fix(chat): prevent shell prefix from corrupting input

packages/ui/src/components/chat/ChatInput.tsx

@@ -1402,6 +1402,19 @@ const ChatInputComponent: React.FC<ChatInputProps> = ({ onOpenSettings, scrollTo
         // Uses keyCode === 229 fallback for WebKit where compositionend fires before keydown.
         if (isIMECompositionEvent(e)) return;
 
+        // Enter shell mode before CodeMirror inserts the trigger. Keeping the
+        // document unchanged also keeps the caret at the start for the first
+        // command character.
+        if (inputMode === 'normal' && e.key === '!') {
+            const selection = composerRef.current?.getSelection();
+            if (selection?.start === 0 && selection.end === 0) {
+                e.preventDefault();
+                setInputMode('shell');
+                closeAutocomplete();
+                return;
+            }
+        }
+
         if (inputMode === 'shell' && e.key === 'Escape') {
             e.preventDefault();
             setInputMode('normal');
@@ -1723,13 +1736,20 @@ const ChatInputComponent: React.FC<ChatInputProps> = ({ onOpenSettings, scrollTo
         const inputSource: FileMentionAutocompleteInputSource = isPasteInput ? 'paste' : 'manual';
 
         // A leading `!` switches the composer into shell mode and is consumed.
+        // Mobile keyboards and paste may update the document without a usable
+        // keydown, so consume the trigger in the same editor transaction rather
+        // than moving the caret in a later frame against stale text.
         if (inputMode === 'normal' && value.startsWith('!')) {
             const shellCommand = value.slice(1);
             const nextCursor = Math.max(0, selection.start - 1);
             setInputMode('shell');
-            setMessage(shellCommand);
             closeAutocomplete();
-            requestAnimationFrame(() => composerRef.current?.setSelection(nextCursor));
+            const editor = composerRef.current;
+            if (editor) {
+                editor.replaceRange(0, 1, '', nextCursor);
+            } else {
+                setMessage(shellCommand);
+            }
             return;
         }