# Diff review

`/diff` is pi-jar's post-edit review UI: it inspects captured before/after content, then lets you accept (stop tracking) or explicitly confirm a revert. It is inspired by the split-pane, hunk-navigation and bounded-rendering ideas in [pi-show-diffs](https://github.com/xRyul/pi-show-diffs), but does not copy its code or change the tool pre-approval flow.

- Type `/` in the file list to filter by absolute/relative path or change status (content search is intentionally omitted to keep keystrokes bounded over large retained snapshots). Press Enter to keep the filter, Escape to clear it, and `n`/`N` to move through matching files.
- The right pane starts with the selected file's absolute path and change summary.
- Normal previews render a viewport of Git-style hunks. Each hunk header is preceded by a `┄ N unchanged lines ┄` label for the region it skips. `PgUp`/`PgDn`, `g`/`G`, `Home`/`End`, or the mouse wheel move through the preview; `n`/`p` jump hunks. Rendering windows the requested rows instead of constructing a rendered row for every file line.
- `t` toggles unified rows and aligned side-by-side Original/Updated columns: within a replacement, the k-th removed line sits beside the k-th added line, and a longer side continues alone. Panes narrower than 70 columns keep the unified layout. Toggling keeps the hunk at the top of the viewport.
- `←`/`→` (or `[`/`]`) step the context through 0, 1, 3 (default), 5, 10, 25 lines and the whole file. `w` wraps long lines onto continuation rows instead of truncating them; with wrapping, `End` shows the last full page.
- Changed lines carry a colored `▌` rail and the theme's tool success/error background. For a replaced line pair, the changed words are shown in inverse video, computed by a bounded token LCS (lines that share no word, very long lines and coarse previews are not emphasized). Files whose language Pi recognizes are syntax-highlighted per line with the active theme; lines over 1,000 characters keep plain diff colours.
- Changes over 256 KiB or 1,500 combined lines initially show summary counts. Press `v` to explicitly review a bounded preview or return to summary. Previews are capped at 100,000 combined lines per file. When exact LCS diff exceeds its existing CPU/memory budget, the full-review choice uses a clearly marked coarse replacement hunk that preserves common prefix/suffix and line order.
- Safe revert tracking remains capped at 1 MiB per file and 8 MiB of retained baselines. Binary, oversized, or otherwise untracked files cannot be reverted from this UI. The summary does not imply content beyond those safety caps is reviewable.

The implementation uses the pi-tui custom component and windowed split-frame renderer already used by pi-jar. Upstream visual reference: [xRyul/pi-show-diffs README](https://github.com/xRyul/pi-show-diffs#diff-review-ux), MIT-licensed: aligned split rows, intraline highlights, rail markers, labeled collapsed regions, adjustable context and wrapping. No upstream source was copied, and pi-show-diffs' pre-apply approval and inline editing are not part of `/diff`, which reviews changes after they are applied.