Swift 6.0 migration causes EXC_BREAKPOINT when calling callback.failure(.noCredentials) in Auth0.swift

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I am facing a crash after migrating an iOS app to Swift 6.0, and it seems related to Swift Concurrency / callbacks in Auth0.swift.

Environment

  • iOS app

  • Swift 6.0

  • Auth0.swift (version: please confirm, possibly < 2.7.2)

  • Using Auth0 WebAuth login flow

Issue

During the authentication flow, the app crashes with the following behavior:

  • The crash occurs exactly at:

    return callback.failure(.noCredentials)

  • Xcode shows:

    Thread 10: EXC_BREAKPOINT

  • The callback is being called, but the app crashes at runtime when this line is executed.

This looks similar to a Swift Concurrency runtime trap, not a normal logical error.

Suspected cause

Based on investigation, this appears related to Swift Concurrency continuation misuse, similar to what was discussed in:

In Swift 6, runtime checks are stricter, and calling a continuation or callback:

  • more than once, or

  • from an unexpected thread / actor

results in an immediate EXC_BREAKPOINT.

Questions

  1. Is this a known Swift 6–specific issue when using Auth0.swift?

  2. Is upgrading to Auth0.swift ≥ 2.7.2 (which addresses concurrent WebAuth / continuation misuse) the recommended solution?

  3. Are there any Swift 6–specific guidelines for safely handling Auth0 callbacks (e.g. MainActor requirements)?

Any confirmation or guidance would be greatly appreciated.

Thank you.