Ctrl+Break still isn't working in Copilot sessions

[JoshuaRowePhantom]

Bug Report

The Ctrl+Break keyboard shortcut does not work in Copilot sessions.

Steps to reproduce

1. Start a Copilot session
2. Press Ctrl+Break

Expected behavior
Ctrl+Break performs its intended action (e.g. interrupting the current operation).

Actual behavior
Nothing happens; the shortcut has no effect.

[JoshuaRowePhantom]

Investigation Findings

Root Cause

Two causes:

Primary — Window-level Cancel binding is missing from Phantom.Workspaces/MainWindow.axaml

AgentChatEditorControl.axaml has a UserControl.KeyBindings block with Gesture="Cancel" bound to InterruptCommand. In Avalonia, a UserControl.KeyBindings entry only fires when the UserControl or a descendant holds keyboard focus.

The standalone Agent.Gui/MainWindow.axaml correctly adds the same gestures at the Window level (lines 11–16), so they fire regardless of focus. Phantom.Workspaces/MainWindow.axaml has no Window.KeyBindings block at all.

When the user is watching a Copilot session stream (focus still on the entity list where they clicked to open it), pressing Ctrl+Break is silently swallowed — it never reaches AgentChatEditorControl. Copilot sessions are especially affected because: (a) they're opened from the entity list, which retains focus, and (b) the CLI takes time to initialize so users watch passively without typing.

Secondary — turnLock.WaitAsync is outside the try-finally in CopilotSdkChatClient.GetStreamingResponseAsync

File: CopilotSdkChatClient.cs, line 229 vs. line 319 (turnLock.Release())

turnLock.WaitAsync is called before the try block that contains turnLock.Release(). If session.On(...) (line 231) throws after the lock is acquired, the iterator exits without entering the try — turnLock.Release() is never called — and every subsequent turn deadlocks. Additionally, a stale SessionIdleEvent from an interrupted turn can fire on the next turn's subscription, immediately completing the new turn's channel and silently producing an empty response.

---

Missing Tests

1. WorkspaceDataTemplates_CancelGesture_IsWiredAtWindowLevel — assert Phantom.Workspaces/MainWindow.axaml contains Gesture="Cancel" and InterruptCommand
2. WorkspaceDataTemplates_PauseGestures_AreWiredAtWindowLevel — assert Gesture="Pause", Gesture="Shift+Pause", Gesture="Ctrl+Shift+Pause" and their commands are present
3. ActiveAgentSession_ReturnsAgentViewModelForFocusedAgentTab — open an agent-session tab, make it active, assert MainWindowViewModel.ActiveAgentSession is the tab's AgentViewModel
4. ActiveAgentSession_ReturnsNull_WhenActiveTabIsNotAgentSession — non-agent tab is active; assert ActiveAgentSession == null
5. Interrupt_WithCopilotSdkClient_StopsStreamingAndRecordsInterruptedDiagnostic — simulate a Copilot-style pre-buffered streaming client, call Interrupt(), assert streaming stops and a diagnostic history item is recorded
6. GetStreamingResponseAsync_TurnLockIsReleasedAfterCancellation — cancel mid-stream; assert a subsequent GetStreamingResponseAsync call completes (i.e. does not deadlock waiting for turnLock)

---

Recommended Fix

Fix 1 — Add ActiveAgentSession property to MainWindowViewModel.cs

private AgentViewModel? activeAgentSession;

public AgentViewModel? ActiveAgentSession
{
    get => this.activeAgentSession;
    private set => this.SetProperty(ref this.activeAgentSession, value);
}

In SyncSelectedWorkspacePaneFromDock (~line 1345), after setting region.SelectedTab:

this.ActiveAgentSession = (activeDocument.TabViewModel as AgentSessionWorkspaceTabViewModel)?.Agent;

Fix 2 — Add Window.KeyBindings to Phantom.Workspaces/MainWindow.axaml

<Window.KeyBindings>
    <!-- Mirror Agent.Gui/MainWindow.axaml — fire regardless of focus location -->
    <KeyBinding Gesture="Cancel"
                Command="{Binding ActiveAgentSession.InterruptCommand}"/>
    <KeyBinding Gesture="Pause"
                Command="{Binding ActiveAgentSession.InputQueue.ToggleHoldAllQueuesCommand}"/>
    <KeyBinding Gesture="Shift+Pause"
                Command="{Binding ActiveAgentSession.InputQueue.HoldAllQueuesCommand}"/>
    <KeyBinding Gesture="Ctrl+Shift+Pause"
                Command="{Binding ActiveAgentSession.InputQueue.UnholdAllQueuesCommand}"/>
</Window.KeyBindings>

When ActiveAgentSession is null, Avalonia resolves the command as null (CanExecute → false) and silently ignores the key — non-agent windows are unaffected.

