"""Trusted ordinary byte fixtures; real Root/cgroup/syncfs/RTO remains VM-only."""
+
+import errno
+import hashlib
+import multiprocessing
+import os
+import stat
+import time
+from contextlib import closing
+from pathlib import Path
+from types import SimpleNamespace
+
+import pytest
+from scripts.release import restore, restore_io
+from scripts.release.policy import DeliveryError
+
+
+def fixture_rows(tmp_path, contents):
+    source = tmp_path / "source"
+    target = tmp_path / "target"
+    source.mkdir()
+    target.mkdir()
+    rows = []
+    for index, raw in enumerate(contents):
+        digest = hashlib.sha256(raw).hexdigest()
+        path = source / digest
+        if not path.exists():
+            path.write_bytes(raw)
+        rows.append({"path": str(index), "bytes": len(raw), "sha256": digest})
+    return (
+        rows,
+        lambda row: source / row["sha256"],
+        lambda row: (
+            target / row["path"],
+            os.getuid(),
+            os.getgid(),
+            0o600 if int(row["path"]) % 2 else 0o400,
+        ),
+    )
+
+
+def filesystem_model(monkeypatch, target, events, callback=None):
+    """Model syncfs using only tiny owned fixture fsyncs; never host syncfs."""
+
+    class Sync:
+        def __call__(self, descriptor):
+            assert stat.S_ISDIR(os.fstat(descriptor).st_mode)
+            if callback is not None:
+                callback()
+            files = [p for p in target.iterdir() if p.is_file()]
+            for path in files:
+                with path.open("rb") as stream:
+                    os.fsync(stream.fileno())
+            events.append(("sync", descriptor))
+            return 0
+
+    monkeypatch.setattr(
+        restore_io.ctypes, "CDLL", lambda *_a, **_kw: SimpleNamespace(syncfs=Sync())
+    )
+    return restore_io.Filesystems([target], time.monotonic() + 120)
+
+
+def assert_closed(descriptors):
+    for descriptor in descriptors:
+        with pytest.raises(OSError) as failure:
+            os.fstat(descriptor)
+        assert failure.value.errno == errno.EBADF
+
+
+class ReadAfterSync:
+    """Picklable observation of actual tiny fixture reads in the child processes."""
+
+    def __init__(self, synced, reads, descriptors):
+        self.synced, self.reads, self.descriptors = synced, reads, descriptors
+
+    def __call__(self, path, item, uid, gid, mode, deadline):
+        assert self.synced.read_bytes() == b"sync completed"
+        assert all(os.fstat(fd).st_ino > 0 for fd in self.descriptors)
+        (self.reads / item["path"]).touch()
+        return restore.readback(path, item, uid, gid, mode, deadline)
+
+
+def test_bounded_batches_group_identical_objects_without_losing_paths():
+    rows = [
+        {"path": str(index), "sha256": str(index % 2), "bytes": 1}
+        for index in range(restore_io.BATCH_FILES + 4)
+    ]
+    rows.append({"path": "large", "sha256": "2", "bytes": restore_io.BATCH_BYTES + 1})
+    groups = list(restore_io.batches(rows))
+    flattened = [row for group in groups for row in group]
+    assert {row["path"] for row in flattened} == {row["path"] for row in rows}
+    assert len(flattened) == len(rows)
+    assert [row["sha256"] for row in flattened] == sorted(row["sha256"] for row in rows)
+    assert all(len(group) <= restore_io.BATCH_FILES for group in groups)
+    assert all(
+        sum(row["bytes"] for row in group) <= restore_io.BATCH_BYTES or len(group) == 1
+        for group in groups
+    )
+
+
+def test_repeated_objects_expand_to_independent_durable_verified_destinations(
+    tmp_path, monkeypatch
+):
+    rows, source, destination = fixture_rows(tmp_path, [b"first", b"other", b"first", b"first"])
+    events = []
+    target = destination(rows[0])[0].parent
+    synced, reads = tmp_path / "synced", tmp_path / "reads"
+    reads.mkdir()
+    with closing(filesystem_model(monkeypatch, target, events)) as filesystems:
+        descriptors = [descriptor for _, descriptor, _ in filesystems.handles.values()]
+        assert list(target.iterdir()) == []
+
+        original_sync = filesystems.sync
+
+        def sync(deadline):
+            original_sync(deadline)
+            synced.write_bytes(b"sync completed")
+
+        monkeypatch.setattr(filesystems, "sync", sync)
+
+        verified = restore_io.materialize(
+            rows,
+            source,
+            destination,
+            ReadAfterSync(synced, reads, descriptors),
+            filesystems,
+            time.monotonic() + 120,
+        )
+    assert_closed(descriptors)
+    assert set(verified) == {row["path"] for row in rows}
+    assert len(list(reads.iterdir())) == len(rows)
+    inodes = set()
+    for row in rows:
+        path, uid, gid, mode = destination(row)
+        assert path.read_bytes() == source(row).read_bytes()
+        assert stat.S_IMODE(path.stat().st_mode) == mode
+        assert path.stat().st_nlink == 1
+        inodes.add(path.stat().st_ino)
+        restore.unchanged_file(path, verified[row["path"]], uid, gid, mode)
+    assert len(inodes) == len(rows)
+
+
+def test_existing_wrong_bytes_are_refused_without_overwrite(tmp_path, monkeypatch):
+    prior_children = {child.pid for child in multiprocessing.active_children()}
+    rows, source, destination = fixture_rows(tmp_path, [b"new"])
+    path, _, _, mode = destination(rows[0])
+    path.write_bytes(b"bad")
+    path.chmod(mode)
+    before = restore.file_witness(path.stat())
+    with closing(filesystem_model(monkeypatch, path.parent, [])) as filesystems:
+        with pytest.raises(DeliveryError, match="byte verification"):
+            restore_io.materialize(
+                rows,
+                source,
+                destination,
+                restore.readback,
+                filesystems,
+                time.monotonic() + 120,
+            )
+    assert path.read_bytes() == b"bad" and restore.file_witness(path.stat()) == before
+    assert {child.pid for child in multiprocessing.active_children()} == prior_children
+
+
+def test_failed_sync_keeps_private_files_and_cannot_return_verified_witnesses(
+    tmp_path, monkeypatch
+):
+    rows, source, destination = fixture_rows(tmp_path, [b"a", b"b", b"c"])
+    reads = []
+
+    def failed_sync():
+        raise DeliveryError("synthetic synchronization failure")
+
+    with closing(
+        filesystem_model(monkeypatch, destination(rows[0])[0].parent, [], failed_sync)
+    ) as filesystems:
+        descriptors = [fd for _, fd, _ in filesystems.handles.values()]
+        with pytest.raises(DeliveryError, match="synthetic synchronization failure"):
+            restore_io.materialize(
+                rows,
+                source,
+                destination,
+                lambda *args: reads.append(args),
