---
phase: 21-chat-foundation
plan: 03
subsystem: ui
tags: [react, tanstack-query, infinite-scroll, chat, intersection-observer, context]

# Dependency graph
requires:
  - phase: 21-chat-foundation/21-01
    provides: Chat API backend (conversations, messages endpoints), shared ChatConversation/ChatMessage types
  - phase: 21-chat-foundation/21-02
    provides: ChatMarkdownMessage and ChatInput presentational components
provides:
  - chatApi fetch wrappers for all chat endpoints
  - ChatPanelProvider with localStorage-persisted open state and active conversation tracking
  - useChatConversations (useInfiniteQuery with cursor pagination)
  - useChatMessages (useInfiniteQuery with cursor pagination)
  - useSendMessage and useCreateConversation mutations
  - ChatConversationList with infinite scroll, inline rename/delete confirmation, pin/archive actions
  - ChatMessageList with role=log, auto-scroll, ChatMarkdownMessage for assistant messages
  - ChatPanel right-side drawer composing conversation list + message area (width transition)
  - Layout integration: MessageSquare toggle, ChatPanel in flex row, effect closing PropertiesPanel when chat opens
affects: [21-chat-foundation/21-04]

# Tech tracking
tech-stack:
  added: []
  patterns:
    - useInfiniteQuery with cursor-based pagination (updatedAt/createdAt as cursor)
    - ChatPanelProvider pattern mirrors PanelContext with localStorage persistence
    - IntersectionObserver sentinel div for infinite scroll trigger
    - Inline delete confirmation (no modal) via conditional render in list item hover state
    - DOM querySelector for focus management across component boundaries

key-files:
  created:
    - ui/src/api/chat.ts
    - ui/src/context/ChatPanelContext.tsx
    - ui/src/hooks/useChatConversations.ts
    - ui/src/hooks/useChatMessages.ts
    - ui/src/components/ChatPanel.tsx
    - ui/src/components/ChatConversationList.tsx
    - ui/src/components/ChatMessageList.tsx
  modified:
    - ui/src/main.tsx
    - ui/src/components/Layout.tsx

key-decisions:
  - "mutateAsync(undefined) required for optional-arg mutations in TanStack Query TypeScript — fixed TS2554 error"
  - "Focus management uses DOM querySelector('[aria-label=Message input]') across component boundaries to avoid ref threading"

patterns-established:
  - "IntersectionObserver sentinel at bottom of scroll list triggers fetchNextPage for infinite scroll"
  - "Inline delete confirmation replaces dropdown with confirmation widget on hover — no modal needed"

requirements-completed: [CHAT-04, CHAT-05, CHAT-06, HIST-02, HIST-03]

# Metrics
duration: 5min
completed: 2026-04-01
---

# Phase 21 Plan 03: Chat Foundation Wire-Up Summary

**Chat UI wired end-to-end: API client, TanStack Query hooks with cursor pagination, ChatPanel drawer with conversation list (infinite scroll + CRUD) and message rendering integrated into Layout**

## Performance

- **Duration:** 5 min
- **Started:** 2026-04-01T11:07:28Z
- **Completed:** 2026-04-01T11:12:11Z
- **Tasks:** 2
- **Files modified:** 9

## Accomplishments
- Created `chatApi` covering all 11 chat endpoints (conversations + messages CRUD, pin/archive)
- Built `ChatPanelContext` with localStorage persistence (`nexus:chat-panel-open`) and active conversation tracking
- Implemented `useChatConversations` and `useChatMessages` with `useInfiniteQuery` cursor pagination plus full mutation hooks
- Built `ChatConversationList` with IntersectionObserver infinite scroll, inline rename, delete confirmation widget, and pin/archive dropdown
- Built `ChatMessageList` with `role="log"` aria semantics, auto-scroll, user/assistant message styling, ChatMarkdownMessage for assistant
- Created `ChatPanel` drawer (width transition 0↔380px) composing both lists with `ChatInput`
- Integrated into `Layout.tsx`: MessageSquare toggle button, ChatPanel in flex row, PropertiesPanel closes when chat opens

## Task Commits

1. **Task 1: Chat API client, context provider, and TanStack Query hooks** - `2a072483` (feat)
2. **Task 2: ChatPanel, ChatConversationList, ChatMessageList, and Layout integration** - `7868b073` (feat)

**Plan metadata:** _(pending docs commit)_

## Files Created/Modified
- `ui/src/api/chat.ts` - chatApi with listConversations, createConversation, getConversation, updateConversation, deleteConversation, archiveConversation, unarchiveConversation, pinConversation, unpinConversation, listMessages, sendMessage
- `ui/src/context/ChatPanelContext.tsx` - ChatPanelProvider with localStorage persistence and active conversation state
- `ui/src/hooks/useChatConversations.ts` - useChatConversations (useInfiniteQuery), useCreateConversation, useConversationActions (pin/unpin/archive/unarchive/remove/rename)
- `ui/src/hooks/useChatMessages.ts` - useChatMessages (useInfiniteQuery), useSendMessage
- `ui/src/components/ChatConversationList.tsx` - Sidebar with IntersectionObserver infinite scroll, inline rename, delete confirmation, pin/archive dropdown
- `ui/src/components/ChatMessageList.tsx` - role=log message thread with auto-scroll and ChatMarkdownMessage
- `ui/src/components/ChatPanel.tsx` - Right-side drawer shell composing conversation list and message area
- `ui/src/main.tsx` - Added ChatPanelProvider to app tree
- `ui/src/components/Layout.tsx` - MessageSquare toggle, ChatPanel, effect closing PropertiesPanel when chat opens

## Decisions Made
- `mutateAsync(undefined)` required for TanStack Query optional-arg mutations — TypeScript infers at least one argument needed and calling with zero causes TS2554 error
- Focus management uses `document.querySelector('[aria-label="Message input"]')` to reach ChatInput textarea across component tree without ref threading

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 1 - Bug] Fixed TypeScript TS2554 for zero-arg mutateAsync calls**
- **Found during:** Task 2 (ChatPanel), build verification
- **Issue:** `createConversation.mutateAsync()` called with 0 args — TanStack Query typing requires at least 1 argument even when mutationFn has optional params
- **Fix:** Changed both call sites to `createConversation.mutateAsync(undefined)`
- **Files modified:** ui/src/components/ChatPanel.tsx
- **Verification:** `pnpm --filter @paperclipai/ui build` succeeds with no TypeScript errors
- **Committed in:** `7868b073` (Task 2 commit)

---

**Total deviations:** 1 auto-fixed (1 bug)
**Impact on plan:** Minimal — single TypeScript fix required for correct compilation. No scope creep.

## Issues Encountered
None beyond the TypeScript fix documented above.

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

## Next Phase Readiness
- Chat UI is fully wired and functional end-to-end
- Users can create conversations, send messages, browse history with infinite scroll
- Opening chat closes PropertiesPanel — no competing panels
- Panel state persists in localStorage across page loads
- Plan 04 (if any) can build on the established chat foundation

---
*Phase: 21-chat-foundation*
*Completed: 2026-04-01*