# Scheduling Schedule tasks to run in the future — whether that's seconds from now, at a specific date/time, or on a recurring cron schedule. Scheduled tasks survive agent restarts and are persisted to SQLite. ## Overview The scheduling system supports four modes: | Mode | Syntax | Use Case | | ------------- | ----------------------------------- | ------------------------- | | **Delayed** | `this.schedule(60, ...)` | Run in 60 seconds | | **Scheduled** | `this.schedule(new Date(...), ...)` | Run at specific time | | **Cron** | `this.schedule("0 8 * * *", ...)` | Run on recurring schedule | | **Interval** | `this.scheduleEvery(30, ...)` | Run every 30 seconds | Under the hood, scheduling uses [Durable Object alarms](https://developers.cloudflare.com/durable-objects/api/alarms/) to wake the agent at the right time. Tasks are stored in a SQLite table and executed in order. ## Quick Start ```typescript import { Agent } from "agents"; export class ReminderAgent extends Agent { async onRequest(request: Request) { const url = new URL(request.url); // Schedule in 30 seconds await this.schedule(30, "sendReminder", { message: "Check your email" }); // Schedule at specific time await this.schedule(new Date("2025-02-01T09:00:00Z"), "sendReminder", { message: "Monthly report due" }); // Schedule recurring (every day at 8am) await this.schedule("0 8 * * *", "dailyDigest", { userId: url.searchParams.get("userId") }); return new Response("Scheduled!"); } async sendReminder(payload: { message: string }) { console.log(`Reminder: ${payload.message}`); // Send notification, email, etc. } async dailyDigest(payload: { userId: string }) { console.log(`Sending daily digest to ${payload.userId}`); // Generate and send digest } } ``` ## Scheduling Modes ### Delayed Execution Pass a number to schedule a task to run after a delay in **seconds**: ```typescript // Run in 10 seconds await this.schedule(10, "processTask", { taskId: "123" }); // Run in 5 minutes (300 seconds) await this.schedule(300, "sendFollowUp", { email: "user@example.com" }); // Run in 1 hour await this.schedule(3600, "checkStatus", { orderId: "abc" }); ``` **Use cases:** - Debouncing rapid events - Delayed notifications ("You left items in your cart") - Retry with backoff - Rate limiting ### Scheduled Execution Pass a `Date` object to schedule a task at a specific time: ```typescript // Run tomorrow at noon const tomorrow = new Date(); tomorrow.setDate(tomorrow.getDate() + 1); tomorrow.setHours(12, 0, 0, 0); await this.schedule(tomorrow, "sendReminder", { message: "Meeting time!" }); // Run at a specific timestamp await this.schedule(new Date("2025-06-15T14:30:00Z"), "triggerEvent", { eventId: "conference-2025" }); // Run in 2 hours using Date math const twoHoursFromNow = new Date(Date.now() + 2 * 60 * 60 * 1000); await this.schedule(twoHoursFromNow, "checkIn", {}); ``` **Use cases:** - Appointment reminders - Deadline notifications - Scheduled content publishing - Time-based triggers ### Recurring (Cron) Pass a cron expression string for recurring schedules: ```typescript // Every day at 8:00 AM await this.schedule("0 8 * * *", "dailyReport", {}); // Every hour await this.schedule("0 * * * *", "hourlyCheck", {}); // Every Monday at 9:00 AM await this.schedule("0 9 * * 1", "weeklySync", {}); // Every 15 minutes await this.schedule("*/15 * * * *", "pollForUpdates", {}); // First day of every month at midnight await this.schedule("0 0 1 * *", "monthlyCleanup", {}); ``` **Cron syntax:** `minute hour day month weekday` | Field | Values | Special Characters | | ------------ | -------------- | ------------------ | | Minute | 0-59 | `*` `,` `-` `/` | | Hour | 0-23 | `*` `,` `-` `/` | | Day of Month | 1-31 | `*` `,` `-` `/` | | Month | 1-12 | `*` `,` `-` `/` | | Day of Week | 0-6 (0=Sunday) | `*` `,` `-` `/` | **Common patterns:** ```typescript "* * * * *"; // Every minute "*/5 * * * *"; // Every 5 minutes "0 * * * *"; // Every hour (on the hour) "0 0 * * *"; // Every day at midnight "0 8 * * 1-5"; // Weekdays at 8am "0 0 * * 0"; // Every Sunday at midnight "0 0 1 * *"; // First of every month ``` **Use cases:** - Daily/weekly reports - Periodic cleanup jobs - Polling external services - Health checks - Subscription renewals ### Interval Use `scheduleEvery()` to run a task at fixed intervals (in seconds). Unlike cron, intervals support sub-minute precision and arbitrary durations: ```typescript // Poll every 30 seconds await this.scheduleEvery(30, "poll", { source: "api" }); // Health check every 45 seconds await this.scheduleEvery(45, "healthCheck", {}); // Sync every 90 seconds (1.5 minutes - can't be expressed in cron) await this.scheduleEvery(90, "syncData", { destination: "warehouse" }); ``` **Idempotency:** `scheduleEvery()` is