cmux NEXT: keep agent chrome lines and tool actions clear
Fix the two agent-chat chrome polish issues Austin reported: remove the focused pane hairline above a hidden-tab-bar chat header, keep the header strip centered in its native chrome band, and reserve a real action slot so a tool row's duration, Copy, and expand controls never overlap at narrow widths.
Leo asked: "also did we alr fix these? but we're just waiting on nightly?"
Austin reported: "^ do you see that there are an extra line here on top? not sure if this is intentional but I hope not at least haha.. could you fix this?" and "And then make sure it's vertically centered". He also reported: "In this case, the copy button and then expand icon are overlapping with each other as well..."
The native fix treats the hidden agent chat's webview strip as a chrome band for PaneOverlayView, so the focus ring starts below it. The webview fix marks rows that own the floating transcript Copy button, reserves the action slot before the chevron, and leaves Shell card actions in flow.
Design references matched: cmux-design-references/topics/tabs-and-panels.md (one centered pane chrome rhythm) and topics/status-and-progress.md (status actions stay readable at the trailing edge).
Before / after captures
Gallery captures on the leased capture mini (cropped to the gallery content area; light and dark, narrow and wide):
| Case | Before | After |
|---|---|---|
| Dark, narrow tool row | before | after |
| Light, narrow tool row | before | after |
| Dark, wide agent pane | before | after |
| Light, wide agent pane | before | after |
Each raw link returned HTTP 200.
Verification
bun test ./test/transcript-copy.test.tsx ./test/transcript-codex-turn.test.tsx(11 pass)bun run typecheck(2564 files, no type errors)python3 scripts/verify-local.py --repo .(11/11 selected checks passed; native compile/test deferred to fleet)python3 scripts/cmux-next/prepush-gate.py(no new violations)scripts/web-lint.shran; existing base reds remain in design-token baseline/text-focus and existing lint warnings. No new changed-file failure remained after formatting.- Native regression test:
AgentHiddenHeaderChromeTests.hiddenAgentHeaderIsAChromeBand(fleet validation required by repository policy).
Observed / Not run
Native macOS build/test remains a managed capture-mini step; the media-tour label requests the head tour. This checkout never builds native code on Big Red.
agent-identity footer
Agent session: big-red