Durable Streams
Persistent, addressable, real-time HTTP-based data streams for building resilient agent sessions and collaborative multi-user, multi-agent AI systems.
At a Glance
About Durable Streams
Durable Streams is an open-source data primitive for the agent loop, providing persistent, addressable, real-time streams over HTTP. It enables resilient AI agent sessions, collaborative multi-user systems, and reliable client-side data delivery with offset-based resumability and exactly-once message delivery. Built on 1.5 years of production use at Electric for real-time Postgres sync, it reliably handles millions of state changes daily. The protocol is content-type agnostic, CDN-friendly, and works across web browsers, mobile apps, native clients, IoT devices, and edge workers.
- Offset-based resumability — clients resume from any point after disconnection, page refresh, or tab switch without losing data
- Real-time tailing — supports long-poll and SSE modes for live streaming with catch-up from any offset
- AI conversation streaming — stream LLM token responses with resume capability across reconnections using the Durable Proxy
- Agentic app support — stream tool outputs and progress events with replay and clean reconnect semantics
- Multi-client SDKs — official client libraries for TypeScript, Python, Go, Elixir, C#/.NET, Swift, PHP, Java, Rust, and Ruby
- CLI tooling — create, read, append to, and tail streams from the command line
- StreamDB & StreamFS — higher-level abstractions including a type-safe reactive database and a filesystem with real-time sync built on streams
- Durable State — sync structured state using insert/update/delete operations over streams
- TanStack AI & Vercel AI SDK integrations — drop-in transport layer for popular AI frameworks
- CDN-native scaling — HTTP-native design enables massive fan-out to millions of concurrent viewers from a single origin
- Production Caddy plugin — deploy a production-grade server using the official Caddy plugin
- MIT licensed — free to use, modify, and distribute; self-host with the Node.js reference server or Caddy plugin
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Pricing
Open Source (MIT)
Free to use, modify, and distribute under the MIT License. Self-host with the Node.js reference server or Caddy plugin.
- Full protocol implementation
- Node.js reference server
- Caddy production server plugin
- CLI tooling
- Multi-language client SDKs (TypeScript, Python, Go, Elixir, C#/.NET, Swift, PHP, Java, Rust, Ruby)
Capabilities
Key Features
- Offset-based resumable streams
- Long-poll and SSE real-time tailing
- Exactly-once message delivery
- AI conversation/token streaming
- Durable Proxy for AI token streams
- Durable State (insert/update/delete over streams)
- StreamDB (type-safe reactive database)
- StreamFS (filesystem with real-time sync)
- Multi-language client SDKs
- CLI tooling
- Caddy server plugin
- Node.js reference server
- CDN-friendly HTTP-native design
- Content-type agnostic byte streams
- Server conformance and client conformance test suites
- Performance benchmarking suite