Guard close-confirmation alert against re-entrant presentation

supacode/Features/Terminal/Models/TerminalCloseConfirmationGate.swift

@@ -0,0 +1,24 @@
+import Foundation
+
+/// App-global guard against re-entrant close-confirmation alerts.
+///
+/// Close requests arrive from independent paths (TCA effects, Ghostty
+/// callbacks, the tab bar, the CLI socket), and `NSAlert.runModal()` keeps
+/// draining main-actor jobs while it spins, so a late request can try to
+/// present a second alert from inside the first one's run loop. AppKit may
+/// answer that nested modal with an uncaught NSException (SIGABRT, Sentry
+/// PROWL-MACOS-FP). While a confirmation is on screen, later ones are
+/// dropped and treated as cancelled.
+@MainActor
+enum TerminalCloseConfirmationGate {
+  private(set) static var isPresenting = false
+
+  /// Runs `present` unless a confirmation is already showing.
+  /// Returns `nil` when the gate is held; callers treat that as "cancelled".
+  static func run<T>(_ present: () -> T) -> T? {
+    guard !isPresenting else { return nil }
+    isPresenting = true
+    defer { isPresenting = false }
+    return present()
+  }
+}

supacode/Features/Terminal/Models/WorktreeTerminalState+Surfaces.swift

@@ -47,13 +47,16 @@ extension WorktreeTerminalState {
     target: TerminalCloseConfirmationTarget,
     decision: TerminalCloseConfirmationDecision
   ) -> Bool {
-    let alert = NSAlert()
-    alert.messageText = target.messageText
-    alert.informativeText = closeConfirmationMessage(for: decision)
-    alert.alertStyle = .warning
-    alert.addButton(withTitle: target.confirmButtonTitle)
-    alert.addButton(withTitle: "Cancel")
-    return alert.runModal() == .alertFirstButtonReturn
+    let confirmed = TerminalCloseConfirmationGate.run {
+      let alert = NSAlert()
+      alert.messageText = target.messageText
+      alert.informativeText = closeConfirmationMessage(for: decision)
+      alert.alertStyle = .warning
+      alert.addButton(withTitle: target.confirmButtonTitle)
+      alert.addButton(withTitle: "Cancel")
+      return alert.runModal() == .alertFirstButtonReturn
+    }
+    return confirmed ?? false
   }
 
   func closeConfirmationMessage(for decision: TerminalCloseConfirmationDecision) -> String {

supacodeTests/TerminalCloseConfirmationGateTests.swift

@@ -0,0 +1,29 @@
+import Testing
+
+@testable import supacode
+
+@MainActor
+struct TerminalCloseConfirmationGateTests {
+  @Test func runExecutesWhenGateIsFree() {
+    let result = TerminalCloseConfirmationGate.run { true }
+    #expect(result == true)
+    #expect(TerminalCloseConfirmationGate.isPresenting == false)
+  }
+
+  @Test func nestedRunIsDropped() {
+    var nestedResult: Bool? = false
+    let outer = TerminalCloseConfirmationGate.run { () -> Bool in
+      #expect(TerminalCloseConfirmationGate.isPresenting)
+      nestedResult = TerminalCloseConfirmationGate.run { true }
+      return true
+    }
+    #expect(outer == true)
+    #expect(nestedResult == nil)
+  }
+
+  @Test func gateIsReleasedAfterRun() {
+    _ = TerminalCloseConfirmationGate.run { true }
+    let second = TerminalCloseConfirmationGate.run { false }
+    #expect(second == false)
+  }
+}