Fix extension MCP server env var loading (#20374)

Author: chrstnb

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

@@ -1792,6 +1792,80 @@ describe('mcp-client', () => {
       expect(callArgs.env!['GEMINI_CLI_EXT_VAR']).toBeUndefined();
     });
 
+    it('should include extension settings with defined values in 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: 'defined-value',
+                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']).toBe('defined-value');
+    });
+
+    it('should resolve environment variables in mcpServerConfig.env using extension settings', async () => {
+      const mockedTransport = vi
+        .spyOn(SdkClientStdioLib, 'StdioClientTransport')
+        .mockReturnValue({} as SdkClientStdioLib.StdioClientTransport);
+
+      await createTransport(
+        'test-server',
+        {
+          command: 'test-command',
+          env: {
+            RESOLVED_VAR: '$GEMINI_CLI_EXT_VAR',
+          },
+          extension: {
+            name: 'test-ext',
+            resolvedSettings: [
+              {
+                envVar: 'GEMINI_CLI_EXT_VAR',
+                value: 'ext-value',
+                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']).toBe('ext-value');
+      expect(callArgs.env!['RESOLVED_VAR']).toBe('ext-value');
+    });
+
     it('should expand environment variables in mcpServerConfig.env and not redact them', async () => {
       const mockedTransport = vi
         .spyOn(SdkClientStdioLib, 'StdioClientTransport')

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

@@ -34,7 +34,11 @@ import {
   ProgressNotificationSchema,
 } from '@modelcontextprotocol/sdk/types.js';
 import { parse } from 'shell-quote';
-import type { Config, MCPServerConfig } from '../config/config.js';
+import type {
+  Config,
+  MCPServerConfig,
+  GeminiCLIExtension,
+} from '../config/config.js';
 import { AuthProviderType } from '../config/config.js';
 import { GoogleCredentialProvider } from '../mcp/google-auth-provider.js';
 import { ServiceAccountImpersonationProvider } from '../mcp/sa-impersonation-provider.js';
@@ -778,15 +782,25 @@ async function handleAutomaticOAuth(
  *
  * @param mcpServerConfig The MCP server configuration
  * @param headers Additional headers
+ * @param sanitizationConfig Configuration for environment sanitization
  */
 function createTransportRequestInit(
   mcpServerConfig: MCPServerConfig,
   headers: Record<string, string>,
+  sanitizationConfig: EnvironmentSanitizationConfig,
 ): RequestInit {
+  const extensionEnv = getExtensionEnvironment(mcpServerConfig.extension);
+  const expansionEnv = { ...process.env, ...extensionEnv };
+
+  const sanitizedEnv = sanitizeEnvironment(expansionEnv, {
+    ...sanitizationConfig,
+    enableEnvironmentVariableRedaction: true,
+  });
+
   const expandedHeaders: Record<string, string> = {};
   if (mcpServerConfig.headers) {
     for (const [key, value] of Object.entries(mcpServerConfig.headers)) {
-      expandedHeaders[key] = expandEnvVars(value, process.env);
+      expandedHeaders[key] = expandEnvVars(value, sanitizedEnv);
     }
   }
 
@@ -826,12 +840,14 @@ function createAuthProvider(
  * @param mcpServerName The name of the MCP server
  * @param mcpServerConfig The MCP server configuration
  * @param accessToken The OAuth access token
+ * @param sanitizationConfig Configuration for environment sanitization
  * @returns The transport with OAuth token, or null if creation fails
  */
 async function createTransportWithOAuth(
   mcpServerName: string,
   mcpServerConfig: MCPServerConfig,
   accessToken: string,
+  sanitizationConfig: EnvironmentSanitizationConfig,
 ): Promise<StreamableHTTPClientTransport | SSEClientTransport | null> {
   try {
     const headers: Record<string, string> = {
@@ -840,7 +856,11 @@ async function createTransportWithOAuth(
     const transportOptions:
       | StreamableHTTPClientTransportOptions
       | SSEClientTransportOptions = {
-      requestInit: createTransportRequestInit(mcpServerConfig, headers),
+      requestInit: createTransportRequestInit(
+        mcpServerConfig,
+        headers,
+        sanitizationConfig,
+      ),
     };
 
