feat: use userTimezone as default for cron schedules

Fixes #3318

Previously, cron schedules without an explicit `tz` field would use
the system timezone, which could cause confusion if the server is in
a different timezone than the user.

Now, `agents.defaults.userTimezone` from the config is used as the
default timezone for cron schedule computations when the schedule
doesn't specify its own `tz`.

Changes:
- Added `defaultTimezone` option to `computeNextRunAtMs()`
- Added `defaultTimezone` to `CronServiceDeps`
- Gateway passes `userTimezone` from config to cron service
- All job computations now respect the default timezone

src/cron/schedule.ts

@@ -1,7 +1,16 @@
 import { Cron } from "croner";
 import type { CronSchedule } from "./types.js";
 
-export function computeNextRunAtMs(schedule: CronSchedule, nowMs: number): number | undefined {
+export type ComputeNextRunOpts = {
+  /** Default timezone to use when schedule.tz is not specified. */
+  defaultTimezone?: string;
+};
+
+export function computeNextRunAtMs(
+  schedule: CronSchedule,
+  nowMs: number,
+  opts?: ComputeNextRunOpts,
+): number | undefined {
   if (schedule.kind === "at") {
     return schedule.atMs > nowMs ? schedule.atMs : undefined;
   }
@@ -17,8 +26,10 @@ export function computeNextRunAtMs(schedule: CronSchedule, nowMs: number): numbe
 
   const expr = schedule.expr.trim();
   if (!expr) return undefined;
+  // Use schedule.tz if specified, otherwise fall back to default timezone
+  const timezone = schedule.tz?.trim() || opts?.defaultTimezone?.trim() || undefined;
   const cron = new Cron(expr, {
-    timezone: schedule.tz?.trim() || undefined,
+    timezone,
     catch: false,
   });
   const next = cron.nextRun(new Date(nowMs));

src/cron/service/jobs.ts

@@ -33,19 +33,24 @@ export function findJobOrThrow(state: CronServiceState, id: string) {
   return job;
 }
 
-export function computeJobNextRunAtMs(job: CronJob, nowMs: number): number | undefined {
+export function computeJobNextRunAtMs(
+  job: CronJob,
+  nowMs: number,
+  opts?: { defaultTimezone?: string },
+): number | undefined {
   if (!job.enabled) return undefined;
   if (job.schedule.kind === "at") {
     // One-shot jobs stay due until they successfully finish.
     if (job.state.lastStatus === "ok" && job.state.lastRunAtMs) return undefined;
     return job.schedule.atMs;
   }
-  return computeNextRunAtMs(job.schedule, nowMs);
+  return computeNextRunAtMs(job.schedule, nowMs, { defaultTimezone: opts?.defaultTimezone });
 }
 
 export function recomputeNextRuns(state: CronServiceState) {
   if (!state.store) return;
   const now = state.deps.nowMs();
+  const defaultTimezone = state.deps.defaultTimezone;
   for (const job of state.store.jobs) {
     if (!job.state) job.state = {};
     if (!job.enabled) {
@@ -61,7 +66,7 @@ export function recomputeNextRuns(state: CronServiceState) {
       );
       job.state.runningAtMs = undefined;
     }
-    job.state.nextRunAtMs = computeJobNextRunAtMs(job, now);
+    job.state.nextRunAtMs = computeJobNextRunAtMs(job, now, { defaultTimezone });
   }
 }
 
@@ -77,6 +82,7 @@ export function nextWakeAtMs(state: CronServiceState) {
 
 export function createJob(state: CronServiceState, input: CronJobCreate): CronJob {
   const now = state.deps.nowMs();
+  const defaultTimezone = state.deps.defaultTimezone;
   const id = crypto.randomUUID();
   const job: CronJob = {
     id,
@@ -97,7 +103,7 @@ export function createJob(state: CronServiceState, input: CronJobCreate): CronJo
     },
   };
   assertSupportedJobSpec(job);
-  job.state.nextRunAtMs = computeJobNextRunAtMs(job, now);
+  job.state.nextRunAtMs = computeJobNextRunAtMs(job, now, { defaultTimezone });
   return job;
 }
 

src/cron/service/state.ts

@@ -24,6 +24,8 @@ export type CronServiceDeps = {
   log: Logger;
   storePath: string;
   cronEnabled: boolean;
+  /** Default timezone (IANA) for cron schedules that don't specify their own. */
+  defaultTimezone?: string;
   enqueueSystemEvent: (text: string, opts?: { agentId?: string }) => void;
   requestHeartbeatNow: (opts?: { reason?: string }) => void;
   runHeartbeatOnce?: (opts?: { reason?: string }) => Promise<HeartbeatRunResult>;

src/gateway/server-cron.ts

@@ -43,9 +43,13 @@ export function buildGatewayCronService(params: {
     return { agentId, cfg: runtimeConfig };
   };
 
+  // Use userTimezone from config as default for cron schedules
+  const defaultTimezone = params.cfg.agents?.defaults?.userTimezone;
+
   const cron = new CronService({
     storePath,
     cronEnabled,
+    defaultTimezone,
     enqueueSystemEvent: (text, opts) => {
       const { agentId, cfg: runtimeConfig } = resolveCronAgent(opts?.agentId);
       const sessionKey = resolveAgentMainSessionKey({