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* fix(subagent): structured subagent_status field over text parsing Closes #3146. ## Why The frontend used to derive subtask card state by string-matching the leading text of the `task` tool's result. That contract surface was fragile — `#3107` BUG-007 and the `#3131` review both surfaced cases where new backend wording (`Task cancelled by user.`, `Task polling timed out after N minutes`, `ToolErrorHandlingMiddleware` exception wrappers) silently broke the card lifecycle. The frontend fallback kept growing more prefixes; any future rewording would break it again. ## Design 1. **Backend → frontend contract**: `ToolMessage.additional_kwargs` carries `subagent_status` (one of `completed | failed | cancelled | timed_out | polling_timed_out`) and an optional `subagent_error` blob. The frontend prefers it over parsing `content`. 2. **Centralised stamping, not 8 sprinkled stamps**: rather than have each of `task_tool.py`'s 5 normal-return + 3 pre-execution `Error:` paths remember to set `additional_kwargs`, `ToolErrorHandlingMiddleware` stamps the field after every task-tool call. Adding a new return path in `task_tool.py` cannot now skip the stamp. 3. **Cross-language contract fixture**: the prefix→status mapping is the one piece both sides must agree on. The shared fixture at `contracts/subagent_status_contract.json` lists every backend return string, the expected status, and what the error substring should contain. Backend test (`backend/tests/test_subagent_status_contract.py`) and frontend test (`frontend/tests/unit/core/tasks/subtask-result.test.ts`) both load that fixture and assert the same cases. A wording drift on either side fails the matching language's test. 4. **Round-trip serialisation pinned**: the round-trip test asserts `ToolMessage.model_dump_json()` → `model_validate_json()` preserves `additional_kwargs.subagent_status`. Catches the case where a future LangChain or Pydantic upgrade silently strips unknown kwargs. 5. **Frontend status collapse documented**: the backend has five status values, the frontend card has three (`completed | failed | in_progress`). `cancelled` / `timed_out` / `polling_timed_out` all collapse to `failed` with the original status preserved in `error`. `parseSubtaskResult` returns `in_progress` for unknown values so a backend that ships a new enum variant before the frontend upgrades degrades to the legacy prefix fallback instead of getting pinned. ## Changes Backend: - `deerflow.subagents.status_contract` — new module exporting `SUBAGENT_STATUS_KEY`, `SUBAGENT_ERROR_KEY`, `SUBAGENT_STATUS_VALUES`, `extract_subagent_status(content)`, and `make_subagent_additional_kwargs(status, error)`. - `ToolErrorHandlingMiddleware`: new `_stamp_task_subagent_status` helper centralises the stamp; `wrap_tool_call` / `awrap_tool_call` stamp on the success path; `_build_error_message` stamps on the wrapper path (carrying `ExcClass: detail` into `subagent_error`). Non-task tools are untouched. - New tests: `test_subagent_status_contract.py` (19 cases from the shared fixture + status-enum / blank-error / unknown-status rejection) and `test_tool_error_handling_subagent_stamp.py` (middleware integration: terminal-content stamps, non-terminal doesn't, non-task tools untouched, async path mirrors sync, existing additional_kwargs survive, JSON round-trip preserved). Frontend: - `parseSubtaskResult(text, additionalKwargs?)` — prefers the structured stamp; falls back to the legacy prefix matcher for historical threads / unknown future status values. - `STRUCTURED_STATUS_TO_SUBTASK` documents the five→three collapse. - `message-list.tsx` passes `message.additional_kwargs` through. - `subtask-result.test.ts` adds a structured-status block + a fixture-driven contract block; legacy prefix tests stay green for the fallback path. Contract: - `contracts/subagent_status_contract.json` — single source of truth both languages load. Whitespace variants, varied N for polling timeouts, the 3 pre-execution `Error:` returns task_tool produces, and the middleware wrapper shape are all in there. ## Test plan - `make lint` clean (backend + frontend). - `pytest tests/test_subagent_status_contract.py tests/test_tool_error_handling_subagent_stamp.py` → 37 passed. - `pnpm test --run` → 103 passed (was 76, +27 new). ## Migration / fallback retirement The text-prefix fallback stays in place until backend telemetry shows the frontend never hits it for newly produced messages. At that point a follow-up PR can drop the prefix branches and keep only the structured-status branch. Refs: bytedance/deer-flow#3138 (split summary), #3107 (origin), #3131 (prior prefix-only fix), #3146 (this issue). * fix(subtask): back-fill result/error from text when structured status present Three follow-ups on the PR #3154 review: 1. `readStructuredStatus` no longer short-circuits the prefix parse. The backend currently stamps only the `subagent_status` enum value; the human-facing `result` body and wrapped-error message still live in `ToolMessage.content`. Dropping the text parse meant successful tasks rendered empty completed pills and wrapped failures lost their diagnostic. Now both shapes get composed: structured status wins, `result`/`error` come from text when both sides agree, and a lying success body under a `failed` stamp is dropped instead of leaking. 2. Replace the ESM-incompatible `__dirname` fixture lookup in subtask-result.test.ts with `fileURLToPath(new URL(..., import.meta.url))`. The frontend package is `"type": "module"`, so the previous path would have thrown at runtime if anything ever changed under the contract directory. 3. Drop the `$schema` reference from contracts/subagent_status_contract.json pointing at a file that doesn't exist in the tree. Three new tests cover the structured + text composition: completed back-fills the success body, failed back-fills the wrapper text, and unrecognised content under a `failed` stamp stays empty rather than echoing noise.
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 Vitest |
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.