Fix narrow pane tab close UX

[teamleaderleo]

What changed

Narrow pane tab bars now keep tabs readable and closable:

• Every tab keeps a minimum width and shows its x on hover, with the selected-tab affordance preserved.
• Middle-click routes through the same explicit close path as the x button, including active-command and agent-session warnings.
• Right-click includes Close Tab and Close Other Tabs.
• Below 520 px, the trailing action cluster collapses to one overflow menu so tab space wins and repeated actions are deduplicated.
• Added regression coverage for middle-click warning routing and narrow action-lane layout.

Verification

• python3 scripts/verify-local.py: 16/16 selected checks passed.
• ./scripts/sync-test-wiring --check: passed.
• python3 scripts/localization_catalog.py check: 10 catalogs, 9 locales, 0 parity errors.
• swift test --filter TabBarLayoutFeedbackTests in the Bonsplit submodule: 5 tests passed.
• Fleet app build and dogfood for feature SHA 01c216216d5fd480d6f7bb60906581eee4846fa7 ran on the managed fleet (tag pr-15957-pane-tab-close-v18). The selected XCUITest passed every tour step; the wrapper was marked failed only because its app-host socket-listener evidence check did not recognize the successful test host output.
• The branch was then caught up with current upstream/main and the Bonsplit pointer was merged forward. Additional current-head fleet submissions hit worker volume cleanup or disk-image attach infrastructure failures before compilation.

Media

Before:

After: narrow-pane tab bar with a persistent minimum tab width, hover close affordance, and collapsed actions:

The fleet dogfood run was 36757777040; its selected UI test passed, with only the wrapper evidence check failing. The merged PR head after catch-up is aa99953d93f3ebc534c214769fb8d14f6276e077.

Changelog

Fixed: Narrow pane tabs retain hover close, middle-click close warnings, context-menu close, and an overflow action menu.

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Summary by cubic

Fixes tab closing across narrow panes and closes a safety gap where a close that would kill a live foreground process could be confirmed or silently executed without an explicit opt-in.

Tab close UX

• Narrow pane tab bars keep a minimum tab width; the x button appears on hover.
• Middle-click routes through the same guarded close path as the x button, wired consistently across Workspace, DockSplitStore, and the remote tmux mirror.
• The tab context menu adds Close Tab and Close Other Tabs, both honoring allowCloseTabs close permissions and pinned-tab restrictions.
• Below 520 px, trailing actions collapse into one overflow menu.

Active-process close guard

• Non-forced closes that would terminate a live process now return an error instead of silently killing it.
• surface.close, workspace.close, window.close, tab.action, the mobile workspace list, and the legacy v1 commands accept force to bypass the confirmation.
• The safety warning can't be silenced by "Don't ask again" — only user-preference warnings are.
• Added regression coverage for middle-click warning routing, force forwarding, disabled close via context menu, and confirmation responses.

^{Written for commit aa99953. Summary will update on new commits.}

Summary by CodeRabbit

• New Features
  • Added --force to close commands for windows, workspaces, tabs, and surfaces. Without it, closing items with active processes prompts for confirmation and explains how to retry.
  • Added middle-click tab closing, with confirmation when a tab has an active process.
• Bug Fixes
  • Tab context-menu close actions now respect close permissions and pinned-tab restrictions.
  • Safety confirmations remain in effect even when other close warnings are disabled.

[coderabbitai]

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Run ID: 25dea5ff-5ec7-497f-a0a3-1f2db57fc32e

📥 Commits

Reviewing files that changed from the base of the PR and between 6171d8c and aa99953.

