fix(webui): sync model badge after preset switch

Co-authored-by: Cursor <cursoragent@cursor.com>

webui/src/App.tsx

@@ -492,6 +492,7 @@ function Shell({ onModelNameChange, onLogout }: { onModelNameChange: (modelName:
             onNewChat={onNewChat}
             onCreateChat={onCreateChat}
             onTurnEnd={onTurnEnd}
+            onModelNameChange={onModelNameChange}
             theme={theme}
             onToggleTheme={toggle}
             hideSidebarToggleOnDesktop={desktopSidebarOpen}

webui/src/components/thread/ThreadShell.tsx

@@ -32,6 +32,7 @@ interface ThreadShellProps {
   onNewChat?: () => void;
   onCreateChat?: () => Promise<string | null>;
   onTurnEnd?: () => void;
+  onModelNameChange?: (modelName: string | null) => void;
   theme?: "light" | "dark";
   onToggleTheme?: () => void;
   hideSidebarToggleOnDesktop?: boolean;
@@ -75,6 +76,7 @@ export function ThreadShell({
   onToggleSidebar,
   onCreateChat,
   onTurnEnd,
+  onModelNameChange,
   theme = "light",
   onToggleTheme = () => {},
   hideSidebarToggleOnDesktop = false,
@@ -103,7 +105,7 @@ export function ThreadShell({
     setMessages,
     streamError,
     dismissStreamError,
-  } = useNanobotStream(chatId, initial, hasPendingToolCalls, onTurnEnd);
+  } = useNanobotStream(chatId, initial, hasPendingToolCalls, onTurnEnd, onModelNameChange);
   const showHeroComposer = messages.length === 0 && !loading;
   const pendingAsk = useMemo(() => {
     for (let index = messages.length - 1; index >= 0; index -= 1) {

webui/src/hooks/useNanobotStream.ts

@@ -44,6 +44,7 @@ export function useNanobotStream(
   initialMessages: UIMessage[] = [],
   hasPendingToolCalls = false,
   onTurnEnd?: () => void,
+  onModelNameChange?: (modelName: string | null) => void,
 ): {
   messages: UIMessage[];
   isStreaming: boolean;
@@ -181,6 +182,9 @@ export function useNanobotStream(
       }
 
       if (ev.event === "message") {
+        if (ev.model_name !== undefined) {
+          onModelNameChange?.(ev.model_name || null);
+        }
         if (
           suppressStreamUntilTurnEndRef.current &&
           (ev.kind === "tool_hint" || ev.kind === "progress")

webui/src/lib/types.ts

@@ -147,6 +147,8 @@ export type InboundEvent =
       /** Present when the frame is an agent breadcrumb (e.g. tool hint,
        * generic progress line) rather than a conversational reply. */
       kind?: "tool_hint" | "progress";
+      /** Runtime model name after commands like `/model fast` update it. */
+      model_name?: string | null;
     }
   | {
       event: "delta";

webui/src/tests/useNanobotStream.test.tsx

@@ -134,6 +134,28 @@ describe("useNanobotStream", () => {
     ]);
   });
 
+  it("reports runtime model name updates from message frames", () => {
+    const fake = fakeClient();
+    const onModelNameChange = vi.fn();
+    renderHook(
+      () => useNanobotStream("chat-model", EMPTY_MESSAGES, false, undefined, onModelNameChange),
+      {
+        wrapper: wrap(fake.client),
+      },
+    );
+
+    act(() => {
+      fake.emit("chat-model", {
+        event: "message",
+        chat_id: "chat-model",
+        text: "Switched model preset to `fast`.",
+        model_name: "openai/gpt-4.1",
+      });
+    });
+
+    expect(onModelNameChange).toHaveBeenCalledWith("openai/gpt-4.1");
+  });
+
   it("suppresses redundant stream confirmation after assistant media", () => {
     const fake = fakeClient();
     const { result } = renderHook(() => useNanobotStream("chat-img-result", EMPTY_MESSAGES), {