yoyo: Local MCP Server for Grounded Codebase Reads and Guarded Writes with Claude Code

What yoyo Does

yoyo is an open-source local MCP server designed for working on real codebases with coding agents, including Claude Code. The tool was built partly with Claude/Claude Code and is designed to be useful from Claude Code itself.

Core Features

• Grounded repo reads: Provides agents with capabilities like inspect, judge_change, and impact
• Guarded writes: Prevents broken edits from silently landing in the codebase
• Structured feedback: Returns machine-readable guard_failure output when a write fails
• Retry mechanism: Adds retry_plan so the next repair step is narrower and more targeted
• Runtime guards: Supports runtime guards for interpreted languages, allowing files to be rolled back if they parse but still fail at runtime

Language Support

Currently supports 16 languages: Rust, Go, Python, TypeScript, JavaScript, C, C++, C#, Clojure, Java, Kotlin, PHP, Ruby, Swift, Bash, and Zig.

Practical Example

A Python edit might pass a syntax check but still fail because of a missing import or undefined name. yoyo can catch that in the runtime guard, restore the original file, and return structured feedback for the next fix attempt.

Recent Updates

Recent work added initial Clojure support and least-privilege runtime config bootstrap.

Availability

The tool is free to try and open source at https://github.com/avirajkhare00/yoyo.