Bundled diff-color catalog stores mis-sourced VS Code theme tokens

[masonmcelvain]

What happened?

• connect Align Everforest themes with official palette #806
• introduced in feat(ui): refactor built-in theme system #450 (commit 8ffe0ba)

Problem

BUNDLED_SHIKI_THEME_DIFF_COLORS in src/core/theme/catalog.ts is supposed to hold each bundled theme's semantic added/removed/modified accents. For ~25 of the 66 themes, the stored values are not accents: they were taken from VS Code theme tokens with the wrong semantics — file-explorer label colors (gitDecoration.*), alpha background tokens flattened onto the editor background at harvest time, or unrelated tokens entirely. buildShikiTheme then treats these values as saturated accents and composites them onto the background again, producing washed-out or wrong-hue diff rows, signs, and badges.

Evidence that the values are flattened composites

The material-theme family shares one VS Code token, gitDecoration.deletedResourceForeground: #f0717890. Compositing that single alpha token over each variant's different background reproduces each variant's different stored removed value byte-for-byte:

Theme	#f0717890 over bg	Stored removed
material-theme	over #263238 → #98565c	#98565c (exact)
material-theme-darker	over #212121 → #964e52	#964e52 (exact)
material-theme-ocean	over #0f111a → #8e474f	#8e474f (exact)
material-theme-palenight	over #292d3e → #99535f	#99535f (exact)

Same exact-match math holds for material-theme-lighter (#e5393590 over #fafafa → #ee8d8b), night-owl (#ef535090 over #011627 → #87383e), and everforest, where all six stored values are gitDecoration.*ResourceForeground tokens (which carry a0 alpha) flattened over the editor background (e.g. #e67e80a0 over #2d353b → #a16366). Four sibling themes producing four different constants that are all exact alpha composites of the same source token rules out hand-picked coincidence: however the table was populated, it flattened alpha tokens and inherited gitDecoration.* semantics, and no sourcing rule was documented (#450 has no generation script or comment about the method).

Affected themes

A. Flattened alpha composites stored as accents

Theme	Slot(s)	Stored	Actually is	Real accent in theme JSON
everforest-dark	all three	#7a8c66 / #a16366 / #608986	gitDecoration.{added,deleted,modified}ResourceForeground (#a7c080a0 / #e67e80a0 / #7fbbb3a0) flattened	palette green/red/blue #a7c080 / #e67e80 / #7fbbb3
everforest-light	all three	#b7c155 / #fa9188 / #83b9d0	same tokens (#8da101a0 / #f85552a0 / #3a94c5a0) flattened	#8da101 / #f85552 / #3a94c5
night-owl	removed	#87383e	gitDecoration.deletedResourceForeground #ef535090 flattened	#ef5350 (editorGutter.deletedBackground)
material-theme ×5	removed, modified	#98565c family	#f0717890 / #82aaff90 flattened	#f07178, #82aaff
horizon, horizon-bright	added	#24a075 / #60c9a0	list.warningForeground #27d797b3 flattened	#29d398 (terminal.ansiGreen)
synthwave-84	added, modified	#63c89e, #ae8cc4	#72f1b8cc / #b893ceee flattened (milder)	#72f1b8, #b893ce

B. Mis-sourced token where the theme publishes real diff accents

Theme	Slot(s)	Stored	Problem	Better source in theme JSON
gruvbox ×6	added	#ebdbb2 dark / #3c3836 light	gruvbox sets gitDecoration.addedResourceForeground to the editor foreground; added rows tint beige/grey, + sign is text-colored	editorGutter.addedBackground #b8bb26 / #79740e
rose-pine ×3	removed	#908caa / #797593	rosé pine's muted purple for deleted file labels; deleted rows read purple-grey	love red #eb6f92 (editorGutter.deletedBackground, diffEditor.removedTextBackground)
laserwave	removed, modified	#b381c5; modified duplicates added	lavender from gitDecoration; modified == added	#eb64b9 (editorGutter.deletedBackground), #40b4c4 (modified)
tokyo-night	added, removed	#449dab, #914c54	deliberately dimmed gitDecoration labels used instead of diff tokens	diffEditor.* #41a6b5 / #db4b4b
slack-dark, slack-ochin	all	removed = #ffffff (white!), added/modified = #ecb22e yellow	theme publishes no usable diff tokens	none — drop the entries so the generic fallback applies
min-light	modified	#e0e0e0	literally badge.background grey	terminal.ansiRed-style tokens exist for the other slots

Themes whose values are genuine palette accents and are fine as data: github ×7, catppuccin, dracula, nord, kanagawa, ayu, houston, plastic, vitesse, monokai, snazzy-light, and solarized.

Why users see it

buildShikiTheme derives everything downstream from these values: sign colors, row tints (addedBg/removedBg), word-level emphasis tints, sidebar badges, and file-state colors. A pre-blended or muted stored value means:

• wrong hue outright (rose-pine deleted rows purple-grey; gruvbox added rows beige; slack removed rows white-tinted), and/or
• double compositing (already-blended color blended onto the background again), and/or
• the value fails the diff-sign contrast guard, whose rescue blend washes it further (see Theme derivation guards wash out diff colors and cause invisible highlighting #824).

Proposed fix

Re-harvest the table under a documented, scripted sourcing policy instead of patching themes one at a time:

1. Per-slot token priority: editorGutter.{added,deleted,modified}Background → diffEditor.{inserted,removed}TextBackground → terminal.ansiGreen/ansiRed → gitDecoration.* last.
2. Strip alpha, never composite. The alpha was VS Code's own blending; Hunk does its own blending downstream.
3. Validate each candidate by hue class and saturation (removed must be red-family, added green/teal-family); a failing candidate falls through to the next source. If nothing passes, omit the entry so Hunk's generic fallback applies (this fixes slack).
4. Check the harvester in (e.g. scripts/generate-theme-diff-colors.ts) so the table is regenerable against @shikijs/themes and provenance can't silently drift again.
5. Table-driven regression tests across all 66 themes: removed is red-family, added is green/teal-family, and stored values are 6-digit palette tokens, not composites.

Steps to reproduce

hunk diff with an affected theme, outlined above

Expected behavior

No response

Version

0.19.0