diff --git a/packages/core/src/telemetry/metrics.test.ts b/packages/core/src/telemetry/metrics.test.ts
index 0bca699b16..4e306af406 100644
--- a/packages/core/src/telemetry/metrics.test.ts
+++ b/packages/core/src/telemetry/metrics.test.ts
@@ -121,8 +121,10 @@ describe('Telemetry Metrics', () => {
       return actualApi;
     });
 
-    const { getCommonAttributes } = await import('./telemetryAttributes.js');
-    (getCommonAttributes as Mock).mockReturnValue({
+    const { getCommonMetricAttributes } = await import(
+      './telemetryAttributes.js'
+    );
+    (getCommonMetricAttributes as Mock).mockReturnValue({
       'session.id': 'test-session-id',
       'installation.id': 'test-installation-id',
       'user.email': 'test@example.com',
diff --git a/packages/core/src/telemetry/metrics.ts b/packages/core/src/telemetry/metrics.ts
index 377479c1e4..227f3fa858 100644
--- a/packages/core/src/telemetry/metrics.ts
+++ b/packages/core/src/telemetry/metrics.ts
@@ -24,7 +24,7 @@ import type {
   TokenStorageInitializationEvent,
 } from './types.js';
 import { AuthType } from '../core/contentGenerator.js';
-import { getCommonAttributes } from './telemetryAttributes.js';
+import { getCommonMetricAttributes } from './telemetryAttributes.js';
 import { sanitizeHookName } from './sanitize.js';
 
 const EVENT_CHAT_COMPRESSION = 'gemini_cli.chat_compression';
@@ -104,7 +104,7 @@ const EXIT_FAIL_COUNT = 'gemini_cli.exit.fail.count';
 const PLAN_EXECUTION_COUNT = 'gemini_cli.plan.execution.count';
 
 const baseMetricDefinition = {
-  getCommonAttributes,
+  getCommonAttributes: getCommonMetricAttributes,
 };
 
