most people implement "block on API response", because that's way easier to reason about, sometimes, even without timeout. Reading through the thread, what I was misunderstanding is that this situation technically gets rolled into what called a "livelock". Fine, but from the higher-level API consumer's POV it's a deadlock.

with blocking semantics, you are sure to run into deadlocks in a single-threaded environment pretty easily a -> b -> c -> a.

grpc f.e. has support for blocking requests but it's 'solution' is to spawn a new thread for the request.