An IDE-managed application server finished compiling and preparing its artifact, but the server never reached deployment. The decisive message was not a compiler error. It was a debugger listener failure: the configured address could not be bound because it was already in use.

The usual explanation …

An IDE displayed a warning that it could not open a configured application URL. A browser opened the same route successfully soon afterward, and the application was already answering real requests. The warning looked like an application failure, yet the user-visible route was healthy.

The useful …