How would you decide between building a custom networking layer vs using URLSession directly in a large-scale Swift app?

Use URLSession directly for simple apps; build a custom layer when cross-cutting concerns and scale require abstraction.

URLSession is sufficient for straightforward apps. However, large systems require retry policies, logging, caching, authentication injection, request interception, and testing support. A custom layer introduces abstraction but increases complexity. Staff-level decision depends on team size, reuse, and cross-feature consistency.