Add Fork Conversation action to tab context menu

[azooz2003-bit]

Summary

• New .forkConversation case in TabContextAction
• New host-provided tabContextForkConversationAvailabilityProvider on BonsplitController
• Menu item added to TabContextMenuBuilder (shown only when the provider returns true)
• English + Japanese strings, test fixture updated for the new canForkConversation field

Used by cmux (see manaflow-ai/cmux companion PR) to surface a Fork Conversation entry when a tab is running an active forkable Claude or Codex session.

Test plan

• swift build --build-tests clean
• Visual: right-click a terminal tab whose host returns true for the provider, confirm "Fork Conversation" appears

🤖 Generated with Claude Code

---

Summary by cubic

Adds a “Fork Conversation” action to the tab context menu, shown only when the host says it’s available. This lets apps surface forking for tabs running an active, forkable agent session.

• New Features

  • Added TabContextAction.forkConversation.
  • Added BonsplitController.tabContextForkConversationAvailabilityProvider to control visibility.
  • Menu item appears only when the provider returns true.
  • Added English and Japanese strings.

• Migration

  • If you switch exhaustively on TabContextAction, add a .forkConversation case (or a default).
  • Implement the new provider to enable the item for tabs with forkable sessions.

^{Written for commit 082bf66. Summary will update on new commits. Review in cubic}

---

^{Need help on this PR? Tag @codesmith with what you need. Autofix is disabled.}

Summary by CodeRabbit

• New Features
  • Added "Fork Conversation" action to the tab context menu, allowing users to fork conversations directly from the interface without additional navigation. The feature is fully localized in English and Japanese. Host applications can selectively enable this action on a per-conversation basis.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 2caf915d-0dac-4878-962a-99347015441f

📥 Commits

Reviewing files that changed from the base of the PR and between cda75f9 and 082bf66.

📒 Files selected for processing (7)

• Sources/Bonsplit/Internal/Views/TabBarView.swift
• Sources/Bonsplit/Internal/Views/TabItemView.swift
• Sources/Bonsplit/Public/BonsplitController.swift
• Sources/Bonsplit/Public/Types/TabContextAction.swift
• Sources/Bonsplit/Resources/en.lproj/Localizable.strings
• Sources/Bonsplit/Resources/ja.lproj/Localizable.strings
• Tests/BonsplitTests/BonsplitTests.swift

---

📝 Walkthrough

Walkthrough

This PR adds a "Fork Conversation" action to tab context menus. It introduces a host-provided availability provider on BonsplitController, extends internal state and menu rendering to support the action conditionally, and includes English and Japanese localizations plus a test fix.

Changes

Fork Conversation Tab Context Menu Action

Layer / File(s)	Summary
Public API and action type Sources/Bonsplit/Public/Types/TabContextAction.swift, Sources/Bonsplit/Public/BonsplitController.swift	New forkConversation enum case added to TabContextAction, and new @ObservationIgnored callback property tabContextForkConversationAvailabilityProvider on BonsplitController lets the host determine whether the action is available for a given tab and pane.
Internal state and context menu state wiring Sources/Bonsplit/Internal/Views/TabBarView.swift	TabContextMenuState gains a canForkConversation boolean field. TabBarView.contextMenuState(for:at:) wires it by calling the provider callback, defaulting to false when absent.
Menu UI construction Sources/Bonsplit/Internal/Views/TabItemView.swift	TabContextMenuBuilder.makeMenu conditionally inserts a separator and "Fork Conversation" menu action when state.canForkConversation is true, dispatching the .forkConversation tab context action.
Localization and test update Sources/Bonsplit/Resources/en.lproj/Localizable.strings, Sources/Bonsplit/Resources/ja.lproj/Localizable.strings, Tests/BonsplitTests/BonsplitTests.swift	English localization tabContext.forkConversation → "Fork Conversation" and Japanese equivalent 会話をフォーク are added. Existing test updated to pass the new canForkConversation: false state field.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 A fork in the conversation path,
With strings both bright and Japanese,
The menu grows with availability,
And state flows true where it should be. 🥕

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: adding a fork conversation action to the tab context menu, which is the primary feature across all modified files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat-fork-conversation

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[greptile-apps]

Greptile Summary

Adds a "Fork Conversation" entry to the tab context menu, surfaced only when a new host-provided tabContextForkConversationAvailabilityProvider closure returns true for a given tab/pane pair. The action is dispatched through the existing didRequestTabContextAction delegate path, so no new delegate method is required.

