diff --git a/.github/workflows/sbom.yml b/.github/workflows/sbom.yml
index 8a645941..bce1056f 100644
--- a/.github/workflows/sbom.yml
+++ b/.github/workflows/sbom.yml
@@ -17,7 +17,6 @@ jobs:
     runs-on: ubuntu-latest
     permissions:
       contents: write
-      id-token: write
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
       - name: Generate SBOM
diff --git a/tests/unit/test_release_validation_permissions.py b/tests/unit/test_release_validation_permissions.py
index e02db2f9..b13ebb10 100644
--- a/tests/unit/test_release_validation_permissions.py
+++ b/tests/unit/test_release_validation_permissions.py
@@ -3,10 +3,100 @@
 from __future__ import annotations
 
 import copy
+import shutil
 from pathlib import Path
 
+import pytest
 import yaml
 
+# Reviewed under agentrust-io/.github#54. Codecov is the sole test-job exception.
+OIDC_JOBS = {
+    ("ci.yml", "test"),  # Codecov tokenless coverage upload
+    ("release.yml", "publish"),  # PyPI trusted publishing
+    ("docker.yml", "build-and-push"),  # Container signing and attestation
+    ("scorecard.yml", "scorecard"),  # Scorecard
+}
+
+
+def _oidc_write(permissions: dict | str) -> bool:
+    if isinstance(permissions, str):
+        assert permissions in {"read-all", "write-all"}, "unsupported permission shorthand"
+        return permissions == "write-all"
+    assert isinstance(permissions, dict), "permissions must be a mapping or shorthand"
+    return permissions.get("id-token") == "write"
+
+
+def _assert_oidc_jobs(directory: Path) -> None:
+    grants = set()
+    paths = sorted([*directory.glob("*.yml"), *directory.glob("*.yaml")])
+    assert paths, "no workflow files found"
+    for path in paths:
+        workflow = yaml.safe_load(path.read_text(encoding="utf-8"))
+        defaults = workflow.get("permissions", {})
+        assert not _oidc_write(defaults), f"{path.name}: workflow-wide OIDC grant"
+        for name, job in workflow["jobs"].items():
+            permissions = job.get("permissions", defaults)
+            assert permissions != "write-all", f"{path.name}/{name}: write-all grant"
+            if _oidc_write(permissions):
+                grants.add((path.name, name))
+    assert grants == OIDC_JOBS, f"OIDC job drift: {grants ^ OIDC_JOBS}"
+
+
+def test_workflow_oidc_grants() -> None:
+    _assert_oidc_jobs(Path(".github/workflows"))
+
+
+@pytest.mark.parametrize(
+    "case",
+    [
+        "validation-job", "sbom-job", "workflow-inheritance", "workflow-write-all",
+        "allowed-job-write-all", "other-job-write-all", "new-yml", "new-yaml",
+        "removed-allowance",
+    ],
+)
+def test_oidc_guard_detects_permission_drift(tmp_path: Path, case: str) -> None:
+    directory = tmp_path / "workflows"
+    shutil.copytree(".github/workflows", directory)
+    _assert_oidc_jobs(directory)
+    if case in {"new-yml", "new-yaml"}:
+        extension = case.removeprefix("new-")
+        (directory / f"unexpected.{extension}").write_text(
+            "permissions: {contents: read}\njobs:\n"
+            "  validation:\n    permissions: {id-token: write}\n",
+            encoding="utf-8",
+        )
+    else:
+        filename = "sbom.yml" if case == "sbom-job" else "release-validation.yml"
+        if case in {"allowed-job-write-all", "removed-allowance"}:
+            filename = "ci.yml"
+        path = directory / filename
+        workflow = yaml.safe_load(path.read_text(encoding="utf-8"))
+        job = workflow["jobs"]["sbom" if case == "sbom-job" else "test"]
+        if case == "workflow-inheritance":
+            workflow["permissions"]["id-token"] = "write"
+            job.pop("permissions", None)
+        elif case == "workflow-write-all":
+            workflow["permissions"] = "write-all"
+        elif case in {"allowed-job-write-all", "other-job-write-all"}:
+            job["permissions"] = "write-all"
+        elif case == "removed-allowance":
+            job["permissions"].pop("id-token")
+        else:
+            job.setdefault("permissions", {})["id-token"] = "write"
+        path.write_text(yaml.safe_dump(workflow), encoding="utf-8")
+    with pytest.raises(AssertionError):
+        _assert_oidc_jobs(directory)
+
+
+def test_oidc_guard_accepts_read_only_inheritance(tmp_path: Path) -> None:
+    directory = tmp_path / "workflows"
+    shutil.copytree(".github/workflows", directory)
+    (directory / "read-only.yaml").write_text(
+        "permissions: read-all\njobs:\n  validation:\n    runs-on: ubuntu-latest\n",
+        encoding="utf-8",
+    )
+    _assert_oidc_jobs(directory)
+
 
 def _workflow(name: str) -> dict:
     return yaml.safe_load(Path(f".github/workflows/{name}.yml").read_text(encoding="utf-8"))