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Introduction

MCP Agent Bridge exposes AI coding agents -- Claude Code, OpenAI Codex, and GitHub Copilot -- as Model Context Protocol (MCP) servers. This lets any MCP client call any agent through a standardized interface, enabling cross-agent code review, second opinions, and multi-model collaboration.

Why?​

AI coding agents are powerful individually, but they each have blind spots. By bridging them behind MCP, you can:

  • Get a second opinion -- Send your diff to a different model for review before merging
  • Cross-validate -- Compare responses from Claude, Codex, and Copilot on the same question
  • Structured reviews -- Get typed JSON output with verdict, issues by severity, and suggestions
  • Automate workflows -- Build pipelines that route work to the best agent for each task

How It Works​

┌──────────────┐     MCP (stdio)      ┌─────────────────┐     CLI subprocess
│  MCP Client  │ ◄──────────────────► │  MCP Server     │ ──────────────────► claude -p
│  (any agent) │     or HTTP/SSE      │  (bridge layer) │                     codex exec
└──────────────┘                      └─────────────────┘                     copilot -p

Each bridge server:

  1. Registers MCP tools (review, ask, code_review, etc.)
  2. Receives tool calls from any MCP client
  3. Spawns the underlying CLI agent as a subprocess
  4. Parses and returns structured results

Architecture​

In production, each server runs as a singleton background service behind an HTTP proxy (mcp-proxy). Multiple clients share a single instance of each agent -- no cold starts, no duplicated processes.

┌─────────────┐
│ Claude Code  │──┐
└─────────────┘  │    HTTP/SSE         ┌───────────┐    stdio    ┌──────────────────┐
                 ├──────────────────► │ mcp-proxy │ ──────────► │ claude-mcp-server│
┌─────────────┐  │   :8940/mcp        └───────────┘             └──────────────────┘
│   Codex      │──┘
└─────────────┘

┌─────────────┐
│ Claude Code  │──────────────────►  :8941/mcp ──► codex-mcp-server
└─────────────┘

┌─────────────┐
│ Claude Code  │──────────────────►  :8945/mcp ──► copilot-mcp-server
└─────────────┘

Key Features​

FeatureDescription
Three agent bridgesClaude, Codex, and Copilot as MCP servers
Structured reviewsJSON output with verdict, issues, suggestions
Singleton servicesBackground daemons shared by multiple clients
Cross-platformmacOS (LaunchAgents), Windows (NSSM), Linux (systemd)
Standalone binariesZero-dependency executables compiled with Bun
Secure defaultsRead-only tools, localhost binding, input limits

Next Steps​