Having the VERCEL env variable set breaks dev server (rewrites to HTTPS & trigger ERR_SSL_PROTOCOL_ERROR)

[benjaminwaterlot]

Reproduction URL

https://github.com/nextauthjs/next-auth-example

Describe the issue

→ Having the VERCEL env variable set to any value breaks the dev server.

Specifically, it seems to:

• ignore NEXTAUTH_URL entirely,
• rewrite every call to the next-auth endpoints to https, leading to ssl errors if you're not developing on a https dev server

→ Problem : the Vercel dev CLI (vercel env pull) adds this variable automatically to your env file! ⚠️

See https://vercel.com/docs/cli/env

Specifically, in a development environment it adds:

VERCEL="1"
VERCEL_ENV="development"
VERCEL_GIT_COMMIT_AUTHOR_LOGIN=""
VERCEL_GIT_COMMIT_AUTHOR_NAME=""
VERCEL_GIT_COMMIT_MESSAGE=""
VERCEL_GIT_COMMIT_REF=""
VERCEL_GIT_COMMIT_SHA=""
VERCEL_GIT_PREVIOUS_SHA=""
VERCEL_GIT_PROVIDER=""
VERCEL_GIT_PULL_REQUEST_ID=""
VERCEL_GIT_REPO_ID=""
VERCEL_GIT_REPO_OWNER=""
VERCEL_GIT_REPO_SLUG=""
VERCEL_URL=""

Therefore, VERCEL="1" should probably not be used to determine if the build is running on Vercel or hosted on Vercel. I suppose VERCEL_ENV or VERCEL_URL could be used to ensure that instead.

ℹ️ Strangely enough the problem only started with next@13.4.13-canary.0

How to reproduce

Set VERCEL="1" in .env.local in any next-auth app.

Try to trigger any call to the /api/auth/... endpoints.

The call will fail if you're on a http dev server, and in any case NEXTAUTH_URL will be ignored.

Expected behavior

VERCEL should not be used alone to determine if the app is built / running on Vercel servers ; therefore the app should work in development even with VERCEL="1", because that's the default for the Vercel env CLI.

In video

CleanShot.2023-08-22.at.11.07.44.mp4

Workaround

I currently workaround by overriding my dev scripts:

"dev": "VERCEL='' next dev"

[balazsorban44]

duplicate of #7962

[hamirmahal]

I just ran into the ERR_SSL_PROTOCOL_ERROR issue a few minutes ago and fixed it by commenting out VERCEL="1" in .env.

I think I got VERCEL="1" because I did vercel env pull .env, which is what https://vercel.com/guides/nextjs-prisma-postgres#step-2-set-up-your-vercel-postgres-database said to do.

[jearthman]

Hmm I've been having the same issue with ERR_SSL_PROTOCOL_ERROR. I commented out VERCEL in my env files and added VERCEL="" to my dev script in package.json. I'm on Next version 13.5.3.

@balazsorban44 i have #8722 open if you want to merge it here.

Have any other work arounds been found?

[toniopelo]

There is a more convenient workaround I just found. That allows you to still use vercel env pull without having to manually remove VERCEL="1" every time. I explained it here