Cron: guard missing expr in schedule parsing

src/cron/service/jobs.schedule-error-isolation.test.ts

@@ -186,4 +186,19 @@ describe("cron schedule error isolation", () => {
     expect(badJob.state.lastError).toMatch(/^schedule error:/);
     expect(badJob.state.lastError).toBeTruthy();
   });
+
+  it("records a clear schedule error when cron expr is missing", () => {
+    const badJob = createJob({
+      id: "missing-expr",
+      name: "Missing Expr",
+      schedule: { kind: "cron" } as unknown as CronJob["schedule"],
+    });
+    const state = createMockState([badJob]);
+
+    recomputeNextRuns(state);
+
+    expect(badJob.state.lastError).toContain("invalid cron schedule: expr is required");
+    expect(badJob.state.lastError).not.toContain("Cannot read properties of undefined");
+    expect(badJob.state.scheduleErrorCount).toBe(1);
+  });
 });