• TabContextAction.forkConversation case added; routing via performContextAction and the existing String raw-value lookup works without changes.
• TabContextMenuState.canForkConversation is computed at menu-build time by calling the provider (consistent with the tabContextMoveDestinationsProvider pattern); separator placement in the menu builder avoids double-separator in all conditional combinations.
• English and Japanese localisation strings added; test fixture updated, though no test covers the canForkConversation: true code path.

Confidence Score: 4/5

Safe to merge; all changes follow established patterns and the build is clean.

The implementation is consistent with the existing provider/action patterns and introduces no new delegate surface. The only gap is that the canForkConversation: true branch — menu item appearance, enabled state, and .forkConversation action dispatch — has no automated test coverage, so a regression in that path could go undetected.

Tests/BonsplitTests/BonsplitTests.swift — the new canForkConversation: true menu path is not exercised by any test.

Important Files Changed

Filename	Overview
Sources/Bonsplit/Public/Types/TabContextAction.swift	Adds forkConversation case to the TabContextAction enum — minimal, consistent with existing cases, and the String raw value routing in performContextAction handles it automatically.
Sources/Bonsplit/Public/BonsplitController.swift	Adds tabContextForkConversationAvailabilityProvider closure property following the exact same pattern as the existing tabContextMoveDestinationsProvider; no concerns.
Sources/Bonsplit/Internal/Views/TabBarView.swift	Adds canForkConversation field to TabContextMenuState and computes it by calling the provider at menu-build time; consistent with existing state fields.
Sources/Bonsplit/Internal/Views/TabItemView.swift	Inserts the Fork Conversation menu item (with separator) only when canForkConversation is true; separator placement is consistent and no double-separator edge case arises, but the new path lacks a dedicated unit test.
Tests/BonsplitTests/BonsplitTests.swift	Fixture updated for the new canForkConversation field, but no test covers the canForkConversation: true path — menu item appearance and action dispatch go untested.
Sources/Bonsplit/Resources/en.lproj/Localizable.strings	Adds tabContext.forkConversation English localisation string; correct.
Sources/Bonsplit/Resources/ja.lproj/Localizable.strings	Adds tabContext.forkConversation Japanese localisation string; correct.

Sequence Diagram

sequenceDiagram
    participant User
    participant TabBarView
    participant Provider as tabContextForkConversationAvailabilityProvider
    participant TabContextMenuBuilder
    participant Delegate as BonsplitDelegate

    User->>TabBarView: right-click tab
    TabBarView->>Provider: (TabID, PaneID) → Bool
    Provider-->>TabBarView: true / false
    TabBarView->>TabBarView: "build TabContextMenuState (canForkConversation = result)"
    TabBarView->>TabContextMenuBuilder: makeMenu(snapshot, target)
    alt "canForkConversation == true"
        TabContextMenuBuilder->>TabContextMenuBuilder: addSeparator + add Fork Conversation item
    end
    TabContextMenuBuilder-->>User: NSMenu displayed
    User->>TabContextMenuBuilder: click Fork Conversation
    TabContextMenuBuilder->>Delegate: didRequestTabContextAction(.forkConversation, tab, pane)

Loading

_{Reviews (1): Last reviewed commit: "Add Fork Conversation action to tab cont..." | Re-trigger Greptile}

[greptile-apps]

Missing test coverage for the true path

The existing test only exercises canForkConversation: false. No test verifies that when the field is true the "Fork Conversation" item actually appears in the built menu, is enabled, and — when activated via target.performContextAction — dispatches exactly .forkConversation to the onContextAction handler. Without this, a future accidental guard inversion (e.g. if !state.canForkConversation) or a typo in the representedObject raw value would go undetected by the suite.