DeerFlow is an open-source, full-stack AI agent harness built on LangGraph/LangChain, providing a production-ready platform for building, deploying, and managing conversational AI agents. The system features a Python/FastAPI backend with a modular architecture that includes agent orchestration, long-term memory (DeerMem), sandboxed code execution, a skill system with static analysis (SkillScan), MCP (Model Context Protocol) tool integration, multi-channel IM support (Telegram, Slack, Discord, Lark, etc.), scheduled tasks, subagent batches, and a comprehensive authorization framework. The frontend is a Next.js/React workspace with real-time streaming, artifact management, and a terminal UI (TUI) for headless operation. The architecture follows a gateway pattern: the FastAPI gateway handles authentication (JWT, OAuth, PATs), routing, and SSE streaming, while the core harness package (`deerflow`) implements agent logic, middleware chains, and runtime components. Persistence uses SQLAlchemy with Alembic migrations, supporting both SQLite and PostgreSQL. The system is highly extensible via a Python extension API (`deerflow-extension-api`) and a plugin system for frontend surfaces. Deployment supports Docker Compose and Kubernetes (Helm chart). While primarily an application, DeerFlow includes research-oriented components such as memory eviction benchmarks, context snapshot evaluations, and tracing integrations (LangSmith, Langfuse, OpenTelemetry). The codebase demonstrates strong engineering practices with extensive unit tests, blocking IO regression tests, and contract tests, though its large feature surface and many configuration options introduce complexity and potential for drift between environments.