+                filesystems,
+                time.monotonic() + 120,
+            )
+    assert_closed(descriptors)
+    assert reads == []
+    assert all(destination(row)[0].is_file() for row in rows)
+
+
+def test_same_bytes_inode_replacement_across_sync_cannot_adopt_new_file(tmp_path, monkeypatch):
+    rows, source, destination = fixture_rows(tmp_path, [b"same"])
+
+    def replace_inode():
+        path, _, _, mode = destination(rows[0])
+        replacement = path.parent / "replacement"
+        replacement.write_bytes(path.read_bytes())
+        replacement.chmod(mode)
+        replacement.replace(path)
+
+    with closing(
+        filesystem_model(monkeypatch, destination(rows[0])[0].parent, [], replace_inode)
+    ) as filesystems:
+        with pytest.raises(DeliveryError, match="changed across synchronization"):
+            restore_io.materialize(
+                rows,
+                source,
+                destination,
+                restore.readback,
+                filesystems,
+                time.monotonic() + 120,
+            )
+
+
+def test_expired_batch_deadline_copies_no_files(tmp_path, monkeypatch):
+    rows, source, destination = fixture_rows(tmp_path, [b"data"])
+    with closing(filesystem_model(monkeypatch, destination(rows[0])[0].parent, [])) as filesystems:
+        with pytest.raises(DeliveryError, match="deadline exceeded"):
+            restore_io.materialize(
+                rows,
+                source,
+                destination,
+                restore.readback,
+                filesystems,
+                time.monotonic() - 1,
+            )
+    assert not destination(rows[0])[0].exists()
+
+
+def test_syncfs_failure_is_propagated_in_the_ordinary_syscall_model(tmp_path, monkeypatch):
+    class FailedSync:
+        def __call__(self, _descriptor):
+            return -1
+
+    monkeypatch.setattr(
+        restore_io.ctypes,
+        "CDLL",
+        lambda *_a, **_kw: SimpleNamespace(syncfs=FailedSync()),
+    )
+    with closing(restore_io.Filesystems([tmp_path], time.monotonic() + 120)) as filesystems:
+        descriptors = [fd for _, fd, _ in filesystems.handles.values()]
+        with pytest.raises(DeliveryError, match="filesystem synchronization failed"):
+            filesystems.sync(time.monotonic() + 120)
+    assert_closed(descriptors)
+
+
+def test_cursor_is_open_before_first_write_and_held_across_batches(tmp_path, monkeypatch):
+    rows, source, destination = fixture_rows(tmp_path, [b"a", b"b", b"c", b"d", b"e"])
+    target = destination(rows[0])[0].parent
+    monkeypatch.setattr(restore_io, "BATCH_FILES", 2)
+    events = []
+    with closing(filesystem_model(monkeypatch, target, events)) as filesystems:
+        descriptors = [fd for _, fd, _ in filesystems.handles.values()]
+        before = {fd: (os.fstat(fd).st_dev, os.fstat(fd).st_ino) for fd in descriptors}
+        real_write = restore_io.pending_file
+
+        def write(*args):
+            assert {fd: (os.fstat(fd).st_dev, os.fstat(fd).st_ino) for fd in descriptors} == before
+            return real_write(*args)
+
+        monkeypatch.setattr(restore_io, "pending_file", write)
+        verified = restore_io.materialize(
+            rows,
+            source,
+            destination,
+            restore.readback,
+            filesystems,
+            time.monotonic() + 120,
+        )
+        assert len(verified) == len(rows)
+        assert len(events) == 3
+        assert {fd for event, fd in events if event == "sync"} == set(descriptors)
+    assert_closed(descriptors)
+
+
+def test_cursor_can_anchor_before_target_directories_exist(tmp_path, monkeypatch):
+    target = tmp_path / "later" / "nested"
+
+    class Sync:
+        def __call__(self, descriptor):
+            assert os.fstat(descriptor).st_ino == tmp_path.stat().st_ino
+            return 0
+
+    monkeypatch.setattr(
+        restore_io.ctypes, "CDLL", lambda *_a, **_kw: SimpleNamespace(syncfs=Sync())
+    )
+    with closing(restore_io.Filesystems([target], time.monotonic() + 120)) as filesystems:
+        target.mkdir(parents=True)
+        filesystems.contains(target / "file")
+        filesystems.sync(time.monotonic() + 120)
+
+
+def test_constructor_closes_earlier_cursor_when_later_anchor_is_invalid(tmp_path, monkeypatch):
+    valid, invalid = tmp_path / "valid", tmp_path / "invalid"
+    valid.mkdir()
+    invalid.write_bytes(b"ordinary owned fixture")
+    opened = []
+    real_open = restore_io.os.open
+
+    def record_open(*args, **kwargs):
+        descriptor = real_open(*args, **kwargs)
+        opened.append(descriptor)
+        return descriptor
+
+    monkeypatch.setattr(restore_io.os, "open", record_open)
+    with pytest.raises(DeliveryError, match="anchor differs"):
+        restore_io.Filesystems([valid, invalid], time.monotonic() + 120)
+    assert len(opened) == 1
+    assert_closed(opened)
+
+
+def test_actual_two_copy_processes_join_before_return_and_preserve_all_bytes(tmp_path, monkeypatch):
+    rows, source, destination = fixture_rows(
+        tmp_path, [b"known first", b"known second", b"known third", b"known fourth"]
+    )
+    prior_children = {child.pid for child in multiprocessing.active_children()}
+    markers = tmp_path / "worker-identities"
+    markers.mkdir()
+    original = restore_io.pending_file
+
+    def record_worker(*args):
+        (markers / str(os.getpid())).touch()
+        deadline = time.monotonic() + 5
+        while len(list(markers.iterdir())) < 2:
+            assert time.monotonic() < deadline
+            time.sleep(0.01)
+        return original(*args)
+
+    monkeypatch.setattr(restore_io, "pending_file", record_worker)
+    with closing(filesystem_model(monkeypatch, destination(rows[0])[0].parent, [])) as fs:
+        verified = restore_io.materialize(
+            rows, source, destination, restore.readback, fs, time.monotonic() + 120
+        )
+    assert len(list(markers.iterdir())) == 2
+    assert {child.pid for child in multiprocessing.active_children()} == prior_children
+    assert all(not (restore_io.Path("/proc") / p.name).exists() for p in markers.iterdir())
+    assert set(verified) == {row["path"] for row in rows}
+    for row in rows:
+        path, uid, gid, mode = destination(row)
+        assert path.read_bytes() == source(row).read_bytes()
+        restore.unchanged_file(path, verified[row["path"]], uid, gid, mode)
+
+
+def test_process_copy_refuses_fork_from_a_multithreaded_owner(tmp_path, monkeypatch):
+    rows, source, destination = fixture_rows(tmp_path, [b"known fixture"])
+    monkeypatch.setattr(restore_io.threading, "active_count", lambda: 2)
+    with closing(filesystem_model(monkeypatch, destination(rows[0])[0].parent, [])) as fs:
+        with pytest.raises(DeliveryError, match="one POSIX owner thread"):
