diff --git a/backend/tests/test_delivery_io.py b/backend/tests/test_delivery_io.py
index 4554731..d16d316 100644
--- a/backend/tests/test_delivery_io.py
+++ b/backend/tests/test_delivery_io.py
@@ -336,7 +336,9 @@ def live_byte_proof_model(ordinary_bundle, monkeypatch, tmp_path):
     path = tmp_path / "byte-proof.json"
     path.write_bytes(policy.canonical(record))
     monkeypatch.setattr(operation_proof, "RECORD", path)
-    monkeypatch.setattr(operation_proof, "_root", lambda: True)
+    for name in ("getuid", "geteuid", "getgid", "getegid"):
+        monkeypatch.setattr(operation_proof.os, name, lambda: 0)
+    monkeypatch.setattr(operation_proof.os, "getgroups", lambda: [0])
     monkeypatch.setattr(operation_proof.preflight, "protected", lambda *a, **kw: None)
     monkeypatch.setattr(
         operation_proof.preflight,
@@ -367,6 +369,69 @@ def test_live_parent_model_reuses_complete_proof_without_remembering_it(
     assert not reads
 
 
+@pytest.mark.parametrize(
+    ("unit", "gid"),
+    [
+        ("postgres", 1203),
+        ("rabbitmq", 1204),
+        ("sandbox-factory", 0),
+        ("coordinator", 1201),
+        ("api", 1200),
+        ("outbox", 1200),
+        ("problem-import", 1200),
+        ("worker", 1202),
+        ("proxy", 1205),
+        ("node-health", 0),
+    ],
+)
+def test_privileged_service_group_model_can_consume_but_not_publish(
+    live_byte_proof_model, monkeypatch, unit, gid
+):
+    bundle, expected, record = live_byte_proof_model
+    monkeypatch.setattr(operation_proof.os, "getgroups", lambda: [gid])
+    monkeypatch.setattr(
+        operation_proof.preflight,
+        "current_cgroup",
+        lambda: Path(operation_proof.GROUP + "kf-" + unit + ".service"),
+    )
+    reads = observed_digests(monkeypatch)
+    assert manifest.verify(bundle, expected)["release_id"] == record["release_id"]
+    assert not reads
+    # Publication still requires Root's own groups, even in a consumer model.
+    assert operation_proof._root() is (gid == 0)
+
+
+@pytest.mark.parametrize(
+    ("unit", "groups", "ordinary_id"),
+    [
+        ("api", [1201], None),
+        ("worker", [1200], None),
+        ("node-health", [1200], None),
+        ("api", [0, 1200, 1201], None),
+        ("api/child", [1200], None),
+        ("api", [1200], "getuid"),
+        ("api", [1200], "geteuid"),
+        ("api", [1200], "getgid"),
+        ("api", [1200], "getegid"),
+    ],
+)
+def test_foreign_groups_and_each_ordinary_identity_model_require_full_bytes(
+    live_byte_proof_model, monkeypatch, unit, groups, ordinary_id
+):
+    bundle, expected, _ = live_byte_proof_model
+    monkeypatch.setattr(operation_proof.os, "getgroups", lambda: groups)
+    if ordinary_id:
+        monkeypatch.setattr(operation_proof.os, ordinary_id, lambda: 1200)
+    monkeypatch.setattr(
+        operation_proof.preflight,
+        "current_cgroup",
+        lambda: Path(operation_proof.GROUP + "kf-" + unit + ".service"),
+    )
+    reads = observed_digests(monkeypatch)
+    manifest.verify(bundle, expected)
+    assert reads
+
+
 @pytest.mark.parametrize(
     ("field", "value"),
     [
@@ -415,7 +480,7 @@ def test_ineligible_parent_proof_model_requires_full_bytes(
 ):
     bundle, expected, _ = live_byte_proof_model
     if reason == "ordinary_uid":
-        monkeypatch.setattr(operation_proof, "_root", lambda: False)
+        monkeypatch.setattr(operation_proof, "_root", lambda *args: False)
