deer-flow/backend/AGENTS.md

AGENTS.md

This file provides guidance to AI coding agents (Claude Code, Codex, and others) when working with code in this repository. It is the source of truth; the sibling CLAUDE.md imports it via @AGENTS.md.

Project Overview

DeerFlow is a LangGraph-based AI super agent system with a full-stack architecture. The backend provides a "super agent" with sandbox execution, persistent memory, subagent delegation, and extensible tool integration - all operating in per-thread isolated environments.

Architecture:

• Gateway API (port 8001): REST API plus embedded LangGraph-compatible agent runtime
• Frontend (port 3000): Next.js web interface
• Nginx (port 2026): Unified reverse proxy entry point
• Provisioner (port 8002, optional in Docker dev): Started only when sandbox is configured for provisioner/Kubernetes mode

Runtime:

• make dev, Docker dev, and production all run the agent runtime in Gateway via RunManager + run_agent() + StreamBridge (packages/harness/deerflow/runtime/). Nginx exposes that runtime at /api/langgraph/* and rewrites it to Gateway's native /api/* routers.
• Gateway streams write_file and str_replace argument deltas in bounded batches when clients also subscribe to values; messages-only consumers retain the original per-chunk contract, while values preserves the complete tool call.
• With stream_subgraphs, subgraph frames keep their namespace in the SSE event name (values|<ns>, LangGraph Platform style) instead of impersonating root frames — a delegated subagent inherits the parent checkpoint namespace, so publishing its values snapshot as bare values replaces the whole thread view in SDK clients (#4399). Root-only consumers (file-tool chunk batcher, subagent event persistence, LLM error-fallback detection) ignore namespaced frames. The web frontend does not request subgraph streaming; subtask progress rides root-namespace task_* custom events.
• Background subagent identity is deliberately split: the provider tool_call_id remains the correlation key for ToolMessage, task_* SSE events, persisted lifecycle events, frontend cards, and the public ExtensionData.scope_id contract (stored as SubagentResult.external_task_id), while SubagentExecutor.execute_async() generates a full server-side execution_id for SubagentResult.task_id, the process-wide registry, polling, cancellation, timeout handling, and cleanup. Provider IDs are not globally unique across parent runs, so they must never become registry ownership keys; scheduler closures retain their own SubagentResult rather than resolving ownership again through the mutable registry. Terminal subagent token usage travels in the current run's ToolMessage.additional_kwargs and is attributed from message state, never through a process-global provider-ID cache.
• Scheduled-task executions must reuse that same Gateway run lifecycle. The scheduler may decide when work runs, but it must dispatch through the existing run path rather than introducing a parallel execution stack. Scheduled launches pass scheduler.recursion_limit (default 1000, matching the web UI's recursion_limit: 1000, clamped by max_recursion_limit) via launch_scheduled_thread_run; the value is read from get_app_config() at dispatch.
• The background scheduler is single-instance by default. scheduler.multi_instance=true opts into lease-aware recovery across Gateway instances and requires shared Postgres, run_ownership.heartbeat_enabled=true, and run_events.backend=db; otherwise startup rejects the configuration. Live scheduled runs are preserved when a peer starts; expired leases are atomically taken over, stale post-launch writes are fenced by the dispatch lease owner, and the Postgres advisory-locked budget makes max_concurrent_runs a shared global cap (including pre-launch reservations).
• Long-running MCP work uses a separate durable task runtime rather than keeping remote task IDs or status polling inside the Agent loop. Explicit task_toolsets bind raw submit/status/cancel names; only submit remains Agent-visible, and its wrapper persists the remote handle before returning a local ID. McpTaskService claims due rows with leases, resolves a protocol-specific McpTaskDriver, and writes normalized snapshots back to mcp_tasks; expired leases are the restart-recovery mechanism, and a result returned after expiry or after a cancel request must be discarded even when the owner token still matches. The first cancel request fences an in-flight poll lease, while repeats preserve an active cancellation lease so they cannot issue