diff --git a/packages/cli/src/gemini.test.tsx b/packages/cli/src/gemini.test.tsx
index 13aae88d38..aac8b3ac60 100644
--- a/packages/cli/src/gemini.test.tsx
+++ b/packages/cli/src/gemini.test.tsx
@@ -21,7 +21,33 @@ import {
 } from './gemini.js';
 import { type LoadedSettings } from './config/settings.js';
 import { appEvents, AppEvent } from './utils/events.js';
-import type { Config } from '@google/gemini-cli-core';
+import { type Config } from '@google/gemini-cli-core';
+import { act } from 'react';
+import { type InitializationResult } from './core/initializer.js';
+
+const performance = vi.hoisted(() => ({
+  now: vi.fn(),
+}));
+vi.stubGlobal('performance', performance);
+
+vi.mock('@google/gemini-cli-core', async (importOriginal) => {
+  const actual =
+    await importOriginal<typeof import('@google/gemini-cli-core')>();
+  return {
+    ...actual,
+    recordSlowRender: vi.fn(),
+  };
+});
+
+vi.mock('ink', async (importOriginal) => {
+  const actual = await importOriginal<typeof import('ink')>();
+  return {
+    ...actual,
+    // Mock here so we can spyOn the render function. ink uses ESM which doesn't
+    // allow us to spyOn it directly.
+    render: vi.fn((_node, options) => actual.render(_node, options)),
+  };
+});
 
 // Custom error to identify mock process.exit calls
 class MockProcessExitError extends Error {
@@ -295,6 +321,7 @@ describe('gemini.tsx main function kitty protocol', () => {
     } else {
       delete process.env['GEMINI_CLI_NO_RELAUNCH'];
     }
+    vi.restoreAllMocks();
   });
 
   it('should call setRawMode and detectAndEnableKittyProtocol when isInteractive is true', async () => {
@@ -367,7 +394,9 @@ describe('gemini.tsx main function kitty protocol', () => {
       recordResponses: undefined,
     });
 
-    await main();
+    await act(async () => {
+      await main();
+    });
 
     expect(setRawModeSpy).toHaveBeenCalledWith(true);
     expect(detectAndEnableKittyProtocol).toHaveBeenCalledTimes(1);
@@ -382,7 +411,7 @@ describe('validateDnsResolutionOrder', () => {
   });
 
   afterEach(() => {
-    consoleWarnSpy.mockRestore();
+    vi.restoreAllMocks();
   });
 
   it('should return "ipv4first" when the input is "ipv4first"', () => {
@@ -423,6 +452,12 @@ describe('startInteractiveUI', () => {
   } as LoadedSettings;
   const mockStartupWarnings = ['warning1'];
   const mockWorkspaceRoot = '/root';
+  const mockInitializationResult = {
+    authError: null,
+    themeError: null,
+    shouldOpenAuthDialog: false,
+    geminiMdFileCount: 0,
+  };
 
   vi.mock('./utils/version.js', () => ({
     getCliVersion: vi.fn(() => Promise.resolve('1.0.0')),
@@ -442,26 +477,33 @@ describe('startInteractiveUI', () => {
     runExitCleanup: vi.fn(),
   }));
 
-  vi.mock('ink', () => ({
-    render: vi.fn().mockReturnValue({ unmount: vi.fn() }),
-  }));
-
-  beforeEach(() => {
-    vi.clearAllMocks();
+  afterEach(() => {
+    vi.restoreAllMocks();
   });
 
+  async function startTestInteractiveUI(
+    config: Config,
+    settings: LoadedSettings,
+    startupWarnings: string[],
+    workspaceRoot: string,
+    initializationResult: InitializationResult,
+  ) {
+    await act(async () => {
+      await startInteractiveUI(
+        config,
+        settings,
+        startupWarnings,
+        workspaceRoot,
+        initializationResult,
+      );
+    });
+  }
+
   it('should render the UI with proper React context and exitOnCtrlC disabled', async () => {
     const { render } = await import('ink');
     const renderSpy = vi.mocked(render);
 
-    const mockInitializationResult = {
-      authError: null,
-      themeError: null,
-      shouldOpenAuthDialog: false,
-      geminiMdFileCount: 0,
-    };
-
-    await startInteractiveUI(
+    await startTestInteractiveUI(
       mockConfig,
       mockSettings,
       mockStartupWarnings,
@@ -477,6 +519,7 @@ describe('startInteractiveUI', () => {
     expect(options).toEqual({
       exitOnCtrlC: false,
       isScreenReaderEnabled: false,
+      onRender: expect.any(Function),
     });
 
