diff --git a/.planning/ROADMAP.md b/.planning/ROADMAP.md
index def45036c..8d380a19c 100644
--- a/.planning/ROADMAP.md
+++ b/.planning/ROADMAP.md
@@ -41,9 +41,9 @@ Decimal phases appear between their surrounding integers in numeric order.
 - [x] **Phase 6: Session Chat Research & Design** - Explore legacy chat implementation, design React patterns
 - [x] **Phase 7: Chat Infrastructure & State Management** - Redux state, WebSocket handlers, API integration
 - [x] **Phase 8: Chat Window UI & Message Display** - Modeless dialog, message list with user info
-- [ ] **Phase 9: Message Composition & Sending** - Text input, send functionality, real-time delivery (1/TBD plans complete)
-- [ ] **Phase 10: Read/Unread Status Management** - Unread tracking, indicator badge, mark-as-read logic
-- [ ] **Phase 11: Chat Finalization** - Error handling, edge cases, performance optimization, UAT
+- [x] **Phase 9: Message Composition & Sending** - Text input, send functionality, real-time delivery (2/2 plans complete)
+- [x] **Phase 10: Read/Unread Status Management** - Unread tracking, indicator badge, mark-as-read logic (1/1 plans complete)
+- [ ] **Phase 11: Chat Finalization** - Error handling, edge cases, performance optimization, UAT (1/2 plans complete)
 
 ## Phase Details
 
@@ -167,10 +167,11 @@ Plans:
 **Goal**: Complete chat with error handling, edge cases, and performance optimization
 **Depends on**: Phase 10
 **Research**: Unlikely (error handling and optimization of established code)
-**Plans**: TBD
+**Plans**: 2 plans
 
 Plans:
-- [ ] 11-01: TBD (run /gsd:plan-phase 11 to break down)
+- [x] 11-01: Error Handling, Accessibility & Polish (3 tasks) - COMPLETE 2026-01-27
+- [ ] 11-02: UAT & Final Integration Testing
 
 ## Progress
 
@@ -188,5 +189,5 @@ Phases execute in numeric order: 1 → 2 → 3 → 4 → 5 → 6 → 7 → 8 →
 | 7. Chat Infrastructure & State Management | v1.1 | 3/3 | Complete | 2026-01-27 |
 | 8. Chat Window UI & Message Display | v1.1 | 3/3 | Complete | 2026-01-27 |
 | 9. Message Composition & Sending | v1.1 | 2/2 | Complete | 2026-01-27 |
-| 10. Read/Unread Status Management | v1.1 | 1/1+ | In progress | 2026-01-27 |
-| 11. Chat Finalization | v1.1 | 0/TBD | Not started | - |
+| 10. Read/Unread Status Management | v1.1 | 1/1 | Complete | 2026-01-27 |
+| 11. Chat Finalization | v1.1 | 1/2 | In progress | 2026-01-27 |
diff --git a/.planning/STATE.md b/.planning/STATE.md
index 621b0fe26..c3c281fc1 100644
--- a/.planning/STATE.md
+++ b/.planning/STATE.md
@@ -9,12 +9,12 @@ See: .planning/PROJECT.md (updated 2026-01-13)
 
 ## Current Position
 
-Phase: 10 of 11 (Read/Unread Status Management)
-Plan: 10-01 complete
-Status: Plan 1 complete (1/? plans)
-Last activity: 2026-01-27 — Completed 10-01-PLAN.md (Read/Unread Status Validation & Testing)
+Phase: 11 of 11 (Chat Finalization)
+Plan: 11-01 complete
+Status: Plan 1 complete (1/2 plans)
+Last activity: 2026-01-27 — Completed 11-01-PLAN.md (Error Handling, Accessibility & Polish)
 
-Progress: █████████░ 85% (v1.1)
+Progress: ██████████ 90% (v1.1)
 
 ## Performance Metrics
 
@@ -35,9 +35,9 @@ Progress: █████████░ 85% (v1.1)
 | 5 | 5 | 54 min | 10.8 min |
 
 **v1.1 Music Session Chat (In Progress):**
-- Total plans completed: 9 (Phase 6: 2, Phase 7: 3, Phase 8: 3, Phase 9: 2, Phase 10: 1)
+- Total plans completed: 10 (Phase 6: 2, Phase 7: 3, Phase 8: 3, Phase 9: 2, Phase 10: 1, Phase 11: 1)
 - Total phases: 6 (phases 6-11)
-- Progress: 85% (Phases 6-9 complete, Phase 10 in progress - 1 plan complete)
+- Progress: 90% (Phases 6-10 complete, Phase 11 in progress - 1/2 plans complete)
 
 **Recent Trend:**
 - Last milestone: v1.0 completed 2026-01-14 with excellent velocity
@@ -287,6 +287,17 @@ Recent decisions affecting current work:
 - Expected behavior noted: Future enhancement could filter by timestamp (messages with createdAt > lastReadAt)
 - Test results: 16/17 passing (94% pass rate) - validates Redux state, localStorage, UI rendering
 
+**From Phase 11 Plan 1 (11-chat-finalization):**
+- Error handling: Color-coded displays (red for critical API failures, yellow for WebSocket disconnection warnings)
+- clearSendError Redux action enables retry functionality for failed sends
+- Retry pattern: Button clears error and re-enables input without auto-resending (prevents duplicate sends)
+- Accessibility: Comprehensive ARIA attributes (role="dialog", aria-labelledby, aria-describedby, aria-invalid, aria-live)
+- ARIA decisions: aria-modal="false" for modeless WindowPortal dialog, live regions for validation messages
+- Keyboard navigation: Escape closes window, Tab order preserved, Enter sends message
+- Focus management: Auto-focus textarea on window open with 100ms delay for DOM readiness
+- Edge cases validated: Rapid actions, disconnection handling, empty states, long messages all working correctly
+- All edge cases already handled by existing implementation from Phases 7-10, verified as robust
+
 ### Deferred Issues
 
 **From Phase 3 Plan 3 UAT:**
@@ -318,7 +329,7 @@ None yet.
 ## Session Continuity
 
 Last session: 2026-01-27
-Stopped at: Phase 10 Plan 1 complete (Read/Unread Status Validation & Testing)
+Stopped at: Phase 11 Plan 1 complete (Error Handling, Accessibility & Polish)
 Resume file: None
 
-**Next:** Phase 11 (Chat Finalization) - Error handling, edge cases, performance optimization, final UAT before milestone completion
+**Next:** Phase 11 Plan 2 (UAT & Final Integration Testing) - Complete final plan to finish Chat Finalization phase and v1.1 milestone