diff --git a/src/cron/service.issue-regressions.test.ts b/src/cron/service.issue-regressions.test.ts
index 1d727bea8..dd82b52ab 100644
--- a/src/cron/service.issue-regressions.test.ts
+++ b/src/cron/service.issue-regressions.test.ts
@@ -9,7 +9,13 @@ import { CronService } from "./service.js";
 import { createDeferred, createRunningCronServiceState } from "./service.test-harness.js";
 import { computeJobNextRunAtMs } from "./service/jobs.js";
 import { createCronServiceState, type CronEvent } from "./service/state.js";
-import { DEFAULT_JOB_TIMEOUT_MS, executeJobCore, onTimer, runMissedJobs } from "./service/timer.js";
+import {
+  DEFAULT_JOB_TIMEOUT_MS,
+  applyJobResult,
+  executeJobCore,
+  onTimer,
+  runMissedJobs,
+} from "./service/timer.js";
 import type { CronJob, CronJobState } from "./types.js";
 
 const noopLogger = {
@@ -1586,4 +1592,81 @@ describe("Cron issue regressions", () => {
     expect(job?.state.lastStatus).toBe("error");
     expect(job?.state.lastError).toContain("timed out");
   });
+
+  it("keeps state updates when cron next-run computation throws after a successful run (#30905)", () => {
+    const startedAt = Date.parse("2026-03-02T12:00:00.000Z");
+    const endedAt = startedAt + 50;
+    const state = createCronServiceState({
+      cronEnabled: true,
+      storePath: "/tmp/cron-30905-success.json",
+      log: noopLogger,
+      nowMs: () => endedAt,
+      enqueueSystemEvent: vi.fn(),
+      requestHeartbeatNow: vi.fn(),
+      runIsolatedAgentJob: createDefaultIsolatedRunner(),
+    });
+    const job = createIsolatedRegressionJob({
+      id: "apply-result-success-30905",
+      name: "apply-result-success-30905",
+      scheduledAt: startedAt,
+      schedule: { kind: "cron", expr: "0 7 * * *", tz: "Invalid/Timezone" },
+      payload: { kind: "agentTurn", message: "ping" },
+      state: { nextRunAtMs: startedAt - 1_000, runningAtMs: startedAt - 500 },
+    });
+
+    const shouldDelete = applyJobResult(state, job, {
+      status: "ok",
+      delivered: true,
+      startedAt,
+      endedAt,
+    });
+
+    expect(shouldDelete).toBe(false);
+    expect(job.state.runningAtMs).toBeUndefined();
+    expect(job.state.lastRunAtMs).toBe(startedAt);
+    expect(job.state.lastStatus).toBe("ok");
+    expect(job.state.scheduleErrorCount).toBe(1);
+    expect(job.state.lastError).toMatch(/^schedule error:/);
+    expect(job.state.nextRunAtMs).toBe(endedAt + 2_000);
+    expect(job.enabled).toBe(true);
+  });
+
+  it("falls back to backoff schedule when cron next-run computation throws on error path (#30905)", () => {
+    const startedAt = Date.parse("2026-03-02T12:05:00.000Z");
+    const endedAt = startedAt + 25;
+    const state = createCronServiceState({
+      cronEnabled: true,
+      storePath: "/tmp/cron-30905-error.json",
+      log: noopLogger,
+      nowMs: () => endedAt,
+      enqueueSystemEvent: vi.fn(),
+      requestHeartbeatNow: vi.fn(),
+      runIsolatedAgentJob: createDefaultIsolatedRunner(),
+    });
+    const job = createIsolatedRegressionJob({
+      id: "apply-result-error-30905",
+      name: "apply-result-error-30905",
+      scheduledAt: startedAt,
+      schedule: { kind: "cron", expr: "0 7 * * *", tz: "Invalid/Timezone" },
+      payload: { kind: "agentTurn", message: "ping" },
+      state: { nextRunAtMs: startedAt - 1_000, runningAtMs: startedAt - 500 },
+    });
+
+    const shouldDelete = applyJobResult(state, job, {
+      status: "error",
+      error: "synthetic failure",
+      startedAt,
+      endedAt,
+    });
+