concurrent remote cancels; cancellation backoff starts when the remote attempt finishes, so a slow timeout cannot consume the retry delay. Cancellation, polling, and notification batches isolate per-task exceptions; an unexpected cancellation/poll failure leaves that record's lease to expire, while notification failures release only the affected lease for retry. Input-required and terminal event snapshots are delivered by idempotent Agent runs and marked delivered only after run success; the trusted notification instruction stays outside the input boundary while the serialized remote event is framed as untrusted data. A busy-thread conflict is normalized back to the service boundary so the queued snapshot coalesces to the latest task event. A missing dispatched run becomes a failed delivery attempt, while transient run-store hydration errors stay distinguishable and retry the same lookup. The database is the source of truth; ThreadState receives only a bounded current-thread projection, and display names are neutralized at that model-state boundary. The installed process-local submitter is the source of truth for management-tool exposure; hot mcp_tasks edits take effect only after restart, and active skills must explicitly declare the list/cancel business tools.
• MCP notification failures use a consecutive counter separate from the idempotency-key dispatch_attempt, capped exponential backoff, latest-event rebuilding before a run launches, and a five-attempt budget before dead_letter. A permanently missing/mismatched target thread is dead-lettered immediately instead of being recreated or reclaimed. HTTP and Agent cancellation requests return after the durable cancel fence; the background loop alone owns the potentially slow remote call and retry schedule. The HTTP cancel endpoint rejects requests with 503 when the loop is not running (mcp_tasks_available false, e.g. mcp_tasks.enabled=false with SQL persistence), so a cancellation is never acknowledged without a worker to perform it. The bounded notification error/count/status join poll and cancellation diagnostics in the task detail API and expanded card.
• extensions_config.json is written at runtime by the Gateway (PUT/PATCH /api/mcp/config, the MCP enable switch, skill updates), so the production compose mounts it read-write while config.yaml stays :ro; Helm copies its ConfigMap seed into a writable home-volume directory before Gateway starts. Every read-modify-write holds both extensions_config_write_lock and the sidecar advisory extensions_config_file_lock, because the process-local lock alone loses updates across workers. Docker mounts the compose file as its own mount point, and Linux refuses rename() over a mount point with EBUSY even when the mount is writable — so atomic_write_extensions_config keeps the temp-file-plus-rename path and falls back to an in-place overwrite only on EBUSY. That fallback is deliberately non-atomic (a crash mid-write truncates the file); it exists because the alternative is a write that can never succeed, and only its first occurrence per target is logged at warning level. Any other errno still propagates. Pinned by tests/test_compose_extensions_config_writable.py, tests/test_extensions_config_atomic_write.py, and tests/test_helm_extensions_config_writable.py.
• Scheduled-task dispatch enforces "at most one active run per task when overlap_policy=skip" at the DB layer via the partial unique index uq_scheduled_task_run_active (scheduled_task_runs.task_id WHERE status IN ('queued','running')). ScheduledTaskService.dispatch_task's has_active_runs check is a non-atomic fast path (its own session, separated from the create() insert by await points), so two concurrent dispatches — a manual POST /scheduled-tasks/{id}/trigger racing the poller, a double-click, or a client retry — can both pass it; the index is the atomic arbiter, and the losing create surfaces as ActiveScheduledRunConflict (translated from IntegrityError in the repository) and collapses to the same outcome as the fast path (manual → 409 conflict, scheduled → a "skipped" tombstone). The scheduled-skip tombstone is created directly as terminal "skipped" (not a transient "queued") so it never occupies the active slot the pre-existing run still holds. Sibling of the runs table's uq_runs_thread_active (PR #4003), which keys on thread_id and so does not cover the default fresh_thread_per_run context where every dispatch gets a new thread. Index is status-only, not overlap_policy-conditional (the policy is fixed to "skip" in the MVP).

