fix(core): update telemetry token count after session resume (#15491)

Co-authored-by: Tommaso Sciortino <sciortino@gmail.com>

packages/core/src/core/client.test.ts

@@ -303,6 +303,17 @@ describe('Gemini Client (client.ts)', () => {
     });
   });
 
+  describe('resumeChat', () => {
+    it('should update telemetry token count when a chat is resumed', async () => {
+      const history: Content[] = [
+        { role: 'user', parts: [{ text: 'resumed message' }] },
+      ];
+      await client.resumeChat(history);
+
+      expect(uiTelemetryService.setLastPromptTokenCount).toHaveBeenCalled();
+    });
+  });
+
   describe('resetChat', () => {
     it('should create a new chat session, clearing the old history', async () => {
       // 1. Get the initial chat instance and add some history.

packages/core/src/core/client.ts

@@ -269,6 +269,7 @@ export class GeminiClient {
     resumedSessionData?: ResumedSessionData,
   ): Promise<void> {
     this.chat = await this.startChat(history, resumedSessionData);
+    this.updateTelemetryTokenCount();
   }
 
   getChatRecordingService(): ChatRecordingService | undefined {