MCP-Flow

WebTransport binding for the Model Context Protocol.

MCP-Flow eliminates head-of-line blocking in MCP by leveraging QUIC streams and datagrams for parallel, mixed-reliability communication.

Why MCP-Flow?

Traditional MCP	MCP-Flow
Single stream blocks all messages	Parallel streams for concurrent operations
Large responses freeze the connection	Bulk data flows on dedicated Execution Streams
No progress updates during transfers	Real-time datagrams for progress, audio, logs

Quick Start

# Build everything
make build

# Terminal 1: Start a server
make run-go

# Terminal 2: Run the test client
./bin/mcp-flow-client

Project Structure

schema/0.1/
├── schema.ts            # TypeScript type definitions
├── schema.json          # JSON Schema for validation
└── IMPLEMENTATION.md    # Wire formats, state machine, examples

examples/
├── go/                  # Go server (quic-go)
├── python/              # Python server (aioquic)
├── typescript/          # TypeScript server (Deno)
└── client/              # Go test client

Key Features

• No head-of-line blocking — Large responses stream independently
• Mixed reliability — Datagrams for progress/audio, streams for data
• Encoding negotiation — JSON or CBOR, negotiated at connection time
• Backward compatible — Standard MCP JSON-RPC messages, new transport

Documentation

Document	Description
Implementation Guide	Wire formats, state machine, error codes
Schema Reference	Type definitions and constants
Examples README	Running the reference servers
Contributing	How to contribute

Status

Version 0.1 — Reference implementations demonstrate the core Control Stream protocol. Execution Streams and Datagrams are specified but not yet implemented in examples.

License

MIT