fix(cron): use maintenance recompute after job execution to prevent 48h skip (#17852)

Root cause: after executing due jobs, onTimer called recomputeNextRuns()
which advances any past-due nextRunAtMs to the next occurrence. If a job
became due between findDueJobs and the post-execution locked block, its
nextRunAtMs would be silently advanced without execution — causing daily
schedules to jump 48h instead of 24h.

Fix: replace recomputeNextRuns with recomputeNextRunsForMaintenance in
the post-execution block. The maintenance variant only fills in missing
nextRunAtMs values and never overwrites existing (including past-due)
ones, ensuring no job runs are silently skipped.

Closes #17852

Signed-off-by: pierreeurope <pierre.europe@pm.me>

src/cron/service.issue-17852-daily-skip.test.ts

@@ -0,0 +1,101 @@
+import { describe, expect, it } from "vitest";
+import type { CronServiceState } from "./service/state.js";
+import type { CronJob } from "./types.js";
+import { recomputeNextRuns, recomputeNextRunsForMaintenance } from "./service/jobs.js";
+
+/**
+ * Regression test for issue #17852: daily cron jobs skip a day (48h jump).
+ *
+ * Root cause: onTimer's results-processing block used the full
+ * recomputeNextRuns which could silently advance a past-due nextRunAtMs
+ * for a job that became due between findDueJobs and the post-execution
+ * locked block — skipping that run and jumping 48h ahead.
+ *
+ * Fix: use recomputeNextRunsForMaintenance in the post-execution block,
+ * which only fills in missing nextRunAtMs values and never overwrites
+ * existing (including past-due) ones.
+ */
+describe("issue #17852 - daily cron jobs should not skip days", () => {
+  const HOUR_MS = 3_600_000;
+  const DAY_MS = 24 * HOUR_MS;
+
+  function createMockState(jobs: CronJob[], nowMs: number): CronServiceState {
+    return {
+      store: { version: 1, jobs },
+      running: false,
+      timer: null,
+      storeLoadedAtMs: nowMs,
+      deps: {
+        storePath: "/mock/path",
+        cronEnabled: true,
+        nowMs: () => nowMs,
+        log: {
+          debug: () => {},
+          info: () => {},
+          warn: () => {},
+          error: () => {},
+        } as never,
+      },
+    };
+  }
+
+  it("recomputeNextRunsForMaintenance should NOT advance past-due nextRunAtMs", () => {
+    // Simulate: job scheduled for 3:00 AM, timer processing happens at 3:00:01
+    // The job was NOT executed in this tick (e.g., it became due between
+    // findDueJobs and the post-execution block).
+    const threeAM = Date.parse("2026-02-16T03:00:00.000Z");
+    const now = threeAM + 1_000; // 3:00:01
+
+    const job: CronJob = {
+      id: "daily-job",
+      name: "daily 3am",
+      enabled: true,
+      schedule: { kind: "cron", expr: "0 3 * * *", tz: "UTC" },
+      payload: { kind: "systemEvent", text: "daily task" },
+      sessionTarget: "main",
+      createdAtMs: threeAM - DAY_MS,
+      updatedAtMs: threeAM - DAY_MS,
+      state: {
+        nextRunAtMs: threeAM, // Past-due by 1 second
+      },
+    };
+
+    const state = createMockState([job], now);
+    recomputeNextRunsForMaintenance(state);
+
+    // Maintenance should NOT touch existing past-due nextRunAtMs.
+    // The job should still be eligible for execution on the next timer tick.
+    expect(job.state.nextRunAtMs).toBe(threeAM);
+  });
+
+  it("full recomputeNextRuns WOULD silently advance past-due nextRunAtMs (the bug)", () => {
+    // This test documents the buggy behavior that caused #17852.
+    // The full recomputeNextRuns sees a past-due nextRunAtMs and advances it
+    // to the next occurrence WITHOUT executing the job.
+    const threeAM = Date.parse("2026-02-16T03:00:00.000Z");
+    const now = threeAM + 1_000; // 3:00:01
+
+    const job: CronJob = {
+      id: "daily-job",
+      name: "daily 3am",
+      enabled: true,
+      schedule: { kind: "cron", expr: "0 3 * * *", tz: "UTC" },
+      payload: { kind: "systemEvent", text: "daily task" },
+      sessionTarget: "main",
+      createdAtMs: threeAM - DAY_MS,
+      updatedAtMs: threeAM - DAY_MS,
+      state: {
+        nextRunAtMs: threeAM, // Past-due by 1 second
+      },
+    };
+
+    const state = createMockState([job], now);
+    recomputeNextRuns(state);
+
+    // The full recomputeNextRuns advances it to TOMORROW — skipping today's
+    // execution entirely.  This is the 48h jump bug: from the previous run
+    // (yesterday 3 AM) to the newly computed next run (tomorrow 3 AM).
+    const tomorrowThreeAM = threeAM + DAY_MS;
+    expect(job.state.nextRunAtMs).toBe(tomorrowThreeAM);
+  });
+});

src/cron/service/timer.ts

@@ -7,7 +7,6 @@ import { sweepCronRunSessions } from "../session-reaper.js";
 import {
   computeJobNextRunAtMs,
   nextWakeAtMs,
-  recomputeNextRuns,
   recomputeNextRunsForMaintenance,
   resolveJobPayloadTextForMain,
 } from "./jobs.js";
@@ -283,7 +282,12 @@ export async function onTimer(state: CronServiceState) {
           }
         }
 
-        recomputeNextRuns(state);
+        // Use maintenance-only recompute to avoid advancing past-due
+        // nextRunAtMs values that became due between findDueJobs and this
+        // locked block.  The full recomputeNextRuns would silently skip
+        // those jobs (advancing nextRunAtMs without execution), causing
+        // daily cron schedules to jump 48 h instead of 24 h (#17852).
+        recomputeNextRunsForMaintenance(state);
         await persist(state);
       });
     }