---
phase: 14-chat-integration-and-display
plan: 03
subsystem: ui
tags: [redux, rest-api, chat, attachments, music-notation]

# Dependency graph
requires:
  - phase: 14-01
    provides: "JKChatMessage component with attachment rendering"
  - phase: 14-02
    provides: "Clickable attachment links with signed URL fetching"
  - phase: 13-03
    provides: "File upload infrastructure with REST API endpoints"
provides:
  - "REST API attachment transformation matching WebSocket format"
  - "Consistent attachment display across both message paths (WebSocket + REST)"
  - "Chat history persistence with attachments across page refresh"
affects: [15-attachment-metadata, 16-file-access-control]

# Tech tracking
tech-stack:
  added: []
  patterns:
    - "Dual-path message normalization: Transform nested API objects to flat WebSocket format in Redux slice"

key-files:
  created: []
  modified:
    - jam-ui/src/store/features/sessionChatSlice.js
    - jam-ui/src/store/features/__tests__/sessionChatSlice.test.js

key-decisions:
  - "Transform REST API music_notation at Redux boundary to match WebSocket format"
  - "Set attachmentSize to null for REST API (field unavailable, only in WebSocket)"

patterns-established:
  - "Message normalization: Both WebSocket and REST API produce identical attachment field structure for consistent rendering"

# Metrics
duration: 4min
completed: 2026-02-05
---

# Phase 14 Plan 03: Chat Integration & Display - Gap Closure Summary

**REST API attachment transformation flattens nested music_notation to match WebSocket format for consistent chat history display**

## Performance

- **Duration:** 4 min
- **Started:** 2026-02-05T20:18:46Z
- **Completed:** 2026-02-05T20:23:10Z
- **Tasks:** 2 (1 TDD implementation, 1 verification)
- **Files modified:** 2

## Accomplishments
- Closed verification gap from 14-VERIFICATION.md (Truth #8 and REQ-2.5)
- Transformed REST API nested `music_notation` object to flat attachment fields
- Attachments now persist correctly across page refresh and when joining sessions
- Fixed 3 pre-existing test bugs discovered during TDD

## Task Commits

Each task was committed atomically:

1. **Task 1: Add REST API attachment transformation (TDD)** - `977d1a9` (feat)
   - RED: Added failing test for music_notation transformation
   - GREEN: Implemented transformation in fetchChatHistory.fulfilled
   - REFACTOR: Fixed 3 pre-existing test bugs (incorrect payload formats)

**Plan metadata:** (to be committed with STATE.md update)

## Files Created/Modified
- `jam-ui/src/store/features/sessionChatSlice.js` - Added attachment field transformation in fetchChatHistory.fulfilled reducer (lines 309-325)
- `jam-ui/src/store/features/__tests__/sessionChatSlice.test.js` - Added REST API attachment test, fixed 3 pre-existing bugs

## Decisions Made

**1. Transform at Redux boundary**
- Rationale: Keep component (JKChatMessage) simple by providing consistent data shape from both paths
- Alternative considered: Transform in component based on source
- Rejected because: Violates single responsibility, duplicates transformation logic

**2. Set attachmentSize to null for REST API**
- Rationale: Field unavailable in REST API response (only in WebSocket)
- Component handles null gracefully (formatFileSize checks for null/undefined)
- Future: Backend could add file_size to REST API if needed

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 1 - Bug] Fixed incorrect sendMessage.fulfilled payload format in tests**
- **Found during:** Task 1 (Running TDD tests)
- **Issue:** Tests wrapped payload in `{ message: {...} }` but code expected flat payload
- **Fix:** Changed test mocks to use flat payload format matching actual API response
- **Files modified:** jam-ui/src/store/features/__tests__/sessionChatSlice.test.js (2 tests)
- **Verification:** Tests now pass (89/89)
- **Committed in:** 977d1a9 (Task 1 commit)

**2. [Rule 1 - Bug] Fixed fetchChatHistory deduplication test using wrong format**
- **Found during:** Task 1 (Running TDD tests)
- **Issue:** Test used internal format (createdAt) instead of API format (created_at, user_id, user)
- **Fix:** Updated test to use correct REST API response format
- **Files modified:** jam-ui/src/store/features/__tests__/sessionChatSlice.test.js (1 test)
- **Verification:** Test now passes
- **Committed in:** 977d1a9 (Task 1 commit)

---

**Total deviations:** 3 auto-fixed bugs (all Rule 1 - pre-existing test bugs)
**Impact on plan:** All fixes necessary for test suite correctness. Improved from 85/88 passing to 89/89 passing. No scope creep.

## Issues Encountered
None - gap closure straightforward once test bugs were fixed.

## User Setup Required
None - no external service configuration required.

## Gap Closure Verification

### From 14-VERIFICATION.md

**Truth #8:** "Chat history includes attachments (persist across page refresh, visible when joining session)"
- **Status before:** FAILED - REST API returned music_notation but Redux didn't transform it
- **Status after:** VERIFIED - fetchChatHistory.fulfilled now transforms to flat attachment fields
- **Evidence:** Unit test confirms transformation, matches WebSocket path format

**REQ-2.5:** "Chat history includes attachments"
- **Status before:** BLOCKED by missing REST API transformation
- **Status after:** SATISFIED - attachments display via both paths (WebSocket real-time + REST API history)

### Dual-Path Consistency Achieved

**WebSocket path (real-time):**
- JKSessionScreen.js handleChatMessage (lines 575-596) → Redux addMessageFromWebSocket
- Produces: `{ attachmentId, attachmentName, attachmentType, purpose, attachmentSize }`

**REST API path (page refresh/join session):**
- sessionChatSlice.js fetchChatHistory.fulfilled (lines 312-325) → Redux state
- Produces: `{ attachmentId, attachmentName, attachmentType, purpose, attachmentSize: null }`

**Component rendering:**
- JKChatMessage.js isAttachmentMessage (line 90) works for both paths
- User experience: Consistent attachment display regardless of message source

## Next Phase Readiness
- Phase 14 COMPLETE - all 3 plans executed successfully
- Ready for Phase 15: Attachment Metadata & Display
- Foundation: Dual-path message normalization pattern established for consistent UI

---
*Phase: 14-chat-integration-and-display*
*Completed: 2026-02-05*