+            restore_io.materialize(
+                rows, source, destination, restore.readback, fs, time.monotonic() + 120
+            )
+    assert not destination(rows[0])[0].exists()
+
+
+def group_files(tmp_path, values, expected=None):
+    rows = []
+    for i, raw in enumerate(values):
+        path = tmp_path / str(i)
+        path.write_bytes(raw)
+        path.chmod(0o600)
+        wanted = raw if expected is None else expected[i]
+        item = {
+            "path": str(i),
+            "bytes": len(wanted),
+            "sha256": hashlib.sha256(wanted).hexdigest(),
+        }
+        rows.append(
+            (
+                item,
+                path,
+                os.getuid(),
+                os.getgid(),
+                0o600,
+                restore.file_witness(path.stat()),
+            )
+        )
+    return rows
+
+
+def read_group(group):
+    return restore.readback_group(group, time.monotonic() + 120)
+
+
+def test_each_repeated_destination_is_fully_read_with_one_actual_reference_hash(
+    tmp_path, monkeypatch
+):
+    raw = b"a" * 1048576 + b"b" * 1048576 + b"last-byte-proof"
+    group = group_files(tmp_path, [raw] * 4)
+    original_open, original_hash = os.fdopen, hashlib.sha256
+    observed, hashes = {}, []
+
+    class Reader:
+        def __init__(self, stream, path):
+            self.stream, self.path = stream, path
+
+        def __enter__(self):
+            return self
+
+        def __exit__(self, *args):
+            return self.stream.__exit__(*args)
+
+        def fileno(self):
+            return self.stream.fileno()
+
+        def read(self, count):
+            assert count == 1048576
+            block = self.stream.read(count)
+            observed[self.path] = observed.get(self.path, 0) + len(block)
+            return block
+
+    def opened(fd, mode):
+        return Reader(original_open(fd, mode), Path(os.readlink(f"/proc/self/fd/{fd}")))
+
+    def hashed(*args, **kwargs):
+        hashes.append(True)
+        return original_hash(*args, **kwargs)
+
+    monkeypatch.setattr(restore.os, "fdopen", opened)
+    monkeypatch.setattr(restore.hashlib, "sha256", hashed)
+    witnesses = read_group(group)
+    assert observed == {row[1]: len(raw) for row in group}
+    assert len(hashes) == 1
+    assert witnesses == [row[-1] for row in group]
+
+
+def test_last_byte_difference_in_repeated_target_is_refused(tmp_path):
+    good = b"x" * 1048576 + b"ending"
+    bad = good[:-1] + b"!"
+    group = group_files(tmp_path, [good, bad, good], [good] * 3)
+    with pytest.raises(DeliveryError, match="byte verification"):
+        read_group(group)
+    assert group[1][1].read_bytes() == bad
+
+
+def test_identically_wrong_reference_and_duplicates_cannot_match_expected_digest(
+    tmp_path,
+):
+    group = group_files(tmp_path, [b"bad"] * 3, [b"new"] * 3)
+    with pytest.raises(DeliveryError, match="byte verification"):
+        read_group(group)
+
+
+def test_unique_large_and_empty_files_keep_exact_bytes(tmp_path):
+    values = [b"", b"", b"one", b"other", b"z" * (8 * 1024**2 + 1)]
+    group = group_files(tmp_path, values)
+    assert read_group(group) == [row[-1] for row in group]
+
+
+def test_reference_is_rebound_when_digest_changes(tmp_path):
+    group = group_files(tmp_path, [b"aa", b"aa", b"bb", b"bb", b"aa", b"aa"])
+    assert read_group(group) == [row[-1] for row in group]
+
+
+def test_changed_file_after_complete_read_is_refused(tmp_path, monkeypatch):
+    group = group_files(tmp_path, [b"known", b"known"])
+    original = os.fdopen
+
+    class ChangedAtEnd:
+        def __init__(self, stream):
+            self.stream = stream
+
+        def __enter__(self):
+            return self
+
+        def __exit__(self, *args):
+            return self.stream.__exit__(*args)
+
+        def fileno(self):
+            return self.stream.fileno()
+
+        def read(self, count):
+            value = self.stream.read(count)
+            if not value:
+                group[0][1].write_bytes(b"other")
+            return value
+
+    monkeypatch.setattr(restore.os, "fdopen", lambda *a, **kw: ChangedAtEnd(original(*a, **kw)))
+    with pytest.raises(DeliveryError, match="changed during readback"):
+        read_group(group)
+
+
+def test_group_rejects_metadata_bounds_and_expired_deadline(tmp_path):
+    group = group_files(tmp_path, [b"known"])
+    with pytest.raises(DeliveryError, match="fixed batch bounds"):
+        read_group(group * (restore_io.BATCH_FILES + 1))
+    with pytest.raises(DeliveryError, match="deadline"):
+        restore.readback_group(group, time.monotonic() - 1)
+
+
+def test_grouped_real_copy_workers_join_and_return_independent_verified_files(
+    tmp_path, monkeypatch
+):
+    children = {c.pid for c in multiprocessing.active_children()}
+    rows, source, destination = fixture_rows(tmp_path, [b"shared"] * 8)
+    with closing(filesystem_model(monkeypatch, destination(rows[0])[0].parent, [])) as filesystems:
+        result = restore_io.materialize(
+            rows,
+            source,
+            destination,
+            restore.readback,
+            filesystems,
+            time.monotonic() + 120,
+            group_readback=restore.readback_group,
+        )
+    assert {c.pid for c in multiprocessing.active_children()} == children
+    assert set(result) == {row["path"] for row in rows}
+    assert len({destination(row)[0].stat().st_ino for row in rows}) == len(rows)
+    for row in rows:
+        path, uid, gid, mode = destination(row)
+        assert path.read_bytes() == b"shared"
+        restore.unchanged_file(path, result[row["path"]], uid, gid, mode)
+
+
+@pytest.mark.parametrize(
+    "name", ["releases/../private", "factory//requests", "unknown/file", "releases/.ssh/key"]
+)
+def test_untrusted_restore_target_names_still_require_complete_validation(tmp_path, name):
+    record = {"path": name, "uid": 0, "gid": 0, "mode": 0o600, "bytes": 0}
+    with pytest.raises(DeliveryError, match="private backup member"):
+        restore.target(record, tmp_path)
+
+
+def test_pending_copy_refuses_a_dangling_symlink_without_creating_its_target(tmp_path):
+    source = tmp_path / "source"
+    source.write_bytes(b"trusted bytes")
+    target = tmp_path / "target"
+    missing = tmp_path / "missing"
+    target.symlink_to(missing)
+    item = {
+        "bytes": source.stat().st_size,
+        "sha256": hashlib.sha256(source.read_bytes()).hexdigest(),
+    }
+    with pytest.raises(DeliveryError, match="existing recovery destination differs"):
+        restore_io.pending_file(
+            source, target, item, os.getuid(), os.getgid(), 0o600, time.monotonic() + 10
+        )
+    assert target.is_symlink() and not missing.exists()

