How to catch the specifics behind a OAuthCallbackError?

[thany]

When an OAuthCallbackError is thrown, I can see the actual error code in the Next.js server console, but in the client, it just appends error=OAuthCallbackError in the url and leaves it there. How do I get to the actual error code? It's important to display the right kind of error message to the end-user. Right now all we can do is basically little more than "Something went wrong" which only adds more frustration for a user, should it ever occur.

So this is on the Next.js app router, if that helps to know. And Auth.js 5.0 beta 29. It's not specific to any single provider or adapter. It's effectively a generic question of "how to catch an error with details".

Unfortunately, the documentation is quite clear on what the errors mean, but is quite vague on how to catch all those errors (including OAuthCallbackError in particular).