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<p align="center"> <strong>Contract-first backend framework for Bun and Node.</strong><br/> Define your API once — get an HTTP API, MCP tools, AI-agent tools, a CLI and a typed client. </p> <p align="center"> <a href="https://www.npmjs.com/package/stitchkit"><img src="https://img.shields.io/npm/v/stitchkit?color=2563eb" alt="npm version" /></a> <a href="https://github.com/max-listov/stitchkit/actions/workflows/ci.yml"><img src="https://github.com/max-listov/stitchkit/actions/workflows/ci.yml/badge.svg" alt="CI" /></a> <a href="./LICENSE"><img src="https://img.shields.io/npm/l/stitchkit?color=2563eb" alt="MIT license" /></a> <img src="https://img.shields.io/badge/runtime-Bun-fbf0df?logo=bun&logoColor=000" alt="Bun" /> <img src="https://img.shields.io/badge/runtime-Node%20%E2%89%A522-339933?logo=nodedotjs&logoColor=fff" alt="Node >= 22" /> </p> <p align="center"> <img src="https://raw.githubusercontent.com/max-listov/stitchkit/master/assets/infographic-hero.jpg" alt="One contract becomes an HTTP API, MCP tools, AI-agent tools and a typed client" width="100%" /> </p> <p align="center"> <em>One <code>defineContract()</code> → an HTTP API, MCP tools, AI-agent tools and a CLI on the server — plus a fully-typed client to call them.</em> </p>

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Why

• One contract, five surfaces. Define your API once — get HTTP routes, MCP tools (for Claude/Cursor), AI SDK tools (for agents), a CLI (for scripts & Skills), and a typed client.
• Zero HTTP framework deps. Built on Bun.serve() (Bun) or srvx (Node). No Hono, no Elysia, no Express.
• Fullstack type safety. Server handlers, client calls, MCP tools — all typed from the same contract.
• Inspectable. A focused core with explicit adapters. No generated application code or framework build step in your app.
• Thin over what you already use. WebSocket = Socket.IO (createSocketIOClient / createSocketIOServer). React data layer = react-query-kit (createCursorQuery). stitchkit owns the contract and the transport — not its own competing WebSocket or hook engine.

The problem it solves

A modern backend exposes the same operations several ways — an HTTP API for the app, MCP tools for assistants like Claude and Cursor, tool definitions for AI agents, and a CLI for scripts and Skills. Written by hand, that is one surface described many times: many places to drift, many places to keep in sync. stitchkit collapses them into a single contract — change it once, every surface and the typed client move together.

<p align="center"> <img src="https://raw.githubusercontent.com/max-listov/stitchkit/master/assets/infographic-compare.jpg" alt="Without stitchkit: the same API hand-written three times. With stitchkit: one contract drives them all." width="100%" /> </p>

Status

Pre-1.0. The core is stable and covered by tests, but the public API may still change between minor versions until 1.0. Bun is first-class; Node ≥ 22 is supported via stitchkit/node.

Install

Start a production-shaped Next.js, Stitchkit and PostgreSQL application:

bun create stitchkit my-app
cd my-app
# Point DATABASE_URL in .env at your PostgreSQL database.
bun run dev

To add Stitchkit to an existing project instead:

bun add stitchkit        # Bun
npm install stitchkit    # Node
pnpm add stitchkit       # pnpm

Import policy

Browser code imports browser-safe entrypoints:

import { defineContract, createClient, createHttpClient } from 'stitchkit'
import { createSocketIOClient } from 'stitchkit'
import { createCursorQuery, createCacheBridge } from 'stitchkit/react'
import { AgentRunSchema, AgentRuntimeEventSchema } from 'stitchkit/agent-runtime/browser'
import { parseSSE } from 'stitchkit'
import { createAuthorizationCodeClient } from 'stitchkit/oauth'

Server code imports server entrypoints:

import { createServer, createHandler, implement } from 'stitchkit/server'
import { createSocketIOServer, createAuthHook } from 'stitchkit/server'
import { createMcpHandler, mountAgent } from 'stitchkit/tools'
import { createAgentRuntime, defineAgentProtocol } from 'stitchkit/agent-runtime'
import { createBunSqliteAgentRuntimeStore } from 'stitchkit/agent-runtime/sqlite/bun'
import { createApplication, defineManagedResource } from 'stitchkit/application'
import { implementRemote } from 'stitchkit/remote'
import { createGoogleOidcClient } from 'stitchkit/google'
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