Stateful activities

Stateful activities span multiple sessions. The client SDK tracks time per session via heartbeats, and the server records completion when the activity is truly done.

For info on shared concepts, see the Activity Tracking overview.

Architecture

Stateful activities split responsibility between frontend and backend:

Responsibility	Owner	Mechanism
Time tracking	Frontend or Backend	Heartbeats or `time: false`
State	Backend	Your app’s database
Completion	Backend	`timeback.activity.record()`

A runId ties all sessions together. The SDK generates one automatically when you call activity.start(), but you can also provide your own. Any unique string works. If your app already has a unique identifier for the activity attempt (e.g. an assignment row ID), pass it as runId directly instead of storing a separate value. On resume, pass the same runId so every heartbeat and the final completion event share the same identifier.

Frontend

The frontend tracks time per session and orchestrates the student’s workflow (starting, resuming, and submitting answers). But completion must come from the server: across multiple sessions, it’s the only part of the system that has the full picture of the student’s accumulated progress.

Starting a session

const activity = timeback.activity.start({
	id: 'lesson-1',
	name: 'Fractions',
	course: { subject: 'Math', grade: 3 },
})

// Your API — persist the runId so you can pass it back on resume
await saveProgress({ lessonId: 'lesson-1', runId: activity.runId })

See the reference for full parameter documentation including time options and callbacks.

Resuming a session

const progress = await loadProgress({ lessonId: 'lesson-1' })

const activity = timeback.activity.start({
	id: 'lesson-1',
	name: 'Fractions',
	course: { subject: 'Math', grade: 3 },
	runId: progress.runId, // reuse the saved runId
})

Ending a session

This is the key difference from single-session activities: the student can leave at any point — close the tab, navigate away, or simply stop for the day — without losing their progress. Calling activity.end() flushes the accumulated time but does not record a completion. The activity stays open, ready to be resumed later with the same runId.

await activity.end() // Flushes time, no completion

The frontend always calls activity.end() without metrics. Completion is recorded by the server.

Framework examples

React
Vue
Svelte
Solid

import { useEffect, useRef } from 'react'
import { useTimeback } from '@timeback/sdk/react'

function ResumableLesson({ lessonId, lessonName }) {
	const timeback = useTimeback()
	const activityRef = useRef(null)

	useEffect(() => {
		if (!timeback) return

		async function startTracking() {
			// Your API — load saved progress (if any)
			const res = await fetch(`/api/progress/${lessonId}`)
			const progress = await res.json()

			activityRef.current = timeback.activity.start({
				id: lessonId,
				name: lessonName,
				course: { subject: 'Math', grade: 3 },
				...(progress?.runId && { runId: progress.runId }),
			})

			// Your API — persist runId on first start
			if (!progress?.runId) {
				await fetch(`/api/progress/${lessonId}`, {
					method: 'POST',
					body: JSON.stringify({ runId: activityRef.current.runId }),
				})
			}
		}

		startTracking()

		return () => {
			// Flush time on unmount — server handles completion
			void activityRef.current?.end()
		}
	}, [timeback, lessonId, lessonName])

	return <div>Lesson content...</div>
}

<script setup>
import { onMounted, onUnmounted, ref } from 'vue'
import { useTimeback } from '@timeback/sdk/vue'

const props = defineProps(['lessonId', 'lessonName'])
const timeback = useTimeback()
const activity = ref(null)

onMounted(async () => {
	if (!timeback.value) return

	// Your API — load saved progress (if any)
	const res = await fetch(`/api/progress/${props.lessonId}`)
	const progress = await res.json()

	activity.value = timeback.value.activity.start({
		id: props.lessonId,
		name: props.lessonName,
		course: { subject: 'Math', grade: 3 },
		...(progress?.runId && { runId: progress.runId }),
	})

	// Your API — persist runId on first start
	if (!progress?.runId) {
		await fetch(`/api/progress/${props.lessonId}`, {
			method: 'POST',
			body: JSON.stringify({ runId: activity.value.runId }),
		})
	}
})

onUnmounted(() => {
	// Flush time on unmount — server handles completion
	void activity.value?.end()
})
</script>

