@langgraph-toolkit/adapter-fastify

Use Fastify for the host, not for graph configuration. This adapter provides graph listing, JSON execution, and SSE streaming while the application resource owns state, MCP, checkpoint, actor, policy, and provider defaults.

Install

npm install fastify @langgraph-toolkit/core @langgraph-toolkit/adapter-fastify

Zero-config factory

import Fastify from "fastify";
import { createFastifyAdapter } from "@langgraph-toolkit/adapter-fastify";
import { resource } from "./resource.js";

const adapter = createFastifyAdapter(resource.runtime);
const app = Fastify();

await app.register(adapter.plugin);
await app.listen({ port: Number(process.env.PORT ?? 3000), host: "0.0.0.0" });

The factory returns { graph, runtime, plugin } and defaults to /agents, /agents/:name/run, and /agents/:name/stream. Pass runPath, streamPath, or apiKey only when the host requires a custom boundary.

Host-native escape hatch

Register langgraphFastify directly when the application needs custom plugin composition. decorateLangGraph exposes the registry as fastify.langgraph; encodeStepEvent remains available for native streaming integrations.

The same resource can move to Express, NestJS, StruxJS, a worker, or a CLI without changing its nodes.

Development

npm install
npm run build
npm test

License

MIT