95a06a20ef
Documents the systemic non-hermetic-test hazard surfaced during ADR-0220: ~340 of 469 ChatRuntime constructions across 123 test files default to the shared engine_state/ dir, so tests read/pollute each other's checkpoints (the spurious test_achat identity-continuity warning). Records the interim rule (new/edited tests must pass engine_state_path=tmp_path or no_load_state) and the recommended future fix (root conftest autouse fixture monkeypatching engine_state._DEFAULT_DIR + CORE_ENGINE_STATE_DIR), deferred to its own full-suite-validated PR. Docs only.
115 lines
5 KiB
Markdown
115 lines
5 KiB
Markdown
# Issue — tests sharing the default `engine_state/` dir (reproducibility hazard)
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Status: open (hygiene; interim rule below, recommended fix deferred to a validated PR)
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Date: 2026-06-15
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Relates: ADR-0146 (engine-state persistence), ADR-0219 (generation-dir checkpoint),
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ADR-0220 (identity/provenance reconcile — surfaced the symptom)
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## Symptom
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During ADR-0220 (PR C) verification, `tests/test_achat.py::test_achat_returns_non_empty_surface`
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emitted a spurious:
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```
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RuntimeWarning: engine identity continuity break: checkpoint was written under
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819c4364d599… but this build computes c9e5968ab1fe… — the ratified identity
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substrate (packs) changed while the engine was down.
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```
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It was **not** a regression from the identity split. Re-running with an isolated
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state dir made it vanish:
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```
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CORE_ENGINE_STATE_DIR=$(mktemp -d)/es pytest tests/test_achat.py # 11 passed, no warning
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```
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## Root cause
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`ChatRuntime(...)` with no `engine_state_path` resolves its store to
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`EngineStateStore(None).path == engine_state._DEFAULT_DIR`, which is
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`$CORE_ENGINE_STATE_DIR` or the in-repo `engine_state/` dir
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(`engine_state/__init__.py:52-56`). That directory is **process-wide shared
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state**:
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- On construction, a runtime READS it (`store.exists()` → `_load_engine_state`),
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so any test reading a **stale checkpoint** left by an earlier test reconciles
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it (ADR-0220) and can emit a phantom identity-continuity warning.
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- Tests that run a turn / checkpoint WRITE a generation-dir checkpoint into the
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same shared dir (the observed pollution was leftover `gen-0583/` `gen-0584/` +
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`current`), so test ordering and prior runs leak into later tests.
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This is a classic non-hermetic-test hazard: behaviour depends on what other
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tests (or prior local runs) left in `engine_state/`.
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## Scope (it is systemic, not a one-off)
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In `tests/` at `main@eed20749`:
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| Metric | Count |
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|---|---|
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| `ChatRuntime(...)` constructions | **469** |
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| test files constructing it | **123** |
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| constructions passing `engine_state_path` (isolated) | 74 |
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| constructions passing `no_load_state` (ephemeral, no persist) | 52 |
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| **constructions defaulting to the shared dir** | **~340** |
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Most defaulting constructions are *victims* (they read the shared dir on
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construction); a subset that checkpoint are also *polluters*. CI runs in a clean
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checkout so the shared dir starts empty there — which is exactly why this hides:
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it bites local runs and ordering-sensitive sessions, not the gate.
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## Interim rule (apply now, in review)
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Any **new or edited** test that constructs a `ChatRuntime` which loads or
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persists runtime state MUST isolate it:
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```python
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ChatRuntime(config=..., engine_state_path=tmp_path / "engine_state")
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# or, for an ephemeral runtime that must not touch persisted state:
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ChatRuntime(config=..., no_load_state=True)
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```
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Subprocess / CLI tests (which re-import in a child process) must set
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`CORE_ENGINE_STATE_DIR` in the child env instead (see
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`tests/test_l10_always_on_daemon.py::test_real_sigterm_stops_the_daemon_cleanly`
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for the pattern).
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Do **not** add a bare `ChatRuntime()` that reads/writes the default dir.
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## Recommended fix (deferred — needs its own validated PR)
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A single root `tests/conftest.py` **autouse** fixture that isolates the default
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engine-state dir per test, fixing all ~340 sites at once instead of editing each:
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```python
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@pytest.fixture(autouse=True)
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def _isolate_default_engine_state(tmp_path, monkeypatch):
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import engine_state
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# _DEFAULT_DIR is bound at import, so monkeypatch the module attribute (not
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# just the env var) for in-process runtimes:
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monkeypatch.setattr(engine_state, "_DEFAULT_DIR", tmp_path / "engine_state")
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# ...and set the env var for subprocess/CLI tests that re-import:
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monkeypatch.setenv("CORE_ENGINE_STATE_DIR", str(tmp_path / "engine_state"))
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```
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Fixture requirements / acceptance criteria for that PR:
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1. **Monkeypatch `engine_state._DEFAULT_DIR`** — it is import-time bound, so an
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env var alone does not redirect already-imported in-process runtimes.
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2. **Also set `CORE_ENGINE_STATE_DIR`** (or the equivalent) so subprocess/CLI
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tests that re-import in a child process inherit the isolation.
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3. **Preserve tests that intentionally verify default-dir behaviour** — opt them
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out via a marker (e.g. `@pytest.mark.uses_default_engine_state`) or an explicit
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override, rather than silently changing their meaning.
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4. **Broad/full-suite comparison against the known baseline reds** — the fixture
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changes default behaviour for all 469 constructions, so the PR must run the
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full suite and confirm it surfaces no *new* failures beyond the documented
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~31 pre-existing reds on `main` (`core test --suite full`). Any genuinely new
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failure is a hidden inter-test dependency to fix, not to mask.
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## Why deferred, not bundled
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The brief is safe and immediately useful (documents the hazard + the rule). The
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fixture, though small in code, changes default behaviour suite-wide and so must
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be validated against the full suite — a deliberate cost that belongs in its own
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PR rather than riding on identity-doctrine or hygiene-doc work.
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