# Vercel Functions

> Vercel Functions expert guidance — Serverless Functions, Edge Functions, Fluid Compute, streaming, Cron Jobs, and runtime configuration. Use when configuring, debugging, or optimizing server-side code running on Vercel.

- **Type:** Skill
- **Install:** `agentstack add skill-build-with-dhiraj-ai-workflow-framework-portability-kit-vercel-functions`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [build-with-dhiraj](https://agentstack.voostack.com/s/build-with-dhiraj)
- **Installs:** 0
- **Category:** [Cloud & Infrastructure](https://agentstack.voostack.com/c/cloud-infrastructure)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [build-with-dhiraj](https://github.com/build-with-dhiraj)
- **Source:** https://github.com/build-with-dhiraj/ai-workflow-framework-portability-kit/tree/main/Plugins/vercel-marketplace-source/skills/vercel-functions

## Install

```sh
agentstack add skill-build-with-dhiraj-ai-workflow-framework-portability-kit-vercel-functions
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Vercel Functions

You are an expert in Vercel Functions — the compute layer of the Vercel platform.

## Function Types

### Serverless Functions (Node.js)
- Full Node.js runtime, all npm packages available
- Default for Next.js API routes, Server Actions, Server Components
- Cold starts: 800ms–2.5s (with DB connections)
- Max duration: 10s (Hobby), 300s (Pro default), 800s (Fluid Compute Pro/Enterprise)

```ts
// app/api/hello/route.ts
export async function GET() {
  return Response.json({ message: 'Hello from Node.js' })
}
```

### Edge Functions (V8 Isolates)
- Lightweight V8 runtime, Web Standard APIs only
- Ultra-low cold starts ( {
    await processAnalytics(data)
    await sendNotification(data)
  })

  return response
}
```

### Next.js `after` (equivalent)

```ts
import { after } from 'next/server'

export async function POST(req: Request) {
  const data = await req.json()

  after(async () => {
    await logToAnalytics(data)
  })

  return Response.json({ ok: true })
}
```

## Streaming

Zero-config streaming for both runtimes. Essential for AI applications.

```ts
export async function POST(req: Request) {
  const encoder = new TextEncoder()
  const stream = new ReadableStream({
    async start(controller) {
      for (const chunk of data) {
        controller.enqueue(encoder.encode(chunk))
        await new Promise(r => setTimeout(r, 100))
      }
      controller.close()
    },
  })

  return new Response(stream, {
    headers: { 'Content-Type': 'text/event-stream' },
  })
}
```

For AI streaming, use the AI SDK's `toUIMessageStreamResponse()` (for chat UIs with `useChat`) which handles SSE formatting automatically.

## Cron Jobs

Schedule function invocations via `vercel.json`:

```json
{
  "crons": [
    {
      "path": "/api/daily-report",
      "schedule": "0 8 * * *"
    },
    {
      "path": "/api/cleanup",
      "schedule": "0 */6 * * *"
    }
  ]
}
```

The cron endpoint receives a normal HTTP request. Verify it's from Vercel:

```ts
export async function GET(req: Request) {
  const authHeader = req.headers.get('authorization')
  if (authHeader !== `Bearer ${process.env.CRON_SECRET}`) {
    return new Response('Unauthorized', { status: 401 })
  }
  // Do scheduled work
  return Response.json({ ok: true })
}
```

## Configuration via vercel.json

**Deprecation notice**: Support for the legacy `now.json` config file will be removed on **March 31, 2026**. Rename `now.json` to `vercel.json` (no content changes required).

```json
{
  "functions": {
    "app/api/heavy/**": {
      "maxDuration": 300,
      "memory": 1024
    },
    "app/api/edge/**": {
      "runtime": "edge"
    }
  }
}
```

## Timeout Limits

All plans now default to 300s execution time with Fluid Compute.

| Plan | Default | Max |
|------|---------|-----|
| Hobby | 300s | 300s |
| Pro | 300s | 800s |
| Enterprise | 300s | 800s |

## Common Pitfalls

1. **Cold starts with DB connections**: Use connection pooling (e.g., Neon's `@neondatabase/serverless`)
2. **Edge limitations**: No `fs`, no native modules, limited `crypto` — use Node.js runtime if needed
3. **Timeout exceeded**: Use Fluid Compute for long-running tasks, or Workflow DevKit for very long processes
4. **Bundle size**: Python runtime supports up to 500MB; Node.js has smaller limits
5. **Environment variables**: Available in all functions automatically; use `vercel env pull` for local dev

## Function Runtime Diagnostics

### Timeout Diagnostics

```
504 Gateway Timeout?
├─ All plans default to 300s with Fluid Compute
├─ Pro/Enterprise: configurable up to 800s
├─ Long-running task?
│  ├─ Under 5 min → Use Fluid Compute with streaming
│  ├─ Up to 15 min → Use Vercel Functions with `maxDuration` in vercel.json
│  └─ Hours/days → Use Workflow DevKit (DurableAgent or workflow steps)
└─ DB query slow? → Add connection pooling, check cold start, use Edge Config
```

### 500 Error Diagnostics

```
500 Internal Server Error?
├─ Check Vercel Runtime Logs (Dashboard → Deployments → Functions tab)
├─ Missing env vars? → Compare `.env.local` against Vercel dashboard settings
├─ Import error? → Verify package is in `dependencies`, not `devDependencies`
└─ Uncaught exception? → Wrap handler in try/catch, use `after()` for error reporting
```

### Invocation Failure Diagnostics

```
"FUNCTION_INVOCATION_FAILED"?
├─ Memory exceeded? → Increase `memory` in vercel.json (up to 3008 MB on Pro)
├─ Crashed during init? → Check top-level await or heavy imports at module scope
└─ Edge Function crash? → Check for Node.js APIs not available in Edge runtime
```

### Cold Start Diagnostics

```
Cold start latency > 1s?
├─ Using Node.js runtime? → Consider Edge Functions for latency-sensitive routes
├─ Large function bundle? → Audit imports, use dynamic imports, tree-shake
├─ DB connection in cold start? → Use connection pooling (Neon serverless driver)
└─ Enable Fluid Compute to reuse warm instances across requests
```

### Edge Function Timeout Diagnostics

```
"EDGE_FUNCTION_INVOCATION_TIMEOUT"?
├─ Edge Functions have 25s hard limit (not configurable)
├─ Move heavy computation to Node.js Serverless Functions
└─ Use streaming to start response early, process in background with `waitUntil`
```

## Official Documentation

- [Vercel Functions](https://vercel.com/docs/functions)
- [Serverless Functions](https://vercel.com/docs/functions)
- [Edge Functions](https://vercel.com/docs/functions)
- [Fluid Compute](https://vercel.com/docs/fluid-compute)
- [Streaming](https://vercel.com/docs/functions/streaming)
- [Cron Jobs](https://vercel.com/docs/cron-jobs)
- [GitHub: Vercel](https://github.com/vercel/vercel)

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [build-with-dhiraj](https://github.com/build-with-dhiraj)
- **Source:** [build-with-dhiraj/ai-workflow-framework-portability-kit](https://github.com/build-with-dhiraj/ai-workflow-framework-portability-kit)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** yes
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-build-with-dhiraj-ai-workflow-framework-portability-kit-vercel-functions
- Seller: https://agentstack.voostack.com/s/build-with-dhiraj
- Browse the marketplace: https://agentstack.voostack.com/browse

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Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.