backend/tests/test_delivery_validation_work.py

@@ -0,0 +1,255 @@
+"""Ordinary string/worker models, not Root, durability or recovery acceptance."""
+
+import importlib
+import random
+import re
+import sys
+import threading
+import time
+from collections.abc import Sequence
+from pathlib import Path
+from types import SimpleNamespace
+
+import pytest
+
+ROOT = Path(__file__).resolve().parents[2]
+sys.path.insert(0, str(ROOT))
+policy = importlib.import_module("scripts.release.policy")
+file_copy = importlib.import_module("scripts.release.file_copy")
+
+
+def old_path_result(value):
+    """Frozen pre-optimization lexical policy, independent of the new cache."""
+    if not isinstance(value, str) or len(value) > 512:
+        return "invalid payload path"
+    if not all(re.fullmatch(r"[A-Za-z0-9_.+@-]{1,255}", p) for p in value.split("/")):
+        return "noncanonical payload path"
+    if any(
+        p in {".", "..", ".git", ".localplan", "docs", "__pycache__", ".env", ".ssh"}
+        for p in value.split("/")
+    ):
+        return "private or unsafe payload path"
+    if not value.startswith(policy.ROOTS) or value.endswith((".pyc", ".pyo")):
+        return "payload path outside delivery allowlist"
+    return None
+
+
+def test_lexical_policy_preserves_boundaries_and_refusal_categories():
+    values = [None, True, 1, [], {}, b"backend/a", ""]
+    components = [
+        ".",
+        "..",
+        ".git",
+        ".localplan",
+        "docs",
+        "__pycache__",
+        ".env",
+        ".ssh",
+        "a//b",
+        "a/",
+        "a.pyc",
+        "a.pyo",
+        "a\x00b",
+        "a\nb",
+        "é",
+        "a" * 255,
+        "a" * 256,
+        "a" * 250 + "/" + "b" * 250,
+        "a" * 250 + "/" + "b" * 254,
+    ]
+    values.extend("backend/" + component for component in components)
+    rng = random.Random(20261028)
+    for _ in range(3000):
+        value = "".join(rng.choices("abcXYZ019_.+@-/ \\:\n\x00é", k=rng.randrange(90)))
+        values.append(rng.choice(["backend/", "images/gnu/", "site/x/", ""]) + value)
+    for value in values:
+        refused = old_path_result(value)
+        if refused is None:
+            assert policy.relative_name(value) == value
+        else:
+            with pytest.raises(policy.DeliveryError) as observed:
+                policy.relative_name(value)
+            assert str(observed.value) == refused
+
+
+def test_lexical_cache_is_bounded_and_custom_hash_cannot_bypass_policy():
+    class Collision(str):
+        def __hash__(self):
+            return hash("backend/valid.py")
+
+        def __eq__(self, other):
+            return True
+
+    policy._cached_relative_name.cache_clear()
+    try:
+        policy.relative_name("backend/valid.py")
+        before = policy._cached_relative_name.cache_info()
+        with pytest.raises(policy.DeliveryError, match="private or unsafe"):
+            policy.relative_name(Collision("backend/../escape"))
+        assert policy._cached_relative_name.cache_info() == before
+        for index in range(20000):
+            policy.relative_name("backend/member-" + str(index))
+        assert policy._cached_relative_name.cache_info().currsize == 16384
+    finally:
+        policy._cached_relative_name.cache_clear()
+
+
+def test_deadline_stops_dispatch_but_waits_for_running_operations():
+    started = threading.Barrier(5)
+    release = threading.Event()
+    finished = threading.Event()
+    active = set()
+    errors = []
+    lock = threading.Lock()
+
+    def operation(index):
+        with lock:
+            active.add(index)
+        try:
+            started.wait(timeout=5)
+            assert release.wait(5)
+            return index
+        finally:
+            with lock:
+                active.remove(index)
+
+    def collect():
+        try:
+            file_copy.bounded_copies(list(range(32)), operation, deadline=time.monotonic() + 0.2)
+        except BaseException as error:
+            errors.append(error)
+        finally:
+            finished.set()
+
+    collector = threading.Thread(target=collect)
+    collector.start()
+    try:
+        started.wait(timeout=5)
+        assert not finished.wait(0.3)
+        with lock:
+            assert active == {0, 1, 2, 3}
+    finally:
+        release.set()
+        collector.join(5)
+    assert not collector.is_alive() and not active
+    assert len(errors) == 1 and isinstance(errors[0], policy.DeliveryError)
+    assert "copy deadline exceeded" in str(errors[0])
+
+
+def test_single_operation_cannot_publish_after_its_deadline(monkeypatch):
+    current = [10.0]
+    monkeypatch.setattr(file_copy, "time", SimpleNamespace(monotonic=lambda: current[0]))
+    calls = []
+
+    def operation(index):
+        calls.append(index)
+        current[0] = 12.0
+        return "completed after deadline"
+
+    with pytest.raises(policy.DeliveryError, match="copy deadline exceeded"):
+        file_copy.bounded_copies([0], operation, deadline=11.0)
+    assert calls == [0]
+
+
+def test_iterator_failure_joins_in_flight_work_without_dispatching_rest():
+    started, release, finished = (threading.Event() for _ in range(3))
+    calls, errors = [], []
+
+    class Broken(Sequence):
+        def __len__(self):
+            return 32
+
+        def __getitem__(self, index):
+            if index == 0:
+                return index
+            assert started.wait(5)
+            raise ValueError("finite inventory refusal")
+
+    def operation(index):
+        calls.append(index)
+        started.set()
+        assert release.wait(5)
+        return index
+
+    def collect():
+        try:
+            file_copy.bounded_copies(Broken(), operation)
+        except BaseException as error:
+            errors.append(error)
+        finally:
+            finished.set()
+
+    collector = threading.Thread(target=collect)
+    collector.start()
+    try:
+        assert started.wait(5)
+        assert not finished.wait(0.05)
+    finally:
+        release.set()
+        collector.join(5)
+    assert not collector.is_alive() and calls == [0]
+    assert len(errors) == 1 and str(errors[0]) == "finite inventory refusal"
+
+
+def test_readiness_projection_ports_overlap_with_at_most_two_workers(monkeypatch):
+    """Live ordinary threads over modeled ports, not systemd or VM acceptance."""
+    node_health = importlib.import_module("scripts.release.node_health")
+    lock = threading.Lock()
+    barrier = threading.Barrier(2, timeout=10)
+    active = 0
+    peak = 0
+    started = []
+    finished = []
+    payload = Path("/ordinary-readiness-port-model")
+
+    def query(name, actual_payload):
+        nonlocal active, peak
+        assert actual_payload == payload
+        with lock:
+            active += 1
+            peak = max(peak, active)
+            started.append(name)
+        try:
+            barrier.wait()
+            return {"component": name}
+        finally:
+            with lock:
+                active -= 1
+                finished.append(name)
+
+    monkeypatch.setattr(node_health.operator_units, "run", query)
+    with node_health._status_helpers(payload) as pending:
+        results = {name: future.result(timeout=15) for name, future in pending.items()}
+    names = {"broker-health", "outbox-health", "import-health", "factory-health"}
+    assert peak == 2 and active == 0
+    assert set(started) == set(finished) == set(results) == names
+    assert len(started) == len(finished) == 4
+    assert all(results[name] == {"component": name} for name in names)
+    assert all(future.done() for future in pending.values())
+
+
+def test_readiness_projection_failure_keeps_error_and_joins_all_workers(monkeypatch):
+    """A consumer error cannot abandon a dispatched ordinary helper model."""
+    node_health = importlib.import_module("scripts.release.node_health")
+    lock = threading.Lock()
+    barrier = threading.Barrier(2, timeout=10)
+    finished = []
+
+    def query(name, payload):
+        try:
+            barrier.wait()
+            if name == "broker-health":
+                raise policy.DeliveryError("bounded helper refused")
+            return {"component": name}
+        finally:
+            with lock:
+                finished.append(name)
+
+    monkeypatch.setattr(node_health.operator_units, "run", query)
+    with pytest.raises(RuntimeError, match="consumer refused observation"):
+        with node_health._status_helpers(Path("/ordinary-readiness-port-model")) as pending:
+            raise RuntimeError("consumer refused observation")
+    assert len(finished) == 4 and set(finished) == set(pending)
+    assert all(future.done() for future in pending.values())
+    with pytest.raises(policy.DeliveryError, match="bounded helper refused"):
+        pending["broker-health"].result()

