AW-8: Migrate EventEmitter2 Events to EventBusService#

Summary#

Incrementally migrate all 6 in-process EventEmitter2 event types to Redis-backed EventBusService (from AW-7 #443) across 6 rounds, then remove @nestjs/event-emitter. Each round is a separate PR — lowest-risk events first, highest-risk (job.created self-trigger) last.

Dependency: Blocked until AW-7 (#443) merges — EventBusService must exist before migration begins.

Files#

File	Action	Rounds	Description
`src/task-state/task-state.service.ts`	modify	1	Replace 4× `eventEmitter.emit('task.updated')` with `eventBus.emit()`
`src/task-state/task-state.module.ts`	modify	1	Import EventBusModule, remove EventEmitterModule
`src/ws-gateway/ws-gateway.service.ts`	modify	1-4	Replace 6× `@OnEvent` decorators with `eventBus.on()` in `onModuleInit()`
`src/ws-gateway/ws-gateway.module.ts`	modify	1, 6	Import EventBusModule; remove EventEmitterModule in R6
`src/metrics/metrics.cache.ts`	modify	1	Replace `@OnEvent('task.updated')` with `eventBus.on()`
`src/metrics/metrics.module.ts`	modify	1	Import EventBusModule, remove EventEmitterModule
`src/watchdog/watchdog.service.ts`	modify	2	Replace `eventEmitter.emit('task.stuck')` with `eventBus.emit()`
`src/watchdog/watchdog.module.ts`	modify	2	Import EventBusModule, remove EventEmitterModule
`src/phase-router/phase-router.service.ts`	modify	3	Replace 2× `eventEmitter.emit('artefacts.synced')` with `eventBus.emit()`
`src/phase-router/phase-router.module.ts`	modify	3	Import EventBusModule
`src/queue/sqlite-job-queue.ts`	modify	4-5	R4: migrate `job.completed`/`job.failed`. R5: replace `job.created` self-trigger with direct `processNext()` call
`src/queue/queue.module.ts`	modify	4	Import EventBusModule, remove EventEmitterModule
`package.json`	modify	6	`npm uninstall @nestjs/event-emitter`
Unit test files (*.spec.ts)	modify	1-6	Update mocks: replace EventEmitter2 with EventBusService

Steps#

Round 1 — task.updated: Inject EventBusService into TaskStateService, WsGatewayService, MetricsCache. Replace 4 emit calls and 2 @OnEvent decorators. Wrap all eventBus.emit() in try/catch. Update modules and specs.
Round 2 — task.stuck: Inject EventBusService into WatchdogService. Replace 1 emit and 1 @OnEvent in WsGatewayService. Update module and specs.
Round 3 — artefacts.synced: Inject EventBusService into PhaseRouterService. Replace 2 emits and 1 @OnEvent in WsGatewayService. Update module and specs.
Round 4 — job.completed + job.failed: Inject EventBusService into SqliteJobQueue. Replace 2 emits and 2 @OnEvent in WsGatewayService. Update module and specs.
Round 5 — job.created: Replace 3× eventEmitter.emit('job.created') with direct void this.processNext(). Also emit to Redis for future multi-instance. Remove @OnEvent('job.created') from processNext(). Remove remaining EventEmitter2 import from SqliteJobQueue.
Round 6 — Cleanup: Remove EventEmitterModule.forRoot() from all modules. npm uninstall @nestjs/event-emitter. Verify no EventEmitter2 or @OnEvent imports remain. Run build + test.

Verification#

npm run build && npm run test passes after each round
WebSocket clients still receive all 6 event types via gateway broadcast
Job queue self-trigger (job.created → processNext()) still processes pending jobs end-to-end

Risks#

Round 5 (job.created) is pipeline-critical: If the self-trigger migration breaks, no new phases execute. Mitigation: direct processNext() call is simpler/more reliable than pub/sub; test thoroughly in test environment before merging.
Dependency on AW-7: Plan is blocked until EventBusService exists. If AW-7 scope changes, this plan may need revision.