diff --git a/packages/cli/src/ui/AppContainer.tsx b/packages/cli/src/ui/AppContainer.tsx
index 174510d066..72fdb0ce48 100644
--- a/packages/cli/src/ui/AppContainer.tsx
+++ b/packages/cli/src/ui/AppContainer.tsx
@@ -1521,6 +1521,7 @@ Logging in with Google... Restarting Gemini CLI to continue.
             );
             await toggleDevToolsPanel(
               config,
+              showErrorDetails,
               () => setShowErrorDetails((prev) => !prev),
               () => setShowErrorDetails(true),
             );
@@ -1660,6 +1661,7 @@ Logging in with Google... Restarting Gemini CLI to continue.
       tabFocusTimeoutRef,
       showTransientMessage,
       settings.merged.general.devtools,
+      showErrorDetails,
     ],
   );
 
diff --git a/packages/cli/src/utils/devtoolsService.test.ts b/packages/cli/src/utils/devtoolsService.test.ts
index 922d4d1483..cb3b907d97 100644
--- a/packages/cli/src/utils/devtoolsService.test.ts
+++ b/packages/cli/src/utils/devtoolsService.test.ts
@@ -437,7 +437,19 @@ describe('devtoolsService', () => {
   });
 
   describe('toggleDevToolsPanel', () => {
-    it('calls toggle when browser opens successfully', async () => {
+    it('calls toggle (to close) when already open', async () => {
+      const config = createMockConfig();
+      const toggle = vi.fn();
+      const setOpen = vi.fn();
+
+      const promise = toggleDevToolsPanel(config, true, toggle, setOpen);
+      await promise;
+
+      expect(toggle).toHaveBeenCalledTimes(1);
+      expect(setOpen).not.toHaveBeenCalled();
+    });
+
+    it('does NOT call toggle or setOpen when browser opens successfully', async () => {
       const config = createMockConfig();
       const toggle = vi.fn();
       const setOpen = vi.fn();
@@ -447,18 +459,18 @@ describe('devtoolsService', () => {
       mockDevToolsInstance.start.mockResolvedValue('http://127.0.0.1:25417');
       mockDevToolsInstance.getPort.mockReturnValue(25417);
 
-      const promise = toggleDevToolsPanel(config, toggle, setOpen);
+      const promise = toggleDevToolsPanel(config, false, toggle, setOpen);
 
       await vi.waitFor(() => expect(MockWebSocket.instances.length).toBe(1));
       MockWebSocket.instances[0].simulateError();
 
       await promise;
 
-      expect(toggle).toHaveBeenCalledTimes(1);
+      expect(toggle).not.toHaveBeenCalled();
       expect(setOpen).not.toHaveBeenCalled();
     });
 
-    it('calls toggle when browser fails to open', async () => {
+    it('calls setOpen when browser fails to open', async () => {
       const config = createMockConfig();
       const toggle = vi.fn();
       const setOpen = vi.fn();
@@ -468,18 +480,18 @@ describe('devtoolsService', () => {
       mockDevToolsInstance.start.mockResolvedValue('http://127.0.0.1:25417');
       mockDevToolsInstance.getPort.mockReturnValue(25417);
 
-      const promise = toggleDevToolsPanel(config, toggle, setOpen);
+      const promise = toggleDevToolsPanel(config, false, toggle, setOpen);
 
       await vi.waitFor(() => expect(MockWebSocket.instances.length).toBe(1));
       MockWebSocket.instances[0].simulateError();
 
       await promise;
 
-      expect(toggle).toHaveBeenCalledTimes(1);
-      expect(setOpen).not.toHaveBeenCalled();
+      expect(toggle).not.toHaveBeenCalled();
+      expect(setOpen).toHaveBeenCalledTimes(1);
     });
 
-    it('calls toggle when shouldLaunchBrowser returns false', async () => {
+    it('calls setOpen when shouldLaunchBrowser returns false', async () => {
       const config = createMockConfig();
       const toggle = vi.fn();
       const setOpen = vi.fn();
@@ -488,15 +500,15 @@ describe('devtoolsService', () => {
       mockDevToolsInstance.start.mockResolvedValue('http://127.0.0.1:25417');
       mockDevToolsInstance.getPort.mockReturnValue(25417);
 
-      const promise = toggleDevToolsPanel(config, toggle, setOpen);
+      const promise = toggleDevToolsPanel(config, false, toggle, setOpen);
 
       await vi.waitFor(() => expect(MockWebSocket.instances.length).toBe(1));
       MockWebSocket.instances[0].simulateError();
 
       await promise;
 
-      expect(toggle).toHaveBeenCalledTimes(1);
-      expect(setOpen).not.toHaveBeenCalled();
+      expect(toggle).not.toHaveBeenCalled();
+      expect(setOpen).toHaveBeenCalledTimes(1);
     });
 
     it('calls setOpen when DevTools server fails to start', async () => {
@@ -506,7 +518,7 @@ describe('devtoolsService', () => {
 
       mockDevToolsInstance.start.mockRejectedValue(new Error('fail'));
 
-      const promise = toggleDevToolsPanel(config, toggle, setOpen);
+      const promise = toggleDevToolsPanel(config, false, toggle, setOpen);
 
       await vi.waitFor(() => expect(MockWebSocket.instances.length).toBe(1));
       MockWebSocket.instances[0].simulateError();
diff --git a/packages/cli/src/utils/devtoolsService.ts b/packages/cli/src/utils/devtoolsService.ts
index 35abf0ec96..5e4b7710c4 100644
--- a/packages/cli/src/utils/devtoolsService.ts
+++ b/packages/cli/src/utils/devtoolsService.ts
@@ -212,14 +212,24 @@ async function startDevToolsServerImpl(config: Config): Promise<string> {
 
 /**
  * Handles the F12 key toggle for the DevTools panel.
- * Starts the DevTools server, attempts to open the browser,
- * and always calls the toggle callback regardless of the outcome.
+ * Starts the DevTools server, attempts to open the browser.
+ * If the panel is already open, it closes it.
+ * If the panel is closed:
+ * - Attempts to open the browser.
+ * - If browser opening is successful, the panel remains closed.
+ * - If browser opening fails or is not possible, the panel is opened.
  */
 export async function toggleDevToolsPanel(
   config: Config,
+  isOpen: boolean,
   toggle: () => void,
   setOpen: () => void,
 ): Promise<void> {
+  if (isOpen) {
+    toggle();
+    return;
+  }
+
   try {
     const { openBrowserSecurely, shouldLaunchBrowser } = await import(
       '@google/gemini-cli-core'
@@ -228,11 +238,14 @@ export async function toggleDevToolsPanel(
     if (shouldLaunchBrowser()) {
       try {
         await openBrowserSecurely(url);
+        // Browser opened successfully, don't open drawer.
+        return;
       } catch (e) {
         debugLogger.warn('Failed to open browser securely:', e);
       }
     }
-    toggle();
+    // If we can't launch browser or it failed, open drawer.
+    setOpen();
   } catch (e) {
     setOpen();
     debugLogger.error('Failed to start DevTools server:', e);