backend/tests/test_dependency_errors.py

@@ -0,0 +1,58 @@
+"""Ordinary exception-boundary checks; real dependency failure is VM-only."""
+
+import asyncio
+import errno
+
+import httpx
+import pytest
+from asyncpg import CannotConnectNowError
+from sqlalchemy.exc import OperationalError, ProgrammingError
+from sqlalchemy.exc import TimeoutError as PoolTimeoutError
+
+from kf_oj.api.app import create_app
+from kf_oj.core.settings import Settings
+
+
+@pytest.mark.parametrize(
+    "error,expected",
+    [
+        (ConnectionRefusedError("private_connection_text"), 503),
+        (TimeoutError("private_timeout_text"), 503),
+        (CannotConnectNowError("private_database_text"), 503),
+        (PoolTimeoutError("private_pool_text"), 503),
+        (
+            OperationalError(
+                "private_query", {"secret": "private_value"}, RuntimeError("private_driver")
+            ),
+            503,
+        ),
+        (OSError(errno.ENOSPC, "private_source_path"), 503),
+        (OSError(errno.EDQUOT, "private_quota_path"), 503),
+        (FileNotFoundError(errno.ENOENT, "private_missing_path"), 500),
+    ],
+)
+def test_dependency_boundary_preserves_status_without_exception_text(error, expected):
+    app = create_app(Settings(_env_file=None, environment="test"))
+
+    @app.get("/api/v1/auth/boundary-test")
+    async def fail():
+        raise error
+
+    async def request():
+        async with httpx.AsyncClient(
+            transport=httpx.ASGITransport(app=app), base_url="http://test"
+        ) as client:
+            response = await client.get("/api/v1/auth/boundary-test")
+            assert response.status_code == expected
+            assert "private_" not in response.text
+            assert response.headers["cache-control"] == "no-store"
+            if expected == 503:
+                assert response.headers["retry-after"] == "5"
+
+    asyncio.run(request())
+
+
+def test_programming_errors_are_not_classified_as_transient_dependency_failures():
+    app = create_app(Settings(_env_file=None, environment="test"))
+    assert ProgrammingError not in app.exception_handlers
+    assert ValueError not in app.exception_handlers

backend/tests/test_identity.py

@@ -219,7 +219,7 @@ def test_real_concurrent_logins_keep_bounded_active_sessions(postgres_url):
     asyncio.run(run())
 
 
-def test_account_cli_hidden_password_and_disable(postgres_url):
+def test_account_cli_hidden_password_and_session_disable(postgres_url):
     password = secrets.token_hex(16)
     # The CLI prompts through a real private PTY; the password is never an argument/environment.
     pid, descriptor = pty.fork()
@@ -264,9 +264,7 @@ def test_account_cli_hidden_password_and_disable(postgres_url):
         try:
             service = IdentityService(sessions)
             issued = await service.login("cli_user", password, peer="cli-fixture")
-            from kf_oj.modules.identity.cli import run
-
-            await run("disable", "cli_user")
+            assert await service.disable_account("cli_user")
             with pytest.raises(AuthenticationFailed):
                 await service.authenticate(issued.token)
         finally:

backend/tests/test_judging_v2_contracts.py

@@ -256,9 +256,18 @@ def test_operator_registry_example_preserves_old_protocol_and_binds_managed_runt
         ceiling = v1.RunLimits.model_validate(selected["per_task_ceiling"])
         assert cap.compile_ceiling.fits(ceiling) and cap.run_ceiling.fits(ceiling)
         manifest = fixture(f"judge-manifest.valid-{cap.language}", v2.JobManifest).model_copy(
-            update={"compile_limits": cap.compile_ceiling, "run_limits": cap.run_ceiling}
+            update={
+                "compile_limits": cap.compile_ceiling,
+                "run_limits": cap.run_ceiling,
+                "job_wall_time_us": policy.multi_runtime.max_job_wall_time_us,
+            }
         )
         policy.admit(manifest, 1)
+        with pytest.raises(ValueError, match="job deadline cannot cover execution budgets"):
+            policy.admit(
+                manifest.model_copy(update={"job_wall_time_us": cap.compile_ceiling.wall_time_us}),
+                1,
+            )
         changed = manifest.model_copy(
             update={"toolchain": manifest.toolchain.model_copy(update={"image_digest": "f" * 64})}
         )

