fix(mcp): Ensure that stdio MCP server execution has the GEMINI_CLI=1 env variable populated. (#18832)

packages/core/src/services/shellExecutionService.ts

@@ -32,6 +32,18 @@ const { Terminal } = pkg;
 
 const MAX_CHILD_PROCESS_BUFFER_SIZE = 16 * 1024 * 1024; // 16MB
 
+/**
+ * An environment variable that is set for shell executions. This can be used
+ * by downstream executables and scripts to identify that they were executed
+ * from within Gemini CLI.
+ */
+export const GEMINI_CLI_IDENTIFICATION_ENV_VAR = 'GEMINI_CLI';
+
+/**
+ * The value of {@link GEMINI_CLI_IDENTIFICATION_ENV_VAR}
+ */
+export const GEMINI_CLI_IDENTIFICATION_ENV_VAR_VALUE = '1';
+
 // We want to allow shell outputs that are close to the context window in size.
 // 300,000 lines is roughly equivalent to a large context window, ensuring
 // we capture significant output from long-running commands.
@@ -302,7 +314,8 @@ export class ShellExecutionService {
         detached: !isWindows,
         env: {
           ...sanitizeEnvironment(process.env, sanitizationConfig),
-          GEMINI_CLI: '1',
+          [GEMINI_CLI_IDENTIFICATION_ENV_VAR]:
+            GEMINI_CLI_IDENTIFICATION_ENV_VAR_VALUE,
           TERM: 'xterm-256color',
           PAGER: 'cat',
           GIT_PAGER: 'cat',