idempotent on the combination of callback name, interval, and payload — calling it multiple times with the same arguments does not create duplicate schedules. This makes it safe to call in `onStart()`, which runs on every Durable Object wake: ```typescript class MyAgent extends Agent { async onStart() { // Safe: only one schedule is created, no matter how many times the DO wakes await this.scheduleEvery(30, "tick"); } async tick() { console.log("tick", new Date().toISOString()); } } ``` Calling `scheduleEvery()` with a different interval or payload creates a separate schedule, even for the same callback: ```typescript // First call creates one schedule await this.scheduleEvery(30, "poll"); // Second call with a different interval creates a second schedule await this.scheduleEvery(60, "poll"); // Two "poll" schedules exist: one every 30s and one every 60s // Third call with the same arguments as the first is a no-op await this.scheduleEvery(30, "poll"); // Still two schedules ``` Different callbacks also get their own independent schedules: ```typescript // These create two separate schedules (different callbacks) await this.scheduleEvery(30, "poll"); await this.scheduleEvery(30, "healthCheck"); ``` **Key differences from cron:** | Feature | Cron | Interval | | ------------------- | ------------------------------ | ---------------------- | | Minimum granularity | 1 minute | 1 second | | Arbitrary intervals | No (must fit cron pattern) | Yes | | Fixed schedule | Yes (e.g., "every day at 8am") | No (relative to start) | | Overlap prevention | No | Yes (built-in) | **Overlap prevention:** If a callback takes longer than the interval, the next execution is skipped (not queued). This prevents runaway resource usage: ```typescript class PollingAgent extends Agent { async poll() { // If this takes 45 seconds and interval is 30 seconds, // the next poll is skipped (with a warning logged) const data = await slowExternalApi(); await this.processData(data); } } // Set up 30-second interval await this.scheduleEvery(30, "poll", {}); ``` When a skip occurs, you'll see a warning in logs: ``` Skipping interval schedule abc123: previous execution still running ``` **Error resilience:** If the callback throws an error, the interval continues — only that execution fails: ```typescript async syncData() { // Even if this throws, the interval keeps running const response = await fetch("https://api.example.com/data"); if (!response.ok) throw new Error("Sync failed"); // ... } ``` **Use cases:** - Sub-minute polling (every 10, 30, 45 seconds) - Intervals that don't map to cron (every 90 seconds, every 7 minutes) - Rate-limited API polling with precise control - Real-time data synchronization ## Keeping the Agent Alive Durable Objects are evicted after a period of inactivity (typically 70-140 seconds with no incoming requests, WebSocket messages, or alarms). During long-running operations — streaming LLM responses, waiting on external APIs, running multi-step computations — the agent can be evicted mid-flight. `keepAlive()` prevents this by creating a 30-second heartbeat schedule that keeps the agent active until you are done: ```typescript const dispose = await this.keepAlive(); try { // Long-running work that must not be interrupted const result = await longRunningComputation(); await sendResults(result); } finally { dispose(); } ``` The returned disposer function cancels the heartbeat. Always call it when the work is done — otherwise the heartbeat continues indefinitely. ### keepAliveWhile() For scoped work, use `keepAliveWhile()` — it runs an async function and automatically cleans up the heartbeat when it completes (or throws): ```typescript const result = await this.keepAliveWhile(async () => { const data = await longRunningComputation(); return data; }); ``` This is the recommended approach since you cannot forget to dispose the heartbeat. ### How it works `keepAlive()` calls `scheduleEvery(30, "_cf_keepAliveHeartbeat")` under the hood. The internal `_cf_keepAliveHeartbeat` callback is a no-op — the alarm firing itself is what resets the inactivity timer. Because it uses the scheduling system: - The heartbeat does not conflict with your own schedules (the scheduling system multiplexes through a single alarm slot) - The heartbeat shows up in `getSchedules()` if you need to inspect it - Multiple concurrent `keepAlive()` calls each get their own schedule, so they do not interfere with each other ### Multiple concurrent callers Each `keepAlive()` call returns an independent disposer: ```typescript const dispose1 = await this.keepAlive(); const dispose2 = await this.keepAlive(); // Both heartbeats are active dispose1(); // Only cancels the first