Fix handling of empty settings (#18131)

packages/core/src/config/config.ts

@@ -158,7 +158,7 @@ export interface ExtensionSetting {
 export interface ResolvedExtensionSetting {
   name: string;
   envVar: string;
-  value: string;
+  value?: string;
   sensitive: boolean;
   scope?: 'user' | 'workspace';
   source?: string;

packages/core/src/tools/mcp-client.test.ts

@@ -1556,6 +1556,41 @@ describe('mcp-client', () => {
       expect(callArgs.env!['GEMINI_CLI_EXT_VAR']).toBe('ext-value');
     });
 
+    it('should exclude extension settings with undefined values from environment', async () => {
+      const mockedTransport = vi
+        .spyOn(SdkClientStdioLib, 'StdioClientTransport')
+        .mockReturnValue({} as SdkClientStdioLib.StdioClientTransport);
+
+      await createTransport(
+        'test-server',
+        {
+          command: 'test-command',
+          extension: {
+            name: 'test-ext',
+            resolvedSettings: [
+              {
+                envVar: 'GEMINI_CLI_EXT_VAR',
+                value: undefined,
+                sensitive: false,
+                name: 'ext-setting',
+              },
+            ],
+            version: '',
+            isActive: false,
+            path: '',
+            contextFiles: [],
+            id: '',
+          },
+        },
+        false,
+        EMPTY_CONFIG,
+      );
+
+      const callArgs = mockedTransport.mock.calls[0][0];
+      expect(callArgs.env).toBeDefined();
+      expect(callArgs.env!['GEMINI_CLI_EXT_VAR']).toBeUndefined();
+    });
+
     describe('useGoogleCredentialProvider', () => {
       beforeEach(() => {
         // Mock GoogleAuth client

packages/core/src/tools/mcp-client.ts

@@ -1948,7 +1948,9 @@ function getExtensionEnvironment(
   const env: Record<string, string> = {};
   if (extension?.resolvedSettings) {
     for (const setting of extension.resolvedSettings) {
-      env[setting.envVar] = setting.value;
+      if (setting.value) {
+        env[setting.envVar] = setting.value;
+      }
     }
   }
   return env;