backend/tests/test_maintenance_authority.py

@@ -0,0 +1,174 @@
+"""Real trusted control-plane identity checks; no grading/security VM claim."""
+
+import asyncio
+import secrets
+from dataclasses import replace
+
+import httpx
+import pytest
+from conftest import connect
+from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine
+from test_identity import restrict_platform_role
+
+from kf_oj.api.app import create_app
+from kf_oj.contracts.identity import AccountCapabilities
+from kf_oj.core.settings import Settings
+from kf_oj.modules.identity.public import AuthenticationFailed, MaintenanceDenied, Principal
+from kf_oj.modules.identity.service import IdentityService
+
+
+def test_capability_wire_version_and_default_denial():
+    assert AccountCapabilities().model_dump() == {
+        "schema_version": 1,
+        "problem_maintenance": False,
+        "authorization_version": "1",
+    }
+    for invalid in (
+        {"schema_version": 2},
+        {"authorization_version": "0"},
+        {"authorization_version": 1},
+        {"role": "admin"},
+    ):
+        with pytest.raises(ValueError):
+            AccountCapabilities.model_validate(invalid)
+
+
+async def set_administrator(connection, account_id, enabled):
+    username = await connection.fetchval("SELECT username FROM accounts WHERE id=$1", account_id)
+    active = await connection.fetchval(
+        "SELECT count(*) FROM accounts WHERE enabled AND is_administrator"
+    )
+    async with connection.transaction():
+        await connection.execute("SET LOCAL ROLE kf_oj_identity_operator")
+        operation = ("grant" if active else "bootstrap") if enabled else "revoke"
+        await connection.execute(
+            "SELECT * FROM public.kf_manage_account_authority($1,$2)", username, operation
+        )
+
+
+async def add_recovery_administrator(connection):
+    await connection.execute(
+        "INSERT INTO accounts(id,username,password_hash) "
+        "VALUES(gen_random_uuid(),'authority_recovery',repeat('synthetic-only-',5))"
+    )
+    async with connection.transaction():
+        await connection.execute("SET LOCAL ROLE kf_oj_identity_operator")
+        await connection.execute(
+            "SELECT * FROM public.kf_manage_account_authority('authority_recovery','grant')"
+        )
+
+
+def test_live_http_capabilities_and_old_cookies_after_grant_and_revoke(postgres_url):
+    async def run():
+        app = create_app(Settings(_env_file=None, environment="test", database_url=postgres_url))
+        connection = await connect(postgres_url)
+        try:
+            async with app.router.lifespan_context(app):
+                restrict_platform_role(app.state.sessions.kw["bind"])
+                password = secrets.token_hex(16)
+                account = await app.state.identity.create_account("authority_user", password)
+                async with httpx.AsyncClient(
+                    transport=httpx.ASGITransport(app=app), base_url="http://localhost:8000"
+                ) as client:
+                    headers = {"Origin": "http://localhost:8000"}
+                    body = {"username": account.username, "password": password}
+                    ordinary = await client.post("/api/v1/auth/login", json=body, headers=headers)
+                    assert ordinary.status_code == 200
+                    assert ordinary.json()["user"]["capabilities"] == {
+                        "schema_version": 1,
+                        "problem_maintenance": False,
+                        "authorization_version": "1",
+                    }
+                    await set_administrator(connection, account.account_id, True)
+                    assert (await client.get("/api/v1/auth/me")).status_code == 401
+                    fresh = await client.post("/api/v1/auth/login", json=body, headers=headers)
+                    assert fresh.status_code == 200
+                    user = fresh.json()["user"]
+                    assert user["capabilities"]["problem_maintenance"] is True
+                    assert user["capabilities"]["authorization_version"] == "2"
+                    actual = await client.get(
+                        "/api/v1/auth/me", headers={"X-Role": "admin", "X-User-ID": "invalid"}
+                    )
+                    assert actual.json() == user
+                    assert actual.headers["cache-control"] == "no-store"
+                    await add_recovery_administrator(connection)
+                    await set_administrator(connection, account.account_id, False)
+                    assert (await client.get("/api/v1/auth/me")).status_code == 401
+                    refused = await client.post(
+                        "/api/v1/auth/login", json=body | {"role": "admin"}, headers=headers
+                    )
+                    assert refused.status_code == 422
+                    ordinary = await client.post("/api/v1/auth/login", json=body, headers=headers)
+                    assert ordinary.json()["user"]["capabilities"]["problem_maintenance"] is False
+                    assert ordinary.json()["user"]["capabilities"]["authorization_version"] == "3"
+        finally:
+            await connection.close()
+
+    asyncio.run(run())
+
+
+def test_write_transaction_rechecks_session_and_serializes_authority_change(postgres_url):
+    async def run():
+        engine = create_async_engine(postgres_url)
+        restrict_platform_role(engine)
+        sessions = async_sessionmaker(engine, expire_on_commit=False)
+        identity = IdentityService(sessions)
+        connection, other = await connect(postgres_url), await connect(postgres_url)
+        pending = None
+        try:
+            password = secrets.token_hex(16)
+            account = await identity.create_account("authority_user", password)
+            await set_administrator(connection, account.account_id, True)
+            issued = await identity.login(account.username, password, peer="authority-fixture")
+            principal = await identity.authenticate(issued.token)
+            assert principal.can_maintain_problems and principal.authorization_version == 2
+            assert principal.session_token_hash not in repr(principal)
+            await add_recovery_administrator(connection)
+            async with sessions.begin() as session:
+                await identity.require_problem_maintenance(session, principal)
+                pending = asyncio.create_task(set_administrator(other, account.account_id, False))
+                await asyncio.sleep(0.1)
+                assert not pending.done()  # Real PG SHARE lock holds through the write transaction.
+            await asyncio.wait_for(pending, timeout=5)
+            with pytest.raises(AuthenticationFailed):
+                await identity.authenticate(issued.token)
+            async with sessions.begin() as session:
+                with pytest.raises(MaintenanceDenied):
+                    await identity.require_problem_maintenance(session, principal)
+            await set_administrator(connection, account.account_id, True)
+            issued = await identity.login(account.username, password, peer="authority-fresh")
+            principal = await identity.authenticate(issued.token)
+            async with sessions.begin() as session:
+                for forged in (
+                    Principal(account.account_id, account.username, True),
+                    replace(principal, session_token_hash="0" * 64),
+                    replace(principal, authorization_version=1),
+                ):
+                    with pytest.raises(MaintenanceDenied):
+                        await identity.require_problem_maintenance(session, forged)
+            await identity.logout(issued.token, issued.csrf_token)
+            async with sessions.begin() as session:
+                with pytest.raises(MaintenanceDenied):
+                    await identity.require_problem_maintenance(session, principal)
+            issued = await identity.login(account.username, password, peer="authority-expiry")
+            principal = await identity.authenticate(issued.token)
+            # Use actual wall-clock expiry even inside an already-open transaction.
+            async with sessions.begin() as session:
+                await session.connection()
+                await connection.execute(
+                    "UPDATE sessions SET expires_at=clock_timestamp()+interval '50 milliseconds' "
+                    "WHERE token_hash=$1",
+                    principal.session_token_hash,
+                )
+                await asyncio.sleep(0.1)
+                with pytest.raises(MaintenanceDenied):
+                    await identity.require_problem_maintenance(session, principal)
+        finally:
+            if pending is not None and not pending.done():
+                pending.cancel()
+                await asyncio.gather(pending, return_exceptions=True)
+            await connection.close()
+            await other.close()
+            await engine.dispose()
+
+    asyncio.run(run())

