2054329 - Incorrect group line color during dragging on nightly build

Status: NEW

(Firefox :: Tabbed Browser, defect, P3)

Description

[Merci chao]

Attachment: 2026_07_12_10_17_18.mp4

When dragging grouped tabs, the inverted version of the group line color is applied incorrectly.

Comment 1

[Nikki Sharpley (:nikkis) (she/her)]

Its possible that this regression came from bug 2023691 but I'll need to take a closer look. Thanks!

Comment 2

[BugBot [:suhaib / :marco]]

This bug has been marked as a regression. Setting status flag for Nightly to affected.

Comment 3

[Dianna Smith [:diannaS]]

nikki any luck on the regressor?

Comment 4

[Hackbot]

Regressor looks like bug 2046942 (88c6bb02c3de, landed 2026-07-08), not bug 2023691 — this was reported 2026-07-12, and blame on the changed Nova ramp points there.

Root cause. That change added a Nova-specific tab group ramp to browser/themes/shared/tabbrowser/tab.nova.tokens.json defining only @base, text and hover per color. The -invert / -text-invert variants are still only defined in the non-Nova layers: @layer tokens-foundation in browser/themes/shared/tabbrowser/tab.tokens.css and the @media not -moz-pref("browser.nova.enabled") block in browser/themes/shared/tabbrowser/tabs.css. Before bug 2046942 the Nova layer overrode no group colors at all, so base and invert were a matched pair.

Result: under Nova, --tab-group-<c>-invert still resolves to the inverse of the old ramp. For blue, base is now light-dark(blue-50, blue-30) (tab.tokens.css#120) but invert is still light-dark(blue-10, blue-50) (tab.tokens.css#21). In dark mode the "inverted" fill (blue-50) is darker and more saturated than the group color itself (blue-30) instead of a pale tint.

Where it shows during a drag — these read --dragover-tab-group-color-invert / --tab-group-color-invert, set unconditionally as var(--tab-group-${code}-invert) in drag-and-drop.js#1082-1093 and tabgroup.js#236-256:

• tabs.css#1019-1031 — drop-target tab background under [movingtab-group] (Nova branch)
• tabs.css#1426-1438 — same for split-view wrappers
• tabs.css#2153-2170 — collapsed group label [dragover-groupTarget] (a dragged group is collapsed for the duration of the drag)

Proposed fix. Add invert and text.invert entries for each color in tab.nova.tokens.json, matched to the Nova ramp per the Figma spec, and regenerate with mach buildtokens. Two notes: -pale is also undefined under Nova (only in tabs.css#85-113) — every current Nova use happens to be shadowed by an override, so it's latent rather than active, but worth closing in the same pass; and bug 2023691 was backed out twice over browser_parsable_css.js allowlist mismatches, so keep browser_parsable_css.js#197-202 in sync.

No existing test asserts drag-time group colors — browser_tab_groups.js#1377-1444 exercises the drag state but checks no colors, so a regression test would be worth adding.

Reasoning from the token layers and consumers, not from a build — I didn't view the attached video.

This is an automated analysis result. If this result is incorrect please add a needinfo and feel free to correct the error.

Comment 5

[BugBot [:suhaib / :marco]]

Set release status flags based on info from the regressing bug 2046942

Comment 6

[BugBot [:suhaib / :marco]]

Redirect a needinfo that is pending on an inactive user to the triage owner.
:sthompson, since the bug has recent activity, could you have a look please?

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