Prevent call to createUser event

[emilnewel]

Hello, I've been looking through the documentation for AuthJS and haven't been able to spot a way to solve my usecase.

• I have a custom OIDC provider that I want to use to authenticate my users.
• I don't want new users to be able to signup. I have a database pre-filled with users.
• My OIDC provider doesn't use email.
• Using the PrismaAdapter with database strategy

It seems that every time a user tries to sign in to my system AuthJS tries to call createUser and because my OIDC provider doesn't use email, that value is always undefined. This causes errors.

Is there a way for me to prevent the call to createUser when a user tries to sign in? Or instead of preventing the call just overriding the user exists check?

// relevant package.json
{
  "dependencies": {
    "@auth/prisma-adapter": "^2.7.4",
    "next": "15.1.4",
    "next-auth": "5.0.0-beta.25",
    "react": "^19.0.0",
  },
  "devDependencies": {
    "@types/node": "^20.17.12",
    "@types/react": "^19",
    "@types/react-dom": "^19",
    "prisma": "^6.3.1",
    "typescript": "^5.7.3"
  }
}