[teamleaderleo]

With the default minimal titlebar, scrolling the left sidebar list slid rows up under the window's traffic lights, and they stayed visible there. On nightly 1.0.0-nightly.3965802926201 (3a63d6d) the "Agents" group header pill sat beside the lights.

Cause: since 94f7db0 (minimal titlebar) the sidebar's header row is Metrics.tabStripHeight tall (28 in compact, WindowRootView.applyTokens), so the list starts level with the panes' content. The traffic lights reach about y=22 and the titlebar row ends at Metrics.titlebarHeight (32 in compact). The list's 18 pt top edge fade (ScrollEdgeFadeView) starts at the list's top, so a scrolled row from y=28 down was only partly faded, right below the lights.

Decision (claude-sr2), verbatim: "Miss 6: keep the list starting level with the panes at rest. When the list is scrolled, extend the top mask so content scrolling under the traffic lights is clipped and faded below the lights (y≈titlebarHeight). Don't use max(tabStripHeight, titlebarHeight) at rest."

Change:

• ScrollEdgeFadeView (CmuxNextDesign) gets a topClip in points. Its gradient's first stop moves down to topClip. While content is hidden above, the top color is clear, so the mask hides everything from the list's top down to topClip and the usual 18 pt fade starts below it. At rest the top color is opaque, so the mask is the same as before. topClip defaults to 0, so the other users (palette, extensions menu, priority panel) don't change.
• SidebarView sets each scrolling band's clip (the list, and the top item band when it shows) to the part above Metrics.titlebarHeight, but only when the traffic lights are over this sidebar (headerHasWindowControls; a right sidebar gets 0). With the full titlebar the list already starts at titlebarHeight, so the clip is 0.
• The list doesn't move. There are no sticky headers, the minimal titlebar is still the default, and no component is removed.
• Motion: no new animation. When the top edge starts hiding content, the clear band appears through the existing Motion.feedback hover crossfade on the mask colors. With animation off it applies in one frame. Changing the geometry (topClip, locations) never animates.
• Observers: none added. The scroll position comes from ScrollEdgeFadeView's existing clip-view bounds/frame and document frame observers, which its deinit removes. No per-row work: the clip is set in SidebarView.layout, and a scroll only changes the mask's colors, as before.

Test: SidebarTopMaskTests (CmuxNextAppTests), committed before the fix. It reads the mask's gradient the way Core Animation draws it and checks:

• At rest with a clip, the mask stays opaque at the top.
• Scrolled, it is clear down to the clip, half-faded in the middle of the fade, and opaque after it.
• With no clip, the fade still starts at the top.
• In the sidebar with the minimal header row, each band's clip ends at max(bandTop, Metrics.titlebarHeight) and the band is not moved up.
• With the full titlebar or no window controls, the clip is 0.

Changelog

Fixed: Sidebar rows no longer show under the window's traffic lights when the list is scrolled with the minimal titlebar.

Observed / Not run

• Ran python3 scripts/cmux-next/prepush-gate.py: no new violations.
• Focused suite on the fleet: cmux-ci run --class light --script scripts/ci/package-test-lane.sh --arg=suite --arg=Packages/macOS/CmuxNext --arg=SidebarTopMaskTests. Red at 0ccf766 (test only) and green at the head: results pending, to be added here when the steps finish.
• Not run: the app itself. I didn't look at a scrolled sidebar in a build. The 4 pt clip in compact (28 to 32) comes from the token values, not from a measurement on screen.

No capture: the before/after capture follows from the next nightly (scrolled sidebar state).

Agent session: cmux16
🤖 Generated with Claude Code

---

^{Need help on this PR? Tag @codesmith-bot with what you need.}

---

Summary by cubic

Fixes sidebar rows staying visible under the window's traffic lights when scrolled with the minimal titlebar.

• ScrollEdgeFadeView gains a topClip that hides content down to the titlebar's bottom and starts the top fade below it; at rest the mask is unchanged.
• The sidebar sets each scrolling band's clip only when traffic lights are over it (headerHasWindowControls); full titlebar and right sidebar behavior is unchanged.
• Adds SidebarTopMaskTests covering the mask at rest, scrolled, with no clip, and with full titlebar or no window controls.
• Logs the fix in the sidebar owner note, since the fix commit reached its branch without a Sidebar-Look trailer.

