Workflow SDK vs Temporal

Temporal is a durable-execution platform with seven language SDKs and large-scale production use. Temporal and the Workflow SDK share the same core model of durable orchestration through event-sourced replay. The operational differences are where your code runs, how you version it, and how it streams to clients.

At a glance

What the limits mean in practice: Temporal caps payloads at 2 MB and event history at 51,200 events. A model context, tool transcript, or embedding batch that exceeds 2 MB requires external blob storage and claim-check plumbing. Long agent loops must use Continue-As-New before the history fills. The Vercel World limits (50 MB payloads, 2 GB of state per run, and no run or sleep caps) provide more space for contexts in the run itself.

The biggest difference: what you operate

Temporal Cloud manages the durable engine, but you still build, deploy, and scale a fleet of Workers that poll task queues and run your Workflow and Activity code. Those workers connect out to Temporal Cloud, typically over the public internet (AWS PrivateLink and Google Cloud Private Service Connect are available as same-region options). To make encrypted payloads readable in the Web UI, you must run a Codec Server.

With the Workflow SDK on Vercel, orchestration, execution, and observability are co-located on one platform with internal networking, and per-run E2E encryption is on by default with no codec server to run. There are no workers, task queues, or a control plane to operate. (Self-hosting via the Postgres World is the closest analog to running your own Temporal cluster.)

Versioning

This is where the two differ most in day-to-day risk. Because both replay code against history, changing workflow code mid-flight is the hazard.

• Temporal: Editing a workflow can produce a non-determinism error that breaks or stalls open executions. You can evolve workflows with patch APIs (patched() / GetVersion(), which accumulate patch branches) or Worker Versioning (Build IDs / Worker Deployments pin workflows to a build and keep the old worker fleet running until it drains). You must manage this process for every long-running workflow.
• Workflow SDK: Runs are pinned to the immutable deployment that started them. Shipping new code never touches in-flight runs because they keep replaying against the exact code they began on. Upgrading a run is explicit and opt-in (start it with deploymentId: 'latest', or self-restart at a checkpoint). This model requires no patch branches or draining worker fleets.

AI agents and streaming

Both target AI agents, but the integration depth differs. The Workflow SDK's WorkflowAgent is a first-class construct inside the AI SDK (@ai-sdk/workflow): the agent loop becomes a durable workflow, each tool execute marked "use step" is an auto-retried durable step, and partial output streams through durable, resumable streams that survive reconnects and cold starts.

Temporal ships a first-party @temporalio/ai-sdk plugin and a "Workflow Streams" library, but both are Public Preview, and streaming is built on Signals/Updates: every chunk is written to history, so it's batched rather than per-token.

Migrating from Temporal

The model maps closely. Keep your orchestration logic; drop the workers, task queues, and activity modules.

A minimal translation, where the orchestrator loses proxyActivities and becomes plain TypeScript:

export async function processOrder(orderId: string) {
  'use workflow';
  await chargePayment(orderId);
  return { orderId, status: 'completed' };
}

async function chargePayment(orderId: string) {
  'use step';
  await fetch(`https://example.com/api/orders/${orderId}/charge`, { method: 'POST' });
}

Signals become hooks, where one createHook() + await replaces a signal definition, handler, and condition() guard:

import { createHook } from 'workflow';

export async function refundWorkflow(refundId: string) {
  'use workflow';
  using approval = createHook<{ approved: boolean }>({
    token: `refund:${refundId}:approval`,
  });
  const { approved } = await approval; // suspends durably until resumed
  return { refundId, approved };
}

npx skills add https://github.com/vercel/workflow --skill migrating-to-workflow-sdk

Temporal features without a direct Workflow SDK equivalent

Each row is a Temporal capability the Workflow SDK does not replicate one-to-one, paired with how to cover it on the Workflow SDK side:

Compiled from public documentation. Verify current Temporal pricing, limits, and preview-feature status against temporal.io/docs. Not based on head-to-head benchmarks.