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      • Inline diff highlighting for edits

      • Date: 2026-07-30
      • Commit: feat(tui): inline highlight for edit diffs and migrate diffy to similar
      • Version cue: 0.12.1-alpha.2

      Previously, when a tool edited a file, the diff only distinguished insertions/deletions/context at the whole-line level, so you couldn't tell "which words actually changed on this line." This change introduces inline highlighting to diffs: the changed fragments within a modified (Replace) line are now marked with a more prominent emphasis style. At the same time, the diff library is migrated from diffy to similar, giving the inline diff detection better Unicode awareness.

      What changed

      1. Inline highlighting of changed fragments in Replace lines
        When a line contains both deleted and added content, the changed fragments are rendered with "segment-level emphasis" — a more saturated background and bold on top of the whole-line tint — so you can see at a glance exactly what changed on that line. Pure context lines and entire insert/delete blocks (Insert/Delete) get no inline emphasis and keep their original whole-line styling.

      2. Diff library migrated to similar (inline + unicode)
        The text diff algorithm moves from diffy to similar, with the inline and unicode features enabled. Inline changed fragments are split by Unicode characters, so changes to multi-byte text such as Chinese are detected more accurately.

      3. Diff colors consolidated into the theme palette
        The inline emphasis color and the whole-line tint are now managed together in theme/palette, adapting to dark/light backgrounds. When the terminal uses its default colors (no explicit background set), they degrade automatically: the whole-line tint falls back to no background, and the emphasized fragments fall back to REVERSED so they stay distinguishable.

      Notes

      • Inline refinement and line-level diff share the same 200ms cooperative computation budget; oversized blocks or very long lines that exceed the budget fall back to whole-line styling, so rendering overhead stays bounded.
      • Each diff content is computed only once; the +N/−N count in the header, the expanded detail, and the compact view all share the same single result.

      Example — deleting the word temporary from a specified line:

      edit-diff

      The temporary word is highlighted with the emphasis color.

      A more readable side-by-side diff view may come later, beyond the current inline diff view!