---
phase: 31-workflow-proposal-system
plan: 02
subsystem: api
tags: [vercel-ai-sdk, streaming, gemini, chat, ai-sdk-google]

# Dependency graph
requires:
  - phase: 31-01
    provides: WorkflowProposal types, domain prompts
provides:
  - Streaming /api/chat endpoint
  - Chat types (ChatMessage, ChatRole, ConversationState)
  - Vercel AI SDK integration with Gemini
affects: [31-03-chat-ui, workflow-planning]

# Tech tracking
tech-stack:
  added: [ai@6.0.49, @ai-sdk/google@3.0.13]
  patterns: [createGoogleGenerativeAI, streamText, toTextStreamResponse]

key-files:
  created:
    - src/types/chat.ts
    - src/app/api/chat/route.ts
  modified:
    - src/types/index.ts
    - package.json

key-decisions:
  - "Use createGoogleGenerativeAI factory for custom API key injection"
  - "toTextStreamResponse for AI SDK v6 streaming (not toDataStreamResponse)"
  - "System prompt contains full Node Banana domain expertise for conversational planning"

patterns-established:
  - "Vercel AI SDK streaming pattern: createGoogleGenerativeAI → streamText → toTextStreamResponse"

issues-created: []

# Metrics
duration: 2min
completed: 2026-01-26
---

# Phase 31 Plan 02: Chat Infrastructure Summary

**Streaming chat endpoint with Vercel AI SDK, Gemini integration, and conversational workflow planning assistant**

## Performance

- **Duration:** 2 min
- **Started:** 2026-01-26T09:37:57Z
- **Completed:** 2026-01-26T09:40:07Z
- **Tasks:** 4
- **Files modified:** 4

## Accomplishments
- Installed Vercel AI SDK packages (ai, @ai-sdk/google)
- Created chat types for conversation state management
- Built streaming /api/chat endpoint with domain expertise
- Exported chat types from central type index

## Task Commits

Each task was committed atomically:

1. **Task 1: Install Vercel AI SDK packages** - `744e0a7` (chore)
2. **Task 2: Create chat types** - `b263c03` (feat)
3. **Task 3: Create streaming chat endpoint** - `727e54d` (feat)
4. **Task 4: Update type exports** - `e558777` (feat)

## Files Created/Modified
- `src/types/chat.ts` - ChatMessage, ChatRole, ConversationState, ChatRequest types
- `src/app/api/chat/route.ts` - Streaming POST endpoint with Node Banana system prompt
- `src/types/index.ts` - Added chat types re-export
- `package.json` - Added ai and @ai-sdk/google dependencies

## Decisions Made
- Used `createGoogleGenerativeAI` factory instead of default `google` export to inject API key from GEMINI_API_KEY env var
- Used `toTextStreamResponse()` which is the correct method in AI SDK v6 (not toDataStreamResponse)
- System prompt includes comprehensive Node Banana domain knowledge for conversational workflow planning

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 3 - Blocking] Fixed google() API usage**
- **Found during:** Task 3 (Create streaming chat endpoint)
- **Issue:** Plan specified `google('gemini-2.5-flash', { apiKey })` but @ai-sdk/google doesn't accept second argument
- **Fix:** Used `createGoogleGenerativeAI({ apiKey })` factory to create provider with custom API key
- **Files modified:** src/app/api/chat/route.ts
- **Verification:** Build succeeds
- **Committed in:** 727e54d (Task 3 commit)

**2. [Rule 3 - Blocking] Fixed streaming response method**
- **Found during:** Task 3 (Create streaming chat endpoint)
- **Issue:** `toDataStreamResponse()` doesn't exist in AI SDK v6
- **Fix:** Changed to `toTextStreamResponse()` which is the correct method
- **Files modified:** src/app/api/chat/route.ts
- **Verification:** Build succeeds
- **Committed in:** 727e54d (Task 3 commit)

---

**Total deviations:** 2 auto-fixed (2 blocking)
**Impact on plan:** Both fixes required for build to succeed. API signature differences between plan and actual AI SDK v6.

## Issues Encountered
None beyond the API fixes above.

## Next Phase Readiness
- Chat streaming infrastructure complete
- Ready for Chat UI integration in WelcomeModal (31-03)
- Vercel AI SDK useChat hook can connect to /api/chat endpoint

---
*Phase: 31-workflow-proposal-system*
*Completed: 2026-01-26*