<script>
	import { onMount, onDestroy } from 'svelte'
	import { timeback } from '@timeback/sdk/svelte'

	export let lessonId
	export let lessonName

	let activity

	onMount(async () => {
		if (!$timeback) return

		// Your API — load saved progress (if any)
		const res = await fetch(`/api/progress/${lessonId}`)
		const progress = await res.json()

		activity = $timeback.activity.start({
			id: lessonId,
			name: lessonName,
			course: { subject: 'Math', grade: 3 },
			...(progress?.runId && { runId: progress.runId }),
		})

		// Your API — persist runId on first start
		if (!progress?.runId) {
			await fetch(`/api/progress/${lessonId}`, {
				method: 'POST',
				body: JSON.stringify({ runId: activity.runId }),
			})
		}
	})

	onDestroy(() => {
		// Flush time on unmount — server handles completion
		void activity?.end()
	})
</script>

import { onMount, onCleanup } from 'solid-js'
import { useTimeback } from '@timeback/sdk/solid'

function ResumableLesson(props) {
	const timeback = useTimeback()
	let activity

	onMount(async () => {
		if (!timeback) return

		// Your API — load saved progress (if any)
		const res = await fetch(`/api/progress/${props.lessonId}`)
		const progress = await res.json()

		activity = timeback.activity.start({
			id: props.lessonId,
			name: props.lessonName,
			course: { subject: 'Math', grade: 3 },
			...(progress?.runId && { runId: progress.runId }),
		})

		// Your API — persist runId on first start
		if (!progress?.runId) {
			await fetch(`/api/progress/${props.lessonId}`, {
				method: 'POST',
				body: JSON.stringify({ runId: activity.runId }),
			})
		}
	})

	onCleanup(() => {
		// Flush time on unmount — server handles completion
		void activity?.end()
	})

	return <div>Lesson content...</div>
}

Server-managed time

If your server already tracks time (e.g. from request logs or its own session model), you can disable heartbeats entirely by passing time: false. The client still provides the activity.end() ergonomics, but no TimeSpentEvents are sent.

const activity = timeback.activity.start({
	id: 'lesson-1',
	name: 'Fractions',
	course: { subject: 'Math', grade: 3 },
	runId: progress.runId,
	time: false,
})

// No heartbeats during the session — end() closes the activity without sending time data
await activity.end()

When using time: false, the server must report time via the time parameter in timeback.activity.record(). Do not use both heartbeats and server-side time — this will double-count. See the server reference for details.

Backend

When a student completes an activity, as determined by your app’s logic, the backend records the result using timeback.activity.record(). This sends an ActivityCompletedEvent to the Caliper API and runs the full pipeline including gradebook and XP. Pass the same runId from the frontend to correlate heartbeats with the completion event.

See the reference for full parameter documentation.

await timeback.activity.record({
	user: { email: 'student@example.com' },
	activity: {
		id: 'lesson-1',
		name: 'Fractions',
		course: { code: 'MATH-3' },
	},
	metrics: {
		totalQuestions: 20,
		correctQuestions: 16,
		xpEarned: 150,
		masteredUnits: 2,
		pctComplete: 100,
	},
	runId: savedProgress.runId,
})

Only include time when the frontend uses time: false. If heartbeats are active (the default), the platform already has the time data — passing time here would double-count. See the full server reference for all parameters.

Best practices

Persist runId immediately after activity.start()

The runId is the correlation key between frontend heartbeats and backend completion. Save it to your database as soon as the activity starts.

Use a fresh runId for new attempts after completion

When a student starts a new attempt of a previously completed activity, do not reuse the old runId. Omit it from activity.start() to generate a fresh one — otherwise new heartbeats would be incorrectly correlated with the old completion event.

Only call activity.end() without args on the frontend

Completion should come from the backend via timeback.activity.record(). The frontend should always use activity.end() (no metrics) to flush time data only.

Next steps

Single-session activities

Simpler model for one-sitting activities

Reference

Full parameter and method reference

Identity

Authentication setup for resolving users

Getting Started

CLI

SDK

Reference

Architecture

Frontend

Starting a session

Resuming a session

Ending a session

Framework examples

Server-managed time

Backend

Best practices

Next steps

Single-session activities

Reference

Identity

Getting Started

CLI

SDK

Reference

​Architecture

​Frontend

​Starting a session

​Resuming a session

​Ending a session

​Framework examples

​Server-managed time

​Backend

​Best practices

​Next steps

Single-session activities

Reference

Identity

Architecture

Frontend

Starting a session

Resuming a session

Ending a session

Framework examples

Server-managed time

Backend

Best practices

Next steps