Vercel Workflow Bug

vercel/workflow#451

Issue

Locally, Workflows run perfectly! I can start, monitor, and cancel them with ease. However, in production, despite building, deploying, and even queueing the workflow run, the run forever stays in pending.

Furthermore, the Observability dashboard claims upwards of 200 of these 'runs' were completed... yet only ~4 ran and all 4 were cancelled by me; sample run IDs: wrun_01KC8624HSAREY1XYRTCC662C0, wrun_01KC850FCA27HC54FA6MJXVN2K, wrun_01KC85KKRR93AV2Q91AFNCZTSS, wrun_01KC850FBYTPXNRM4V96F0S2XH

In Runtime Logs, Vercel shows outgoing requests when I trigger the workflow, and they succeed:

POST
vercel-workflow.com/api/v1/runs/create
200

POST
vercel-queue.com/api/v2/messages
201

POST
vercel-workflow.com/api/v1/runs/create
200

POST
vercel-queue.com/api/v2/messages
201

Stack

• Latest React Router
• "rr-next-routes" (just fills out routes.ts for me)
• Latest Workflow SDK

Deployment

Check out the deployment at https://vercel-workflow-bug.vercel.app. Trigger as many workflows as you'd like via:

curl -X POST https://vercel-workflow-bug.vercel.app/api/start

Here's a production run ID: wrun_01KC9X1RQHC024Q8B8Y3VZ6NYT

Attempted Fixes

Attempt 1 (current impl. here)

Originally only debugging locally, my main goal was to ensure Workflow had access to the generated files (flow, step, and webhook.js). My stack is a bit different from a normal React Router 7 application, as I use a library that makes file-based routing feel more like Next.js.

Eventually, I added the routes to routes.ts:

const routes = [
    // Workflow DevKit routes
    route(".well-known/workflow/v1/flow", "./handlers/workflow/flow.js"),
    route(".well-known/workflow/v1/step", "./handlers/workflow/step.js"),
    route(".well-known/workflow/v1/webhook/:token", "./handlers/workflow/webhook.js"),
    ...nextRoutes({ ...pageRouterStyle, print: "tree" }),
];

and wrote 3 handler files:

// /app/handlers/workflow/flow.js (step is identical, just a different path)
import path from "path"
import { createRequire } from "module"

const require_cjs = createRequire(import.meta.url)
const flow = require_cjs(path.join(process.cwd(), ".well-known/workflow/v1/flow.js"))

export async function action({ request }) {
	return flow.POST(request)
}

export async function loader({ request }) {
	if (flow.GET) {
		return flow.GET(request)
	}
	return new Response("Method not allowed", { status: 405 })
}

// /app/handlers/workflow/webhook.js
import { resumeWebhook } from "workflow/api"

async function handler(request, params) {
	const token = params?.token
	
	if (!token) {
		return new Response("Missing token", { status: 400 })
	}

	try {
		const response = await resumeWebhook(token, request)
		return response
	} catch (error) {
		console.error("Error during resumeWebhook", error)
		return new Response(null, { status: 404 })
	}
}

export async function action({ request, params }) {
	return handler(request, params)
}

export async function loader({ request, params }) {
	return handler(request, params)
}

With this, all of my workflows began to work! (e.g.)

curl -X POST http://localhost:5173/api/start
> {"data":{"runId":"wrun_01KC9W9CMW84KCYHYNWMZD2ZJB","world":{"runs":{},"steps":{},"events":{},"hooks":{}}}}

// Workflow Logs
Starting test workflow
Random Step 1
Random Step 2
Step 1: test-0.9702199053237919@example.com; Step 2: 23 11

The test in the docs also passes:

"Start your server and verify routes respond:"
curl -X POST http://localhost:3000/.well-known/workflow/v1/flow
curl -X POST http://localhost:3000/.well-known/workflow/v1/step
curl -X POST http://localhost:3000/.well-known/workflow/v1/webhook/test

Other Attempts

I've read these docs extensively (https://useworkflow.dev/docs/how-it-works/framework-integrations#adapting-to-other-frameworks), and have tried:

• a Vite plugin that uses @swc/transform
• Using @swc/transform in the Workflow handlers
• Copying the Bun integration word for word
• Adding Nitro
• Copying "Adapting to Other Frameworks" line-for-line
• Copying the "Bun Example" nearly line-for-line

Note: In most, if not all, of these attempts, Workflow worked locally, but remained queued indefinitely in Vercel World.