Express Server Adapter Example

This example demonstrates how to use the @mastra/express server adapter to run Mastra with Express.

What it shows

• Basic server setup with MastraServer
• Required express.json() middleware for body parsing
• Custom routes added after init() with access to Mastra context
• Accessing the Mastra instance via res.locals

Getting started

1. Install dependencies:

pnpm install

2. Copy .env.example to .env and add your OpenAI API key:

cp .env.example .env

3. Start the server:

pnpm start

Testing the endpoints

List agents:

curl http://localhost:4111/api/agents

Health check (custom route):

curl http://localhost:4111/health

Generate a response:

curl -X POST http://localhost:4111/api/agents/assistantAgent/generate \
  -H "Content-Type: application/json" \
  -d '{"messages": "What is 2+2?"}'

Key differences from Hono

• Express requires express.json() middleware for JSON body parsing
• Context is accessed via res.locals instead of c.get()

Documentation

• Express Adapter docs
• Server Adapters overview