backend/tests/test_operator_diagnostics.py

@@ -0,0 +1,227 @@
+"""Ordinary controller/codec models; no service or isolation acceptance."""
+
+import copy
+import hashlib
+import importlib
+import json
+import subprocess
+import sys
+from pathlib import Path
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).resolve().parents[2]))
+units = importlib.import_module("scripts.release.operator_units")
+install = importlib.import_module("scripts.release.install")
+service_install = importlib.import_module("scripts.release.service_install")
+
+
+def record():
+    return units.failure_record(
+        "factory-health",
+        "exit",
+        subprocess.CompletedProcess([], 1, b"private-output", b"private-error"),
+        units.DeliveryError("operator helper unavailable"),
+    )
+
+
+@pytest.fixture
+def dispatched(monkeypatch):
+    selected = {"release_id": "sd-" + "a" * 12, "configuration_id": "cfg-" + "b" * 24}
+    payload = install.RELEASES / selected["release_id"] / "payload"
+    monkeypatch.setattr(units.os, "getuid", lambda: 0)
+    monkeypatch.setattr(units.os, "geteuid", lambda: 0)
+    monkeypatch.setattr(install, "selection", lambda **_: selected)
+    calls = []
+
+    def manager(*args):
+        calls.append(args)
+        return "LoadState=not-found\nActiveState=inactive\nMainPID=0\n"
+
+    monkeypatch.setattr(service_install, "systemctl", manager)
+    return payload, calls
+
+
+@pytest.mark.parametrize("failure", ["exit", "timeout", "decode", "stderr_bound"])
+def test_dispatch_diagnostics_keep_limits_cleanup_and_only_output_digests(
+    monkeypatch, dispatched, failure
+):
+    payload, calls = dispatched
+
+    def execute(command, **kwargs):
+        assert kwargs["timeout"] == 915
+        assert "--property=MemoryMax=256M" in command
+        assert "--property=RuntimeMaxSec=900" in command
+        if failure == "timeout":
+            raise subprocess.TimeoutExpired(
+                command, 915, output=b"private-output", stderr=b"private-error"
+            )
+        return subprocess.CompletedProcess(
+            command,
+            1 if failure == "exit" else 0,
+            b"private-output",
+            b"private-error" * (400 if failure == "stderr_bound" else 1),
+        )
+
+    monkeypatch.setattr(units.subprocess, "run", execute)
+    with pytest.raises(units.OperatorExecutionError) as caught:
+        units.run("node-maintenance", payload, action="start")
+    error = caught.value
+    assert len(calls) == 2
+    row = error.failures[0]
+    assert row["helper"] == "node-maintenance"
+    assert row["outcome"] == ("exit" if failure == "stderr_bound" else failure)
+    assert row["stdout_bytes"] == 14
+    assert row["stdout_sha256"] == hashlib.sha256(b"private-output").hexdigest()
+    text = units.diagnostic_suffix(error)
+    assert "private-" not in text and len(text) <= 3072
+    assert units.diagnostic_chain(text.encode()) == error.failures
+
+
+def test_nested_failure_retains_inner_helper_and_outer_actual_exit(monkeypatch, dispatched):
+    payload, calls = dispatched
+    child = units.OperatorExecutionError("private-message", [record()])
+    stderr = b"private-error\n" + units.diagnostic_suffix(child).encode()
+    monkeypatch.setattr(
+        units.subprocess,
+        "run",
+        lambda command, **_: subprocess.CompletedProcess(command, 1, b"", stderr),
+    )
+    with pytest.raises(units.OperatorExecutionError) as caught:
+        units.run("node-maintenance", payload, action="start")
+    rows = caught.value.failures
+    assert [r["helper"] for r in rows] == ["factory-health", "node-maintenance"]
+    assert (
+        rows[1]["returncode"] == 1
+        and rows[1]["stderr_sha256"] == hashlib.sha256(stderr).hexdigest()
+    )
+    assert len(calls) == 2 and "private-" not in units.diagnostic_suffix(caught.value)
+
+
+@pytest.mark.parametrize(
+    "mutation",
+    [
+        "unknown_field",
+        "helper",
+        "outcome",
+        "boolean_code",
+        "boolean_size",
+        "digest",
+        "unknown_readiness",
+        "deep",
+        "schema",
+        "duplicate",
+        "oversize",
+        "invalid_json",
+    ],
+)
+def test_untrusted_child_diagnostic_shape_is_discarded(mutation):
+    value = {"schema_version": 1, "failures": [record()]}
+    row = value["failures"][0]
+    if mutation == "unknown_field":
+        row["private"] = "must-not-escape"
+    elif mutation == "helper":
+        row["helper"] = "/private/command"
+    elif mutation == "outcome":
+        row["outcome"] = ["private-error"]
+    elif mutation == "boolean_code":
+        row["returncode"] = True
+    elif mutation == "boolean_size":
+        row["stdout_bytes"] = True
+    elif mutation == "digest":
+        row["stderr_sha256"] = "private-error"
+    elif mutation == "unknown_readiness":
+        row["readiness_errors"] = ["private-error"]
+    elif mutation == "deep":
+        value["failures"] *= 4
+    elif mutation == "schema":
+        value["schema_version"] = True
+    text = (units.DIAGNOSTIC_PREFIX + json.dumps(value) + "\n").encode()
+    if mutation == "duplicate":
+        text *= 2
+    elif mutation == "oversize":
+        text += b"x" * 4097
+    elif mutation == "invalid_json":
+        text = units.DIAGNOSTIC_PREFIX.encode() + b"{broken"
+    assert units.diagnostic_chain(text) == []
+
+
+def test_readiness_preserves_two_inner_failures_and_only_fixed_codes():
+    rows = [record(), copy.deepcopy(record()), copy.deepcopy(record())]
+    error = units.readiness_failure(
+        "preconditions unavailable",
+        {
+            "errors": ["factory_status_unavailable"],
+            "operator_failures": rows,
+            "password": "private-value",
+        },
+    )
+    assert len(error.failures) == 3
+    assert error.failures[-1]["readiness_errors"] == ["factory_status_unavailable"]
+    assert "private-" not in units.diagnostic_suffix(error)
+    refused = units.readiness_failure(
+        "admission unavailable", {"errors": ["private-value"]}, admission=True
+    )
+    assert refused.failures[0]["outcome"] == "admission"
+    assert "readiness_errors" not in refused.failures[0]
+
+
+def test_readonly_health_keeps_failed_components_and_bounded_nested_causes(monkeypatch, tmp_path):
+    from concurrent.futures import Future
+    from contextlib import nullcontext
+
+    health = importlib.import_module("scripts.release.node_health")
+    selected = {"release_id": "sd-" + "a" * 12, "configuration_id": "cfg-" + "b" * 24}
+    payload = tmp_path / "payload"
+    monkeypatch.setattr(units, "guarded", lambda _: None)
+    monkeypatch.setattr(
+        health, "binding", lambda: (selected, {"coordinator.json": Path("coordinator")}, payload)
+    )
+    monkeypatch.setattr(
+        health,
+        "read_json",
+        lambda path, *args: (
+            {"source_sha": "a" * 40}
+            if path.name == "manifest.json"
+            else {"platform_token": "private-token", "admission": {}}
+        ),
+    )
+    monkeypatch.setattr(health.journal, "check_ready", lambda: {})
+    monkeypatch.setattr(health.proxy_install, "check_binding", lambda *args: None)
+    monkeypatch.setattr(health.proxy_health, "observe", lambda _: {})
+    monkeypatch.setattr(health, "inspect_unit", lambda *args: {})
+    monkeypatch.setattr(health.dependency_install, "installed_endpoints", lambda _: {})
+
+    async def roles(_):
+        return {}
+
+    monkeypatch.setattr(health, "roles", roles)
+    monkeypatch.setattr(
+        health, "http", lambda *args, **kwargs: {"status": "ok", "service": "platform"}
+    )
+    monkeypatch.setattr(health, "validate_execution", lambda *args: {})
+    monkeypatch.setattr(install, "selection", lambda **kwargs: selected)
+    pending = {}
+    for name in ("broker-health", "outbox-health", "import-health", "factory-health"):
+        future = Future()
+        row = record()
+        row["helper"] = name
+        future.set_exception(units.OperatorExecutionError("operator helper unavailable", [row]))
+        pending[name] = future
+    monkeypatch.setattr(health, "_status_helpers", lambda _: nullcontext(pending))
+    observed = health.observe(probe=False)
+    assert observed["ready_for_admission"] is False
+    assert observed["service_preconditions_met"] is False
+    assert observed["errors"] == [
+        "broker_metadata_unavailable",
+        "outbox_pipeline_unavailable",
+        "import_pipeline_unavailable",
+        "factory_status_unavailable",
+    ]
+    error = units.readiness_failure("service preconditions unavailable", observed)
+    assert [r["helper"] for r in error.failures] == [
+        "broker-health",
+        "outbox-health",
+        "node-health",
+    ]
+    assert "private-" not in units.diagnostic_suffix(error)

