Quadruple Consensus MCP Server for Claude Code

Tetrad is a high‑performance MCP server written in Rust that coordinates three AI‑powered CLI evaluation tools to validate code produced by Claude Code. It implements a quadruple consensus protocol, requiring approval from Codex, Gemini, Qwen, and Claude Code itself before code is accepted, ensuring robust verification and safer code generation workflows.

How to use

You run Tetrad as an MCP server and connect Claude Code or another MCP client to it. When Claude Code asks you to write code, Tetrad automatically validates the output by sending it to Codex, Gemini, and Qwen for assessment and then returns a consolidated consensus decision. You can customize evaluation hooks, inspect evaluation history, and manage patterns with the ReasoningBank.

How to install

Prerequisites: you need Node.js and Cargo installed on your system. You will install Tetrad, configure access to Codex, Gemini, and Qwen CLIs, and set up Claude Code to call the MCP server.

Step 1 — Install Tetrad (recommended method that works smoothly with Claude Code):

# Via npm (recommended - integrates well with Claude Code)
npm install -g @samoradc/tetrad

# Or via cargo (requires Rust toolchain)
cargo install tetrad
sudo cp ~/.cargo/bin/tetrad /usr/local/bin/

Step 2 — Initialize in your project (optional):

npx @samoradc/tetrad init

Step 3 — Verify installation and readiness:

# Check version and status
tetrad version
tetrad status

tetrad doctor

Step 4 — Add Tetrad to Claude Code MCP configuration so Claude Code can use it as an MCP server:

# Add Tetrad as MCP server for all projects
claude mcp add --scope user tetrad -- npx @samoradc/tetrad serve

# Verify configuration
claude mcp list

Alternative installation methods include configuring a per‑project MCP entry or using a cargo‑installed binary if needed. A manual configuration example is provided later for reference.

Configuration and security

The server can be wired via a simple local process (stdio) or through explicit MCP configuration. You provide the command to start Tetrad and any necessary environment variables for external AI CLIs. A sample per‑project configuration is shown below.

Example per‑project MCP configuration (stdio):

{
  "mcpServers": {
    "tetrad": {
      "type": "stdio",
      "command": "npx",
      "args": ["@samoradc/tetrad", "serve"],
      "env": {
        "OPENAI_API_KEY": "${OPENAI_API_KEY}",
        "GOOGLE_API_KEY": "${GOOGLE_API_KEY}",
        "DASHSCOPE_API_KEY": "${DASHSCOPE_API_KEY}"
      }
    }
  }
}

Alternatively, global user configuration can be placed in the MCP config file at ~/.claude.json under the mcpServers section with the same shape but without necessarily redefining environment defaults.

Troubleshooting and notes

If you encounter issues like the CLI not being found or a JSON response error from evaluators, ensure the executor commands are correct for each tool and that the MCP server is reachable by Claude Code. Common checks include confirming that each CLI is installed and authenticated, and that the MCP server command and arguments exactly match the expected structure.

Key notes to remember: you must have at least one of Codex, Gemini, or Qwen CLI tools installed and authenticated to use Tetrad. You can run status and doctor commands to verify installation and configuration. If you split configuration across projects, keep environment keys consistent to avoid authentication mismatches.

Advanced usage and patterns

Tetrad offers a set of CLI commands to manage evaluations, history, and patterns via the ReasoningBank. You can inspect evaluation history, export patterns for sharing, and import patterns from other ReasoningBank instances. These features help you iterate on code generation while tracking and consolidating best practices.

Available tools

tetrad_review_plan

Review implementation plans before coding

tetrad_review_code

Review code before saving

tetrad_review_tests

Review tests before finalizing

tetrad_confirm

Confirm agreement with received feedback

tetrad_final_check

Final verification before commit

tetrad_status

Check health of evaluators