fix: adapt frontend for legacy Chrome and runtime config

frontend-web/src/components/ai-elements/prompt-input.tsx

@@ -846,7 +846,10 @@ export const PromptInput = ({
         ref={formRef}
         {...props}
       >
-        <InputGroup>{children}</InputGroup>
+        {/* Do not rely on InputGroup's :has(textarea) selector here: Chrome
+            versions before 105 ignore :has(), retain h-9, and clip the whole
+            multi-line composer to a single row. */}
+        <InputGroup className="h-auto min-h-16">{children}</InputGroup>
       </form>
     </PromptInputValidationContext.Provider>
   );
@@ -873,16 +876,48 @@ export type PromptInputTextareaProps = ComponentProps<
   typeof InputGroupTextarea
 >;
 
-export const PromptInputTextarea = ({
-  onChange,
-  className,
-  placeholder = "What would you like to know?",
-  ...props
-}: PromptInputTextareaProps) => {
-  const controller = useOptionalPromptInputController();
-  const attachments = usePromptInputAttachments();
-  const sanitizeIncomingFiles = usePromptInputValidation();
-  const [isComposing, setIsComposing] = useState(false);
+export const PromptInputTextarea = ({
+  onChange,
+  onInput,
+  className,
+  placeholder = "What would you like to know?",
+  ...props
+}: PromptInputTextareaProps) => {
+  const controller = useOptionalPromptInputController();
+  const attachments = usePromptInputAttachments();
+  const sanitizeIncomingFiles = usePromptInputValidation();
+  const [isComposing, setIsComposing] = useState(false);
+  const textareaRef = useRef<HTMLTextAreaElement | null>(null);
+
+  const resizeForLegacyChrome = useCallback((textarea: HTMLTextAreaElement) => {
+    if (
+      typeof CSS !== "undefined" &&
+      typeof CSS.supports === "function" &&
+      CSS.supports("field-sizing", "content")
+    ) {
+      return;
+    }
+
+    // Chrome 109 ignores field-sizing: content. Preserve the same 4rem–12rem
+    // autosize range used by min-h-16/max-h-48 instead of leaving the prompt
+    // stuck at its minimum height.
+    textarea.style.height = "auto";
+    const height = Math.max(64, Math.min(textarea.scrollHeight, 192));
+    textarea.style.height = `${height}px`;
+    textarea.style.overflowY = textarea.scrollHeight > 192 ? "auto" : "hidden";
+  }, []);
+
+  // onInput does not run for a controlled value filled by a suggested question
+  // or restored draft. Resize once after every render in legacy Chrome too.
+  useEffect(() => {
+    const textarea = textareaRef.current;
+    if (!textarea) return;
+
+    const frame = window.requestAnimationFrame(() => {
+      resizeForLegacyChrome(textarea);
+    });
+    return () => window.cancelAnimationFrame(frame);
+  }, [controller?.textInput.value, resizeForLegacyChrome]);
 
   const handleKeyDown: KeyboardEventHandler<HTMLTextAreaElement> = (e) => {
     if (e.key === "Enter") {
@@ -962,12 +997,18 @@ export const PromptInputTextarea = ({
       };
 
   return (
-    <InputGroupTextarea
-      className={cn("field-sizing-content max-h-48 min-h-16", className)}
-      name="message"
+    <InputGroupTextarea
+      className={cn("field-sizing-content max-h-48 min-h-16", className)}
+      name="message"
+      ref={textareaRef}
+      rows={3}
       onCompositionEnd={() => setIsComposing(false)}
       onCompositionStart={() => setIsComposing(true)}
-      onKeyDown={handleKeyDown}
+      onKeyDown={handleKeyDown}
+      onInput={(event) => {
+        resizeForLegacyChrome(event.currentTarget);
+        onInput?.(event);
+      }}
       onPaste={handlePaste}
       placeholder={placeholder}
       {...props}