backend/tests/test_operator_imports.py

@@ -0,0 +1,55 @@
+"""Read-only observers must not load delivery or archive mutation implementations."""
+
+import os
+import subprocess
+import sys
+from pathlib import Path
+
+import pytest
+
+
+@pytest.mark.parametrize(
+    ("observer", "forbidden"),
+    [
+        (
+            "kf_oj.workers.outbox_status",
+            ["kf_oj.infra.messaging.publisher", "aio_pika", "aiormq"],
+        ),
+        (
+            "kf_oj.workers.problem_status",
+            [
+                "kf_oj.modules.problems.imports",
+                "kf_oj.modules.problems.maintenance",
+                "kf_oj.infra.artifacts.staging",
+            ],
+        ),
+    ],
+)
+def test_read_only_observer_imports_exclude_mutation_implementations(observer, forbidden):
+    source = Path(__file__).resolve().parents[1] / "src"
+    probe = """import importlib, importlib.abc, sys
+class RefuseMutation(importlib.abc.MetaPathFinder):
+    def find_spec(self, fullname, path, target=None):
+        if any(fullname == name or fullname.startswith(name + '.') for name in sys.argv[2:]):
+            raise AssertionError('read-only observer loaded mutation implementation')
+sys.meta_path.insert(0, RefuseMutation())
+importlib.import_module(sys.argv[1])
+"""
+    result = subprocess.run(
+        [sys.executable, "-s", "-P", "-c", probe, observer, *forbidden],
+        env={
+            "PATH": os.defpath,
+            "PYTHONPATH": str(source),
+            "PYTHONDONTWRITEBYTECODE": "1",
+        },
+        capture_output=True,
+        timeout=15,
+    )
+    assert result.returncode == 0, result.stderr.decode(errors="replace")
+
+
+def test_import_policy_identity_and_availability_error_remain_shared():
+    from kf_oj.modules.problems import import_policy, imports
+
+    assert imports.ImportUnavailable is import_policy.ImportUnavailable
+    assert imports.policy_digest is import_policy.policy_digest

backend/tests/test_performance_projection.py

@@ -0,0 +1,115 @@
+"""Finite actual control-plane PG/HTTP tests; all reports explicitly synthetic.
+
+No user program runs here. Privilege/tamper/fault acceptance runs in the VM.
+"""
+
+import asyncio
+import subprocess
+
+from test_coordinator import (
+    ROOT,
+    claim,
+    fixture,
+    manifest,
+    stages,
+    synthetic_report,
+    worker_headers,
+)
+
+
+def test_final_projection_atomic_idempotent_and_bound(postgres_url, tmp_path, monkeypatch):
+    async def run():
+        async with fixture(
+            postgres_url, tmp_path, monkeypatch, measurement_epochs=["a" * 64, "b" * 64]
+        ) as (client, c, workers, _, create):
+            groups = []
+            for index in [0, 0, 1]:
+                created = await create()
+                worker = workers[index]
+                grant = await claim(client, created, worker)
+                await stages(client, worker, grant)
+                report = synthetic_report(grant, await manifest(c, grant))
+                result = await client.post(
+                    "/internal/report", json=report, headers=worker_headers(worker, grant)
+                )
+                assert result.status_code == 204, result.text
+                row = await c.fetchrow(
+                    "SELECT p.*,e.final_report_digest,a.report_digest AS attempt_digest "
+                    "FROM evaluation_performance p JOIN evaluations e ON e.id=p.evaluation_id "
+                    "JOIN judge_attempts a ON a.id=p.attempt_id WHERE p.evaluation_id=$1",
+                    created.evaluation_id,
+                )
+                assert row is not None
+                assert row["cpu_time_us"] == report["run_cpu_time_us"]
+                assert row["memory_peak_bytes"] == report["run_memory_peak_bytes"]
+                assert row["measurement_epoch"] == worker["measurement_epoch"]
+                assert row["report_digest"] == row["final_report_digest"] == row["attempt_digest"]
+                groups.append(row["comparison_group"])
+                repeated = await client.post(
+                    "/internal/report", json=report, headers=worker_headers(worker, grant)
+                )
+                assert repeated.status_code == 204
+                assert (
+                    await c.fetchval(
+                        "SELECT count(*) FROM evaluation_performance WHERE evaluation_id=$1",
+                        created.evaluation_id,
+                    )
+                    == 1
+                )
+                backfill = await asyncio.to_thread(
+                    subprocess.run,
+                    [
+                        str(ROOT / "judge/target/debug/kf-coordinator"),
+                        "--config",
+                        str(client.coordinator_config),
+                        "--backfill-performance",
+                        str(created.evaluation_id),
+                    ],
+                    capture_output=True,
+                    text=True,
+                    timeout=15,
+                )
+                assert backfill.returncode == 0, backfill.stderr
+                assert backfill.stdout.strip() == "trusted performance rows created: 0"
+            assert groups[0] == groups[1] and groups[2] != groups[0]
+            assert await c.fetchval("SELECT count(*) FROM evaluation_performance") == 3
+            # Read grants rather than attempting denied writes on this host.
+            grants = await c.fetchrow(
+                "SELECT has_table_privilege('kf_oj_platform','evaluation_performance','SELECT') "
+                "AS read,has_table_privilege('kf_oj_platform','evaluation_performance','INSERT') "
+                "AS platform_insert,has_table_privilege('kf_oj_coordinator',"
+                "'evaluation_performance','INSERT') AS coord_insert,has_table_privilege("
+                "'kf_oj_coordinator','evaluation_performance','UPDATE') AS coord_update,"
+                "has_column_privilege('kf_oj_coordinator','judge_attempts',"
+                "'measurement_epoch','UPDATE') AS epoch_update"
+            )
+            assert dict(grants) == dict(
+                read=True,
+                platform_insert=False,
+                coord_insert=True,
+                coord_update=False,
+                epoch_update=False,
+            )
+
+    asyncio.run(run())
+
+
+def test_unbound_legacy_and_nonaccepted_stay_out(postgres_url, tmp_path, monkeypatch):
+    async def run():
+        async with fixture(postgres_url, tmp_path, monkeypatch) as (client, c, workers, _, create):
+            for verdict in ["accepted", "wrong_answer"]:
+                created = await create()
+                grant = await claim(client, created, workers[0])
+                await stages(client, workers[0], grant)
+                report = synthetic_report(grant, await manifest(c, grant), verdict)
+                result = await client.post(
+                    "/internal/report", json=report, headers=worker_headers(workers[0], grant)
+                )
+                assert result.status_code == 204, result.text
+                assert await c.fetchval(
+                    "SELECT final_report_digest IS NOT NULL FROM evaluations WHERE id=$1",
+                    created.evaluation_id,
+                )
+            assert await c.fetchval("SELECT count(*) FROM evaluation_performance") == 0
+
+    asyncio.run(run())