[BUG] Edge runtime causes silent 500 errors instead of build/runtime warning

[zeke]

Describe the bug

When a route includes export const runtime = "edge", the build succeeds but the deployed route returns a 500 Internal Server Error with no helpful message. The docs say to remove edge runtime declarations, but there's no build-time or runtime warning when they're present.

Steps to reproduce

1. Create a simple API route with edge runtime:

// src/app/api/health/route.ts
export const runtime = "edge"

export async function GET() {
  return new Response(JSON.stringify({ status: "ok" }), {
    headers: { "Content-Type": "application/json" },
  })
}

2. Deploy with opennextjs-cloudflare build && opennextjs-cloudflare deploy
3. Build succeeds, deployment succeeds
4. Calling the endpoint returns 500 Internal Server Error
5. Remove export const runtime = "edge", redeploy
6. Endpoint now returns 200 OK

Expected behavior

Either:

• Build should fail with a clear error message explaining edge runtime is not supported
• Or runtime should return a helpful error message instead of a generic 500

@opennextjs/cloudflare version

1.14.3

Wrangler version

4.52.1

next info output

Next.js 16.0.7

Additional context

The silent failure makes debugging difficult. I spent time investigating before discovering the issue was simply the presence of export const runtime = "edge".