feat(core): differentiate User-Agent for a2a-server and ACP clients

docs/cli/telemetry.md

@@ -45,6 +45,7 @@ Environment variables can override these settings.
 | `logPrompts`   | `GEMINI_TELEMETRY_LOG_PROMPTS`   | Include prompts in telemetry logs                   | `true`/`false`    | `true`                  |
 | `useCollector` | `GEMINI_TELEMETRY_USE_COLLECTOR` | Use external OTLP collector (advanced)              | `true`/`false`    | `false`                 |
 | `useCliAuth`   | `GEMINI_TELEMETRY_USE_CLI_AUTH`  | Use CLI credentials for telemetry (GCP target only) | `true`/`false`    | `false`                 |
+| -              | `GEMINI_CLI_SURFACE`             | Optional custom label for traffic reporting         | string            | -                       |
 
 **Note on boolean environment variables:** For boolean settings like `enabled`,
 setting the environment variable to `true` or `1` enables the feature.
@@ -216,6 +217,50 @@ recommend using file-based output for local development.
 For advanced local telemetry setups (such as Jaeger or Genkit), see the
 [Local development guide](../local-development.md#viewing-traces).
 
+## Client identification
+
+Gemini CLI includes identifiers in its `User-Agent` header to help you
+differentiate and report on API traffic from different environments (for
+example, identifying calls from Gemini Code Assist versus a standard terminal).
+
+### Automatic identification
+
+Most integrated environments are identified automatically without additional
+configuration. The identifier is included as a prefix to the `User-Agent` and as
+a "surface" tag in the parenthetical metadata.
+
+| Environment                         | User-Agent Prefix            | Surface Tag |
+| :---------------------------------- | :--------------------------- | :---------- |
+| **Gemini Code Assist (Agent Mode)** | `GeminiCLI-a2a-server`       | `vscode`    |
+| **Zed (via ACP)**                   | `GeminiCLI-acp-zed`          | `zed`       |
+| **XCode (via ACP)**                 | `GeminiCLI-acp-xcode`        | `xcode`     |
+| **IntelliJ IDEA (via ACP)**         | `GeminiCLI-acp-intellijidea` | `jetbrains` |
+| **Standard Terminal**               | `GeminiCLI`                  | `terminal`  |
+
+**Example User-Agent:**
+`GeminiCLI-a2a-server/0.34.0/gemini-pro (linux; x64; vscode)`
+
+### Custom identification
+
+You can provide a custom identifier for your own scripts or automation by
+setting the `GEMINI_CLI_SURFACE` environment variable. This is useful for
+tracking specific internal tools or distribution channels in your GCP logs.
+
+**macOS/Linux**
+
+```bash
+export GEMINI_CLI_SURFACE="my-custom-tool"
+```
+
+**Windows (PowerShell)**
+
+```powershell
+$env:GEMINI_CLI_SURFACE="my-custom-tool"
+```
+
+When set, the value appears at the end of the `User-Agent` parenthetical:
+`GeminiCLI/0.34.0/gemini-pro (linux; x64; my-custom-tool)`
+
 ## Logs, metrics, and traces
 
 This section describes the structure of logs, metrics, and traces generated by

docs/reference/configuration.md

@@ -1384,6 +1384,13 @@ the `advanced.excludedEnvVars` setting in your `settings.json` file.
   - Useful for shared compute environments or keeping CLI state isolated.
   - Example: `export GEMINI_CLI_HOME="/path/to/user/config"` (Windows
     PowerShell: `$env:GEMINI_CLI_HOME="C:\path\to\user\config"`)
+- **`GEMINI_CLI_SURFACE`**:
+  - Specifies a custom label to include in the `User-Agent` header for API
+    traffic reporting.
+  - This is useful for tracking specific internal tools or distribution
+    channels.
+  - Example: `export GEMINI_CLI_SURFACE="my-custom-tool"` (Windows PowerShell:
+    `$env:GEMINI_CLI_SURFACE="my-custom-tool"`)
 - **`GOOGLE_API_KEY`**:
   - Your Google Cloud API key.
   - Required for using Vertex AI in express mode.

packages/a2a-server/src/config/config.test.ts

@@ -91,6 +91,15 @@ describe('loadConfig', () => {
       expect(fetchAdminControlsOnce).not.toHaveBeenCalled();
     });
 
