From 45faf4d31b10792582cdce5ca693fc5a548d1edc Mon Sep 17 00:00:00 2001
From: Jack Wotherspoon <jackwoth@google.com>
Date: Thu, 12 Mar 2026 14:38:09 +0100
Subject: [PATCH] fix: register themes on extension load not start (#22148)

---
 .../cli/src/config/extension-manager.test.ts  | 65 ++++++++++++++++++-
 packages/cli/src/config/extension-manager.ts  |  9 ++-
 packages/cli/src/ui/themes/theme-manager.ts   | 11 ++++
 3 files changed, 83 insertions(+), 2 deletions(-)

diff --git a/packages/cli/src/config/extension-manager.test.ts b/packages/cli/src/config/extension-manager.test.ts
index 5b44c07194..13c1de15fa 100644
--- a/packages/cli/src/config/extension-manager.test.ts
+++ b/packages/cli/src/config/extension-manager.test.ts
@@ -12,12 +12,13 @@ import { ExtensionManager } from './extension-manager.js';
 import { createTestMergedSettings, type MergedSettings } from './settings.js';
 import { createExtension } from '../test-utils/createExtension.js';
 import { EXTENSIONS_DIRECTORY_NAME } from './extensions/variables.js';
+import { themeManager } from '../ui/themes/theme-manager.js';
 import {
   TrustLevel,
   loadTrustedFolders,
   isWorkspaceTrusted,
 } from './trustedFolders.js';
-import { getRealPath } from '@google/gemini-cli-core';
+import { getRealPath, type CustomTheme } from '@google/gemini-cli-core';
 
 const mockHomedir = vi.hoisted(() => vi.fn(() => '/tmp/mock-home'));
 
@@ -38,6 +39,26 @@ vi.mock('@google/gemini-cli-core', async (importOriginal) => {
   };
 });
 
+const testTheme: CustomTheme = {
+  type: 'custom',
+  name: 'MyTheme',
+  background: {
+    primary: '#282828',
+    diff: { added: '#2b3312', removed: '#341212' },
+  },
+  text: {
+    primary: '#ebdbb2',
+    secondary: '#a89984',
+    link: '#83a598',
+    accent: '#d3869b',
+  },
+  status: {
+    success: '#b8bb26',
+    warning: '#fabd2f',
+    error: '#fb4934',
+  },
+};
+
 describe('ExtensionManager', () => {
   let tempHomeDir: string;
   let tempWorkspaceDir: string;
@@ -65,6 +86,7 @@ describe('ExtensionManager', () => {
   });
 
   afterEach(() => {
+    themeManager.clearExtensionThemes();
     try {
       fs.rmSync(tempHomeDir, { recursive: true, force: true });
     } catch (_e) {
@@ -484,4 +506,45 @@ describe('ExtensionManager', () => {
       ).rejects.toThrow(/already installed/);
     });
   });
+
+  describe('early theme registration', () => {
+    it('should register themes with ThemeManager during loadExtensions for active extensions', async () => {
+      createExtension({
+        extensionsDir: userExtensionsDir,
+        name: 'themed-ext',
+        version: '1.0.0',
+        themes: [testTheme],
+      });
+
+      await extensionManager.loadExtensions();
+
+      expect(themeManager.getCustomThemeNames()).toContain(
+        'MyTheme (themed-ext)',
+      );
+    });
+
+    it('should not register themes for inactive extensions', async () => {
+      createExtension({
+        extensionsDir: userExtensionsDir,
+        name: 'disabled-ext',
+        version: '1.0.0',
+        themes: [testTheme],
+      });
+
+      // Disable the extension by creating an enablement override
+      const manager = new ExtensionManager({
+        enabledExtensionOverrides: ['none'],
+        settings: createTestMergedSettings(),
+        workspaceDir: tempWorkspaceDir,
+        requestConsent: vi.fn().mockResolvedValue(true),
+        requestSetting: null,
+      });
+
+      await manager.loadExtensions();
+
+      expect(themeManager.getCustomThemeNames()).not.toContain(
+        'MyTheme (disabled-ext)',
+      );
+    });
+  });
 });
diff --git a/packages/cli/src/config/extension-manager.ts b/packages/cli/src/config/extension-manager.ts
index 80c48193e2..68617bcbcd 100644
--- a/packages/cli/src/config/extension-manager.ts
+++ b/packages/cli/src/config/extension-manager.ts
@@ -564,7 +564,7 @@ Would you like to attempt to install via "git clone" instead?`,
 
   protected override async startExtension(extension: GeminiCLIExtension) {
     await super.startExtension(extension);
-    if (extension.themes) {
+    if (extension.themes && !themeManager.hasExtensionThemes(extension.name)) {
       themeManager.registerExtensionThemes(extension.name, extension.themes);
     }
   }
@@ -624,6 +624,13 @@ Would you like to attempt to install via "git clone" instead?`,
 
         this.loadedExtensions = builtExtensions;
 
+        // Register extension themes early so they're available at startup.
+        for (const ext of this.loadedExtensions) {
+          if (ext.isActive && ext.themes) {
+            themeManager.registerExtensionThemes(ext.name, ext.themes);
+          }
+        }
+
         await Promise.all(
           this.loadedExtensions.map((ext) => this.maybeStartExtension(ext)),
         );
diff --git a/packages/cli/src/ui/themes/theme-manager.ts b/packages/cli/src/ui/themes/theme-manager.ts
index 00fed5ce20..66826bb87e 100644
--- a/packages/cli/src/ui/themes/theme-manager.ts
+++ b/packages/cli/src/ui/themes/theme-manager.ts
@@ -240,6 +240,17 @@ class ThemeManager {
     }
   }
 
+  /**
+   * Checks if themes for a given extension are already registered.
+   * @param extensionName The name of the extension.
+   * @returns True if any themes from the extension are registered.
+   */
+  hasExtensionThemes(extensionName: string): boolean {
+    return Array.from(this.extensionThemes.keys()).some((name) =>
+      name.endsWith(`(${extensionName})`),
+    );
+  }
+
   /**
    * Clears all registered extension themes.
    * This is primarily for testing purposes to reset state between tests.