@agenisea/sse-kit

Server-Sent Events streaming for TypeScript. Zero dependencies. Works with Next.js, Express, Hono, and any runtime that supports ReadableStream.

Features

• Server orchestration — heartbeat, abort signals, observability hooks
• Client parsing — stateful chunked and full response modes
• Resilience — exponential backoff, circuit breaker, timeouts
• React hook — full lifecycle management with retry support
• Tree-shakeable — import only what you need

Design Philosophy

event: = protocol (stream lifecycle). data: = application (your data, any shape).

sse-kit is a pure transport layer. The SSE event: line drives state transitions. The data: line carries your payload — no wrappers, no reshaping. What you send is what you get.

Install

pnpm add @agenisea/sse-kit

Quick Start

Server

import { createStreamingResponse, createSSEResponse } from '@agenisea/sse-kit/server'

export async function POST(request: Request) {
  const { stream, orchestrator } = createStreamingResponse({
    signal: request.signal,
    heartbeat: { intervalMs: 3000, enabled: true }, // default: 5000ms
  })

  ;(async () => {
    orchestrator.startHeartbeat()
    await orchestrator.sendUpdate('stage', { name: 'parsing', status: 'running' })
    await orchestrator.sendData({ sections: 12, title: 'Report' })
    await orchestrator.close()
  })()

  return createSSEResponse(stream)
}

Client

import { useSSEStream } from '@agenisea/sse-kit/client'

function App() {
  const { state, start, cancel } = useSSEStream({
    endpoint: '/api/stream',
    initialEvent: 'idle',
    completeEvent: 'complete',
    errorEvent: 'error',
    onUpdate: (event, data) => {
      if (event === 'stage') console.log('Stage:', data)
    },
    onComplete: (result) => console.log('Done:', result),
  })

  return (
    <button onClick={() => start({ query: 'test' })}>
      {state.isStreaming ? 'Streaming...' : 'Start'}
    </button>
  )
}

Documentation

• API Reference — full API documentation
• Security — security considerations
• Changelog — version history

License

MIT

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Built by Agenisea

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© 2025-2026 Patrick Pena / Agenisea