Project Structure:

deer-flow/
├── Makefile                    # Root commands (check, install, dev, stop)
├── config.yaml                 # Main application configuration
├── extensions_config.json      # MCP servers and skills configuration
├── backend/                    # Backend application (this directory)
│   ├── Makefile               # Backend-only commands (dev, gateway, lint)
│   ├── langgraph.json         # LangGraph Studio graph configuration
│   ├── packages/
│   │   ├── extension-api/     # public, host-independent extension contracts (import: deerflow_extension_api.*)
│   │   └── harness/           # deerflow-harness package (import: deerflow.*)
│   │       ├── pyproject.toml
│   │       └── deerflow/
│   │           ├── agents/            # LangGraph agent system
│   │           │   ├── lead_agent/    # Main agent (factory + system prompt)
│   │           │   ├── middlewares/   # middleware components (see Middleware Chain section)
│   │           │   ├── memory/        # Memory extraction, queue, prompts
│   │           │   └── thread_state.py # ThreadState schema
│   │           ├── sandbox/           # Sandbox execution system
│   │           │   ├── local/         # Local filesystem provider
│   │           │   ├── sandbox.py     # Abstract Sandbox interface
│   │           │   ├── tools.py       # bash, ls, read/write/str_replace
│   │           │   └── middleware.py  # Sandbox lifecycle management
│   │           ├── subagents/         # Subagent delegation system
│   │           │   ├── builtins/      # general-purpose, bash agents
│   │           │   ├── executor.py    # Background execution engine
│   │           │   └── registry.py    # Agent registry
│   │           ├── tools/builtins/    # Built-in tools (present_files, ask_clarification, view_image, review_skill_package)
│   │           ├── mcp/               # MCP integration (tools, cache, client)
│   │           ├── integrations/      # Managed first-party integration installers (e.g. Lark CLI skill pack)
│   │           ├── extensions/        # Python plugin loader, registry, placement, and isolation
│   │           ├── models/            # Model factory with thinking/vision support
│   │           ├── skills/            # Skills discovery, loading, parsing
│   │           ├── config/            # Configuration system (app, model, sandbox, tool, etc.)
│   │           ├── community/         # Community tools (search/fetch/scrape, image search, AIO sandbox)
│   │           ├── reflection/        # Dynamic module loading (resolve_variable, resolve_class)
│   │           ├── utils/             # Utilities (network, readability)
│   │           └── client.py          # Embedded Python client (DeerFlowClient)
│   ├── app/                   # Application layer (import: app.*)
│   │   ├── gateway/           # FastAPI Gateway API
│   │   │   ├── app.py         # FastAPI application
│   │   │   └── routers/       # FastAPI route modules (models, mcp, memory, skills, uploads, threads, artifacts, agents, suggestions, channels)
│   │   └── channels/          # IM platform integrations
│   ├── tests/                 # Test suite
│   └── docs/                  # Documentation
├── frontend/                   # Next.js frontend application
└── skills/                     # Agent skills directory
    ├── public/                # Public skills (committed)
    └── custom/                # Custom skills (gitignored)

Important Development Guidelines

Documentation Update Policy

CRITICAL: Always update README.md and AGENTS.md after every code change

When making code changes, you MUST update the relevant documentation:

• Update README.md for user-facing changes (features, setup, usage instructions)
• Update AGENTS.md for development changes (architecture, commands, workflows, internal systems). CLAUDE.md imports it via @AGENTS.md, so editing AGENTS.md updates both.
• Keep documentation synchronized with the codebase at all times
• Ensure accuracy and timeliness of all documentation

Commands

Root directory (for full application):

make check      # Check system requirements
make install    # Install all dependencies (frontend + backend)
make extension-install SOURCE=...  # Install and enable a trusted Python extension
make extension-list                # List configured Python extensions
make extension-enable NAME=...     # Enable an installed extension
make extension-disable NAME=...    # Disable an extension without uninstalling it
make extension-remove NAME=...     # Remove a managed extension
make detect-thread-boundaries  # Inventory backend executor/thread/event-loop boundaries
make dev        # Start all services (Gateway + Frontend + Nginx), with config.yaml preflight
make start      # Start production services locally
make stop       # Stop all services

Backend directory (for backend development only):

make install            # Install backend dependencies
make dev                # Run Gateway API with runtime-safe reload (port 8001)
make gateway            # Run Gateway API only (port 8001)
make test               # Run offline backend tests (excludes live external-API tests)
make test-live          # Explicitly run live DeerFlowClient tests with real APIs
make test-blocking-io   # Run strict Blockbuster runtime gate on tests/blocking_io/
make lint               # Lint with ruff
make format             # Format code with ruff
make migrate-rev MSG="..."  # Autogenerate a new alembic revision (see Schema Migrations section)

The backend make dev target pre-creates and excludes DEER_FLOW_HOME (default: backend/.deer-flow) and backend/sandbox from Uvicorn's reload watcher. Do not replace it with a bare uvicorn --reload: agent tasks write Python and other runtime files below DEER_FLOW_HOME, which would otherwise restart the Gateway during an active run.

