fix(fts): Don't cache failed FTS index ensure; invalidate on pool teardown

[Copilot]

ensureFTSIndexViaExecutor recorded the (repoId, table) ensure-key on every code path, including the catch-all branch. A single transient CREATE_FTS_INDEX failure (e.g. lock contention on first query after MCP server start) therefore disabled BM25 for that repo for the lifetime of the process — silently, since the query path turns FTS errors into [].

Changes

• gitnexus/src/core/search/bm25-index.ts — Move ensuredPoolFTS.add(key) into the two success branches: CREATE_FTS_INDEX succeeded, or it failed with 'already exists'. All other errors leave the key unset and emit a console.warn with repoId / table / index / message so the failure is no longer invisible.
• gitnexus/src/core/lbug/pool-adapter.ts — Add an addPoolCloseListener(listener) → disposer registry and fire registered listeners from closeOne after pool.delete(repoId). Listener exceptions are isolated so teardown always completes.
• gitnexus/src/core/search/bm25-index.ts — Lazily register a pool-close listener (idempotent, on first MCP-pool-backed query) that calls a new exported invalidateEnsuredFTSForRepo(repoId) so LRU eviction / idle close / explicit closeLbug drop the matching ensure-state instead of letting it outlive the pool that produced it.
• Tests — gitnexus/test/unit/bm25-search.test.ts adds four regression cases: transient CREATE failure → second call retries (5 CREATEs again); 'already exists' is cached (0 CREATEs on retry); explicit invalidateEnsuredFTSForRepo clears entries; pool-close listener invalidates only the closed repo, leaving siblings intact.

Before / after

// before — key cached on EVERY path, including transient failures
} catch (e: any) {
  const msg = String(e?.message ?? '');
  if (!msg.includes('already exists')) {
    // swallow
  }
}
ensuredPoolFTS.add(key); // ← poisons the cache on failure

// after — cache only on confirmed success
try {
  await executor(`CALL CREATE_FTS_INDEX(...)`);
  ensuredPoolFTS.add(key);
} catch (e: any) {
  const msg = String(e?.message ?? '');
  if (msg.includes('already exists')) {
    ensuredPoolFTS.add(key);
  } else {
    console.warn(`[gitnexus] FTS index ensure failed for repo "${repoId}" ...`);
    // key left unset → next query retries
  }
}

Notes

• CLI/pipeline FTS path (lbug-adapter.ts) is untouched; this only affects the MCP-pool path.
• No retry/backoff added — first-retry-works is sufficient per the issue; repeated failures still fall through to [] and re-warn.
• No schema, MCP contract, or persistence changes.

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Project	Deployment	Actions	Updated (UTC)
gitnexus	Ready	Preview, Comment	Apr 21, 2026 7:38am

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Claude finished @magyargergo's task in 4m 32s —— View job

---

PR Review — Don't cache failed FTS index ensure; invalidate on pool teardown

Tasks:

• Read repo docs (AGENTS.md, GUARDRAILS.md, CONTRIBUTING.md, TESTING.md, ARCHITECTURE.md)
• Read changed files (bm25-index.ts, pool-adapter.ts, bm25-search.test.ts)
• Define production-ready bar
• Review diff against bar
• Post final review

---

Production-ready bar for this PR

Based on repo docs and the affected area (MCP pool path → BM25/FTS search):

• Correctness: The ensure-cache must only be set on confirmed success; transient failures must leave the key unset and retry transparently.
• Operational safety: Pool teardown (LRU eviction, idle close, explicit closeLbug) must invalidate per-repo FTS ensure-state so a fresh pool re-creates indexes rather than trusting stale state from a previous pool lifetime.
• Listener isolation: A throwing close listener must not abort teardown for other listeners or break the overall pool lifecycle.
• LadybugDB single-writer invariant: No writes introduced to the read-only pool path beyond what was already there; no new lock-contention surface.
• Test coverage: Unit tests in gitnexus/test/unit/ covering (a) transient failure → retry, (b) "already exists" → cached, (c) explicit invalidation, (d) pool-close listener scoping.
• Contract stability: No changes to MCP tool schemas, resource URIs, or exported public API shapes beyond the new addPoolCloseListener export.
• PR title: Must follow <type>[(scope)]: <subject> per CONTRIBUTING.md.
• No secrets, no unscoped renames, no drive-by refactors per GUARDRAILS.md.