📒 Files selected for processing (8)

• Packages/macOS/CmuxAppKitSupportUI/Tests/CmuxAppKitSupportUITests/MiddleClickCaptureViewTests.swift
• Resources/Localizable.xcstrings
• Sources/DockSplitStore+TabContextActions.swift
• Sources/DockSplitStore.swift
• Sources/RemoteTmuxWindowMirror+Bonsplit.swift
• Sources/Workspace.swift
• cmuxTests/WorkspaceCloseTabsContextMenuTests.swift
• vendor/bonsplit

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[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[github-actions]

Automatic catch-up couldn't merge main (6d7ad149121a): vendor/bonsplit (both sides changed it). Nothing was pushed; merge it by hand. A new push or /catch-up tries again.

_{Label no-auto-catch-up to opt out · Catch-up run}

[github-actions]

Dogfood build of aa99953d93f3ebc534c214769fb8d14f6276e077

cmux DEV pr-15957-aa99953d.app

The link opens this exact commit in the cmux dev menu bar app; the page waits until the build is ready. Builds run only while this PR has the dev-build label. Under load the fleet builds the newest push each time a worker frees up, so some pushes are skipped. It signs in against production, so Cloud or backend changes still need a tagged build with a development backend.

Covers 58d1509d..aa99953d (commits: 32) since the previous link, cmux DEV pr-15957-58d1509d.app; if that push was skipped, its page names the newer build. To build a commit in between: cmux-ci build cmux --ref <sha> --tag bisect-<sha8> --workspace https://github.com/manaflow-ai/cmux/pull/15957.

[github-actions]

CI failure attribution

CI stopped on 01c216216d (run 36753490274 attempt 2): 1 code.

Job	Verdict	Why
macos / swift-package-tests	code	a test failed

Matched log lines

macos / swift-package-tests: /Users/cmux/actions-runner-glaeda-1/_work/cmux/cmux/vendor/bonsplit/Tests/BonsplitTests/BonsplitTests.swift:3590: error: -[BonsplitTests.BonsplitTests testSelectedTabIndicatorFadesWithTabContentBeforeSplitButtonBackdrop] : XCTAssertLessThan failed: ("1.0") is not less than ("0.9") - The indicator sh

Not re-run automatically: macos / swift-package-tests 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.

[teamleaderleo]

Review: Fresh subagent review of 01c2162 with Bonsplit 1b673629f300e3ec0b13fe5cef53f299bcabeaf5 found no concrete findings. It verified the shared MiddleClickCapture injection, close-setting and pinned-tab guards, narrow overflow layout, and warning routing.
Fixed: Context-menu Close Tab now respects allowCloseTabs and pinned tabs; middle-click uses the shared press-time capture view and follows the x-button warning path; narrow panes reserve no hidden action lane; the Bonsplit pointer is forward-compatible with main.
Left: Fleet app build and exact-SHA dogfood are still pending; native compilation and UI tests remain fleet-owned.

[cursor]

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[teamleaderleo]

Review: Latest subagent review of 58d1509 found no concrete pane-tab-close regressions or Bonsplit conflicts.
Fixed: No new fixes needed after the current-main catch-up merge; the shared MiddleClickCapture path, close warning routing, context gating, 48pt minimum tab width, 520pt narrow threshold, and 36pt overflow lane remain intact.
Left: Fleet CI and current-head dogfood evidence.

[teamleaderleo]

recheck

[github-actions]

Merge receipt for aa99953d93, merged 2026-09-30 20:18:20 UTC

• Not verified at merge: ci-status (not reported), macOS compile admission (in progress), CI fast guards (in progress), GhosttyKit release check (in progress), guards (18) (in progress), package-conventions-lint (in progress), swift-package-tests (in progress)
• Verified: catalog-structure, detect-ios-changes, Dogfood build #​15957, Fast static checks, runner, Testbox broker trust boundary, Web complexity, web-validation
• Skipped by policy: admission-placement, browser, Claude wrapper regressions, full-suite-coverage, remote-daemon, suite-coverage, web, web-build, web-database-tests, web-tests
• Full suite: runs on main after merge.

Labeled merged-unverified: if main breaks near this merge, look here first.