More specific AGENTS.md files in backend code directories contain the subsystem sections split from this file. Follow the nearest file in the directory tree.

Architecture

Harness / App Split

The backend is split into two layers with a strict dependency direction:

• Harness (packages/harness/deerflow/): Publishable agent framework package (deerflow-harness). Import prefix: deerflow.*. Contains agent orchestration, tools, sandbox, models, MCP, skills, config — everything needed to build and run agents.
• App (app/): Unpublished application code. Import prefix: app.*. Contains the FastAPI Gateway API and IM channel integrations (Feishu, Slack, Telegram, DingTalk).

Dependency rule: App imports deerflow, but deerflow never imports app. This boundary is enforced by tests/test_harness_boundary.py which runs in CI.

Import conventions:

# Harness internal
from deerflow.agents import make_lead_agent
from deerflow.models import create_chat_model

# App internal
from app.gateway.app import app
from app.channels.service import start_channel_service

# App → Harness (allowed)
from deerflow.config import get_app_config

# Harness → App (FORBIDDEN — enforced by test_harness_boundary.py)
# from app.gateway.routers.uploads import ...  # ← will fail CI

Package import hygiene: the deerflow.agents and deerflow.subagents package roots expose heavyweight graph/executor entrypoints lazily. The deerflow.agents:make_lead_agent LangGraph Server entrypoint is a concrete thin module-level function because the server resolves graph factories directly from the module dictionary; the wrapper keeps the lead-agent and skill-cache imports inside the function so importing the package remains lightweight. Internal modules that only need lightweight types, config, or registries should import the concrete submodule instead of adding eager package-root imports that pull in the tool graph or subagent executor during state/schema imports.

Development Workflow

Test-Driven Development (TDD) — MANDATORY

Every new feature or bug fix MUST be accompanied by unit tests. No exceptions.

• Write tests in backend/tests/ following the existing naming convention test_<feature>.py
• Run the full offline suite before and after your change: make test
• Tests must pass before a feature is considered complete
• For lightweight config/utility modules, prefer pure unit tests with no external dependencies
• If a module causes circular import issues in tests, add a sys.modules mock in tests/conftest.py (see existing example for deerflow.subagents.executor)

# Run all offline tests
make test

# Explicit live integration tests (requires config.yaml and credentials;
# calls real APIs and may create local side effects)
make test-live

# Run a specific test file
PYTHONPATH=. uv run pytest tests/test_<feature>.py -v

Direct pytest collection or execution of tests/test_client_live.py remains skipped unless DEER_FLOW_RUN_LIVE_TESTS=1 is set. Do not add that opt-in to default CI workflows.

Running the Full Application

From the project root directory:

make dev

This starts all services and makes the application available at http://localhost:2026.

All startup modes:

	Local Foreground	Local Daemon	Docker Dev	Docker Prod
Dev	./scripts/serve.sh --dev make dev	./scripts/serve.sh --dev --daemon make dev-daemon	./scripts/docker.sh start make docker-start	—
Prod	./scripts/serve.sh --prod make start	./scripts/serve.sh --prod --daemon make start-daemon	—	./scripts/deploy.sh make up

Action	Local	Docker Dev	Docker Prod
Stop	./scripts/serve.sh --stop make stop	./scripts/docker.sh stop make docker-stop	./scripts/deploy.sh down make down
Restart	./scripts/serve.sh --restart [flags]	./scripts/docker.sh restart	—

Nginx routing:

• /api/langgraph/* → Gateway embedded runtime (8001), rewritten to /api/*
• /api/* (other) → Gateway API (8001)
• / (non-API) → Frontend (3000)

Running Backend Services Separately

From the backend directory:

# Gateway API
make gateway

Direct access (without nginx):

• Gateway: http://localhost:8001

Frontend Configuration

The frontend uses environment variables to connect to backend services:

• NEXT_PUBLIC_LANGGRAPH_BASE_URL - Defaults to /api/langgraph (through nginx)
• NEXT_PUBLIC_BACKEND_BASE_URL - Defaults to empty string (through nginx)

When using make dev from root, the frontend automatically connects through nginx.

