diff --git a/sources/SquirrelApplicationDelegate.swift b/sources/SquirrelApplicationDelegate.swift
index 840b6c9ac..27f5f02ae 100644
--- a/sources/SquirrelApplicationDelegate.swift
+++ b/sources/SquirrelApplicationDelegate.swift
@@ -245,6 +245,7 @@ final class SquirrelApplicationDelegate: NSObject, NSApplicationDelegate, SPUSta
     notifCenter.addObserver(forName: .init("SquirrelGetASCIIModeNotification"), object: nil, queue: nil, using: rimeGetASCIIMode)
     notifCenter.addObserver(forName: .init(kTISNotifySelectedKeyboardInputSourceChanged as String), object: nil, queue: .main) { [weak self] _ in
       self?.updateStatusItemVisibility()
+      self?.finalizeStrandedComposition()
     }
   }
 
@@ -357,8 +358,23 @@ private extension SquirrelApplicationDelegate {
 
   func updateStatusItemVisibility() {
     guard let statusItem = statusItem else { return }
-    let id = SquirrelInstaller.currentInputSourceID() ?? ""
-    statusItem.isVisible = id.hasPrefix("im.rime.inputmethod.Squirrel")
+    let currentInputSourceID = SquirrelInstaller.currentInputSourceID() ?? ""
+    statusItem.isVisible = currentInputSourceID.hasPrefix("im.rime.inputmethod.Squirrel")
+  }
+
+  // macOS 26 does not call deactivateServer when the input source is switched
+  // away by another process via TISSelectInputSource() (e.g. macism, Input
+  // Source Pro): the pending composition is stranded and the candidate panel
+  // is left orphaned on screen (#1140). The input-source-changed notification
+  // is still delivered, so finalize the composition here as a fallback.
+  // Switching via the menu bar calls deactivateServer first, making this a
+  // no-op.
+  func finalizeStrandedComposition() {
+    let currentInputSourceID = SquirrelInstaller.currentInputSourceID() ?? ""
+    guard !currentInputSourceID.hasPrefix("im.rime.inputmethod.Squirrel") else { return }
+    if let inputController = panel?.inputController {
+      inputController.deactivateServer(inputController.client())
+    }
   }
 
   func applyStatusIcon(asciiMode: Bool, schemaLabel: String?) {
@@ -393,7 +409,7 @@ private extension SquirrelApplicationDelegate {
   func rimeToggleASCIIMode(_ notification: Notification) {
     guard let mode = notification.object as? String else { return }
     let enableASCII = mode == "ascii"
-    
+
     if enableASCII {
       NotificationCenter.default.post(name: .init("SquirrelSetASCIIModeNotification"), object: true)
     } else {
diff --git a/sources/SquirrelInputController.swift b/sources/SquirrelInputController.swift
index 889443e08..75b7ebb27 100644
--- a/sources/SquirrelInputController.swift
+++ b/sources/SquirrelInputController.swift
@@ -197,7 +197,7 @@ final class SquirrelInputController: IMKInputController {
     preedit = ""
     // Update menu bar icon
     if session != 0 {
-      let state = rimeAPI.get_option(session, "ascii_mode");
+      let state = rimeAPI.get_option(session, "ascii_mode")
       let label = rimeAPI.get_state_label_abbreviated(session, "ascii_mode", state, true).asString
       NSApp.squirrelAppDelegate.updateStatusIcon(asciiMode: state, schemaLabel: label)
     }
@@ -208,7 +208,7 @@ final class SquirrelInputController: IMKInputController {
     // print("[DEBUG] initWithServer: \(server ?? .init()) delegate: \(delegate ?? "nil") client:\(client ?? "nil")")
     super.init(server: server, delegate: delegate, client: client)
     createSession()
-    
+
     // Listen for ASCII mode toggle notifications
     NotificationCenter.default.addObserver(
       forName: .init("SquirrelSetASCIIModeNotification"),
@@ -217,7 +217,7 @@ final class SquirrelInputController: IMKInputController {
     ) { [weak self] notification in
       self?.handleASCIIModeToggle(notification)
     }
-    
+
     // Listen for ASCII mode status requests
     NotificationCenter.default.addObserver(
       forName: .init("SquirrelReportASCIIModeNotification"),
@@ -226,8 +226,6 @@ final class SquirrelInputController: IMKInputController {
     ) { [weak self] notification in
       self?.reportASCIIMode(notification)
     }
-    
-
   }
 
   override func deactivateServer(_ sender: Any!) {
@@ -637,27 +635,26 @@ private extension SquirrelInputController {
   private func handleASCIIModeToggle(_ notification: Notification) {
     guard let enableASCII = notification.object as? Bool else { return }
     guard session != 0 && rimeAPI.find_session(session) else { return }
-    
+
     rimeAPI.set_option(session, "ascii_mode", enableASCII)
-    
+
     // Force update the UI to reflect the mode change
     rimeUpdate()
   }
-  
+
   private func reportASCIIMode(_: Notification) {
     // Only active input controller should respond
     guard let client = client else { return }
     guard session != 0 && rimeAPI.find_session(session) else { return }
-    
+
     let isASCIIMode = rimeAPI.get_option(session, "ascii_mode")
     let status = isASCIIMode ? "ascii" : "nascii"
-    
+
     // Directly respond with the status
     DistributedNotificationCenter.default().postNotificationName(
-      .init("SquirrelASCIIModeResponse"), 
+      .init("SquirrelASCIIModeResponse"),
       object: status
     )
   }
 
-
 }