+    it('should pass clientName as a2a-server to Config', async () => {
+      await loadConfig(mockSettings, mockExtensionLoader, taskId);
+      expect(Config).toHaveBeenCalledWith(
+        expect.objectContaining({
+          clientName: 'a2a-server',
+        }),
+      );
+    });
+
     describe('when admin controls experiment is enabled', () => {
       beforeEach(() => {
         // We need to cast to any here to modify the mock implementation

packages/a2a-server/src/config/config.ts

@@ -62,6 +62,7 @@ export async function loadConfig(
 
   const configParams: ConfigParameters = {
     sessionId: taskId,
+    clientName: 'a2a-server',
     model: PREVIEW_GEMINI_MODEL,
     embeddingModel: DEFAULT_GEMINI_EMBEDDING_MODEL,
     sandbox: undefined, // Sandbox might not be relevant for a server-side agent

packages/cli/src/config/config.test.ts

@@ -3616,3 +3616,54 @@ describe('loadCliConfig mcpEnabled', () => {
     });
   });
 });
+
+describe('loadCliConfig acpMode and clientName', () => {
+  beforeEach(() => {
+    vi.resetAllMocks();
+    vi.mocked(os.homedir).mockReturnValue('/mock/home/user');
+    vi.stubEnv('GEMINI_API_KEY', 'test-api-key');
+    vi.spyOn(ExtensionManager.prototype, 'getExtensions').mockReturnValue([]);
+  });
+
+  afterEach(() => {
+    vi.unstubAllEnvs();
+  });
+
+  it('should set acpMode to true and detect clientName when --acp flag is used', async () => {
+    process.argv = ['node', 'script.js', '--acp'];
+    vi.stubEnv('TERM_PROGRAM', 'vscode');
+    const argv = await parseArguments(createTestMergedSettings());
+    const config = await loadCliConfig(
+      createTestMergedSettings(),
+      'test-session',
+      argv,
+    );
+    expect(config.getAcpMode()).toBe(true);
+    expect(config.getClientName()).toBe('acp-vscode');
+  });
+
+  it('should set acpMode to true but leave clientName undefined for generic terminals', async () => {
+    process.argv = ['node', 'script.js', '--acp'];
+    vi.stubEnv('TERM_PROGRAM', 'iTerm.app'); // Generic terminal
+    const argv = await parseArguments(createTestMergedSettings());
+    const config = await loadCliConfig(
+      createTestMergedSettings(),
+      'test-session',
+      argv,
+    );
+    expect(config.getAcpMode()).toBe(true);
+    expect(config.getClientName()).toBeUndefined();
+  });
+
+  it('should set acpMode to false and clientName to undefined by default', async () => {
+    process.argv = ['node', 'script.js'];
+    const argv = await parseArguments(createTestMergedSettings());
+    const config = await loadCliConfig(
+      createTestMergedSettings(),
+      'test-session',
+      argv,
+    );
+    expect(config.getAcpMode()).toBe(false);
+    expect(config.getClientName()).toBeUndefined();
+  });
+});

packages/cli/src/config/config.ts

@@ -40,6 +40,7 @@ import {
   type HookDefinition,
   type HookEventName,
   type OutputFormat,
+  detectIdeFromEnv,
 } from '@google/gemini-cli-core';
 import {
   type Settings,
@@ -710,8 +711,21 @@ export async function loadCliConfig(
     }
   }
 
+  const isAcpMode = !!argv.acp || !!argv.experimentalAcp;
+  let clientName: string | undefined = undefined;
+  if (isAcpMode) {
+    const ide = detectIdeFromEnv();
+    if (
+      ide &&
+      (ide.name !== 'vscode' || process.env['TERM_PROGRAM'] === 'vscode')
+    ) {
+      clientName = `acp-${ide.name}`;
+    }
+  }
+
   return new Config({
-    acpMode: !!argv.acp || !!argv.experimentalAcp,
+    acpMode: isAcpMode,
+    clientName,
     sessionId,
     clientVersion: await getVersion(),
     embeddingModel: DEFAULT_GEMINI_EMBEDDING_MODEL,

packages/core/src/config/config.ts

@@ -502,6 +502,7 @@ export interface PolicyUpdateConfirmationRequest {
 
 export interface ConfigParameters {
   sessionId: string;
+  clientName?: string;
   clientVersion?: string;
   embeddingModel?: string;
   sandbox?: SandboxConfig;
@@ -646,6 +647,7 @@ export class Config implements McpContext, AgentLoopContext {
   private readonly acknowledgedAgentsService: AcknowledgedAgentsService;
   private skillManager!: SkillManager;
   private _sessionId: string;
+  private readonly clientName: string | undefined;
   private clientVersion: string;
   private fileSystemService: FileSystemService;
   private trackerService?: TrackerService;
@@ -843,6 +845,7 @@ export class Config implements McpContext, AgentLoopContext {
 
   constructor(params: ConfigParameters) {
     this._sessionId = params.sessionId;
+    this.clientName = params.clientName;
     this.clientVersion = params.clientVersion ?? 'unknown';
     this.approvedPlanPath = undefined;
     this.embeddingModel =
@@ -1408,6 +1411,10 @@ export class Config implements McpContext, AgentLoopContext {
     return this.promptId;
   }
 
+  getClientName(): string | undefined {
+    return this.clientName;
+  }
+
   setSessionId(sessionId: string): void {
     this._sessionId = sessionId;
   }