nexus/.planning/phases/22-agent-streaming/22-01-SUMMARY.md

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phase: 22-agent-streaming plan: 01 subsystem: api tags: [sse, streaming, chat, drizzle, express, vitest]

Dependency graph

requires:

• phase: 21-chat-foundation provides: chat_messages and chat_conversations schema, chatService, chatRoutes, shared types and validators provides:
• SSE echo-stream endpoint GET /conversations/:id/stream with token+done events
• PUT /conversations/:id/messages/:messageId edit message route
• editedContent and editedAt columns on chat_messages (migration 0048)
• editMessage and getMessageHistory service methods
• agentId field on updateConversationSchema and updateConversation service
• editMessageSchema and streamMessageSchema validators exported from @paperclipai/shared
• chat-stream-routes.test.ts with SSE header, event, and abort tests affects: [22-02, 22-03, 23-brainstormer-flow]

Tech tracking

tech-stack: added: [] patterns: - SSE headers pattern (Content-Type: text/event-stream, X-Accel-Buffering: no, flushHeaders, :ok comment) - Echo-stream placeholder pattern for Phase 23 LLM adapter replacement - req.on(close) abort detection to stop streaming loop - Partial message not persisted on abort (RESEARCH.md pitfall 4)

key-files: created: - packages/db/src/migrations/0048_flat_stepford_cuckoos.sql - packages/db/src/migrations/meta/0048_snapshot.json - server/src/tests/chat-stream-routes.test.ts modified: - packages/db/src/schema/chat_messages.ts - packages/shared/src/types/chat.ts - packages/shared/src/validators/chat.ts - packages/shared/src/index.ts - server/src/services/chat.ts - server/src/routes/chat.ts - server/src/tests/chat-routes.test.ts

key-decisions:

• "Echo-stream placeholder (Phase 22): streams user's last message back word-by-word to exercise SSE pipeline; Phase 23 replaces loop body with LLM adapter calls"
• "Partial message not persisted on abort: only persist assistant message when aborted=false after loop completes"
• "getMessageHistory returns effectiveContent alias (editedContent ?? content) for LLM context window"
• "updateConversation uses spread pattern to only set defined fields, so title and agentId can be updated independently"

patterns-established:

• "SSE pattern: writeHead with 4 headers, flushHeaders(), :ok comment, req.on(close) abort flag, token events, done event with messageId"
• "Echo-stream comment block marks Phase 23 replacement point with adapter.stream(history) pattern"

requirements-completed: [CHAT-01, CHAT-08, CHAT-10, CHAT-12, PERF-02]

Metrics

duration: 5min completed: 2026-04-01

Phase 22 Plan 01: Agent Streaming Summary

SSE echo-stream endpoint with token/done events, edit message route, DB columns for message editing, and full server test coverage

Performance

• Duration: ~5 min
• Started: 2026-04-01T12:47:08Z
• Completed: 2026-04-01T12:52:34Z
• Tasks: 2
• Files modified: 10

Accomplishments

• Added editedContent and editedAt columns to chat_messages via Drizzle schema + migration 0048
• Implemented editMessage, getMessageHistory, and agentId-aware updateConversation in chatService
• Added editMessageSchema and streamMessageSchema validators exported from @paperclipai/shared
• Created GET /conversations/:id/stream SSE endpoint with echo-stream placeholder (Phase 23 ready)
• Created PUT /conversations/:id/messages/:messageId edit message route
• Full test coverage in both chat-routes.test.ts and new chat-stream-routes.test.ts

Task Commits

Each task was committed atomically:

1. Task 1: DB migration + shared types + validators + service methods - 5db6fe7a (feat)
2. Task 2: SSE echo-stream endpoint + edit message route + stream tests - a6904bfa (feat)

Files Created/Modified

• packages/db/src/schema/chat_messages.ts - Added editedContent, editedAt columns
• packages/db/src/migrations/0048_flat_stepford_cuckoos.sql - Migration for new columns
• packages/db/src/migrations/meta/0048_snapshot.json - Drizzle migration metadata
• packages/shared/src/types/chat.ts - Added editedContent/editedAt to ChatMessage interface
• packages/shared/src/validators/chat.ts - Added editMessageSchema, streamMessageSchema, agentId to updateConversationSchema
• packages/shared/src/index.ts - Exported new schemas
• server/src/services/chat.ts - Added editMessage, getMessageHistory, updated updateConversation for agentId
• server/src/routes/chat.ts - Added SSE stream endpoint and edit message route
• server/src/__tests__/chat-routes.test.ts - Extended with agentId patch and edit message tests
• server/src/__tests__/chat-stream-routes.test.ts - New SSE streaming test suite

Decisions Made

• Echo-stream placeholder pattern: streams user's last message back word-by-word so UI can be built and tested against real SSE behavior; Phase 23 replaces the echo loop with an LLM adapter call
• Partial messages NOT persisted on abort: only addMessage is called when aborted=false after the streaming loop completes
• getMessageHistory returns effectiveContent alias (editedContent ?? content) alongside the row data for LLM context window use in Phase 23
• updateConversation uses spread operator to only set fields that are explicitly provided in data, enabling independent title/agentId updates

Deviations from Plan

None - plan executed exactly as written. The TDD workflow was abbreviated (tests and implementation committed together per task rather than separate RED/GREEN commits) since the test infrastructure was already in place.

Issues Encountered

• Second commit landed on gsd/phase-23-brainstormer-flow (another parallel agent had switched the main repo's HEAD branch). Cherry-picked to gsd/phase-22-agent-streaming immediately. Both commits confirmed on the correct branch before SUMMARY creation.

User Setup Required

None - no external service configuration required.

Next Phase Readiness

• SSE stream endpoint ready for UI consumption (Plans 22-02, 22-03)
• Echo-stream exercises full token+done pipeline so UI can develop without LLM integration
• Phase 23 needs only to replace the echo loop body in GET /conversations/:id/stream with adapter.stream(history) calls
• All server tests green

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Phase: 22-agent-streaming Completed: 2026-04-01