Context

CommandsToBubbleUp and CommandBridge currently only work for Command.Accept and Command.Activate:

• TryBubbleUp — only called from DefaultAcceptHandler/DefaultActivateHandler. Unbound commands hit DefaultCommandNotBoundHandler which just raises CommandNotBound and stops.
• CommandBridge — hard-codes Accepted/Activated event subscriptions. Cannot bridge arbitrary commands.
• DefaultCommandNotBoundHandler — currently a one-liner that raises CommandNotBound. Has no dispatch, no TryBubbleUp, no composite view support.

Tabs needs directional commands (Command.Up/Down/Left/Right) from a focused TitleView to bubble up to the owning Tabs view. Upgrading the not-bound path to support the full lifecycle (dispatch, bubbling, composite views) makes CommandsToBubbleUp work for any command generically.

Phases

Phase A: Reorganize existing tests

Move all bubbling-focused tests from ViewCommandTests.cs to a new CommandBubblingTests.cs. No behavior changes — just reorganization. All tests must pass before and after.

Tests to move → Tests/UnitTestsParallelizable/ViewBase/CommandBubblingTests.cs:

From #region Command Propagation Tests (lines 355-923) — move entire region:

• CommandsToBubbleUp_DefaultIsEmpty
• Accept_Command_DoesNotBubbleByDefault
• Activate_Command_DoesNotBubbleByDefault
• CommandsToBubbleUp_CanDisableAllPropagation
• CommandsToBubbleUp_CanBeCustomized
• Activate_BubblingUp_Fires_Activated_On_SuperView
• Activate_BubblingUp_Fires_Activated_In_Deep_Hierarchy
• ConsumeDispatch_Blocks_Further_Bubbling
• CommandsToBubbleUp_StopsWhenHandled
• CommandsToBubbleUp_WorksInDeepHierarchy
• CommandsToBubbleUp_StopsAtIntermediateHandler
• All 9 Padding bubble tests
• All 6 Border bubble tests

From #region DispatchDown Tests (lines 1689-1959) — move entire region + helper class

From #region IAcceptTarget Tests — move bubbling subset:

• Button_BubblesUp_To_SuperView
• IAcceptTarget_In_Deep_Hierarchy_BubblesUp (1/2/3)
• IAcceptTarget_Handled_Does_Not_BubbleUp

From #region DefaultAcceptView Tests — move bubbling subset:

• DefaultAcceptView_Peer_Accept_Bubbles_To_DefaultAcceptView
• DefaultAcceptView_Non_IAcceptTarget_Peer_Accept_Bubbles_To_DefaultAcceptView
• DefaultAcceptView_Peer_IAcceptTarget_NonDefault_Accept_Bubbles_To_DefaultAcceptView
• DefaultAcceptView_Accept_DoesNotBubble_To_DefaultAcceptView_WhenHandled
• NonIAcceptTarget_Without_CommandsToBubbleUp_DoesNotRedirect_To_DefaultAcceptView

From #region OnAccept/Accept tests:

• Accept_Command_Bubbles_Up_To_SuperView

From #region Values Chain Tests:

• Values_BubbleActivatedUp_Carries_Composite_Value_To_Ancestor

From #region Bridge Cancellation Bug (lines 2739-3008) — move entire region + helper classes

Phase B: Write failing tests proving the gap

Add tests to CommandBubblingTests.cs that demonstrate unbound commands cannot bubble today. These tests must fail initially, proving the limitation.

Unbound command bubbling (via DefaultCommandNotBoundHandler):

• UnboundCommand_BubblesToSuperView_ViaCommandsToBubbleUp — subview invokes Command.Up (unbound), superView has CommandsToBubbleUp = [Command.Up]
• UnboundCommand_DoesNotBubble_WhenNotInCommandsToBubbleUp
• UnboundCommand_BubblesFromPaddingSubView_ToOwner
• UnboundCommand_BubblesFromBorderSubView_ToOwner
• UnboundCommand_BubblesInDeepHierarchy
• UnboundCommand_StopsWhenHandled
• UnboundCommand_BubblingUp_ReturnsNotHandled — notification-only semantics

Composite view support for unbound commands:

• UnboundCommand_DispatchesToTarget_InCompositeView — composite view with dispatch target receives unbound command, verifies TryDispatchToTarget fires
• UnboundCommand_CompositeView_RaisesPostEvent_AfterDispatch

CommandBridge for arbitrary commands:

• CommandBridge_BridgesUnboundCommand — bridge connects Command.Up, remote fires it, owner receives it
• CommandBridge_IgnoresUnregisteredCommand — bridge for Command.Up only, Command.Down does not bridge

Phase C: Upgrade CommandBridge to support arbitrary commands

CommandBridge currently hard-codes Accepted/Activated subscriptions. Generalize to support any command.

File: Terminal.Gui/Input/CommandBridge.cs

Phase D: Upgrade DefaultCommandNotBoundHandler

Upgrade RaiseCommandNotBound and DefaultCommandNotBoundHandler to follow the full Activate-like lifecycle:

RaiseCommandNotBound — add TryDispatchToTarget and TryBubbleUp:

1. OnCommandNotBound(args) → if handled, return true
2. CommandNotBound?.Invoke(args)
3. if (!handled) TryDispatchToTarget(ctx)        ← NEW
4. if (!handled) TryBubbleUp(ctx, handled)       ← NEW
5. return args.Handled

DefaultCommandNotBoundHandler — full lifecycle with dispatch, bubbling, composite view support, and BubbleActivatedUp. No SetFocus. Includes _dispatchState reset/tracking, dispatch-routing guard, RefreshValue, BubbleActivatedUp, and CommandWillBubbleToAncestor.

ArrangerButton.cs — remove AddCommand(Command.Up/Down/Left/Right, DefaultAcceptHandler). These fall through to the upgraded DefaultCommandNotBoundHandler.

Files:

• Terminal.Gui/ViewBase/View.Command.cs
• Terminal.Gui/ViewBase/Adornment/ArrangerButton.cs

Files Summary

1. Tests/UnitTestsParallelizable/ViewBase/CommandBubblingTests.cs — NEW (phases A+B)
2. Tests/UnitTestsParallelizable/ViewBase/ViewCommandTests.cs — remove moved tests (phase A)
3. Terminal.Gui/Input/CommandBridge.cs — generalize (phase C)
4. Terminal.Gui/ViewBase/View.Command.cs — upgrade handler + raise method (phase D)
5. Terminal.Gui/ViewBase/Adornment/ArrangerButton.cs — remove AddCommand calls (phase D)

Verification

After each phase:

• dotnet test --project Tests/UnitTestsParallelizable --filter-class "*CommandBubblingTests"
• dotnet test --project Tests/UnitTestsParallelizable --filter-class "*ViewCommandTests"
• Phase B: new tests must FAIL (proving the gap)
• Phase C+D: all tests must PASS
• Full suite: only pre-existing TabsTests failures