heartbeat // Agent is still alive via dispose2's heartbeat dispose2(); // Now the agent can go idle ``` ### AIChatAgent `AIChatAgent` automatically calls `keepAlive()` during streaming responses. You do not need to add it yourself when using `AIChatAgent` — every LLM stream is protected from idle eviction by default. ### When to use keepAlive() | Scenario | Use keepAlive()? | | ------------------------------------------- | -------------------------------------- | | Streaming LLM responses via `AIChatAgent` | No — already built in | | Long-running computation in a custom Agent | Yes | | Waiting on a slow external API call | Yes | | Multi-step tool execution | Yes | | Short request-response handlers | No — not needed | | Background work via scheduling or workflows | No — alarms already keep the DO active | > **Note:** `keepAlive()` is marked `@experimental` and may change between releases. ## Managing Schedules ### Get a Schedule Retrieve a scheduled task by its ID: ```typescript const schedule = await this.getSchedule(scheduleId); if (schedule) { console.log( `Task ${schedule.id} will run at ${new Date(schedule.time * 1000)}` ); console.log(`Callback: ${schedule.callback}`); console.log(`Type: ${schedule.type}`); // "scheduled" | "delayed" | "cron" | "interval" } else { console.log("Schedule not found"); } ``` ### List Schedules Query scheduled tasks with optional filters: ```typescript // Get all scheduled tasks const allSchedules = this.getSchedules(); // Get only cron jobs const cronJobs = this.getSchedules({ type: "cron" }); // Get tasks in the next hour const upcoming = this.getSchedules({ timeRange: { start: new Date(), end: new Date(Date.now() + 60 * 60 * 1000) } }); // Get a specific task by ID const specific = this.getSchedules({ id: "abc123" }); // Combine filters const upcomingCronJobs = this.getSchedules({ type: "cron", timeRange: { start: new Date(), end: new Date(Date.now() + 24 * 60 * 60 * 1000) } }); ``` ### Cancel a Schedule Remove a scheduled task before it executes: ```typescript const cancelled = await this.cancelSchedule(scheduleId); if (cancelled) { console.log("Schedule cancelled successfully"); } else { console.log("Schedule not found (may have already executed)"); } ``` **Example: Cancellable reminders** ```typescript class ReminderAgent extends Agent { async setReminder(userId: string, message: string, delaySeconds: number) { const schedule = await this.schedule(delaySeconds, "sendReminder", { userId, message }); // Store the schedule ID so user can cancel later this.sql` INSERT INTO user_reminders (user_id, schedule_id, message) VALUES (${userId}, ${schedule.id}, ${message}) `; return schedule.id; } async cancelReminder(scheduleId: string) { const cancelled = await this.cancelSchedule(scheduleId); if (cancelled) { this.sql`DELETE FROM user_reminders WHERE schedule_id = ${scheduleId}`; } return cancelled; } async sendReminder(payload: { userId: string; message: string }) { // Send the reminder... // Clean up the record this.sql`DELETE FROM user_reminders WHERE user_id = ${payload.userId}`; } } ``` ## The Schedule Object When you create or retrieve a schedule, you get a `Schedule` object: ```typescript type Schedule = { id: string; // Unique identifier callback: string; // Method name to call payload: T; // Data passed to the callback retry?: RetryOptions; // Retry options (if configured) time: number; // Unix timestamp (seconds) of next execution } & ( | { type: "scheduled" } // One-time at specific date | { type: "delayed"; delayInSeconds: number } // One-time after delay | { type: "cron"; cron: string } // Recurring (cron expression) | { type: "interval"; intervalSeconds: number } // Recurring (fixed interval) ); ``` **Example:** ```typescript const schedule = await this.schedule( 60, "myTask", { foo: "bar" }, { retry: { maxAttempts: 5 } } ); console.log(schedule); // { // id: "abc123xyz", // callback: "myTask", // payload: { foo: "bar" }, // retry: { maxAttempts: 5 }, // time: 1706745600, // type: "delayed", // delayInSeconds: 60 // } ``` ## Patterns ### Rescheduling from Callbacks For dynamic recurring schedules, schedule the next run from within the callback: ```typescript class PollingAgent extends Agent { async startPolling(intervalSeconds: number) { await this.schedule(intervalSeconds, "poll", { interval: intervalSeconds }); } async poll(payload: { interval: number }) { try { const data = await fetch("https://api.example.com/updates"); await this.processUpdates(await data.json()); } catch (error) { console.error("Polling failed:", error); } // Schedule the next poll (regardless of success/failure) await this.schedule(payload.interval, "poll", payload); } async stopPolling() { // Cancel all polling schedules const