[teamleaderleo]

Leo, 2026-11-03: "What the hell, why is there now a black bar on everything at the top row instead of a tiny blur at the top"

The band's cause was fixed at its source by #32944, which merged while this PR was open: the document root's chat colour (WebTheme's html rule) and the native strip behind the tabs (#32039) both painted under the tab row, so over window art the row read as a dark band. This PR first painted the page colour under the row as well. That would have brought back the plate behind the header tools that #32944 and Leo's 11-02 ask removed, so it now takes #32944's design and adds only the guard Leo's ask needs.

• New browser test in chat-header-tab-row-surface.test.ts: the transcript's top edge under the row is a gradient mask, never an opaque band. The mask image is a linear-gradient. Black rows under the row read as the page colour at the edge, half faded at 9px, and full ink below the 18px fade.

Observed / Not run

• Fleet: bun test test/chat-header-tab-row-surface.test.ts, 34 pass, 0 fail (with Agent chat: no opaque rectangle behind the header buttons in the tab row #32944's tests).
• Not run: a real-app capture over window art. It follows in a comment.

Changelog

none

Agent session: agent session

🤖 Generated with Claude Code

[teamleaderleo]

Owned by an agent session · session

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[github-actions]

cmux status _{(one comment, edited in place; each line is updated by the job that owns it)}

Review ee640d5: HQ feed card · gallery before/after runs · checks

App of this head (app.zip, kept 1 day)

gh workflow run reload-build.yml -R manaflow-ai/cmux --ref feat-cmux-next -f tag=pr32971 -f ref=lane/top-row-band -f platform=macos -f backend_mode=local

Unclear: web / react-apps-check failed: no known signature; failed step: Check webview test shards. CI was cancelled before it finished. This PR merged before its CI finished: fix forward on main.

CI stopped on ee640d50f8 (run 41574995772 attempt 1): 1 unknown.

Job	Verdict	Why
web / react-apps-check	unknown	no known signature; failed step: Check webview test shards

Not re-run automatically: web / react-apps-check is not a machine failure.

Written by scripts/ci/classify_failures.py (ci-failure-attribution.yml); signatures are its SIGNATURES table. A machine verdict is the runner's fault, not this PR's; yours means the failing file is one this PR changes, also red on main that main's latest full suite fails the same way, seen on other PRs that it failed on another pull request's run lately.

red: web / Web status; a job it gathers is red on this change (its line here); do not merge until green; see lane-rules
red: web / react-apps-check; a job it gathers ended without a verdict (web / react-apps-check (1): cancelled); do not merge until green; see lane-rules

Shipped in:

• cmux NEXT nightly 1.0.0-nightly.4157787538001 (cc7cdf2066)
• cmux NEXT nightly 1.0.0-nightly.4158055269401 (e5e182cf5b)

[teamleaderleo]

Review (subagent opus medium): SHIP at ee640d5

Visual verdict: unchanged by this diff (test only).

Checked the new pixel test against the shipped sheets: with the [data-fade-top] mask removed, red(top) and mid drop to 0 and the test fails; an opaque dark band over the row or the first 18px also fails it. The sampling is stable: viewport DPR 1, the row is a whole 40px, x=150 is clear of the 16px scrollbar lane mask, and the bounds (>200, 40..220) leave wide margins around the gradient values (~248 at the edge, ~128 at the midpoint).

Follow-ups: [follow-up] the test pins html to red, overriding #32944's html:has(.acpmux-shell[data-tab-row]){background:transparent}, so an opaque page-colored band over the row would not fail it. The existing omitBackground test in the same file covers that case, so this is a gap in this test only, not in coverage.

[teamleaderleo]

Capture tour-glass at a21619526efa (fleet build, capture mini, text checked for private data)

Light	Dark

These stills are the tour's last step: the window art is off and the chat is empty. They show the chat's tab row with no band behind its tools, but not a transcript fading under the row over window art. A tour state that shows a long chat over art is a follow-up.