+    expect(shouldDelete).toBe(false);
+    expect(job.state.runningAtMs).toBeUndefined();
+    expect(job.state.lastRunAtMs).toBe(startedAt);
+    expect(job.state.lastStatus).toBe("error");
+    expect(job.state.consecutiveErrors).toBe(1);
+    expect(job.state.scheduleErrorCount).toBe(1);
+    expect(job.state.lastError).toMatch(/^schedule error:/);
+    expect(job.state.nextRunAtMs).toBe(endedAt + 30_000);
+    expect(job.enabled).toBe(true);
+  });
 });
diff --git a/src/cron/service/jobs.ts b/src/cron/service/jobs.ts
index 8c602cd62..ed5f57d78 100644
--- a/src/cron/service/jobs.ts
+++ b/src/cron/service/jobs.ts
@@ -214,7 +214,7 @@ export function computeJobNextRunAtMs(job: CronJob, nowMs: number): number | und
 /** Maximum consecutive schedule errors before auto-disabling a job. */
 const MAX_SCHEDULE_ERRORS = 3;
 
-function recordScheduleComputeError(params: {
+export function recordScheduleComputeError(params: {
   state: CronServiceState;
   job: CronJob;
   err: unknown;
diff --git a/src/cron/service/timer.ts b/src/cron/service/timer.ts
index 4d38e7c33..9bf9d894e 100644
--- a/src/cron/service/timer.ts
+++ b/src/cron/service/timer.ts
@@ -15,6 +15,7 @@ import {
   computeJobNextRunAtMs,
   nextWakeAtMs,
   recomputeNextRunsForMaintenance,
+  recordScheduleComputeError,
   resolveJobPayloadTextForMain,
 } from "./jobs.js";
 import { locked } from "./locked.js";
@@ -356,7 +357,15 @@ export function applyJobResult(
     } else if (result.status === "error" && job.enabled) {
       // Apply exponential backoff for errored jobs to prevent retry storms.
       const backoff = errorBackoffMs(job.state.consecutiveErrors ?? 1);
-      const normalNext = computeJobNextRunAtMs(job, result.endedAt);
+      let normalNext: number | undefined;
+      try {
+        normalNext = computeJobNextRunAtMs(job, result.endedAt);
+      } catch (err) {
+        // If the schedule expression/timezone throws (croner edge cases),
+        // record the schedule error (auto-disables after repeated failures)
+        // and fall back to backoff-only schedule so the state update is not lost.
+        recordScheduleComputeError({ state, job, err });
+      }
       const backoffNext = result.endedAt + backoff;
       // Use whichever is later: the natural next run or the backoff delay.
       job.state.nextRunAtMs =
@@ -371,7 +380,15 @@ export function applyJobResult(
         "cron: applying error backoff",
       );
     } else if (job.enabled) {
-      const naturalNext = computeJobNextRunAtMs(job, result.endedAt);
+      let naturalNext: number | undefined;
+      try {
+        naturalNext = computeJobNextRunAtMs(job, result.endedAt);
+      } catch (err) {
+        // If the schedule expression/timezone throws (croner edge cases),
+        // record the schedule error (auto-disables after repeated failures)
+        // so a persistent throw doesn't cause a MIN_REFIRE_GAP_MS hot loop.
+        recordScheduleComputeError({ state, job, err });
+      }
       if (job.schedule.kind === "cron") {
         // Safety net: ensure the next fire is at least MIN_REFIRE_GAP_MS
         // after the current run ended.  Prevents spin-loops when the
@@ -399,6 +416,10 @@ function applyOutcomeToStoredJob(state: CronServiceState, result: TimedCronRunOu
   const jobs = store.jobs;
   const job = jobs.find((entry) => entry.id === result.jobId);
   if (!job) {
+    state.deps.log.warn(
+      { jobId: result.jobId },
+      "cron: applyOutcomeToStoredJob — job not found after forceReload, result discarded",
+    );
     return;
   }