---
phase: 09-faster-write-back
verified: 2026-06-12T17:07:00Z
status: passed
score: 5/5 must-haves verified
overrides_applied: 0
---

# Phase 09: Faster Write-Back Verification Report

**Phase Goal:** A created, edited, or deleted event reaches Fastmail within ~1-2 seconds (event-driven outbox drain) instead of waiting up to ~15s for the next interval tick — with every existing durability guarantee intact.
**Verified:** 2026-06-12T17:07:00Z
**Status:** passed
**Re-verification:** No — initial verification

## Goal Achievement

### Observable Truths

| # | Truth | Status | Evidence |
|---|-------|--------|----------|
| 1 | After creating/editing/deleting an event, the change is signalled to drain on enqueue (not waited-for on the interval) — the drain fires promptly, not on the 15s tick. | VERIFIED | `signalOutboxDrain()` called at all 4 enqueue sites in events.ts (lines 310, 434, 450, 525). Test SC-1 in outboxWorker.test.ts confirms drain fires via EventEmitter signal without advancing any timer. |
| 2 | The route handler still returns an optimistic 202 immediately and never makes a CalDAV call inline — the signal is fire-and-forget (never awaited). | VERIFIED | No `await signalOutboxDrain` in events.ts. All 4 sites call `signalOutboxDrain();` then immediately `return c.json(..., 202)`. events.test.ts (23 tests) confirms 202 + no-inline-CalDAV contract still holds. |
| 3 | Edit-as-move still writes the new event before deleting the old one (create-before-delete preserved); the signal fires AFTER the db.transaction resolves, never inside it. | VERIFIED | events.ts line 410 opens `await db.transaction(async (tx) => { ... });` closing at line 432. `signalOutboxDrain()` appears at line 434 — after the `await db.transaction(...)` statement, not inside the callback. Confirmed: no `signalOutboxDrain` between the two `tx.insert` calls. |
| 4 | No duplicate CalDAV PUTs for the same outbox row when signal and the 15s fallback overlap (exactly-once per uid preserved via the isDraining guard + drainRequested trailing-re-drain). | VERIFIED | `scheduleOutboxDrain` checks `if (isDraining) { drainRequested = true; return; }` before calling `runOutboxDrain()`. Test D-07 (Test C) verifies two concurrent `scheduleOutboxDrain()` calls result in `createCalendarEvent` called exactly once. Test D-05 (Test B) verifies mid-drain signals collapse to exactly one trailing re-drain. |
| 5 | The 15s setInterval fallback still runs and recovers missed rows. | VERIFIED | `startOutboxWorker` in outboxWorker.ts line 857: `setInterval(() => { scheduleOutboxDrain(); }, 15 * 1000)` — interval length unchanged, body routes through `scheduleOutboxDrain` wrapper. |

**Score:** 5/5 truths verified

### Required Artifacts

| Artifact | Expected | Status | Details |
|----------|----------|--------|---------|
| `apps/api/src/lib/outboxTrigger.ts` | Zero-dependency EventEmitter signal (signalOutboxDrain, onOutboxDrain) | VERIFIED | Exists. Imports only `node:events`. Exports `signalOutboxDrain` and `onOutboxDrain`. No `setMaxListeners`. No internal project imports. |
| `apps/api/src/broker/outboxWorker.ts` | scheduleOutboxDrain + drainRequested + initOutboxTrigger | VERIFIED | Exports `scheduleOutboxDrain`, `initOutboxTrigger`. Declares `let drainRequested = false` at line 172. `drainRequested = false` reset precedes recursive `scheduleOutboxDrain()` call (line 199 before 200 — Pitfall 3 correct). |
| `apps/api/src/routes/events.ts` | Four post-commit signalOutboxDrain() publish sites | VERIFIED | Exactly 4 calls (lines 310, 434, 450, 525). Import at line 37. None awaited. None inside transaction callback or catch blocks. |
| `apps/api/src/index.ts` | initOutboxTrigger() wired under isMainModule(), after startOutboxWorker() | VERIFIED | Line 138: `startOutboxWorker()`. Line 139: `initOutboxTrigger(); // subscribe drain signal listener (D-01)`. Both inside the `if (isMainModule())` block. |
| `apps/api/tests/broker/outboxWorker.test.ts` | Trigger-wiring test block (SC-1, D-05, D-07) — 3 new tests | VERIFIED | `describe('scheduleOutboxDrain — trigger wiring (D-09)', ...)` block at line 747 with `beforeAll(() => { initOutboxTrigger(); })` and 3 tests. All 30 outboxWorker tests pass. |

