Reject cron steps that would silently run hourly (#8607)

* fix(schedules): reject ignored numeric cron steps

* fix(schedules): preserve saved numeric steps during recovery

Reject unsupported numeric steps at create/update while keeping saved
schedules executable with their previous singleton cadence.

Co-authored-by: 见安 <73627805+Mar-garet@users.noreply.github.com>

---------

Co-authored-by: 见安 <73627805+Mar-garet@users.noreply.github.com>

packages/protocol/src/schedule/cron-expression.test.ts

@@ -13,6 +13,37 @@ describe("cron expression parser", () => {
     expect(cron.dayOfWeek.matches(0)).toBe(false);
   });
 
+  it("rejects a step after a standalone number", () => {
+    expect(validateCronExpression("0/15 * * * *")).toBe(
+      "Invalid cron minute step: use * or a range before /",
+    );
+  });
+
+  it.each([
+    ["5/1 * * * *", "minute"],
+    ["0,5/15 * * * *", "minute"],
+    ["* 1/2 * * *", "hour"],
+    ["* * 1/2 * *", "day-of-month"],
+    ["* * * 1/2 *", "month"],
+    ["* * * * 1/2", "day-of-week"],
+  ])("rejects ignored numeric steps in %s", (expression, field) => {
+    expect(validateCronExpression(expression)).toBe(
+      `Invalid cron ${field} step: use * or a range before /`,
+    );
+  });
+
+  it.each([
+    { expression: "*/15 * * * *", expected: [0, 15, 30, 45] },
+    { expression: "0-59/15 * * * *", expected: [0, 15, 30, 45] },
+    { expression: "5-59/15 * * * *", expected: [5, 20, 35, 50] },
+  ])("preserves supported steps in $expression", ({ expression, expected }) => {
+    const cron = parseCronExpression(expression);
+    const minutes = Array.from({ length: 60 }, (_, minute) => minute);
+    const matches = minutes.filter((minute) => cron.minute.matches(minute));
+
+    expect(matches).toEqual(expected);
+  });
+
   it("reports invalid expressions with server-facing copy", () => {
     expect(validateCronExpression("* * *")).toBe("Cron expressions must have 5 fields");
     expect(validateCronExpression("*/5/2 * * * *")).toBe("Invalid cron minute step");

packages/protocol/src/schedule/cron-expression.ts

@@ -90,6 +90,9 @@ function parseField(source: string, bounds: CronFieldBounds): CronFieldMatcher {
     if (!/^\d+$/.test(base)) {
       throw new Error(`Invalid cron ${bounds.name} value`);
     }
+    // COMPAT(cronNumericSteps): added in v0.12.0, remove after 2027-04-17 once
+    // persisted numeric steps are migrated. Validation rejects new numeric steps;
+    // existing schedules retain their historical singleton match.
     const value = Number.parseInt(base, 10);
     if (!Number.isInteger(value) || value < bounds.min || value > bounds.max) {
       throw new Error(`Invalid cron ${bounds.name} value`);
@@ -122,6 +125,12 @@ export function parseCronExpression(expression: string): ParsedCronExpression {
 export function validateCronExpression(expression: string): string | null {
   try {
     parseCronExpression(expression);
+    const fields = expression.trim().split(/\s+/);
+    for (const [index, field] of fields.entries()) {
+      if (field.split(",").some((part) => /^\d+\//.test(part))) {
+        return `Invalid cron ${CRON_FIELD_BOUNDS[index].name} step: use * or a range before /`;
+      }
+    }
     return null;
   } catch (error) {
     return error instanceof Error ? error.message : "Invalid cron expression";

packages/server/src/server/schedule/cron.ts

@@ -1,4 +1,7 @@
-import { parseCronExpression } from "@getpaseo/protocol/schedule/cron-expression";
+import {
+  parseCronExpression,
+  validateCronExpression,
+} from "@getpaseo/protocol/schedule/cron-expression";
 import type { ScheduleCadence } from "@getpaseo/protocol/schedule/types";
 
