Langflow
Langflow is an open-source low-code visual builder for AI agents, RAG pipelines, and LangChain-based workflows. It pairs a drag-and-drop React Flow frontend with a FastAPI backend that exposes every flow as a REST API, an MCP server, and an OpenAI-compatible Responses endpoint. Components are editable Python and ship with integrations across most major LLMs, vector stores, and observability platforms. Langflow was acquired by DataStax in 2025; DataStax itself was acquired by IBM and the deal closed on May 28, 2025, making Langflow an IBM property while remaining MIT-licensed open source. The project is the canonical reference implementation for visually composing LangChain agents — 149k+ GitHub stars, distributed via PyPI, Docker, Helm, and native Desktop apps, with a hosted cloud option run by DataStax.
APIs
Langflow API
Langflow's FastAPI-based REST API exposes every capability of a running Langflow server — running flows, building flows, managing projects, files, users, API keys, MCP servers, ...
Langflow Flows API
Create, read, update, delete, upload, download, and list flows. A flow is the canonical Langflow unit — a directed graph of components representing an AI agent or workflow. Incl...
Langflow Run API
Execute a flow by id or name via POST `/api/v1/run/{flow_id_or_name}` (simplified), POST `/api/v1/run/advanced/{flow_id_or_name}` (experimental advanced), or POST `/api/v1/webho...
Langflow Build API
Build endpoints run a flow with full vertex-level streaming. POST `/api/v1/build/{flow_id}/flow` kicks off a build job and returns a job id; GET `/api/v1/build/{job_id}/events` ...
Langflow Projects API
Create, list, read, update, delete, upload, and download Langflow projects. Projects are containers that group flows and provide MCP server installation context.
Langflow Files API
Upload, download, list, and delete files attached to a flow (v1) or to the authenticated user (v2). The v2 Files API supports batch upload/download, batch delete, and profile-pi...
Langflow Monitor API
Inspect and manage execution history — vertex builds, chat messages, sessions, and shared sessions. Supports listing, updating, renaming, and deleting messages and entire sessio...
Langflow Traces API
Retrieve and delete execution traces. GET `/api/v1/monitor/traces` lists traces with flow-id filtering; GET `/api/v1/monitor/traces/{trace_id}` returns a single trace. Integrate...
Langflow Users API
User management endpoints — create, read, patch, and delete users; `/api/v1/users/whoami` returns the current authenticated user; reset-password endpoint for superuser-driven cr...
Langflow MCP API
Manage MCP (Model Context Protocol) servers attached to Langflow projects and globally. Every Langflow project can be exposed as an MCP server so its flows are callable as MCP t...
Langflow Workflow API
v2 Workflow execution API — POST `/api/v2/workflows` executes a workflow; GET returns workflow status; POST `/api/v2/workflows/stop` halts a running workflow. The v2 workflow su...
Langflow OpenAI Responses API
OpenAI-compatible Responses endpoint at POST `/api/v1/responses`. Lets clients written against OpenAI's Responses API point at a Langflow flow without code changes — the flow pl...
Langflow API Keys API
Create, list, rotate, and delete Langflow API keys. Keys authenticate requests against any of the Langflow REST endpoints via the `x-api-key` header. Also creatable via the `lan...