unseen-eval group 1: used set (1,029 repositories, every source read), extended guard, usage ledger; record 01

Implemented with Codex; task 1.5 run by the coordinator against the real
sources (S3 memory read-only).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

tests/test_unseen_ledger.py

@@ -0,0 +1,63 @@
+"""Append-only use and tamper detection, with opaque fixture identifiers."""
+
+import json
+from pathlib import Path
+
+import pytest
+
+with pytest.MonkeyPatch.context() as patch:
+    patch.syspath_prepend(str(Path(__file__).resolve().parents[1] / "benchmarks/unseen"))
+    import ledger
+
+
+def row(**extra):
+    return {
+        "slice": 1,
+        "decision": "decision-001",
+        "purpose": "baseline",
+        "date": "2026-10-04",
+        "result_digest": "a" * 64,
+        "freeze_digest": "b" * 64,
+        **extra,
+    }
+
+
+def test_append_and_refuse_rewrite(tmp_path):
+    path = tmp_path / "usage-p1.jsonl"
+    ledger.append(path, row())
+    original = path.read_bytes()
+    ledger.append(path, row(purpose="exploratory"))
+    assert path.read_bytes().startswith(original)
+    assert len(ledger.read(path)) == 2
+    with pytest.raises(ValueError, match="duplicate"):
+        ledger.append(path, row())
+
+
+def test_informed_slice_cannot_qualify_same_decision(tmp_path):
+    path = tmp_path / "usage-p1.jsonl"
+    ledger.append(path, row(purpose="informed"))
+    before = path.read_bytes()
+    with pytest.raises(ValueError, match="informed"):
+        ledger.append(path, row(purpose="qualifies"))
+    assert path.read_bytes() == before
+    ledger.append(path, row(purpose="qualifies", slice=2))
+    ledger.append(path, row(purpose="qualifies", decision="decision-002"))
+
+
+def test_rewritten_row_breaks_digest_chain(tmp_path):
+    path = tmp_path / "usage-p1.jsonl"
+    ledger.append(path, row())
+    ledger.append(path, row(purpose="exploratory"))
+    rows = [json.loads(line) for line in path.read_text().splitlines()]
+    rows[0]["purpose"] = "informed"
+    path.write_text("".join(json.dumps(r) + "\n" for r in rows))
+    with pytest.raises(ValueError, match="chain"):
+        ledger.read(path)
+    with pytest.raises(ValueError, match="chain"):
+        ledger.append(path, row(slice=2))
+
+
+@pytest.mark.parametrize("extra", [{"decision": "owner/name"}, {"purpose": "other"}, {"freeze_digest": "bad"}, {"slice": 0}])
+def test_invalid_rows_refused(tmp_path, extra):
+    with pytest.raises(ValueError):
+        ledger.append(tmp_path / "usage-p1.jsonl", row(**extra))