rederive: learn a codebase by re-deriving its design

Summary

rederive (MIT) is an agent skill that teaches you an unfamiliar codebase by questioning you rather than explaining it. You work out 5 to 10 of the codebase's design problems yourself, in the order the system would have been built. It appeared under "New this week" in today's GitHub trends (246 stars in 7 days, 71 commits). The publication date is approximate.

Key points

• Install (any of about 25 agents): npx skills add EricJujianZou/rederive (add -g to install it for all projects), then type /rederive in the agent.
• Install as a Claude Code plugin: /plugin marketplace add EricJujianZou/rederive, then /plugin install rederive@rederive. It needs git, bash, and python3.
• How it works: it starts from why the project exists. Meanwhile a background agent maps the repo from the code, imports, and commit history into .rederive/map.md (the answers, so do not open it). When you are stuck it narrows the options, and after two wrong answers it offers to sketch the problem.
• Progress log: .rederive/log.md records where you struggled. .rederive/ is added to the repo's local git exclude list, everything stays local, and the README says there is no telemetry.
• Good for: onboarding to a new repo, or really understanding code an agent wrote for you, instead of reading a summary you will forget.

Why it matters

Most codebase skills make the agent do more of the work. This one uses the agent to make you learn the code, which helps when agents write most of it and people review it.