onboard onto an unfamiliar codebase
You just inherited a repo and need a working map — where things live, what not to touch — without a week of tab-hopping.
recs
| model | best when | avoid when | cost vibe |
|---|---|---|---|
| Sonnet-class | The repo is large, messy, or the real question is “what breaks if i change this.” | You only need a file tree and a one-paragraph readme. | $$$ |
| Faster / cheaper cloud | First pass: entrypoints, main modules, how to run tests. | Architecture is implicit and wrong guesses are expensive. | $ |
| Local mid | Private code, and you want a disposable map you can throw away. | You need cross-file judgment, not a summary of the files you opened. | ~free |
why
- Onboarding is a map problem. Speed matters less than not inventing a structure that isn’t there.
- Cheap models narrate the files you showed them. Frontier earns it when the answer is “this looks unused but three jobs depend on it.”
- Local is fine for private repos if you treat the map as a draft, not a spec.
- Pair with pr-review once you start changing things — the map is not the review.