Vesper Review — Branch #7 `fix/wal-checkpoint-hardening`¶

To: Katja CC: Orion, Atlas From: Vesper Date: 2026-04-19

Verdict: APPROVED ✅¶

Single commit reviewed. All five Q rulings and all four Atlas additions correctly implemented and documented. No blocking issues. One minor nit.

Config + YAML¶

EngineConfig.wal_checkpoint_interval_seconds: int = 60 placed correctly. Loader comment names the Q1 ruling explicitly. Negative coercion (_wal_checkpoint_raw if _wal_checkpoint_raw > 0 else 0) is clean. Both YAMLs updated with value and purpose comment. No issues.

`state_manager.py`¶

Imports: threading, time, statistics, deque, Deque — all correct, all new to this codebase.

__init__ additions: Four fields initialized (interval, thread handle, stop event, deque(maxlen=512)). Clean. The _checkpoint_stop Event is initialized in __init__ so it's always present, even when the loop is disabled — correct, avoids AttributeError in close() when the loop was never started.

start_wal_checkpoint_loop: Idempotent (duplicate-start warning, no second thread). _checkpoint_stop.clear() before thread start handles the edge case of a stop-then-restart if it ever arises. Daemon thread so hard kills don't hang. Correct.

_checkpoint_loop: The sequential wait→run→wait→run structure is the explicit overlap-prevention mechanism per Atlas #2 — documented in the class-level audit comment. _checkpoint_stop.wait(timeout=interval) returns immediately on stop signal, so shutdown is responsive. Correct.

_run_checkpoint: Structure is right. INFO always emitted, WARNING additionally when elapsed_ms > 200 with same fields (Atlas #1). row is None guard is defensive and correct — SQLite's PRAGMA wal_checkpoint always returns a row in practice, but the guard costs nothing. ERROR with exc_info=True on PRAGMA failure (Atlas #4). No silent passes.

_log_checkpoint_aggregate: statistics.quantiles(samples, n=100, method="inclusive") at indices 49/94 for p50/p95 is correct. Single-sample edge case handled with direct assignment. Outer try/except logs at ERROR (Atlas #4). Quiet no-op on empty samples — correct for the disabled-thread case.

close() — 5-step sequence: Matches Atlas #3 exactly. Notable: thread.is_alive() check after join(timeout=5.0) with log.error if the thread didn't exit — this is the right guard for a stuck checkpoint and it's not in the spec but it's the correct defensive addition. Step 4 calls self._run_checkpoint("TRUNCATE") which reuses the full logging + field-extraction path for the shutdown TRUNCATE — clean, avoids duplicating field-extraction code. _conn.close() runs unconditionally in all code paths.

One minor nit: close() wraps self._run_checkpoint("TRUNCATE") in an outer try/except Exception: log.error(...). Since _run_checkpoint already catches all exceptions internally and never re-raises, the outer guard is unreachable. Harmless belt-and-suspenders; fix in a future cleanup pass only.

`main_loop.py`¶

One line inserted in the correct position: after _check_config_invariants() and before set_engine_state("engine_status", RUNNING). Comment names the ruling. No other changes. Correct.

Tests¶

All four on-disk via tempfile.TemporaryDirectory. :memory: correctly excluded — the rationale is documented in the test file header.

Test 1 (periodic log + aggregate): ≥2 PASSIVE records, all required fields present, aggregate monotone assertion. Correct.
Test 2 (integrity under concurrent writes): 200 writes + checkpoint loop + quick_check == "ok" + row count. The correct test for proving no corruption.
Test 3 (TRUNCATE zeroes WAL): pins the shutdown contract at the file-system level.
Test 4 (slow checkpoint warning): _SlowExecuteConn proxy is the right approach — sqlite3.Connection.execute is a C-level read-only attribute that mock.patch.object cannot patch. Documented in the test file. The 250ms sleep reliably triggers the 200ms threshold.

test_halt_reason_lifecycle.py fixture update (set wal_checkpoint_interval_seconds = 0) is correct and consistent with the Branch #5 pattern.

Apply commands — Windows VS Code terminal¶

git fetch origin
git checkout -b fix/wal-checkpoint-hardening

git am "C:\Users\Katja\Documents\Claude Homebase Neo\02 Projects\NEO Trading Engine\patches\branch-7-wal-checkpoint-hardening\0001-feat-state-periodic-WAL-checkpoint-TRUNCATE-at-shutd.patch"

git log --oneline -2
python -m pytest tests/test_wal_checkpoint_hardening.py tests/test_halt_reason_lifecycle.py -q

Expected: 4 passed in test_wal_checkpoint_hardening.py + halt lifecycle tests still green. Note: Test 1 sleeps 2.5s and Test 4 sleeps briefly — the suite will take ~5–6 seconds, that's normal. Merge when clean:

git checkout main
git merge --no-ff fix/wal-checkpoint-hardening -m "Merge branch 'fix/wal-checkpoint-hardening' into main"
git push

Then we're at S40.

Branch status¶

Branch	Status
#1–#6	✅ Merged
#7 fix/wal-checkpoint-hardening	✅ Approved — apply and merge
S40	⏳ Next — 30-min clean paper run post-merge
Phase 7.3	⏳ Unlocks after S40 passes

— Vesper

Vesper Review — Branch #7 fix/wal-checkpoint-hardening¶