schedules = this.getSchedules({ type: "delayed" }); for (const schedule of schedules) { if (schedule.callback === "poll") { await this.cancelSchedule(schedule.id); } } } } ``` ### Retry on Failure For immediate retries (within seconds), use the built-in retry option: ```typescript // Retry up to 5 times with exponential backoff await this.schedule( 60, "processTask", { taskId: "123" }, { retry: { maxAttempts: 5 } } ); ``` For longer recovery windows (minutes or hours), combine `this.retry()` for immediate retries with scheduled retries for extended outages: ```typescript class RetryAgent extends Agent { async attemptTask(payload: { taskId: string; attempt: number; maxAttempts: number; }) { try { // Immediate retries for transient failures await this.retry(() => this.doWork(payload.taskId), { maxAttempts: 3 }); console.log( `Task ${payload.taskId} succeeded on attempt ${payload.attempt}` ); } catch (error) { if (payload.attempt >= payload.maxAttempts) { console.error( `Task ${payload.taskId} failed after ${payload.maxAttempts} attempts` ); return; } // Schedule a retry in the future for longer outages const delaySeconds = Math.pow(2, payload.attempt) * 60; await this.schedule(delaySeconds, "attemptTask", { ...payload, attempt: payload.attempt + 1 }); console.log(`Scheduled retry in ${delaySeconds}s`); } } async doWork(taskId: string) { // Your actual work here } } ``` See [Retries](./retries.md) for full documentation on retry options and patterns. ### Self-Destructing Agents You can safely call `this.destroy()` from within a scheduled callback: ```typescript class TemporaryAgent extends Agent { async onStart() { // Self-destruct in 24 hours await this.schedule(24 * 60 * 60, "cleanup", {}); } async cleanup() { // Perform final cleanup console.log("Agent lifetime expired, cleaning up..."); // This is safe to call from a scheduled callback await this.destroy(); } } ``` ### Timezone-Aware Scheduling JavaScript Dates are UTC by default. For timezone-aware scheduling: ```typescript class TimezoneAgent extends Agent { async scheduleForTimezone( hour: number, minute: number, timezone: string, callback: keyof this ) { // Create a date in the target timezone const now = new Date(); const formatter = new Intl.DateTimeFormat("en-US", { timeZone: timezone, year: "numeric", month: "2-digit", day: "2-digit", hour: "2-digit", minute: "2-digit", hour12: false }); // Parse and construct target time const targetDate = new Date( now.toLocaleString("en-US", { timeZone: timezone }) ); targetDate.setHours(hour, minute, 0, 0); // If time already passed today, schedule for tomorrow if (targetDate <= now) { targetDate.setDate(targetDate.getDate() + 1); } return this.schedule(targetDate, callback, { timezone }); } } ``` ## AI-Assisted Scheduling The SDK includes utilities for parsing natural language scheduling requests with AI. ### getSchedulePrompt() Returns a system prompt for parsing natural language into scheduling parameters: ```typescript import { getSchedulePrompt, scheduleSchema } from "agents"; import { generateObject } from "ai"; import { openai } from "@ai-sdk/openai"; class SmartScheduler extends Agent { async parseScheduleRequest(userInput: string) { const result = await generateObject({ model: openai("gpt-4o"), system: getSchedulePrompt({ date: new Date() }), prompt: userInput, schema: scheduleSchema }); return result.object; } async handleUserRequest(input: string) { // Parse: "remind me to call mom tomorrow at 3pm" const parsed = await this.parseScheduleRequest(input); // parsed = { // description: "call mom", // when: { // type: "scheduled", // date: "2025-01-30T15:00:00Z" // } // } if (parsed.when.type === "scheduled" && parsed.when.date) { await this.schedule(new Date(parsed.when.date), "sendReminder", { message: parsed.description }); } else if (parsed.when.type === "delayed" && parsed.when.delayInSeconds) { await this.schedule(parsed.when.delayInSeconds, "sendReminder", { message: parsed.description }); } else if (parsed.when.type === "cron" && parsed.when.cron) { await this.schedule(parsed.when.cron, "sendReminder", { message: parsed.description }); } } async sendReminder(payload: { message: string }) { console.log(`Reminder: ${payload.message}`); } } ``` ### scheduleSchema A Zod schema for validating parsed scheduling data: ```typescript import { scheduleSchema } from "agents"; // The schema uses a discriminated union on `when.type`: // { // description: string, // when: // | { type: "scheduled", date: string } // ISO 8601 date string // | { type: "delayed", delayInSeconds: number } // | { type: "cron", cron: string } // | { type: "no-schedule" } // } ``` When using this schema with OpenAI models via the AI SDK, you must pass `providerOptions: { openai: { strictJsonSchema: false } }` to `generateObject`. This is because the schema uses a discriminated union which is not compatible with OpenAI's strict structured outputs mode. ## Scheduling vs Queue vs Workflows | Feature | Queue | Scheduling | Workflows | | ------------------ | ------------------ | ----------------- | ------------------- | | **When** | Immediately (FIFO) | Future time | Future time | | **Execution** | Sequential | At scheduled time | Multi-step | | **Retries** | Automatic | Automatic | Automatic | | **Persistence** | SQLite | SQLite | Workflow engine | | **Recurring** | No | Yes (cron) | No (use scheduling) | | **Complex logic** | No | No | Yes | | **Human approval** | No | No | Yes | **Use Queue when:** - You need background processing without blocking the response - Tasks should run ASAP but don't need to block - Order matters (FIFO) **Use Scheduling when:** - Tasks need to run at a specific time - You need recurring jobs (cron) - Delayed execution (debouncing, retries) **Use Workflows when:** - Multi-step processes with dependencies - Automatic retries with backoff - Human-in-the-loop approvals - Long-running tasks (minutes to hours) ## API Reference ### schedule() ```typescript async schedule( when: Date | string | number, callback: keyof this, payload?: T, options?: { retry?: RetryOptions } ): Promise> ``` Schedule a task for future execution. **Parameters:** - `when` - When to execute: `number` (seconds delay), `Date` (specific time), or `string` (cron expression) - `callback` - Name of the method to call - `payload` - Data to pass to the callback (must be JSON-serializable) - `options.retry` - Optional retry configuration. See [Retries](./retries.md) for details. **Returns:** A `Schedule` object with the task details ### scheduleEvery() ```typescript async scheduleEvery( intervalSeconds: number, callback: keyof this, payload?: T, options?: { retry?: RetryOptions } ): Promise> ``` Schedule a task to run repeatedly at a fixed interval. **Parameters:** - `intervalSeconds` - Number of seconds between executions (must be > 0) - `callback` - Name of the method to call - `payload` - Data to pass to the callback (must be JSON-serializable) - `options.retry` - Optional retry configuration. See [Retries](./retries.md) for details. **Returns:** A `Schedule` object with `type: "interval"` **Behavior:** - **Idempotent on (callback, interval, payload)** — calling with the same callback, interval, and payload returns the existing schedule instead of creating a duplicate. A different interval or payload creates a new, independent schedule. - First execution occurs after `intervalSeconds` (not immediately) - If callback is still running when next execution is due, it's skipped (overlap prevention) - If callback throws an error, the interval continues - Cancel with `cancelSchedule(id)` to stop the entire interval ### getSchedule() ```typescript getSchedule(id: string): Schedule | undefined ``` Get a scheduled task by ID. This method is synchronous. ### getSchedules() ```typescript getSchedules(criteria?: { id?: string; type?: "scheduled" | "delayed" | "cron" | "interval"; timeRange?: { start?: Date; end?: Date }; }): Schedule[] ``` Get scheduled tasks matching the criteria. This method is synchronous. ### cancelSchedule() ```typescript async cancelSchedule(id: string): Promise ``` Cancel a scheduled task. Returns `true` if cancelled, `false` if not found. ### keepAlive() ```typescript async keepAlive(): Promise<() => void> ``` Create a 30-second heartbeat schedule that prevents the Durable Object from being evicted due to inactivity. Returns a disposer function that cancels the heartbeat when called. The disposer is idempotent — calling it multiple times is safe. See [Keeping the Agent Alive](#keeping-the-agent-alive) for usage details. ### keepAliveWhile() ```typescript async keepAliveWhile(fn: () => Promise): Promise ``` Run an async function while keeping the Durable Object alive. The heartbeat is automatically started before the function runs and stopped when it completes (whether it succeeds or throws). Returns the value returned by the function. This is the recommended way to use keepAlive — it guarantees cleanup. ## Limits - **Maximum tasks:** Limited by SQLite storage (each task is a row). Practical limit is tens of thousands per agent. - **Task size:** Each task (including payload) can be up to 2MB. - **Minimum delay:** 0 seconds (runs on next alarm tick) - **Cron precision:** Minute-level (not seconds) - **Interval precision:** Second-level - **Cron jobs:** After execution, automatically rescheduled for the next occurrence - **Interval jobs:** After execution, rescheduled for `now + intervalSeconds`; skipped if still running