fix(cron): add spin-loop regression coverage

src/cron/service.issue-regressions.test.ts

@@ -2,7 +2,9 @@ import fs from "node:fs/promises";
 import os from "node:os";
 import path from "node:path";
 import { afterAll, afterEach, beforeAll, beforeEach, describe, expect, it, vi } from "vitest";
+import * as schedule from "./schedule.js";
 import { CronService } from "./service.js";
+import { computeJobNextRunAtMs } from "./service/jobs.js";
 import { createCronServiceState, type CronEvent } from "./service/state.js";
 import { onTimer } from "./service/timer.js";
 import type { CronJob, CronJobState } from "./types.js";
@@ -593,6 +595,87 @@ describe("Cron issue regressions", () => {
     expect(fireCount).toBe(1);
   });
 
+  it("enforces a minimum refire gap for second-granularity cron schedules (#17821)", async () => {
+    const store = await makeStorePath();
+    const scheduledAt = Date.parse("2026-02-15T13:00:00.000Z");
+
+    const cronJob: CronJob = {
+      id: "spin-gap-17821",
+      name: "second-granularity",
+      enabled: true,
+      createdAtMs: scheduledAt - 86_400_000,
+      updatedAtMs: scheduledAt - 86_400_000,
+      schedule: { kind: "cron", expr: "* * * * * *", tz: "UTC" },
+      sessionTarget: "isolated",
+      wakeMode: "next-heartbeat",
+      payload: { kind: "agentTurn", message: "pulse" },
+      delivery: { mode: "announce" },
+      state: { nextRunAtMs: scheduledAt },
+    };
+    await fs.writeFile(
+      store.storePath,
+      JSON.stringify({ version: 1, jobs: [cronJob] }, null, 2),
+      "utf-8",
+    );
+
+    let now = scheduledAt;
+    const state = createCronServiceState({
+      cronEnabled: true,
+      storePath: store.storePath,
+      log: noopLogger,
+      nowMs: () => now,
+      enqueueSystemEvent: vi.fn(),
+      requestHeartbeatNow: vi.fn(),
+      runIsolatedAgentJob: vi.fn(async () => {
+        now += 100;
+        return { status: "ok" as const, summary: "done" };
+      }),
+    });
+
+    await onTimer(state);
+
+    const job = state.store?.jobs.find((j) => j.id === "spin-gap-17821");
+    expect(job).toBeDefined();
+    const endedAt = now;
+    const minNext = endedAt + 2_000;
+    expect(job!.state.nextRunAtMs).toBeDefined();
+    expect(job!.state.nextRunAtMs).toBeGreaterThanOrEqual(minNext);
+  });
+
+  it("retries cron schedule computation from the next second when the first attempt returns undefined (#17821)", () => {
+    const scheduledAt = Date.parse("2026-02-15T13:00:00.000Z");
+    const cronJob: CronJob = {
+      id: "retry-next-second-17821",
+      name: "retry",
+      enabled: true,
+      createdAtMs: scheduledAt - 86_400_000,
+      updatedAtMs: scheduledAt - 86_400_000,
+      schedule: { kind: "cron", expr: "0 13 * * *", tz: "UTC" },
+      sessionTarget: "isolated",
+      wakeMode: "next-heartbeat",
+      payload: { kind: "agentTurn", message: "briefing" },
+      delivery: { mode: "announce" },
+      state: {},
+    };
+
+    const original = schedule.computeNextRunAtMs;
+    const spy = vi.spyOn(schedule, "computeNextRunAtMs");
+    try {
+      spy
+        .mockImplementationOnce(() => undefined)
+        .mockImplementation((sched, nowMs) => original(sched, nowMs));
+
+      const expected = original(cronJob.schedule, scheduledAt + 1_000);
+      expect(expected).toBeDefined();
+
+      const next = computeJobNextRunAtMs(cronJob, scheduledAt);
+      expect(next).toBe(expected);
+      expect(spy).toHaveBeenCalledTimes(2);
+    } finally {
+      spy.mockRestore();
+    }
+  });
+
   it("records per-job start time and duration for batched due jobs", async () => {
     const store = await makeStorePath();
     const dueAt = Date.parse("2026-02-06T10:05:01.000Z");