docs(21-04): complete subscription error handling plan

Tasks completed: 2/2
- Add subscription error handling with toast feedback on all pages
- Verify SpawnArchitectDropdown error toast coverage (no-op)

SUMMARY: .planning/phases/21-polish-integration/21-04-SUMMARY.md

.planning/ROADMAP.md

@@ -325,7 +325,7 @@ Plans:
 - [ ] 21-01: Error Boundary & Toast Notifications
 - [ ] 21-02: Skeleton Loading States
 - [x] 21-03: Cross-Screen Navigation & Mobile Responsive
-- [ ] 21-04: Subscription Error Handling
+- [x] 21-04: Subscription Error Handling
 - [ ] 21-05: Code Splitting & Performance
 - [ ] 21-06: Integration Smoke Test
 
@@ -358,7 +358,7 @@ Phases execute in numeric order: 1 → 1.1 → 2 → 3 → 4 → 5 → 6 → 7
 | 18. Initiative Detail | v2.0 | 4/4 | Complete | 2026-02-04 |
 | 19. Agent Inbox | v2.0 | 4/4 | Complete | 2026-02-04 |
 | 20. Real-time Subscriptions | v2.0 | 2/2 | Complete | 2026-02-04 |
-| 21. Polish & Integration | v2.0 | 3/6 | In progress | - |
+| 21. Polish & Integration | v2.0 | 4/6 | In progress | - |
 
 ---
 *Roadmap created: 2026-01-30*

.planning/STATE.md

@@ -10,18 +10,18 @@ See: .planning/PROJECT.md (updated 2026-02-04)
 ## Current Position
 
 Phase: 21 of 21 (Polish & Integration) - In progress
-Plan: 3 of 6 in current phase
-Status: Completed 21-03 (Cross-Screen Navigation & Mobile Responsive)
-Last activity: 2026-02-05 - Completed 21-03-PLAN.md (navigation links + mobile responsive)
+Plan: 4 of 6 in current phase
+Status: Completed 21-04 (Subscription Error Handling)
+Last activity: 2026-02-05 - Completed 21-04-PLAN.md (subscription error toasts)
 
 Progress: █████████░ 99%
 
 ## Performance Metrics
 
 **Velocity:**
-- Total plans completed: 72
+- Total plans completed: 73
 - Average duration: 3 min
-- Total execution time: 204 min
+- Total execution time: 206 min
 
 **By Phase (v1.0):**
 
@@ -243,6 +243,10 @@ Recent decisions affecting current work:
 - 21-03: TaskRow agent names link to /inbox — simplest cross-screen navigation for agent context
 - 21-03: Inbox task links go to /initiatives — no direct task-to-initiative mapping on frontend
 - 21-03: Mobile drill-down pattern hides list on mobile when detail selected, shows back button
+- 21-04: Fixed toast ID 'sub-error' prevents duplicate notifications across concurrent subscription failures
+- 21-04: duration: Infinity keeps error toast visible until user dismisses — persistent connection feedback
+- 21-04: No reconnection logic — tRPC SSE httpSubscriptionLink handles reconnection via EventSource retry
+- 21-04: SpawnArchitectDropdown already covered by 21-01 — verification task was no-op
 
 ### Pending Todos
 
@@ -265,5 +269,5 @@ None.
 ## Session Continuity
 
 Last session: 2026-02-05
-Stopped at: Completed 21-03 (Cross-Screen Navigation & Mobile Responsive)
+Stopped at: Completed 21-04 (Subscription Error Handling)
 Resume file: None

.planning/phases/21-polish-integration/21-04-SUMMARY.md

@@ -0,0 +1,95 @@
+---
+phase: 21-polish-integration
+plan: 04
+subsystem: ui
+tags: [sse, subscriptions, toast, sonner, error-handling, trpc]
+
+# Dependency graph
+requires:
+  - phase: 21-01
+    provides: Toast notification system (sonner Toaster component)
+  - phase: 20-02
+    provides: SSE subscription hooks on all three pages
+provides:
+  - Subscription error feedback with sticky toast notifications
+  - User awareness when live updates disconnect
+affects: [21-06]
+
+# Tech tracking
+tech-stack:
+  added: []
+  patterns:
+    - "Fixed toast ID for deduplication across concurrent subscription errors"
+    - "Sticky (Infinity duration) toast for persistent connection state feedback"
+
+key-files:
+  created: []
+  modified:
+    - packages/web/src/routes/initiatives/index.tsx
+    - packages/web/src/routes/initiatives/$id.tsx
+    - packages/web/src/routes/inbox.tsx
+
+key-decisions:
+  - "21-04: Same toast ID 'sub-error' across all subscriptions prevents duplicate error notifications"
+  - "21-04: duration: Infinity keeps toast visible until user dismisses — intentionally sticky"
+  - "21-04: No reconnection logic added — tRPC SSE httpSubscriptionLink handles reconnection via EventSource retry"
+  - "21-04: SpawnArchitectDropdown already covered by 21-01 — Task 2 was a verified no-op"
+
+# Metrics
+duration: 2min
+completed: 2026-02-05
+---
+
+# Phase 21 Plan 04: Subscription Error Handling Summary
+
+**Sticky toast notifications for SSE subscription errors with fixed ID deduplication across all three pages**
+
+## Performance
+
+- **Duration:** 2 min
+- **Started:** 2026-02-05
+- **Completed:** 2026-02-05
+- **Tasks:** 2 (1 implemented, 1 verified no-op)
+- **Files modified:** 3
+
+## Accomplishments
+- Replaced all silent `onError: () => {}` callbacks with sticky toast notifications on initiatives dashboard, initiative detail, and inbox pages
+- Used fixed toast ID `sub-error` so multiple concurrent subscription failures show only one notification
+- Verified SpawnArchitectDropdown already has full toast coverage from plan 21-01
+
+## Task Commits
+
+Each task was committed atomically:
+
+1. **Task 1: Add subscription error handling with toast feedback on all pages** - `4ae85da` (feat)
+2. **Task 2: Verify SpawnArchitectDropdown error toast coverage** - no-op (21-01 already applied)
+
+## Files Created/Modified
+- `packages/web/src/routes/initiatives/index.tsx` - Added toast import, replaced onError with error toast
+- `packages/web/src/routes/initiatives/$id.tsx` - Added toast import, replaced both onError callbacks with error toast
+- `packages/web/src/routes/inbox.tsx` - Replaced onError with error toast (toast already imported)
+
+## Decisions Made
+- Same toast ID `sub-error` across all subscriptions prevents duplicate error notifications when multiple subscriptions fail simultaneously
+- `duration: Infinity` keeps toast visible until user dismisses it — intentionally sticky so users know live updates are broken
+- No reconnection logic added — tRPC SSE httpSubscriptionLink already handles reconnection via EventSource retry
+- SpawnArchitectDropdown was already fully covered by 21-01 (toast.error on onError, toast.success on onSuccess for both mutations)
+
+## Deviations from Plan
+
+None - plan executed exactly as written.
+
+## Issues Encountered
+None
+
+## User Setup Required
+None - no external service configuration required.
+
+## Next Phase Readiness
+- Ready for 21-05-PLAN.md (Code Splitting & Performance)
+- All subscription error handling in place
+- No blockers
+
+---
+*Phase: 21-polish-integration*
+*Completed: 2026-02-05*