feat: gstack-detach — run agent eval/bench jobs in their own session

Long agent-run jobs (30-60 min evals, benchmarks) die when the harness sends SIGTERM to a background task's process group on turn boundaries / monitor stops / interruptions (observed: 'script test:gate terminated by signal SIGTERM'). gstack-detach runs the command in a fresh session (python3 os.setsid, or setsid on Linux, nohup fallback) so a group SIGTERM can't reach it, and wraps it in caffeinate -i on macOS so idle-sleep can't kill it either. Returns immediately; caller polls the logfile. Secrets stay in env, never argv. The guard test pins the contract: the command runs in a different process group than the caller and outlives the launching shell. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
2026-06-17 23:30:09 +02:00 · 2026-06-11 23:05:59 -07:00
parent 0f165cbed0
commit d1fc21cbca
2 changed files with 122 additions and 0 deletions
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+/**
+ * gstack-detach — the SIGTERM-survival guard.
+ *
+ * Proves the wrapper runs its command in a DIFFERENT process group than the
+ * caller (so a group SIGTERM from the harness can't reach it) and that the
+ * command outlives the launching shell (returns immediately, completes later).
+ * This is the regression guard that keeps the eval-killer dead.
+ */
+import { describe, test, expect } from 'bun:test';
+import { spawnSync } from 'child_process';
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+
+const ROOT = path.resolve(import.meta.dir, '..');
+const DETACH = path.join(ROOT, 'bin', 'gstack-detach');
+
+function ownPgid(): string {
+  const r = spawnSync('ps', ['-o', 'pgid=', '-p', String(process.pid)], { encoding: 'utf-8' });
+  return (r.stdout || '').trim();
+}
+
+describe('gstack-detach', () => {
+  test('returns immediately and the command keeps running detached', () => {
+    const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'gstack-detach-'));
+    const log = path.join(dir, 'run.log');
+    const marker = path.join(dir, 'marker');
+    const pgidFile = path.join(dir, 'child.pgid');
+    try {
+      const started = Date.now();
+      // Child records its own pgid, sleeps past the launcher's return, then writes
+      // a marker — proving it ran to completion independently of this shell.
+      const cmd = `ps -o pgid= -p $$ | tr -d ' ' > '${pgidFile}'; sleep 2; echo ok > '${marker}'`;
+      const r = spawnSync(DETACH, [log, '--', 'bash', '-c', cmd], { encoding: 'utf-8', timeout: 10000 });
+      const elapsed = Date.now() - started;
+
+      expect(r.status).toBe(0);
+      expect(r.stdout).toMatch(/PID \d+ {2}LOG /);
+      // Non-blocking: the launcher returns well before the child's 2s sleep ends.
+      expect(elapsed).toBeLessThan(1500);
+
+      // Poll for the marker — the detached child finishes after the launcher exited.
+      let survived = false;
+      const deadline = Date.now() + 6000;
+      while (Date.now() < deadline) {
+        if (fs.existsSync(marker)) { survived = true; break; }
+        spawnSync('sleep', ['0.2']);
+      }
+      expect(survived).toBe(true);
+
+      // Detached: the child's process group differs from ours, so a group SIGTERM
+      // aimed at this process can't reach it.
+      const childPgid = fs.readFileSync(pgidFile, 'utf-8').trim();
+      expect(childPgid).not.toBe('');
+      expect(childPgid).not.toBe(ownPgid());
+    } finally {
+      fs.rmSync(dir, { recursive: true, force: true });
+    }
+  }, 15000);
+
+  test('rejects missing command (exit 2)', () => {
+    const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'gstack-detach-'));
+    try {
+      const r = spawnSync(DETACH, [path.join(dir, 'x.log')], { encoding: 'utf-8' });
+      expect(r.status).toBe(2);
+    } finally {
+      fs.rmSync(dir, { recursive: true, force: true });
+    }
+  });
+});