Key Features

File Upload

Multi-file upload with automatic document conversion:

• Endpoint: POST /api/threads/{thread_id}/uploads
• Supports: PDF, PPT, Excel, Word documents (converted via markitdown)
• Rejects directory inputs before copying so uploads stay all-or-nothing
• Reuses one conversion worker per request when called from an active event loop
• Files stored in thread-isolated directories under the resolving user's bucket (users/{user_id}/threads/{thread_id}/user-data/uploads). For IM channels the owner is threaded explicitly via the user_id= kwarg (see IM Channels → Owner-scoped file storage); HTTP/embedded callers resolve it from get_effective_user_id()
• Duplicate filenames in a single upload request are auto-renamed with _N suffixes so later files do not truncate earlier files
• Gateway HTTP uploads stage bytes as .upload-*.part files and atomically replace the destination only after size validation. These staging files are hidden from upload listings, agent upload context, and sandbox listing/search tools, and swept on Gateway startup if a hard crash leaves one behind.
• Gateway HTTP upload/list/delete handlers offload filesystem work through deerflow.utils.file_io.run_file_io, a dedicated ContextVar-preserving file IO executor. Non-mounted sandbox uploads acquire sandboxes with SandboxProvider.acquire_async() and offload read_bytes() plus sandbox.update_file() together.
• Mounted upload paths skip both sandbox acquisition and per-file synchronization. For AIO remote/provisioner deployments this requires an explicit, accurate sandbox.thread_data_mounts: true; omission preserves backend auto-detection.
• Agent receives uploaded file list via UploadsMiddleware

See docs/FILE_UPLOAD.md for details.

Plan Mode

TodoList middleware for complex multi-step tasks:

• Controlled via runtime config: config.configurable.is_plan_mode = True
• Provides write_todos tool for task tracking
• One task in_progress at a time, real-time updates

See docs/plan_mode_usage.md for details.

Context Summarization

Automatic conversation summarization when approaching token limits:

• Configured in config.yaml under summarization key
• Trigger types: tokens, messages, or fraction of max input
• Keeps recent messages while summarizing older ones
• Manual compaction uses POST /api/threads/{id}/compact, reuses the same DeerFlowSummarizationMiddleware, writes a new checkpoint with updated messages and summary_text, and bumps only those channel versions. The route uses the shared reserve_checkpoint_write() boundary (also used by manual state updates). Its short-lived checkpoint_write thread operation shares the durable active-thread uniqueness constraint with run admission, preventing either worker-local or cross-worker checkpoint-write races.

See docs/summarization.md for details.

Vision Support

For models with supports_vision: true:

• ViewImageMiddleware processes images in conversation
• view_image_tool added to agent's toolset
• Images are converted to base64 and injected into a hidden message carrying both a reserved ID prefix and a server-owned metadata marker for the model call; Gateway strips that marker from untrusted input, and the middleware requires both identifiers before removing the message. The before_model and model node checkpoints for that call still contain the payload; after after_model cleanup, subsequent checkpoints retain only lightweight viewed_images metadata, while client-chosen IDs survive

Code Style

• Uses ruff for linting and formatting
• Line length: 240 characters
• Python 3.12+ with type hints
• Double quotes, space indentation

Documentation

See docs/ directory for detailed documentation:

• CONFIGURATION.md - Configuration options
• ARCHITECTURE.md - Architecture details
• API.md - API reference
• SETUP.md - Setup guide
• FILE_UPLOAD.md - File upload feature
• PATH_EXAMPLES.md - Path types and usage
• summarization.md - Context summarization
• plan_mode_usage.md - Plan mode with TodoList