fix: prevent orphaned processes from consuming 100% CPU when terminal closes (#16965)

Co-authored-by: Tommaso Sciortino <sciortino@gmail.com>

packages/cli/src/utils/cleanup.ts

@@ -10,12 +10,14 @@ import {
   Storage,
   shutdownTelemetry,
   isTelemetrySdkInitialized,
+  ExitCodes,
 } from '@google/gemini-cli-core';
 import type { Config } from '@google/gemini-cli-core';
 
 const cleanupFunctions: Array<(() => void) | (() => Promise<void>)> = [];
 const syncCleanupFunctions: Array<() => void> = [];
 let configForTelemetry: Config | null = null;
+let isShuttingDown = false;
 
 export function registerCleanup(fn: (() => void) | (() => Promise<void>)) {
   cleanupFunctions.push(fn);
@@ -33,6 +35,7 @@ export function resetCleanupForTesting() {
   cleanupFunctions.length = 0;
   syncCleanupFunctions.length = 0;
   configForTelemetry = null;
+  isShuttingDown = false;
 }
 
 export function runSyncCleanup() {
@@ -100,6 +103,65 @@ async function drainStdin() {
   await new Promise((resolve) => setTimeout(resolve, 50));
 }
 
+/**
+ * Gracefully shuts down the process, ensuring cleanup runs exactly once.
+ * Guards against concurrent shutdown from signals (SIGHUP, SIGTERM, SIGINT)
+ * and TTY loss detection racing each other.
+ *
+ * @see https://github.com/google-gemini/gemini-cli/issues/15874
+ */
+async function gracefulShutdown(_reason: string) {
+  if (isShuttingDown) {
+    return;
+  }
+  isShuttingDown = true;
+
+  await runExitCleanup();
+  process.exit(ExitCodes.SUCCESS);
+}
+
+export function setupSignalHandlers() {
+  process.on('SIGHUP', () => gracefulShutdown('SIGHUP'));
+  process.on('SIGTERM', () => gracefulShutdown('SIGTERM'));
+  process.on('SIGINT', () => gracefulShutdown('SIGINT'));
+}
+
+export function setupTtyCheck(): () => void {
+  let intervalId: ReturnType<typeof setInterval> | null = null;
+  let isCheckingTty = false;
+
+  intervalId = setInterval(async () => {
+    if (isCheckingTty || isShuttingDown) {
+      return;
+    }
+
+    if (process.env['SANDBOX']) {
+      return;
+    }
+
+    if (!process.stdin.isTTY && !process.stdout.isTTY) {
+      isCheckingTty = true;
+
+      if (intervalId) {
+        clearInterval(intervalId);
+        intervalId = null;
+      }
+
+      await gracefulShutdown('TTY loss');
+    }
+  }, 5000);
+
+  // Don't keep the process alive just for this interval
+  intervalId.unref();
+
+  return () => {
+    if (intervalId) {
+      clearInterval(intervalId);
+      intervalId = null;
+    }
+  };
+}
+
 export async function cleanupCheckpoints() {
   const storage = new Storage(process.cwd());
   await storage.initialize();