ClosePrompt nil check closes #4788 (#4827)

* Add test demonstrating bug #4788 - ClosePrompt panics with nil

Adds TestClosePromptNilCancelPanic that reproduces the bug where
ClosePrompt() panics with a nil pointer dereference when cancelPrompt
is nil. This can happen if ClosePrompt is called before the prompt is
fully initialized.

Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Fix #4788: Add nil check before calling cancelPrompt

Prevents panic in ClosePrompt() when cancelPrompt is nil.
This can happen if ClosePrompt is called before the prompt
is fully initialized.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

---------

Co-authored-by: Claude <noreply@anthropic.com>

pkg/interactive/cancel_test.go

@@ -220,6 +220,31 @@ func TestClosePrompt(t *testing.T) {
 	}
 }
 
+// TestClosePromptNilCancelPanic tests that ClosePrompt doesn't panic
+// when cancelPrompt is nil.
+//
+// This can happen if ClosePrompt is called before the prompt is fully
+// initialized or after manual nil assignment.
+//
+// Bug: #4788
+func TestClosePromptNilCancelPanic(t *testing.T) {
+	// Create an InteractiveClient with nil cancelPrompt
+	c := &InteractiveClient{
+		cancelPrompt: nil,
+	}
+
+	// This should not panic
+	defer func() {
+		if r := recover(); r != nil {
+			t.Errorf("ClosePrompt() panicked with nil cancelPrompt: %v", r)
+		}
+	}()
+
+	// Call ClosePrompt with nil cancelPrompt
+	// This will panic without the fix
+	c.ClosePrompt(AfterPromptCloseExit)
+}
+
 // TestContextCancellationPropagation tests that parent context cancellation propagates
 func TestContextCancellationPropagation(t *testing.T) {
 	c := &InteractiveClient{}

pkg/interactive/interactive_client.go

@@ -169,7 +169,10 @@ func (c *InteractiveClient) InteractivePrompt(parentContext context.Context) {
 // ClosePrompt cancels the running prompt, setting the action to take after close
 func (c *InteractiveClient) ClosePrompt(afterClose AfterPromptCloseAction) {
 	c.afterClose = afterClose
-	c.cancelPrompt()
+	// only call cancelPrompt if it is not nil (to prevent panic)
+	if c.cancelPrompt != nil {
+		c.cancelPrompt()
+	}
 }
 
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