---

Findings

1. Correctness & functional completeness

The core fix is verified correct. In the original code, ensuredPoolFTS.add(key) appeared unconditionally after the try/catch block, so any error path — including transient lock contention — would poison the cache. The diff moves the add into exactly two branches: CREATE succeeded (bm25-index.ts:101) and CREATE threw "already exists" (bm25-index.ts:111). All other error paths leave the key unset and emit a console.warn (bm25-index.ts:113–117). This precisely matches the stated intent.

The pool-close listener machinery is wired correctly:

• closeOne fires listeners after pool.delete(repoId) (pool-adapter.ts:185–195), so isLbugReady(repoId) === false is already true when invalidateEnsuredFTSForRepo runs — no TOCTOU window.
• registerPoolCloseListenerOnce (bm25-index.ts:78–84) is idempotent via a module-level flag, preventing duplicate listener registration across repeated MCP-pool queries.
• invalidateEnsuredFTSForRepo iterates the Set by prefix (repoId:), correctly scoping invalidation to one repo without touching siblings.

No missing wiring, no dead branches, no MCP contract changes.

---

2. Code clarity & clean code

## NIT — Parameter shadow: addPoolCloseListener reused as parameter name

• Evidence: bm25-index.ts:79
• Why it matters: The function registerPoolCloseListenerOnce names its parameter addPoolCloseListener, which is the same identifier as the export from pool-adapter.ts. Inside the function body the parameter is used, not the module import — this is correct but creates a subtle naming collision that makes grep and impact-analysis harder.
• Recommendation: Rename the parameter to register or registerListener.
• Confidence: High

## NIT — Disposer silently discarded

• Evidence: bm25-index.ts:83 — addPoolCloseListener((repoId) => ...) returns a () => void disposer that is never stored.
• Why it matters: The listener can never be removed. Intentional for process lifetime but undocumented; a future contributor may copy this pattern and expect cleanup to work.
• Recommendation: Add an inline comment: // Disposer intentionally discarded — listener must fire for the process lifetime.
• Confidence: High

No drive-by refactors, no barrel regressions, no // removed comments, no unused re-exports.

---

3. Test coverage & change safety

Four new cases in gitnexus/test/unit/bm25-search.test.ts (lines 204–312):

Case	Behavior tested	Assertion quality
Transient failure → retry	5 CREATEs on call 1; 5 CREATEs again on call 2	Meaningful — directly guards the regression
"already exists" → cached	0 CREATEs on call 2	Meaningful
invalidateEnsuredFTSForRepo	0 CREATEs before, 5 CREATEs after	Meaningful
Pool-close listener scoping	REPO re-creates; OTHER does not	Meaningful

## NON-BLOCKING — poolCloseListenerRegistered not reset between tests; test relies on call ordering

• Evidence: bm25-index.ts:77 (module-level let poolCloseListenerRegistered = false); bm25-search.test.ts:288 (expect(poolCloseListeners.length).toBeGreaterThanOrEqual(1)).
• Why it matters: The assertion >= 1 is only true because an earlier test within the same file already triggered registerPoolCloseListenerOnce. If the pool-close listener test ever runs in isolation (e.g. vitest run --filter "pool-close") with module re-evaluation, poolCloseListeners could be empty and the assertion would still pass (>= 1 would fail — actually would break the test, which is the right outcome). More importantly, if Vitest module isolation resets bm25-index.ts between test files but the mock module is shared, the listener count and poolCloseListenerRegistered could desync. Currently this works because the tests run in the same module evaluation.
• Recommendation: The test could be made self-contained by calling searchFTSFromLbug once before the assertion, or by asserting >= 1 only after the first pooled call within that it block. Low urgency — the existing tests pass and this is a test-isolation concern, not a production concern.
• Confidence: Medium

## NON-BLOCKING — OTHER repo state not cleaned up in beforeEach

• Evidence: bm25-search.test.ts:311 — invalidateEnsuredFTSForRepo(OTHER) is called at the end of the pool-close test, not in beforeEach/afterEach.
• Why it matters: If the test fails before line 311, OTHER state bleeds into subsequent test reruns within the same process. beforeEach only resets REPO (line 199).
• Recommendation: Move cleanup for OTHER into an afterEach or reset all known repos at the start of each test.
• Confidence: High

TypeScript compile (tsc --noEmit) and vitest run test/unit cannot be verified from the diff alone — CI results in the PR checks tab are the authoritative source.

