Reverse-engineer an inherited codebase into a spec, then test the rewrite plan

Before you start

Run Repomix as a local MCP server with npx -y repomix --mcp. For code you didn't write, add --sandbox: its file tools stay inside one workspace folder, config files aren't loaded, and remote packing is off, so clone the repository first. Install Fullstack Dev Skills with /plugin marketplace add jeffallan/claude-skills, then /plugin install fullstack-dev-skills@fullstack-dev-skills. Name your stack in each request so the right skills switch on.

Repomix respects .gitignore and uses Secretlint to leave out files that match known credential formats. Pack only what you need, using glob patterns.

The packed output can be searched with regular expressions, so the agent reads only what matters.