 const COUNTER_DEFINITIONS = {
diff --git a/packages/core/src/telemetry/telemetryAttributes.test.ts b/packages/core/src/telemetry/telemetryAttributes.test.ts
new file mode 100644
index 0000000000..075d55e659
--- /dev/null
+++ b/packages/core/src/telemetry/telemetryAttributes.test.ts
@@ -0,0 +1,115 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach, type Mock } from 'vitest';
+import {
+  getCommonAttributes,
+  getCommonMetricAttributes,
+} from './telemetryAttributes.js';
+import type { Config } from '../config/config.js';
+import { UserAccountManager } from '../utils/userAccountManager.js';
+import { InstallationManager } from '../utils/installationManager.js';
+
+vi.mock('../utils/userAccountManager.js');
+vi.mock('../utils/installationManager.js');
+
+describe('telemetryAttributes', () => {
+  let mockConfig: Partial<Config>;
+
+  beforeEach(() => {
+    vi.resetAllMocks();
+
+    mockConfig = {
+      getSessionId: vi.fn().mockReturnValue('mock-session-id'),
+      isInteractive: vi.fn().mockReturnValue(true),
+      getExperiments: vi.fn().mockReturnValue(undefined),
+      getContentGeneratorConfig: vi.fn().mockReturnValue(undefined),
+    };
+
+    (
+      UserAccountManager.prototype.getCachedGoogleAccount as Mock
+    ).mockReturnValue(undefined);
+    (InstallationManager.prototype.getInstallationId as Mock).mockReturnValue(
+      'mock-install-id',
+    );
+  });
+
+  describe('getCommonMetricAttributes', () => {
+    it('should return interactive and auth_type when defined', () => {
+      mockConfig.getContentGeneratorConfig = vi
+        .fn()
+        .mockReturnValue({ authType: 'oauth-personal' });
+
+      const attributes = getCommonMetricAttributes(mockConfig as Config);
+
+      expect(attributes).toEqual({
+        interactive: true,
+        auth_type: 'oauth-personal',
+      });
+    });
+
+    it('should return only interactive when auth_type is not defined', () => {
+      const attributes = getCommonMetricAttributes(mockConfig as Config);
+
+      expect(attributes).toEqual({
+        interactive: true,
+      });
+    });
+  });
+
+  describe('getCommonAttributes', () => {
+    it('should include all common attributes', () => {
+      (
+        UserAccountManager.prototype.getCachedGoogleAccount as Mock
+      ).mockReturnValue('test@google.com');
+      mockConfig.getExperiments = vi
+        .fn()
+        .mockReturnValue({ experimentIds: [123, 456] });
+      mockConfig.getContentGeneratorConfig = vi
+        .fn()
+        .mockReturnValue({ authType: 'adc' });
+
+      const attributes = getCommonAttributes(mockConfig as Config);
+
+      expect(attributes).toEqual({
+        'session.id': 'mock-session-id',
+        'installation.id': 'mock-install-id',
+        interactive: true,
+        'user.email': 'test@google.com',
+        auth_type: 'adc',
+        'experiments.ids': '123,456',
+      });
+    });
+
+    it('should safely truncate experiments string to not exceed 1000 characters and not cut mid-ID', () => {
+      // Generate a list of experiment IDs that will produce a string > 1000 chars
+      const expIds = [];
+      for (let i = 0; i < 200; i++) {
+        // e.g., 100000000 -> 9 chars + 1 comma = 10 chars per ID
+        expIds.push(100000000 + i);
+      }
+      mockConfig.getExperiments = vi
+        .fn()
+        .mockReturnValue({ experimentIds: expIds });
+
+      const attributes = getCommonAttributes(mockConfig as Config);
+      const expString = attributes['experiments.ids'] as string;
+
+      expect(expString.length).toBeLessThanOrEqual(1000);
+
+      // Verify the last ID is complete (not cut off) by checking if it's one of our expected IDs
+      const ids = expString.split(',');
+      const lastIdStr = ids[ids.length - 1];
+      const lastIdNumber = parseInt(lastIdStr, 10);
+
+      expect(lastIdNumber).toBeGreaterThanOrEqual(100000000);
+      expect(lastIdNumber).toBeLessThan(100000200);
+
+      // Also ensure no trailing comma
+      expect(expString.endsWith(',')).toBe(false);
+    });
+  });
+});
diff --git a/packages/core/src/telemetry/telemetryAttributes.ts b/packages/core/src/telemetry/telemetryAttributes.ts
index d2139e32df..0632fc453c 100644
--- a/packages/core/src/telemetry/telemetryAttributes.ts
+++ b/packages/core/src/telemetry/telemetryAttributes.ts
@@ -12,19 +12,36 @@ import { UserAccountManager } from '../utils/userAccountManager.js';
 const userAccountManager = new UserAccountManager();
 const installationManager = new InstallationManager();
 
+export function getCommonMetricAttributes(config: Config): Attributes {
+  const authType = config.getContentGeneratorConfig()?.authType;
+
+  return {
+    interactive: config.isInteractive(),
+    ...(authType && { auth_type: authType }),
+  };
+}
+
 export function getCommonAttributes(config: Config): Attributes {
   const email = userAccountManager.getCachedGoogleAccount();
   const experiments = config.getExperiments();
-  const authType = config.getContentGeneratorConfig()?.authType;
+
+  let experimentsIdsStr = '';
+  if (experiments && experiments.experimentIds.length > 0) {
+    experimentsIdsStr = experiments.experimentIds.join(',');
+    if (experimentsIdsStr.length > 1000) {
+      experimentsIdsStr = experimentsIdsStr.substring(0, 1000);
+      const lastCommaIndex = experimentsIdsStr.lastIndexOf(',');
+      if (lastCommaIndex > 0) {
+        experimentsIdsStr = experimentsIdsStr.substring(0, lastCommaIndex);
+      }
+    }
+  }
+
   return {
+    ...getCommonMetricAttributes(config),
     'session.id': config.getSessionId(),
     'installation.id': installationManager.getInstallationId(),
-    interactive: config.isInteractive(),
     ...(email && { 'user.email': email }),
-    ...(authType && { auth_type: authType }),
-    ...(experiments &&
-      experiments.experimentIds.length > 0 && {
-        'experiments.ids': experiments.experimentIds,
-      }),
+    ...(experimentsIdsStr && { 'experiments.ids': experimentsIdsStr }),
   };
 }