### Key Link Verification

| From | To | Via | Status | Details |
|------|----|-----|--------|---------|
| `outboxWorker.ts (initOutboxTrigger)` | `outboxTrigger.ts (onOutboxDrain)` | `onOutboxDrain(() => scheduleOutboxDrain())` | WIRED | Line 845: `onOutboxDrain(() => scheduleOutboxDrain())`. Import at line 39. |
| `outboxWorker.ts (scheduleOutboxDrain)` | `outboxWorker.ts (runOutboxDrain)` | isDraining guard + drainRequested trailing-re-drain | WIRED | Lines 187-203: guard checks `isDraining`, calls `runOutboxDrain()`, finally resets `drainRequested` before recursive call. |
| `routes/events.ts` | `outboxTrigger.ts (signalOutboxDrain)` | import + call after each enqueue commit | WIRED | Import at line 37. 4 call sites verified present and not awaited. |
| `index.ts (isMainModule block)` | `outboxWorker.ts (initOutboxTrigger)` | `initOutboxTrigger()` after `startOutboxWorker()` | WIRED | Lines 138-139 inside `isMainModule()` guard. |
| `startOutboxWorker setInterval` | `scheduleOutboxDrain` | bare `scheduleOutboxDrain()` call in 15s interval | WIRED | Lines 857-859: `setInterval(() => { scheduleOutboxDrain(); }, 15 * 1000)`. |

### Data-Flow Trace (Level 4)

Not applicable — phase adds a signal/trigger path, not a data-rendering path. The signal carries no payload; it triggers an existing drain that queries the DB for pending rows. The drain's data path (outbox rows → CalDAV) is unchanged and was verified in prior phases.

### Behavioral Spot-Checks

| Behavior | Command | Result | Status |
|----------|---------|--------|--------|
| SC-1: signalOutboxDrain() triggers drain without timer advance | `npx vitest run tests/broker/outboxWorker.test.ts` — Test A | 30/30 passed | PASS |
| D-05: mid-drain signals collapse to one trailing re-drain | Test B in same run | 30/30 passed | PASS |
| D-07: concurrent scheduleOutboxDrain() calls are exactly-once | Test C in same run | 30/30 passed | PASS |
| 202 + no-inline-CalDAV route contract preserved | `npx vitest run tests/routes/events.test.ts` | 23/23 passed | PASS |
| tsc clean across all phase-9 files | `npx tsc --noEmit` | No output (clean) | PASS |

### Probe Execution

No conventional `scripts/*/tests/probe-*.sh` probes declared or found for this phase.

### Requirements Coverage

| Requirement | Source Plan | Description | Status | Evidence |
|-------------|------------|-------------|--------|----------|
| CAL-15 | 09-01-PLAN.md, 09-02-PLAN.md | Event reaches Fastmail within ~2s (event-driven drain) instead of up to ~15s, while preserving optimistic-202 and all outbox durability guarantees. | SATISFIED | `signalOutboxDrain()` fires immediately post-enqueue. SC-1 test confirms no timer advance needed. isDraining guard + drainRequested preserve exactly-once. 15s fallback intact. REQUIREMENTS.md marks CAL-15 as Complete. |

### Anti-Patterns Found

No debt markers (TBD/FIXME/XXX/TODO/HACK/PLACEHOLDER) found in any phase-9 modified file. No stub patterns found. No `return null`, empty handlers, or hardcoded empty data in the signal path.

### Human Verification Required

None. The phase goal (latency reduction via event-driven drain) is fully verifiable through automated tests and static code inspection:

- SC-1 (no 15s wait): automated by the trigger-wiring Vitest test using `setImmediate` flush — no stopwatch needed.
- D-04 (fire-and-forget): verified by static grep — no `await signalOutboxDrain` anywhere.
- D-03 (signal after transaction): verified by static line-number inspection — `signalOutboxDrain()` at line 434 is after `await db.transaction(...)` closes at line 432.
- Fallback interval: verified by reading the `startOutboxWorker` body.

### Gaps Summary

No gaps. All 5 must-have truths are VERIFIED with direct codebase evidence:

1. All 4 enqueue sites in events.ts call `signalOutboxDrain()` post-commit, pre-202.
2. No call is awaited; the signal is synchronous EventEmitter emit.
3. The edit-as-move signal is provably outside the transaction callback at the source level.
4. The `isDraining` guard + `drainRequested` boolean collapses concurrent/mid-drain signals correctly; verified by 2 dedicated automated tests.
5. The 15s setInterval fallback routes through `scheduleOutboxDrain()` at the same 15-second cadence.

CAL-15 is marked Complete in REQUIREMENTS.md (line 78) and all its behavioral guarantees are implemented and tested.

---

_Verified: 2026-06-12T17:07:00Z_
_Verifier: Claude (gsd-verifier)_