^{Written for commit e582cd8. Summary will update on new commits.}

[github-actions]

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

Review e582cd8: 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=pr24073 -f ref=live-qa-sidebar-top-mask -f platform=macos -f backend_mode=local

red: cmux-next checks (god files, concurrency, crash safety, l10n); no finished base run on 90e1666 to compare; do not merge until green; see lane-rules

[blacksmith-sh]

Found 6 test failures on Blacksmith runners:

Failures

Test	View Logs
/tmp/tmpscxl1eeu/summary-fail.json (live):/summary-fail.json (live):	View Logs
/tmp/tmpspktw20d/summary-missing.json (live):/summary-missing.json (live):	View Logs
[new_workspaces] debug.new_workspace timed 0 of 50 new workspace rows/ [new_workspaces] debug.new_workspace timed 0 of 50 new workspace rows	View Logs
[new_workspaces] the window draws no frames/[new_workspaces] the window draws no frames	View Logs
[tabs] debug.tab_switch timed 0 of 40 switches/ [tabs] debug.tab_switch timed 0 of 40 switches	View Logs
[tabs] the window draws no frames/[tabs] the window draws no frames	View Logs

^{Need help on this PR? Tag @codesmith-bot with what you need.}

[teamleaderleo]

Bead cx-sais8 created for this PR by the cmux coordinator.

[teamleaderleo]

Orphaned: no activity for 17 h, and no lane holds a lease on it. Adopted by the orphan sweep: merged feat-cmux-next in at 8ddd55d. A later pass queues it for the merge hub if it is reviewed, small and red only on base reds.

[teamleaderleo]

cmux-next crash-class rules / cmux-next crash-class rules is red on 12 of 12 fresh feat-cmux-next PR heads in the last 2:00:00, so it is most likely a base red, not this PR's. The base-reds lane has it; a base merge picks up the fix once it lands.

[teamleaderleo]

Review (codex gpt-6-astra xhigh, next-review): SHIP at 8ddd55d

No blocking findings.

[cursor]

Bugbot needs on-demand usage enabled

Bugbot uses usage-based billing for this team and requires on-demand usage to be enabled.

A team admin can enable on-demand usage in the Cursor dashboard.

[teamleaderleo]

high-signal review link / link is red on 17 of 21 fresh feat-cmux-next PR heads in the last 2:00:00, so it is most likely a base red, not this PR's. The base-reds lane has it; a base merge picks up the fix once it lands.

[cursor]

Bugbot needs on-demand usage enabled

Bugbot uses usage-based billing for this team and requires on-demand usage to be enabled.

A team admin can enable on-demand usage in the Cursor dashboard.

[teamleaderleo]

Owned by an agent session · took over from an earlier session · session

[teamleaderleo]

Review (codex gpt-6-astra high, review-router): SHIP at 88fe218

No blocking findings at this head (base merge plus conflict resolution reviewed with the full diff). Two non-blocking P3 notes on test strength.

Agent session: agent session

[teamleaderleo]

Review (codex-review-box/gpt-6-astra high, lane-place): SHIP at e582cd8

SHIP

No findings.

[github-actions]

Shipped in:

• cmux NEXT nightly 1.0.0-nightly.4093446036501 (6c1a5ab8bf)
• cmux NEXT nightly 1.0.0-nightly.4093534569301 (9ccc194b46)
• cmux NEXT nightly 1.0.0-nightly.4093630103101 (58286343a8)
• cmux NEXT nightly 1.0.0-nightly.4094037008001 (fcfd1d87dd)

[lawrencecchen]

The "Sidebar look owner sweep" step of the cmux-next checks names this PR's commit on feat-cmux-next. It scans every commit since 342462c, so every PR's checks print this line (job 123695447456 on #27454):

4367c16e12c Sidebar: hide scrolled rows under the traffic lights (minimal titlebar (Packages/macOS/CmuxNext/Sources/CmuxNextSidebar/Views/SidebarView+TrafficLightsClip.swift and 1 more): no `Sidebar-Look:` trailer. Add `Sidebar-Look: <the user's words>` (and edit plans/cmux-next/sidebar-owner.md) or `Sidebar-Look: no visual change`.

The commit has landed, so a trailer is no longer possible. The fix is an entry for 4367c16 in plans/cmux-next/sidebar-owner.md. A question for Leo, the author: what text should the entry have? Your words for the look, or "no visual change". This is an ##[error] line, not a red check, so it blocks nothing.

[lawrencecchen]

Why your entry is waited for: #27634 makes the "Pushed commits add no violations" step fail when the sidebar sweep finds a commit with no record. Today the step never fails, because its pipe has no pipefail. Without an entry for 4367c16 in plans/cmux-next/sidebar-owner.md, every push run of feat-cmux-next would go red. So #27634 is held, without ready-to-land, until your entries for 4367c16 and 6c1a5ab are in. Pull request runs already show this commit only as a warning (#27632).