docs(20): complete plan 20-01 SSE streaming summary and state update

.planning/STATE.md

@@ -9,19 +9,19 @@ See: .planning/PROJECT.md (updated 2026-02-04)
 
 ## Current Position
 
-Phase: 19 of 21 (Agent Inbox) - COMPLETE
-Plan: 4 of 4 in current phase
-Status: Phase 19 complete
-Last activity: 2026-02-04 - Completed 19-04-PLAN.md (Inbox Page Assembly)
+Phase: 20 of 21 (Real-Time Subscriptions) - IN PROGRESS
+Plan: 1 of 2 in current phase
+Status: Completed 20-01 (SSE Streaming & Subscription Procedures)
+Last activity: 2026-02-04 - Completed 20-01-PLAN.md (SSE backend)
 
-Progress: █████████░ 98%
+Progress: █████████░ 99%
 
 ## Performance Metrics
 
 **Velocity:**
-- Total plans completed: 70
+- Total plans completed: 71
 - Average duration: 3 min
-- Total execution time: 197 min
+- Total execution time: 201 min
 
 **By Phase (v1.0):**
 
@@ -225,6 +225,10 @@ Recent decisions affecting current work:
 - 19-04: Detail panel inline in page file (not a separate component) — page-specific layout
 - 19-04: useUtils() for query invalidation on mutation success (same pattern as initiative detail)
 - 19-04: Serialize agent/message data to string dates for InboxList props (wire format consistency)
+- 20-01: Queue + deferred promise pattern for bridging push (EventBus) to pull (async generator)
+- 20-01: tracked() wrapper on each event for client-side reconnection via lastEventId
+- 20-01: Fallback AbortSignal (new AbortController().signal) when opts.signal is undefined
+- 20-01: Vite proxy works for SSE without changes (http-proxy streams chunked responses by default)
 
 ### Pending Todos
 
@@ -247,5 +251,5 @@ None.
 ## Session Continuity
 
 Last session: 2026-02-04
-Stopped at: Completed 19-04 (Inbox Page Assembly) — Phase 19 complete
+Stopped at: Completed 20-01 (SSE Streaming & Subscription Procedures)
 Resume file: None

