I'm wondering how service oriented architectures can follow the 12-factor principles.

Designing an architecture as microservices means (to me) that you separate the features in services. This means you have multiple code source for the different services.

The first principle of a 12 factor application is "One codebase". So if we have multiple services, we have several codebases and the first principle is broken.

Are the two architectures mutually exclusive or did I misunderstand something?