codebase-exploration

Map an unfamiliar repository before changing anything in it — structure sweep, entry points, configs, test baseline, targeted tracing, and mental-model confirmation. Trigger this the FIRST time you work in a repo (or an unfamiliar subsystem of a known repo) in a session, before your first edit there — whenever the user says "fix/add/change X" in code you have not yet mapped. Do NOT trigger for repos or areas you already mapped this session, for single-file scripts with no surrounding project, or for parsing the request itself (use task-planning) — this skill is about understanding the code, not the ask.