Fix 3 — Move turnLock acquire inside try-finally in CopilotSdkChatClient.cs

await this.turnLock.WaitAsync(cancellationToken).ConfigureAwait(false);
try                                              // ← NEW outer try
{
    using var subscription = session.On(...);   // now inside the guarded scope
    // ... queueManager subscribe ...
    try
    {
        await session.SendAsync(...);
        await foreach (var update in channel.Reader.ReadAllAsync(cancellationToken))
            yield return update;
    }
    finally
    {
        // ... queueManager unsubscribe ...
    }
}
finally
{
    this.turnLock.Release();                     // always reached
}

Fix 4 — Invalidate copilotSession after interrupt to prevent stale SessionIdleEvent

In the inner finally block, after unsubscribing queueManager:

if (cancellationToken.IsCancellationRequested)
{
    this.InvalidateCopilotSession();
}

private void InvalidateCopilotSession()
{
    var sessionToDispose = this.copilotSession;
    this.copilotSession = null;
    this.currentSessionSignature = null;
    if (sessionToDispose is not null)
    {
        _ = Task.Run(async () =>
        {
            try { await sessionToDispose.DisposeAsync().ConfigureAwait(false); }
            catch { /* best-effort cleanup */ }
        });
    }
}

---

Edge Cases

• ActiveAgentSession staleness — if a tab closes without triggering SyncSelectedWorkspacePaneFromDock, the property could briefly point to a disposed agent. InterruptCommand calls agentChat.Interrupt() which is already a safe no-op when disposed.
• Window-level binding fires for all agent types — intentional; matches Agent.Gui behavior. InterruptCommand handles null cancellation token gracefully.
• Fix 4 adds ~1–3s CLI restart latency after interrupt — correct trade-off; a silent empty response is worse than a short delay.
• InvalidateCopilotSession races with CleanUpRunAsync — both may call DisposeAsync on the session; verify CopilotSession.DisposeAsync is idempotent or add an Interlocked.CompareExchange guard.

[JoshuaRowePhantom]

Fixed in 68cf772. Two root causes: (1) Ctrl+Break arrives as Key.Cancel + Control on Windows, so the gesture bindings were corrected to Ctrl+Cancel / Ctrl+Shift+Cancel; (2) cancellation now calls CopilotSession.AbortAsync and invalidates the cached session so the in-flight CLI turn is actually aborted. Covered by deterministic unit tests.

[JoshuaRowePhantom]

Verification Passed ✅

Commit verified: 68cf772 (Fix Ctrl+Break interrupt for Copilot sessions (#21))

What was checked

Fix 1 — Gesture correction in AgentChatEditorControl.axaml:

• Ctrl+Cancel is now used for InterruptCommand (was plain Cancel)
• Ctrl+Shift+Cancel is now used for UnholdAllQueuesCommand (was Ctrl+Shift+Pause)
• Comment documents the Windows VK_CANCEL behaviour

Fix 2 — RunStreamingTurnAsync in CopilotSdkChatClient.cs:

• turnLock.WaitAsync is immediately followed by try { ... } finally { turnLock.Release(); } — lock can no longer leak
• Cancellation calls turn.OnCancelledAsync() → AbortAndInvalidateSessionAsync → session.AbortAsync() — the in-flight CLI turn is actually stopped

Agent.Gui MainWindow.axaml: window-level Ctrl+Cancel / Ctrl+Shift+Cancel bindings added (lines 11–18).

Tests

Suite	Result
CopilotSdkChatClientTests (34 tests)	✅ Passed 34/34
MainWindowAxamlTests	⚠️ Could not build — pre-existing RenderContent signature mismatch in ChatOutputHtmlModels.cs introduced by Fix #286, unrelated to #21

Key tests for #21 that exist and are syntactically verified:

• RunStreamingTurn_OnCancellation_AbortsTheTurn_AndReleasesTheLock — verifies abort + lock release ✅
• RunStreamingTurn_OnNormalCompletion_DoesNotAbort_AndDisposesSubscription ✅
• AfterInterrupt_InvalidateCopilotSession_SetsPendingResumeSessionId ✅
• EditorControl_InterruptGesture_MatchesCtrlBreak_NotPlainCancel (exists, can't run due to Enhancement: add toggle to show/hide diagnostic content in agent chat output #286 build break)
• EditorControl_UnholdGesture_MatchesCtrlShiftBreak (exists, can't run due to Enhancement: add toggle to show/hide diagnostic content in agent chat output #286 build break)

The Agent.Gui.Tests build failure is caused by a separate newer commit (Fix #286) and does not affect the correctness of the #21 fix.