.planning/phases/20-real-time-subscriptions/20-01-SUMMARY.md

@@ -0,0 +1,124 @@
+---
+phase: 20-real-time-subscriptions
+plan: 01
+subsystem: api
+tags: [trpc, sse, subscriptions, async-generators, streaming, event-bus]
+
+requires:
+  - phase: 01.1-hexagonal-events
+    provides: EventBus port interface and EventEmitterBus adapter
+  - phase: 16-frontend-scaffold
+    provides: tRPC HTTP adapter and Vite proxy configuration
+
+provides:
+  - SSE streaming support in tRPC HTTP adapter
+  - Three subscription procedures (onEvent, onAgentUpdate, onTaskUpdate)
+  - EventBus-to-async-generator bridge (eventBusIterable helper)
+  - SubscriptionEvent type in shared package for frontend consumption
+
+affects: [20-02-frontend-subscriptions, 21-frontend-polish]
+
+tech-stack:
+  added: []
+  patterns: [queue-based async generator for event bridge, tracked SSE for reconnection]
+
+key-files:
+  created:
+    - src/trpc/subscriptions.ts
+  modified:
+    - src/server/trpc-adapter.ts
+    - src/trpc/router.ts
+    - packages/shared/src/types.ts
+    - packages/shared/src/index.ts
+
+key-decisions:
+  - "Queue + deferred promise pattern for bridging push (EventBus) to pull (async generator)"
+  - "tracked() wrapper on each event for client-side reconnection via lastEventId"
+  - "Fallback AbortSignal when opts.signal is undefined (AbortController().signal)"
+  - "Vite proxy works for SSE without changes (http-proxy streams by default)"
+
+patterns-established:
+  - "eventBusIterable: Reusable async generator factory for any subset of EventBus events"
+  - "Subscription procedure pattern: input with optional lastEventId, yield* from eventBusIterable"
+
+duration: 4min
+completed: 2026-02-04
+---
+
+# Plan 20-01: SSE Streaming & Subscription Procedures Summary
+
+**tRPC SSE streaming via async generators bridging EventBus domain events to three subscription endpoints**
+
+## Performance
+
+- **Duration:** 4 min
+- **Started:** 2026-02-04
+- **Completed:** 2026-02-04
+- **Tasks:** 2
+- **Files modified:** 5
+
+## Accomplishments
+- Fixed tRPC HTTP adapter to stream ReadableStream responses instead of buffering (required for SSE)
+- Created subscriptions module with queue-based async generator bridging EventBus to tRPC subscriptions
+- Added onEvent, onAgentUpdate, and onTaskUpdate subscription procedures to the router
+- Exported SubscriptionEvent type from shared package for frontend consumption
+
+## Task Commits
+
+Each task was committed atomically:
+
+1. **Task 1: Fix HTTP adapter for SSE streaming and add subscription procedures** - `e5d8dbb` (feat)
+2. **Task 2: Update shared types and verify SSE integration** - `42154d6` (feat)
+
+## Files Created/Modified
+- `src/trpc/subscriptions.ts` - EventBus-to-async-generator bridge with tracked SSE events
+- `src/server/trpc-adapter.ts` - Stream ReadableStream responses instead of buffering
+- `src/trpc/router.ts` - Three subscription procedures (onEvent, onAgentUpdate, onTaskUpdate)
+- `packages/shared/src/types.ts` - SubscriptionEvent interface for frontend
+- `packages/shared/src/index.ts` - Re-export SubscriptionEvent
+
+## Decisions Made
+- 20-01: Queue + deferred promise pattern for bridging push (EventBus) to pull (async generator)
+- 20-01: tracked() wrapper on each event for client-side reconnection via lastEventId
+- 20-01: Fallback AbortSignal (new AbortController().signal) when opts.signal is undefined
+- 20-01: Vite proxy works for SSE without changes (http-proxy streams chunked responses by default)
+
+## Deviations from Plan
+
+### Auto-fixed Issues
+
+**1. [Rule 3 - Blocking] TrackedEnvelope type annotation**
+- **Found during:** Task 1 (subscriptions module)
+- **Issue:** `ReturnType<typeof tracked<string, SubscriptionEventData>>` is invalid TS — generic type inference on `typeof` of a generic function doesn't work
+- **Fix:** Import `TrackedEnvelope` type directly from `@trpc/server` and use `TrackedEnvelope<SubscriptionEventData>` as return type
+- **Files modified:** src/trpc/subscriptions.ts
+- **Verification:** `npm run build` succeeds
+- **Committed in:** e5d8dbb (Task 1 commit)
+
+**2. [Rule 3 - Blocking] opts.signal potentially undefined**
+- **Found during:** Task 1 (subscription procedures)
+- **Issue:** `opts.signal` has type `AbortSignal | undefined` in tRPC subscription context, but eventBusIterable requires `AbortSignal`
+- **Fix:** Fallback to `new AbortController().signal` when opts.signal is undefined
+- **Files modified:** src/trpc/router.ts
+- **Verification:** `npm run build` succeeds
+- **Committed in:** e5d8dbb (Task 1 commit)
+
+---
+
+**Total deviations:** 2 auto-fixed (2 blocking)
+**Impact on plan:** Both auto-fixes necessary for type safety. No scope creep.
+
+## Issues Encountered
+None
+
+## User Setup Required
+None - no external service configuration required.
+
+## Next Phase Readiness
+- Backend SSE streaming ready for frontend consumption
+- Plan 20-02 can add httpSubscriptionLink to the tRPC client and wire subscription hooks
+- All existing queries/mutations verified working (452 tests pass)
+
+---
+*Phase: 20-real-time-subscriptions*
+*Completed: 2026-02-04*