     // Verify React element structure is valid (but don't deep dive into JSX internals)
@@ -488,14 +531,7 @@ describe('startInteractiveUI', () => {
     const { checkForUpdates } = await import('./ui/utils/updateCheck.js');
     const { registerCleanup } = await import('./utils/cleanup.js');
 
-    const mockInitializationResult = {
-      authError: null,
-      themeError: null,
-      shouldOpenAuthDialog: false,
-      geminiMdFileCount: 0,
-    };
-
-    await startInteractiveUI(
+    await startTestInteractiveUI(
       mockConfig,
       mockSettings,
       mockStartupWarnings,
@@ -517,6 +553,36 @@ describe('startInteractiveUI', () => {
     expect(checkForUpdates).toHaveBeenCalledTimes(1);
   });
 
+  it('should not recordSlowRender when less than threshold', async () => {
+    const { recordSlowRender } = await import('@google/gemini-cli-core');
+    performance.now.mockReturnValueOnce(0);
+    await startTestInteractiveUI(
+      mockConfig,
+      mockSettings,
+      mockStartupWarnings,
+      mockWorkspaceRoot,
+      mockInitializationResult,
+    );
+
+    expect(recordSlowRender).not.toHaveBeenCalled();
+  });
+
+  it('should call recordSlowRender when more than threshold', async () => {
+    const { recordSlowRender } = await import('@google/gemini-cli-core');
+    performance.now.mockReturnValueOnce(0);
+    performance.now.mockReturnValueOnce(300);
+
+    await startTestInteractiveUI(
+      mockConfig,
+      mockSettings,
+      mockStartupWarnings,
+      mockWorkspaceRoot,
+      mockInitializationResult,
+    );
+
+    expect(recordSlowRender).toHaveBeenCalledWith(mockConfig, 300);
+  });
+
   it.each([
     {
       screenReader: true,
@@ -537,14 +603,7 @@ describe('startInteractiveUI', () => {
       getScreenReader: () => screenReader,
     } as Config;
 
-    const mockInitializationResult = {
-      authError: null,
-      themeError: null,
-      shouldOpenAuthDialog: false,
-      geminiMdFileCount: 0,
-    };
-
-    await startInteractiveUI(
+    await startTestInteractiveUI(
       mockConfigWithScreenReader,
       mockSettings,
       mockStartupWarnings,
diff --git a/packages/cli/src/gemini.tsx b/packages/cli/src/gemini.tsx
index 17c5b807ef..ef9239ca66 100644
--- a/packages/cli/src/gemini.tsx
+++ b/packages/cli/src/gemini.tsx
@@ -5,7 +5,7 @@
  */
 
 import React from 'react';
-import { render } from 'ink';
+import { render, type RenderOptions } from 'ink';
 import { AppContainer } from './ui/AppContainer.js';
 import { loadCliConfig, parseArguments } from './config/config.js';
 import * as cliConfig from './config/config.js';
@@ -32,7 +32,7 @@ import {
   runExitCleanup,
 } from './utils/cleanup.js';
 import { getCliVersion } from './utils/version.js';
-import type { Config } from '@google/gemini-cli-core';
+import { type Config } from '@google/gemini-cli-core';
 import {
   sessionId,
   logUserPrompt,
@@ -40,6 +40,7 @@ import {
   getOauthClient,
   UserPromptEvent,
   debugLogger,
+  recordSlowRender,
 } from '@google/gemini-cli-core';
 import {
   initializeApp,
@@ -70,6 +71,8 @@ import { ExtensionManager } from './config/extension-manager.js';
 import { createPolicyUpdater } from './config/policy.js';
 import { requestConsentNonInteractive } from './config/extensions/consent.js';
 
+const SLOW_RENDER_MS = 200;
+
 export function validateDnsResolutionOrder(
   order: string | undefined,
 ): DnsResolutionOrder {
@@ -205,7 +208,12 @@ export async function startInteractiveUI(
     {
       exitOnCtrlC: false,
       isScreenReaderEnabled: config.getScreenReader(),
-    },
+      onRender: ({ renderTime }: { renderTime: number }) => {
+        if (renderTime > SLOW_RENDER_MS) {
+          recordSlowRender(config, renderTime);
+        }
+      },
+    } as RenderOptions,
   );
 
   checkForUpdates(settings)