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# Fastify adapter

The `@mastra/fastify` package provides a server adapter for running Mastra with [Fastify](https://fastify.dev). For general adapter concepts (constructor options, initialization flow, etc.), see [Server Adapters](https://mastra.ai/docs/server/server-adapters).

## Installation

Install the Fastify adapter and Fastify framework:

**npm**:

```bash
npm install @mastra/fastify@latest fastify
```

**pnpm**:

```bash
pnpm add @mastra/fastify@latest fastify
```

**Yarn**:

```bash
yarn add @mastra/fastify@latest fastify
```

**Bun**:

```bash
bun add @mastra/fastify@latest fastify
```

## Usage example

```typescript
import Fastify from 'fastify'
import { MastraServer } from '@mastra/fastify'
import { mastra } from './mastra'

const app = Fastify({ logger: true })
const server = new MastraServer({ app, mastra })

await server.init()

app.listen({ port: 3000 }, (err, address) => {
  if (err) {
    console.error(err)
    process.exit(1)
  }
  console.log(`Server running on ${address}`)
})
```

## Constructor parameters

**app** (`FastifyInstance`): Fastify app instance

**mastra** (`Mastra`): Mastra instance

**prefix** (`string`): Route path prefix (e.g., /api/v2) (Default: `''`)

**openapiPath** (`string`): Path to serve OpenAPI spec (e.g., /openapi.json) (Default: `''`)

**bodyLimitOptions** (`BodyLimitOptions`): Request body size limits

**streamOptions** (`StreamOptions`): Stream redaction config. When true (default), redacts sensitive data (system prompts, tool definitions, API keys) from stream chunks before sending to clients. (Default: `{ redact: true }`)

**customRouteAuthConfig** (`Map<string, boolean>`): Per-route auth overrides. Keys are METHOD:PATH (e.g., GET:/api/health). Value false makes route public, true requires auth.

**tools** (`ToolsInput`): Available tools for the server

**taskStore** (`InMemoryTaskStore`): Task store for A2A (Agent-to-Agent) operations

**mcpOptions** (`MCPOptions`): MCP transport options. Set serverless: true for stateless environments like Cloudflare Workers or Vercel Edge.

## Protecting raw routes

When you want Mastra-managed auth and route metadata such as `requiresAuth`, prefer [`registerApiRoute()`](https://mastra.ai/reference/server/register-api-route). For raw Fastify routes mounted directly on the app, use `createAuthMiddleware()`:

```typescript
import Fastify from 'fastify'
import { createAuthMiddleware, MastraServer } from '@mastra/fastify'
import { mastra } from './mastra'

const app = Fastify()
const server = new MastraServer({ app, mastra })

await server.init()

app.get('/custom/protected', { preHandler: createAuthMiddleware({ mastra }) }, async request => {
  const user = request.requestContext.get('user')
  return { user }
})

app.get(
  '/custom/public',
  { preHandler: createAuthMiddleware({ mastra, requiresAuth: false }) },
  async () => {
    return { ok: true }
  },
)
```

## Manual initialization

For custom middleware ordering, call each method separately instead of `init()`. See [manual initialization](https://mastra.ai/docs/server/server-adapters) for details.

## Examples

- [Fastify Adapter](https://github.com/mastra-ai/mastra/tree/main/examples/server-fastify-adapter): Basic Fastify server setup

## Related

- [Server Adapters](https://mastra.ai/docs/server/server-adapters): Shared adapter concepts
- [MastraServer Reference](https://mastra.ai/reference/server/mastra-server): Full API reference
- [createRoute() Reference](https://mastra.ai/reference/server/create-route): Creating type-safe custom routes