     return createUrlTransport(mcpServerName, mcpServerConfig, transportOptions);
@@ -1435,13 +1455,15 @@ async function showAuthRequiredMessage(serverName: string): Promise<never> {
  * @param config The MCP server configuration
  * @param accessToken The OAuth access token to use
  * @param httpReturned404 Whether the HTTP transport returned 404 (indicating SSE-only server)
+ * @param sanitizationConfig Configuration for environment sanitization
  */
 async function retryWithOAuth(
   client: Client,
   serverName: string,
   config: MCPServerConfig,
   accessToken: string,
   httpReturned404: boolean,
+  sanitizationConfig: EnvironmentSanitizationConfig,
 ): Promise<void> {
   if (httpReturned404) {
     // HTTP returned 404, only try SSE
@@ -1462,6 +1484,7 @@ async function retryWithOAuth(
     serverName,
     config,
     accessToken,
+    sanitizationConfig,
   );
   if (!httpTransport) {
     throw new Error(
@@ -1741,6 +1764,7 @@ export async function connectToMcpServer(
             mcpServerConfig,
             accessToken,
             httpReturned404,
+            sanitizationConfig,
           );
           return mcpClient;
         } else {
@@ -1813,6 +1837,7 @@ export async function connectToMcpServer(
               mcpServerName,
               mcpServerConfig,
               accessToken,
+              sanitizationConfig,
             );
             if (!oauthTransport) {
               throw new Error(
@@ -1960,23 +1985,31 @@ export async function createTransport(
     const transportOptions:
       | StreamableHTTPClientTransportOptions
       | SSEClientTransportOptions = {
-      requestInit: createTransportRequestInit(mcpServerConfig, headers),
+      requestInit: createTransportRequestInit(
+        mcpServerConfig,
+        headers,
+        sanitizationConfig,
+      ),
       authProvider,
     };
 
     return createUrlTransport(mcpServerName, mcpServerConfig, transportOptions);
   }
 
   if (mcpServerConfig.command) {
+    const extensionEnv = getExtensionEnvironment(mcpServerConfig.extension);
+    const expansionEnv = { ...process.env, ...extensionEnv };
+
     // 1. Sanitize the base process environment to prevent unintended leaks of system-wide secrets.
-    const sanitizedEnv = sanitizeEnvironment(process.env, {
+    const sanitizedEnv = sanitizeEnvironment(expansionEnv, {
       ...sanitizationConfig,
       enableEnvironmentVariableRedaction: true,
     });
 
     const finalEnv: Record<string, string> = {
       [GEMINI_CLI_IDENTIFICATION_ENV_VAR]:
         GEMINI_CLI_IDENTIFICATION_ENV_VAR_VALUE,
+      ...extensionEnv,
     };
     for (const [key, value] of Object.entries(sanitizedEnv)) {
       if (value !== undefined) {
@@ -1987,7 +2020,7 @@ export async function createTransport(
     // Expand and merge explicit environment variables from the MCP configuration.
     if (mcpServerConfig.env) {
       for (const [key, value] of Object.entries(mcpServerConfig.env)) {
-        finalEnv[key] = expandEnvVars(value, process.env);
+        finalEnv[key] = expandEnvVars(value, expansionEnv);
       }
     }
 
@@ -2045,6 +2078,20 @@ interface NamedTool {
   name?: string;
 }
 
+function getExtensionEnvironment(
+  extension?: GeminiCLIExtension,
+): Record<string, string> {
+  const env: Record<string, string> = {};
+  if (extension?.resolvedSettings) {
+    for (const setting of extension.resolvedSettings) {
+      if (setting.value !== undefined) {
+        env[setting.envVar] = setting.value;
+      }
+    }
+  }
+  return env;
+}
+
 /** Visible for testing */
 export function isEnabled(
   funcDecl: NamedTool,