chore(core): remove legacy fallback flags and migrate loop detection (#15213)

packages/core/src/utils/events.ts

@@ -34,16 +34,6 @@ export interface UserFeedbackPayload {
   error?: unknown;
 }
 
-/**
- * Payload for the 'fallback-mode-changed' event.
- */
-export interface FallbackModeChangedPayload {
-  /**
-   * Whether fallback mode is now active.
-   */
-  isInFallbackMode: boolean;
-}
-
 /**
  * Payload for the 'model-changed' event.
  */
@@ -78,7 +68,6 @@ export type MemoryChangedPayload = LoadServerHierarchicalMemoryResponse;
 
 export enum CoreEvent {
   UserFeedback = 'user-feedback',
-  FallbackModeChanged = 'fallback-mode-changed',
   ModelChanged = 'model-changed',
   ConsoleLog = 'console-log',
   Output = 'output',
@@ -88,7 +77,6 @@ export enum CoreEvent {
 
 export interface CoreEvents {
   [CoreEvent.UserFeedback]: [UserFeedbackPayload];
-  [CoreEvent.FallbackModeChanged]: [FallbackModeChangedPayload];
   [CoreEvent.ModelChanged]: [ModelChangedPayload];
   [CoreEvent.ConsoleLog]: [ConsoleLogPayload];
   [CoreEvent.Output]: [OutputPayload];
@@ -166,15 +154,6 @@ export class CoreEventEmitter extends EventEmitter<CoreEvents> {
     this._emitOrQueue(CoreEvent.Output, payload);
   }
 
-  /**
-   * 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);
-  }
-
   /**
    * Notifies subscribers that the model has changed.
    */