feat: Add agent detection via env vars and tag GA4 with user property agent (#9070)

Add agent detection via env vars and tag GA4 with user property agent. Supported signals:

- CODEX_SANDBOX -> codex_cli
- CLAUDECODE -> claude_code
- GEMINI_CLI -> gemini_cli
- CURSOR_AGENT -> cursor
- OPENCODE -> open_code

Author: taeold

CHANGELOG.md

@@ -1,3 +1,4 @@
 - Support auth token JSON in `dataconnect_execute` MPC tool. (#9046)
 - Fixed the bugs when MCP tools cannot connect to emulator due to CLI version mis-matched. (#9068)
 - Fix bug when `firebase dataconnect:sdk:generate --watch` swallow all logs. (#9055)
+- Add GA4 agent user property to tag CLI usage by coding agents. (#9070)

src/track.ts

@@ -7,6 +7,16 @@ import { logger } from "./logger";
 import { isFirebaseStudio } from "./env";
 const pkg = require("../package.json");
 
+// Detect if the CLI was invoked by a coding agent, based on well-known env vars.
+function detectAIAgent(): string {
+  if (process.env.CODEX_SANDBOX) return "codex_cli";
+  if (process.env.CLAUDECODE) return "claude_code";
+  if (process.env.GEMINI_CLI) return "gemini_cli";
+  if (process.env.CURSOR_AGENT) return "cursor";
+  if (process.env.OPENCODE) return "open_code";
+  return "unknown";
+}
+
 type cliEventNames =
   | "command_execution"
   | "product_deploy"
@@ -85,6 +95,9 @@ const GA4_USER_PROPS = {
   is_firebase_studio: {
     value: isFirebaseStudio().toString(),
   },
+  ai_agent: {
+    value: detectAIAgent(),
+  },
 };
 
 export interface AnalyticsParams {