vercel-common-errors

name	vercel-common-errors
description	Diagnose and fix common Vercel deployment and function errors. Use when encountering Vercel errors, debugging failed deployments, or troubleshooting serverless function issues. Trigger with phrases like "vercel error", "fix vercel", "vercel not working", "debug vercel", "vercel 500", "vercel build failed".
allowed-tools	Read, Grep, Bash(vercel:*), Bash(curl:*)
version	1.18.0
license	MIT
author	Jeremy Longshore <[e-mail]>
tags	["saas","vercel","debugging","errors"]
compatibility	Designed for Claude Code, also compatible with Codex and OpenClaw

Vercel Common Errors

Overview

Diagnose and resolve the most common Vercel errors across three layers: build pipeline, serverless function runtime, and edge network. Each error includes the error code, root cause, and step-by-step fix.

Prerequisites

• Vercel CLI installed
• Access to deployment logs (vercel logs <url>)
• Access to Vercel dashboard for build logs

Instructions

Step 1: Identify the Error Layer

# Check deployment status and error details
vercel inspect <deployment-url>

# View function runtime logs
vercel logs <deployment-url> --follow

# View build logs via API
curl -s -H "Authorization: Bearer $VERCEL_TOKEN" \
  "https://api.vercel.com/v13/deployments/dpl_xxx" | jq '.state, .errorMessage'

Three error layers:

1. Build errors — appear during vercel deploy, exit codes in build log
2. Runtime errors — appear when functions are invoked, visible in function logs
3. Edge/routing errors — HTTP errors from Vercel's edge network

Step 2: Build Errors

BUILD_FAILED — Build command exited with non-zero code

Error: Command "npm run build" exited with 1

• Check: vercel.json → buildCommand matches your build script
• Check: all dependencies listed in package.json (not just devDependencies for runtime deps)
• Fix: run npm run build locally to reproduce

MISSING_BUILD_SCRIPT — No build command found

Error: Missing Build Command

• Fix: add "build" to package.json scripts or set buildCommand in vercel.json
• For static sites: set buildCommand to empty string or "true"

FUNCTION_PAYLOAD_TOO_LARGE — Serverless function bundle > 250 MB

Error: The Serverless Function "api/heavy" is 267 MB which exceeds the maximum size of 250 MB

• Fix: add unused packages to .vercelignore, use dynamic imports, split into smaller functions