 interface CronDateParts {
@@ -78,7 +81,10 @@ function createCronDatePartsReader(timeZone: string | undefined): (date: Date) =
 
 export function validateScheduleCadence(cadence: ScheduleCadence): void {
   if (cadence.type === "cron") {
-    parseCronExpression(cadence.expression);
+    const error = validateCronExpression(cadence.expression);
+    if (error) {
+      throw new Error(error);
+    }
     if (cadence.timezone !== undefined) {
       assertValidTimeZone(cadence.timezone);
     }

packages/server/src/server/schedule/service.test.ts

@@ -2114,6 +2114,81 @@ describe("ScheduleService", () => {
     });
   });
 
+  test("rejects numeric cron steps when creating or updating a schedule", async () => {
+    const service = createScheduleService({
+      paseoHome: tempDir,
+      logger: createTestLogger(),
+      agentManager: new AgentManager({ logger: createTestLogger() }),
+      agentStorage,
+      providerSnapshotManager: NO_UNATTENDED_SCHEDULE_POLICY,
+      now: () => now,
+    });
+    const input = {
+      prompt: "Periodic check",
+      cadence: { type: "cron" as const, expression: "*/15 * * * *" },
+      target: {
+        type: "new-agent" as const,
+        config: { provider: "claude" as const, cwd: tempDir },
+      },
+      runOnCreate: false,
+    };
+
+    await expect(
+      service.create({ ...input, cadence: { type: "cron", expression: "0/15 * * * *" } }),
+    ).rejects.toThrow("Invalid cron minute step: use * or a range before /");
+    expect(await service.list()).toEqual([]);
+
+    const created = await service.create(input);
+    await expect(
+      service.update({ id: created.id, cadence: { type: "cron", expression: "0/15 * * * *" } }),
+    ).rejects.toThrow("Invalid cron minute step: use * or a range before /");
+    expect((await service.inspect(created.id)).cadence).toEqual(input.cadence);
+  });
+
+  test("recovers and runs numeric cron steps persisted by an older daemon", async () => {
+    const service = createScheduleService({
+      paseoHome: tempDir,
+      logger: createTestLogger(),
+      agentManager: new AgentManager({ logger: createTestLogger() }),
+      agentStorage,
+      providerSnapshotManager: NO_UNATTENDED_SCHEDULE_POLICY,
+      now: () => now,
+      runner: async () => ({ agentId: null, output: "ok" }),
+    });
+    const created = await service.create({
+      prompt: "Periodic check",
+      cadence: { type: "cron", expression: "0 * * * *" },
+      target: {
+        type: "new-agent",
+        config: { provider: "claude", cwd: tempDir },
+      },
+      runOnCreate: false,
+    });
+    const store = new ScheduleStore(join(tempDir, "schedules"), createTestLogger());
+    await store.update(created.id, (schedule) => ({
+      ...schedule,
+      cadence: { type: "cron", expression: "0/15 * * * *" },
+    }));
+
+    now = new Date("2026-01-01T03:10:00.000Z");
+    try {
+      await service.start();
+      await service.stop();
+      expect((await service.inspect(created.id)).nextRunAt).toBe("2026-01-01T04:00:00.000Z");
+
+      now = new Date("2026-01-01T04:00:00.000Z");
+      await service.tick();
+      const inspected = await service.inspect(created.id);
+      expect(inspected.cadence).toEqual({ type: "cron", expression: "0/15 * * * *" });
+      expect(inspected.status).toBe("active");
+      expect(inspected.nextRunAt).toBe("2026-01-01T05:00:00.000Z");
+      expect(inspected.runs).toHaveLength(1);
+      expect(inspected.runs[0]).toMatchObject({ status: "succeeded", output: "ok" });
+    } finally {
+      await service.stop();
+    }
+  });
+
   test("advances stale nextRunAt on daemon restart", async () => {
     const service1 = createScheduleService({
       paseoHome: tempDir,