Add an opt-in compact pane tab bar setting

[teamleaderleo]

Try it

• Settings: Settings > App > Compact Pane Tab Bar (toggle on). Takes effect immediately in open windows.
• cmux.json: { "app": { "compactPaneTabBar": true } }
• Remove any ui.surfaceTabBar.buttons list first; a configured list overrides the setting.
• Build: fleet build in progress; link to follow.

What changes

#17395 reverted the compact pane tab bar (#17360) to restore the 0.64.25 pane tab bar. This PR keeps that default and brings the compact bar back as an opt-in setting for Leo to try out.

• Default unchanged from the revert. The new setting app.compactPaneTabBar is off by default. With it off, the pane tab bar shows the 0.64.25 buttons: New Terminal, New Browser, Split Right, Split Down. They keep the same order, icons and click behavior, and there are no per-pane overrides.
• Opt-in. The setting is under Settings > App > Compact Pane Tab Bar, and "app": { "compactPaneTabBar": true } in cmux.json. Turning it on brings back the Compact pane tab bar actions by tab kind #17360 cluster:
  • Standard panes: "+" (click opens a terminal like Cmd-T; right-click or press and hold lists Agent Chat, Terminal, Browser), one split button (click splits right, Option-click splits down), and "..." (Files, Open Folder, New Window).
  • Agent chat panes: "+" and "...", with the splits moved into "...".
  • A ui.surfaceTabBar.buttons list in cmux.json still takes precedence either way.
  • Toggling takes effect live in open workspaces.
• CodeRabbit finding from Compact pane tab bar actions by tab kind #17360. The button and menu policy now lives on Workspace instance methods instead of static methods on CompactSurfaceTabBarCluster. The enum keeps only the identifiers, row values, and the pure agent-chat URL matcher.
• vendor/bonsplit moves forward from 8bc81c8 (Add wall of love and screenshot to homepage #273) to bddc73d, bonsplit main. bddc73d contains both Add wall of love and screenshot to homepage #273 and Follow up PR 242: refresh browser under-page background on theme updates #272 (e52609f, the menu and Option-click support the compact bar needs). It is a fast-forward of both, not a rollback.
  • I checked Follow up PR 242: refresh browser under-page background on theme updates #272's diff for the default case. With no menuBehavior, no alternateAction, and no per-pane override, buttons render and click through the same Button / mouse-down branches as before.
  • The per-pane override is nil, so appearance.splitButtons is used as before.
  • Double-click on empty tab bar space still finds the New Terminal button.
  • The narrow-pane collapse that Add wall of love and screenshot to homepage #273 removed stays removed.
• A configured button list bypasses the setting. If ui.surfaceTabBar.buttons (or the older surfaceTabBarButtons) is set in any cmux.json, the pane tab bar shows exactly that list, whether the setting is on or off. To try the compact bar, remove that list first. The seven-icon bar that prompted Compact pane tab bar actions by tab kind #17360 came from such a list in a terminal-kit cmux.json, which terminal-kit Release v0.46.0 #75 has since removed.
• The drag-and-drop UI test (BonsplitTabDragUITests) still targets paneTabBarControl.newTerminal, since the setting is off there.

Tests

cmuxTests/CompactSurfaceTabBarClusterTests.swift:

• CompactPaneTabBarSettingTests:
  • default off: the setting defaults to false, and an applied workspace shows exactly the 0.64.25 actions with no menus, alternates or pane overrides;
  • on: at most 4 symbols, chosen by pane kind;
  • off again: the baseline comes back;
  • a configured button list wins over the setting.
• CompactSurfaceTabBarClusterTests: the Compact pane tab bar actions by tab kind #17360 policy tests, now against Workspace. Standard panes show +, split and ...; agent chat panes show + and ....

Settings plumbing: catalog key, cmux.json path and parser mapping, settings template, web/data/cmux.schema.json plus the regenerated embedded schema, the all-keys.md row, the Settings row and curated search entry, and the row-anchor test path.

Checked locally with the Python checks (test_cmux_schema_parity, test_cmux_settings_supported_paths, test_cmux_config_schema_embed, test_settings_configuration_review_paths, test_localization_defaults, test_localizable_xcstrings_structure, test_localization_catalog) and sync-test-wiring --check. The Swift tests run in CI.

Localization audit: the two new strings (settings.app.compactPaneTabBar and .subtitle) are translated in all 9 app locales. The cluster strings from #17360 were never removed from the catalog. The schema description has no descriptionKey, matching other app booleans such as equalizeSplitsOnCreate.

Screenshots

Dark theme, from the fleet build of this head on a capture mini: off and on for a terminal pane, and off and on for an agent chat pane (agent chat flag on).

Capturing from the fleet build; stills will be added here.

🤖 Generated with Claude Code

[github-actions]

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[teamleaderleo]

Closing: cancelled. Leo's call is that with only four pane tab bar buttons, hiding them in menus makes no sense, so the compact bar will not come back as an option. main keeps Austin's revert (#17395) and the current vendor/bonsplit pin; nothing here was merged.

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⛔ Files ignored due to path filters (1)

• Packages/macOS/CmuxFoundation/Sources/CmuxFoundation/ConfigValidation/CmuxConfigSchema.generated.swift is excluded by !**/*.generated.*

📒 Files selected for processing (21)

• Packages/macOS/CmuxSettings/Sources/CmuxSettings/Keys/AppCatalogSection.swift
• Packages/macOS/CmuxSettingsUI/Sources/CmuxSettingsUI/Navigation/CuratedSettingEntry+Default.swift
• Packages/macOS/CmuxSettingsUI/Sources/CmuxSettingsUI/Sections/AppSection.swift
• Packages/macOS/CmuxSettingsUI/Tests/CmuxSettingsUITests/SettingsRowAnchorResolutionTests.swift
• Resources/Localizable.xcstrings
• Sources/BonsplitConfiguration+RemoteTmuxEmbedded.swift
• Sources/CmuxConfig.swift
• Sources/CmuxSettingsFileStore+SupportedPaths.swift
• Sources/CmuxSettingsJSONPathSupport.swift
• Sources/CompactSurfaceTabBarCluster.swift
• Sources/KeyboardShortcutSettingsFileStore+Template.swift
• Sources/SurfaceTabBarButtonConfiguration.swift
• Sources/TabManager.swift
• Sources/Workspace+AgentChat.swift
• Sources/Workspace+CompactSurfaceTabBar.swift
• Sources/Workspace.swift
• cmux.xcodeproj/project.pbxproj
• cmuxTests/CompactSurfaceTabBarClusterTests.swift
• skills/cmux-settings/references/all-keys.md
• vendor/bonsplit
• web/data/cmux.schema.json

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