(fix): appcontainer should not poll and footer should use currentModel from ui state (#11923)

packages/core/src/utils/events.ts

@@ -33,8 +33,19 @@ export interface UserFeedbackPayload {
   error?: unknown;
 }
 
+/**
+ * Payload for the 'fallback-mode-changed' event.
+ */
+export interface FallbackModeChangedPayload {
+  /**
+   * Whether fallback mode is now active.
+   */
+  isInFallbackMode: boolean;
+}
+
 export enum CoreEvent {
   UserFeedback = 'user-feedback',
+  FallbackModeChanged = 'fallback-mode-changed',
 }
 
 export class CoreEventEmitter extends EventEmitter {
@@ -66,6 +77,15 @@ export class CoreEventEmitter extends EventEmitter {
     }
   }
 
+  /**
+   * Notifies subscribers that fallback mode has changed.
+   * This is synchronous and doesn't use backlog (UI should already be initialized).
+   */
+  emitFallbackModeChanged(isInFallbackMode: boolean): void {
+    const payload: FallbackModeChangedPayload = { isInFallbackMode };
+    this.emit(CoreEvent.FallbackModeChanged, payload);
+  }
+
   /**
    * Flushes buffered messages. Call this immediately after primary UI listener
    * subscribes.
@@ -82,6 +102,10 @@ export class CoreEventEmitter extends EventEmitter {
     event: CoreEvent.UserFeedback,
     listener: (payload: UserFeedbackPayload) => void,
   ): this;
+  override on(
+    event: CoreEvent.FallbackModeChanged,
+    listener: (payload: FallbackModeChangedPayload) => void,
+  ): this;
   override on(
     event: string | symbol,
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -94,6 +118,10 @@ export class CoreEventEmitter extends EventEmitter {
     event: CoreEvent.UserFeedback,
     listener: (payload: UserFeedbackPayload) => void,
   ): this;
+  override off(
+    event: CoreEvent.FallbackModeChanged,
+    listener: (payload: FallbackModeChangedPayload) => void,
+  ): this;
   override off(
     event: string | symbol,
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -106,6 +134,10 @@ export class CoreEventEmitter extends EventEmitter {
     event: CoreEvent.UserFeedback,
     payload: UserFeedbackPayload,
   ): boolean;
+  override emit(
+    event: CoreEvent.FallbackModeChanged,
+    payload: FallbackModeChangedPayload,
+  ): boolean;
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   override emit(event: string | symbol, ...args: any[]): boolean {
     return super.emit(event, ...args);