fix(knowledge): 保证笔记创建与索引更新一致性

backend/app/repository.py

@@ -9,6 +9,7 @@ from __future__ import annotations
 
 import json
 import sqlite3
+from contextlib import nullcontext
 from dataclasses import dataclass, field
 from datetime import datetime
 
@@ -235,14 +236,19 @@ def get_block_hits(block_ids: list[str]) -> list[BlockHit]:
         conn.close()
 
 
-def set_index_meta(kv: dict[str, str]) -> None:
+def set_index_meta(
-    conn = connect()
+    kv: dict[str, str], *, conn: sqlite3.Connection | None = None
+) -> None:
+    """写入索引元信息；传入连接时加入调用方现有事务。"""
+    owns = conn is None
+    conn = conn or connect()
     try:
-        with transaction(conn):
+        with transaction(conn) if owns else nullcontext():
             for key, value in kv.items():
                 conn.execute("INSERT OR REPLACE INTO index_meta (key, value) VALUES (?, ?)", (key, value))
     finally:
-        conn.close()
+        if owns:
+            conn.close()
 
 
 def get_index_meta() -> dict[str, str]:

backend/app/services/note_service.py

@@ -83,6 +83,22 @@ def _write_markdown(rel_path: str, markdown: str) -> None:
     path.write_text(markdown, encoding="utf-8")
 
 
+def _create_markdown(rel_path: str, markdown: str) -> None:
+    """排他创建 Markdown；目标已存在时返回资源冲突，不覆盖用户文件。"""
+    path = _abs_path(rel_path)
+    path.parent.mkdir(parents=True, exist_ok=True)
+    try:
+        with path.open("x", encoding="utf-8") as handle:
+            handle.write(markdown)
+    except FileExistsError as exc:
+        raise ApiError(
+            409,
+            "RESOURCE_CONFLICT",
+            "a note already exists at this path",
+            {"file_path": rel_path},
+        ) from exc
+
+
 def _delete_markdown(rel_path: str) -> None:
     path = _abs_path(rel_path)
     if path.exists():
@@ -123,9 +139,12 @@ async def index_note(parsed: ParsedNote) -> None:
                 if block.block_id in missing_ids
             ]
             await vector_store.upsert(records, conn=conn)
+            repository.set_index_meta(
+                {"embedding_model": embedding.model_id, "embedding_dim": str(embedding.dim)},
+                conn=conn,
+            )
     finally:
         conn.close()
-    repository.set_index_meta({"embedding_model": embedding.model_id, "embedding_dim": str(embedding.dim)})
 
 
 async def create_note(*, title: str, markdown: str, folder: str | None, tags: list[str]) -> Note:
@@ -137,7 +156,14 @@ async def create_note(*, title: str, markdown: str, folder: str | None, tags: li
         created_at=now, updated_at=now,
     )
     parsed.title = title  # 显式传入的 title 优先于正文推导（与 update_note 保持一致）
-    _write_markdown(rel_path, markdown)
+    if repository.get_note_record(parsed.note_id) is not None:
+        raise ApiError(
+            409,
+            "RESOURCE_CONFLICT",
+            "a note already exists at this path",
+            {"note_id": parsed.note_id, "file_path": rel_path},
+        )
+    _create_markdown(rel_path, markdown)
     try:
         await index_note(parsed)
     except BaseException:

backend/tests/test_retrieval.py

@@ -281,6 +281,49 @@ def test_update_note_rolls_back_file_on_index_error(vault, monkeypatch) -> None:
     assert path.read_text(encoding="utf-8") == before  # 文件已回滚，无部分提交
 
 
+def test_update_note_rolls_back_index_when_index_meta_fails(vault, monkeypatch) -> None:
+    """索引元信息失败时，Markdown 与完整索引都保持旧版本。"""
+    from app import repository
+    from app.services import note_service
+
+    note = asyncio.run(
+        note_service.create_note(title="原子更新", markdown="旧正文", folder="", tags=[])
+    )
+
+    def _boom(*_args, **_kwargs):
+        raise RuntimeError("index meta failed")
+
+    monkeypatch.setattr(repository, "set_index_meta", _boom)
+    with pytest.raises(RuntimeError):
+        asyncio.run(note_service.update_note(note.note_id, markdown="新正文"))
+
+    got = asyncio.run(note_service.get_note(note.note_id))
+    record = repository.get_note_record(note.note_id)
+    assert got is not None and got.markdown == "旧正文"
+    assert record is not None
+    assert [block.content for block in record.blocks] == ["旧正文"]
+
+
+def test_create_note_rejects_existing_path_without_overwrite(vault) -> None:
+    """POST 同目录同标题返回 409，且不改动已有 Markdown 和索引。"""
+    from app.errors import ApiError
+    from app.services import note_service
+
+    original = asyncio.run(
+        note_service.create_note(title="不能覆盖", markdown="原始正文", folder="测试", tags=[])
+    )
+
+    with pytest.raises(ApiError) as exc:
+        asyncio.run(
+            note_service.create_note(title="不能覆盖", markdown="替换正文", folder="测试", tags=[])
+        )
+
+    assert exc.value.status_code == 409
+    assert exc.value.code == "RESOURCE_CONFLICT"
+    got = asyncio.run(note_service.get_note(original.note_id))
+    assert got is not None and got.markdown == "原始正文"
+
+
 def test_update_removes_stale_vectors(vault) -> None:
     from app.database.db import connect
     from app.services import note_service