Code Relay MCP server

Code Relay

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Build. Prove. Relay.

Code Relay lets your coding agent develop on one machine and prove the result on another.

Relay is an MCP-based coding-agent integration for cross-machine development and verification. AI on the Dev Host implements the request; the Target Host runs the real validation; a structured receipt comes back to guide the next repair iteration. It works with Codex, Claude Code, Cursor, VS Code, and other MCP-capable coding agents.

When Relay is useful

• Different environments — develop on Windows or macOS, verify on Linux, a private network, or a production-like host.
• Special hardware — send model code to a CUDA/GPU machine, or verify a camera, serial device, or sensor where it is connected.
• Real integrations — exercise payment callbacks, queues, databases, browsers, or internal services that cannot be reproduced locally.
• AI-driven iteration — return concrete expected/actual results so the coding agent can repair, republish, and retry.

What Relay provides

• Branch-scoped project binding and short-lived join links.
• Exact source-commit verification in an isolated worktree.
• Checkpoint execution through a code-relay-checkpoint GitHub Actions self-hosted runner.
• Safe, allowlisted validation commands with bounded output and timeouts.
• Structured receipt.json and human-readable receipts for passed, failed, and blocked runs.

Quick start

AI client installation

Let your coding agent read and follow the instructions:

https://raw.githubusercontent.com/zarcherlot/code-relay/main/install.md

npm fallback

npx -y code-relay-mcp@latest install --client codex

Replace codex with claude-code, cursor, vscode, or generic as needed.

MCP server details

Code Relay is a local MCP server that communicates over stdio. The npm package starts the server with:

npx -y code-relay-mcp@3.1.0

The server implements the MCP JSON-RPC surface directly in Go (without a third-party MCP SDK). It supports initialize, ping, tools/list, and tools/call, and exposes these tools:

The implementation and transport loop are in internal/relay/mcp.go.

How it works

the Dev Host sends a repository- and branch-bound runbook through Relay; the Target Host checks the exact source commit in its real environment and returns a Receipt recording the Checkpoint result.

Every runbook is bound to a repository, branch, and source commit. The Target Host acts as the Checkpoint, and the resulting receipt records passed, failed, or blocked verification for the next iteration.

Documentation

Shortened. The full README is on GitHub.