---
phase: 25-file-system
plan: 02
subsystem: ui
tags: [react, file-upload, drag-and-drop, clipboard, xhr, lucide]

# Dependency graph
requires:
  - phase: 25-file-system-00
    provides: shared types (ChatFile, ChatFileUploadResponse), validators
  - phase: 25-file-system-01
    provides: server endpoint POST /api/conversations/:id/files
provides:
  - ChatFileDropZone component with drag-and-drop overlay
  - useChatFileUpload hook with upload lifecycle (uploading/done/error)
  - chatApi.uploadFile using XHR with progress callbacks
  - ChatInput updated with file picker button, paste handler, and pending file chips
affects: [25-03, 25-04, chat-panel-integration]

# Tech tracking
tech-stack:
  added: []
  patterns:
    - XHR for upload progress tracking (not fetch, which lacks upload progress)
    - PendingFile client-side state lifecycle before server confirmation
    - ChatFileDropZone wraps children with drag overlay without breaking layout

key-files:
  created:
    - ui/src/components/ChatFileDropZone.tsx
    - ui/src/hooks/useChatFileUpload.ts
  modified:
    - ui/src/api/chat.ts
    - ui/src/components/ChatInput.tsx
    - ui/src/components/ChatInput.test.tsx

key-decisions:
  - "Used XHR instead of fetch for chatApi.uploadFile to enable upload progress events (fetch lacks upload.onprogress)"
  - "ChatFileDropZone checks e.currentTarget.contains(e.relatedTarget) to avoid false drag-leave when crossing child elements"
  - "onFilesPicked is optional — ChatInput works without file support when prop not provided (backward compatible)"

patterns-established:
  - "PendingFile pattern: temp client ID assigned immediately, replaced with server ChatFile.id on completion"
  - "Drop zone overlay uses bg-primary/10 and border-primary for theme-neutral visual feedback"

requirements-completed: [FILE-05]

# Metrics
duration: 15min
completed: 2026-04-01
---

# Phase 25 Plan 02: File Upload UI Summary

**Drag-and-drop, clipboard paste, and file picker wired into ChatInput via ChatFileDropZone and useChatFileUpload with XHR progress tracking**

## Performance

- **Duration:** ~15 min
- **Started:** 2026-04-01T23:10:00Z
- **Completed:** 2026-04-01T23:25:00Z
- **Tasks:** 2
- **Files modified:** 5

## Accomplishments
- chatApi.uploadFile implemented with XMLHttpRequest for upload progress callbacks
- useChatFileUpload hook manages PendingFile lifecycle (uploading → done/error)
- ChatFileDropZone component provides drag-over overlay with dashed border and theme-neutral colors
- ChatInput now accepts all three file input methods: drag-and-drop, clipboard paste (onPaste), file picker (Paperclip button)
- Pending file chips shown above textarea with spinner, progress %, and remove button
- 3 new tests added: file attach button presence, onFilesPicked callback, pending chip rendering

## Task Commits

Each task was committed atomically:

1. **Task 1: Add chatApi.uploadFile and create useChatFileUpload hook** - `6a83a362` (feat)
2. **Task 2: Create ChatFileDropZone and integrate into ChatInput** - `6b530afa` (feat)

## Files Created/Modified
- `ui/src/api/chat.ts` - Added uploadFile method using XHR with FormData and progress callbacks
- `ui/src/hooks/useChatFileUpload.ts` - Created PendingFile state management hook
- `ui/src/components/ChatFileDropZone.tsx` - Created drag-and-drop wrapper with overlay
- `ui/src/components/ChatInput.tsx` - Added file props, paste handler, Paperclip button, pending chips, ChatFileDropZone wrapper
- `ui/src/components/ChatInput.test.tsx` - Added 3 file upload tests

## Decisions Made
- Used XHR for uploadFile to get upload progress events (fetch API doesn't expose upload.onprogress)
- ChatFileDropZone uses `e.currentTarget.contains(e.relatedTarget)` guard on dragLeave to prevent flicker when cursor moves over child elements
- ChatInput backward-compatible: onFilesPicked/pendingFiles/onRemoveFile are all optional props

## Deviations from Plan

None — plan executed exactly as written.

## Issues Encountered
None.

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

## Next Phase Readiness
- File upload UI complete; ChatPanel needs wiring to call useChatFileUpload and pass pendingFiles/onFilesPicked/onRemoveFile to ChatInput
- Plan 25-03 (server routes) and Plan 25-04 (ChatPanel wiring) can proceed

---
*Phase: 25-file-system*
*Completed: 2026-04-01*