     elif reason in {"foreign_group", "parent"}:
         unit = "unrelated.service" if reason == "foreign_group" else operation_proof.PARENT
         monkeypatch.setattr(
diff --git a/scripts/release/README.md b/scripts/release/README.md
index 2ccfca4..9047b3e 100644
--- a/scripts/release/README.md
+++ b/scripts/release/README.md
@@ -434,6 +434,10 @@ identities again before returning. All readers are joined on success or failure.
 During one `start`, `resume` or `restart`, the fixed Root maintenance helper reads
 the complete bundle once. Its Root startup checks and node-health helpers can
 reuse that proof while the same transient maintenance invocation is running.
+Consumers require real and effective UID/GID 0 and the exact fixed service
+cgroup. A privileged service precheck may retain only Root's group and that
+service's fixed group; ordinary service processes still read the complete bytes.
+The publishing maintenance helper accepts only Root's own group.
 A Root-only systemd runtime directory holds a record of at most 4096 bytes,
 binding the full metadata digest to the selected manifest, release, configuration,
 boot, MainPID and InvocationID. Each consumer checks the live owner and every
diff --git a/scripts/release/operation_proof.py b/scripts/release/operation_proof.py
index 4f15d03..1b61a13 100644
--- a/scripts/release/operation_proof.py
+++ b/scripts/release/operation_proof.py
@@ -15,33 +15,32 @@ DIRECTORY = Path("/run/kf-node-verification")
 RECORD = DIRECTORY / "byte-proof.json"
 PARENT = "kf-node-maintenance.service"
 GROUP = "/sys/fs/cgroup/kfonlinejudge.slice/"
-CONSUMERS = frozenset(
-    "kf-" + name + ".service"
-    for name in (
-        "postgres",
-        "rabbitmq",
-        "sandbox-factory",
-        "coordinator",
-        "api",
-        "outbox",
-        "problem-import",
-        "worker",
-        "proxy",
-        "node-health",
-    )
-)
+# Privileged ExecStartPre checks retain their ordinary service's supplementary
+# group. These are fixed unit identities, never groups supplied by a proof.
+CONSUMERS = {
+    "kf-postgres.service": 1203,
+    "kf-rabbitmq.service": 1204,
+    "kf-sandbox-factory.service": 0,
+    "kf-coordinator.service": 1201,
+    "kf-api.service": 1200,
+    "kf-outbox.service": 1200,
+    "kf-problem-import.service": 1200,
+    "kf-worker.service": 1202,
+    "kf-proxy.service": 1205,
+    "kf-node-health.service": 0,
+}
 MAX_AGE_NS = 900 * 10**9
 MAX_RECORD = 4096
 _REPORTED: tuple[int, str] | None = None
 
 
-def _root() -> bool:
+def _root(allowed_groups: frozenset[int] = frozenset({0})) -> bool:
     return (os.getuid(), os.geteuid(), os.getgid(), os.getegid()) == (
         0,
         0,
         0,
         0,
-    ) and set(os.getgroups()) <= {0}
+    ) and set(os.getgroups()) <= allowed_groups
 
 
 def _now() -> int:
@@ -194,7 +193,10 @@ def _observed(value: dict) -> None:
 
 def reuse(bundle: Path, expected: str) -> dict | None:
     """Missing/ineligible proofs use full bytes; eligible corrupt proofs refuse."""
-    if not _root() or str(preflight.current_cgroup()) not in {GROUP + unit for unit in CONSUMERS}:
+    allowed_groups = {GROUP + unit: frozenset({0, gid}) for unit, gid in CONSUMERS.items()}.get(
+        str(preflight.current_cgroup())
+    )
+    if allowed_groups is None or not _root(allowed_groups):
         return None
     try:
         RECORD.lstat()