@react-ai-stream/express

Express middleware for RAIS Protocol AI streaming — drop-in SSE handler for any Express app.

Install

npm install @react-ai-stream/express

Usage

import express from 'express'
import { raisMiddleware } from '@react-ai-stream/express'

const app = express()
app.use(express.json())

// With a provider (needs API key in env)
app.post('/api/chat', raisMiddleware({
  provider: 'anthropic',
  apiKey: process.env.ANTHROPIC_API_KEY,
  model: 'claude-sonnet-4-6',
}))

app.listen(3000)

Custom handler

app.post('/api/chat', raisMiddleware({
  handler: async function* (messages, signal) {
    yield { type: 'text', text: 'Hello ' }
    yield { type: 'text', text: 'world!' }
    yield { type: 'done' }
  }
}))

The handler receives the full message history and an AbortSignal. Yield RAIS events and the middleware handles all SSE headers, formatting, and abort cleanup.

Options

| Option | Type | Description | |---|---|---| | handler | AsyncGenerator | Custom streaming handler | | provider | 'openai' \| 'anthropic' | Use a built-in provider | | apiKey | string | Provider API key | | model | string | Model name | | system | string | System prompt |

What it handles for you

• Sets Content-Type: text/event-stream, Cache-Control: no-cache, X-Accel-Buffering: no
• Formats each yielded object as data: {...}\n\n
• Calls res.end() after done or error
• Wires req.on('close') to the AbortSignal — cleans up on client disconnect

Verify compliance

npx rais-compliance http://localhost:3000/api/chat
# ✓ All 10 tests passed — RAIS v1 Recommended

License

MIT — part of react-ai-stream