core/docs/decisions/ADR-0157-revision-mismatch-warning.md
Shay fbff161a2e
feat(W-023): revision-mismatch warning on engine-state load (L10b.2, ADR-0157) (#283)
* feat(W-022): ratify-proposal workflow_dispatch for mobile ratification

Adds .github/workflows/ratify-proposal.yml — a manually triggered
workflow that lets the operator ratify engine-authored proposals from
the GitHub mobile app without needing terminal access.

Inputs: proposal_id (required), review_date (default: today UTC),
operator_note (optional).  Runs `core teaching review --accept`,
commits the updated corpus + proposal log to main, and posts a
job summary with the accepted chain_id.

Shared CONTEMPLATION_ENABLED kill switch disables the entire
learning-arc loop (contemplation + ratification) with one toggle.

ADR-0155 / ADR-0057

* feat(W-023): revision-mismatch warning on engine-state load (L10b.2, ADR-0157)

ADR-0146 §Risks line 127 specified that load_manifest() should compare
written_at_revision against the current git SHA and warn if they differ,
but never refuse to load (reboot is recovery, not control flow).

- EngineStateStore.load_manifest() emits RuntimeWarning when stored and
  current revisions are both known and do not match
- Suppresses warning when either side is "unknown" (offline/packaged builds)
- Always returns the manifest; no state is cleared or rejected
- Pinned by 8 tests covering match, mismatch, unknown suppression, and
  missing/empty manifest edge cases

ADR-0156 §Out of scope closes; L10b.3 (reboot_event audit entry, W-024) remains.
2026-05-25 19:56:07 -07:00

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# ADR-0157 — Revision-mismatch warning on engine-state load (W-023 / L10b.2)
Status: accepted
Date: 2026-05-26
## Context
ADR-0146 §Risks line 127 specified:
> "Compare `written_at_revision` in `manifest.json` with the current git
> SHA. If they mismatch, log a warning but continue startup (do not refuse
> to start, as a reboot is recovery, not control flow)."
W-008 and W-022 implemented the manifest write path but never implemented
the read-side comparison. After a `git pull` or a branch switch the engine
silently loads a checkpoint written by a different code version, which can
produce confusing behaviour if serialization formats changed.
## Decision
Inside `EngineStateStore.load_manifest()`, after parsing the JSON:
1. Read `manifest["written_at_revision"]` (stored revision).
2. Call `_git_revision()` to obtain the current HEAD short SHA.
3. If both values are non-empty and not `"unknown"`, and they differ,
emit `warnings.warn(..., RuntimeWarning, stacklevel=2)`.
4. Always return the manifest — never raise, never clear state.
The warning message names both revisions and suggests clearing
`engine_state/` if unexpected behaviour is observed.
### Why `warnings.warn` not `logging`
`warnings` is already used in the codebase (`core/physics/identity.py`).
It is testable via `pytest.warns` without logger configuration, fits
`RuntimeWarning` semantics (a recoverable runtime anomaly), and respects
the standard Python warning filter so operators can suppress or escalate it
via `-W` flags or `PYTHONWARNINGS`.
### Why suppress when either side is `"unknown"`
`_git_revision()` returns `"unknown"` when `git` is unavailable (CI
containers, packaged builds, offline environments). Storing `"unknown"` or
comparing against it would always trigger a spurious warning in those
environments. Suppressing when either side is unknown is the
lowest-surprise behaviour.
## Invariants pinned by tests
`tests/test_adr_0157_revision_mismatch_warning.py` (8 tests):
- Matching revision → no `RuntimeWarning`
- Mismatched revision → `RuntimeWarning` emitted, manifest returned intact
- Warning message contains both the stored and current revisions
- `written_at_revision: "unknown"` in stored manifest → no warning
- `_git_revision()` returns `"unknown"` → no warning
- Missing manifest file → `None` returned, no warning
- Empty manifest file → `None` returned, no warning
## Out of scope
- **Schema-version migration.** A `schema_version` bump requires a
migration or clear-slate fallback (ADR-0146 §Risks line 125). That is
separate from the revision warning and deferred to a future ADR when
`_SCHEMA_VERSION` is actually incremented.
- **`reboot_event` audit trail entry** — L10b.3 / W-024.
## Validation
- `tests/test_adr_0157_revision_mismatch_warning.py` (8 passed)
- `tests/test_adr_0146_engine_state.py` (8 passed — round-trip regression guard)
- `core test --suite smoke` (67 passed)