---

4. Performance

• invalidateEnsuredFTSForRepo iterates the full ensuredPoolFTS Set on every pool close (bm25-index.ts:67–69). With 5 FTS indexes × N repos, Set size is O(5N). At MAX_POOL_SIZE = 5 repos, max size is 25 entries. Iteration cost is negligible.
• poolCloseListeners is a Set<PoolCloseListener> (pool-adapter.ts:49). The close path iterates it synchronously after pool.delete (pool-adapter.ts:189–195). With one registered listener in practice, this is O(1).
• No new hot-path overhead on the query path. Ensure-check is a Set.has O(1) guard (bm25-index.ts:94).

No performance concerns.

---

5. Operational risk

## NON-BLOCKING — CREATE_FTS_INDEX dispatched through the read-only pool

• Evidence: bm25-index.ts:97–99; pool-adapter.ts:308–315 (readOnly: true); pool-adapter.ts:552–554 (isWriteQuery check).
• Why it matters: The DB is opened read-only. CALL CREATE_FTS_INDEX(...) passes isWriteQuery (the regex \bCREATE\b does not match CREATE_FTS_INDEX because _ is a word character — no word boundary after E). Whether the FTS call actually succeeds against a read-only DB depends on LadybugDB internals. In practice the happy path is "already exists" (analyze created the index during ingest), so this never surfaces. A fresh DB with no prior analyze would fail with something other than "already exists"; with this PR that failure is correctly not cached, and the query falls back to []. This is pre-existing behavior — not introduced by this PR — but the comment at pool-adapter.ts:638–641 should arguably acknowledge CALL CREATE_FTS_INDEX alongside CALL QUERY_FTS_INDEX to prevent future confusion.
• Recommendation: Add CREATE_FTS_INDEX to the inline comment on CYPHER_WRITE_RE explaining why it's not blocked. Fix this →
• Confidence: High (pre-existing gap; not introduced here)

Rollback safety: Reverting this PR restores the poisoned-cache behavior but does not require re-analyze. The ensuredPoolFTS Set is process-scoped and ephemeral; no on-disk state changes. Safe to revert.

MCP contracts: No changes to tool schemas, resource URIs, or response shapes. addPoolCloseListener is a new export on an internal module; no MCP surface change.

LadybugDB single-writer invariant: Preserved. No new write paths introduced.

Embeddings, staleness, Windows paths: Untouched by this PR.

---

6. Maintainability

The close-listener pattern is clean and discoverable: addPoolCloseListener is exported from pool-adapter.ts with a JSDoc and the listener registration in bm25-index.ts has an inline comment explaining why. The pipeline phase DAG is not touched. No cross-phase coupling introduced.

---

Non-negotiables verification

Check	Status
No secrets / tokens / machine paths	✅ Verified
No blind find-and-replace renames	✅ No renames
No HIGH/CRITICAL impact left unaddressed	✅ N/A — no shared symbol renames
PolyForm Noncommercial license untouched	✅ Verified
PR title follows conventional commit format	❌ Title is Don't cache failed FTS index ensure; invalidate on pool teardown — missing <type> prefix. CONTRIBUTING.md states this MUST follow the format (e.g., fix(search): don't cache failed FTS index ensure; invalidate on pool teardown). pr-labeler.yml enforces this in CI.

---

What I could not fully verify

• Whether tsc --noEmit and vitest run test/unit pass — CI is the authoritative source (the PR's firewall note shows tests were attempted; results need confirmation in the Checks tab).
• Whether LadybugDB's CREATE_FTS_INDEX procedure actually errors on a read-only connection vs. succeeds silently — this affects which catch branch fires in practice, but both branches are now handled correctly regardless.
• The pre-existing CLI path (lbug-adapter.ts ensureFTSIndex) behavior is unchanged by this PR and was not reviewed.

---

Final verdict

✅ Ready to merge — no blocking issues.

The core bug fix is correct and directly addresses the root cause. The pool-close listener wiring is sound. The four regression tests are meaningful and guard the critical behaviors. Non-blocking items (test isolation hygiene, disposer comment, pre-existing read-only/CREATE gap) do not affect production correctness. The PR title format violation is flagged for cleanup before or after merge.