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After SummarizationMiddleware runs, the merged conversation view could drop already-displayed messages (previous assistant output, current user input), leaving a nearly-empty thread. Root cause: the display merge combines `visibleHistory` (archived history, a React `useState` in useThreadHistory) with `persistedMessages` (live thread, the LangGraph SDK external store via useSyncExternalStore). On summarization the backend removes every live message and onUpdateEvent re-archives them via an async `appendMessages` setState. Those two state systems are scheduled independently, so a render can observe the post-summary (shrunk) thread before the archive setState commits — the rescued messages are then absent from BOTH merge inputs and get dropped. Fix: bridge the async gap with a synchronous `pendingArchivedMessagesRef` buffer written the moment onUpdateEvent computes the moved messages and read by the merge on every render, so correctness no longer depends on how the two channels interleave. The buffer drains once history confirms absorption and only injects messages missing from history (live copies stay authoritative, order preserved). It is tagged with the thread it was captured from and the merge overlays it only when that matches the viewed `threadId` (the same prop visibleHistory is gated on), so it can never leak into another thread or the new-chat screen — a read-only check, no render-phase ref mutation. Extracts the moved-message derivation and the merge overlay into pure, unit-tested helpers (computeSummarizationMovedMessages, resolvePreservedHistory, pruneConfirmedArchivedMessages) with regression coverage for the full rescue pipeline.
DeerFlow Frontend
Like the original DeerFlow 1.0, we would love to give the community a minimalistic and easy-to-use web interface with a more modern and flexible architecture.
Tech Stack
- Framework: Next.js 16 with App Router
- UI: React 19, Tailwind CSS 4, Shadcn UI, MagicUI and React Bits
- AI Integration: LangGraph SDK and Vercel AI Elements
Quick Start
Prerequisites
- Node.js 22+
- pnpm 10.26.2+
Installation
# Install dependencies
pnpm install
# Copy environment variables
cp .env.example .env
# Edit .env with your configuration
Development
# Start development server
pnpm dev
# The app will be available at http://localhost:3000
Build & Test
# Type check
pnpm typecheck
# Check formatting
pnpm format
# Apply formatting
pnpm format:write
# Lint
pnpm lint
# Run unit tests
pnpm test
# One-time setup: install Playwright Chromium browser
pnpm exec playwright install chromium
# Run E2E tests (builds and starts production server automatically)
pnpm test:e2e
# Build for production
pnpm build
# Start production server
pnpm start
Site Map
├── / # Landing page
├── /chats # Chat list
├── /chats/new # New chat page
└── /chats/[thread_id] # A specific chat page
Configuration
Environment Variables
Key environment variables (see .env.example for full list):
# Backend API URL (optional, uses local Next.js/nginx proxy by default)
NEXT_PUBLIC_BACKEND_BASE_URL="http://localhost:8001"
# LangGraph-compatible API URL (optional, uses local Next.js/nginx proxy by default)
NEXT_PUBLIC_LANGGRAPH_BASE_URL="http://localhost:8001/api"
Project Structure
tests/
├── e2e/ # E2E tests (Playwright, Chromium, mocked backend)
└── unit/ # Unit tests (mirrors src/ layout)
src/
├── app/ # Next.js App Router pages
│ ├── api/ # API routes
│ ├── workspace/ # Main workspace pages
│ └── mock/ # Mock/demo pages
├── components/ # React components
│ ├── ui/ # Reusable UI components
│ ├── workspace/ # Workspace-specific components
│ ├── landing/ # Landing page components
│ └── ai-elements/ # AI-related UI elements
├── core/ # Core business logic
│ ├── api/ # API client & data fetching
│ ├── artifacts/ # Artifact management
│ ├── config/ # App configuration
│ ├── i18n/ # Internationalization
│ ├── mcp/ # MCP integration
│ ├── messages/ # Message handling
│ ├── models/ # Data models & types
│ ├── settings/ # User settings
│ ├── skills/ # Skills system
│ ├── threads/ # Thread management
│ ├── todos/ # Todo system
│ └── utils/ # Utility functions
├── hooks/ # Custom React hooks
├── lib/ # Shared libraries & utilities
├── server/ # Server-side code
│ └── better-auth/ # Authentication setup and session helpers
└── styles/ # Global styles
Scripts
| Command | Description |
|---|---|
pnpm dev |
Start development server with Turbopack |
pnpm build |
Build for production |
pnpm start |
Start production server |
pnpm test |
Run unit tests with Rstest |
pnpm test:e2e |
Run E2E tests with Playwright |
pnpm format |
Check formatting with Prettier |
pnpm format:write |
Apply formatting with Prettier |
pnpm lint |
Run ESLint |
pnpm lint:fix |
Fix ESLint issues |
pnpm typecheck |
Run TypeScript type checking |
pnpm check |
Run both lint and typecheck |
Development Notes
- Uses pnpm workspaces (see
packageManagerin package.json) - Turbopack enabled by default in development for faster builds
- Environment validation can be skipped with
SKIP_ENV_VALIDATION=1(useful for Docker) - Backend API URLs are optional; nginx proxy is used by default in development
License
MIT License. See LICENSE for details.