## Phase 0 — Gather the diff Run `git diff @{upstream}...HEAD` (or `git diff main...HEAD` / `git diff HEAD~1` if there's no upstream) to get the unified diff under review. If there are uncommitted changes, or the range diff is empty, also run `git diff HEAD` and include the working-tree changes in scope — the review often runs before the commit. If a PR number, branch name, or file path was passed as an argument, review that target instead. Treat this diff as the review scope.