The UMA Runtime Layer

The first version exists in the design: clean contracts, well-named capabilities, and a diagram that makes the architecture legible. The second version exists on the machine, where timing, resource limits, and host differences modify that design in ways no diagram captures. A service can compile cleanly and pass contract validation, then behave differently across environments because background tasks finish in a different order, network calls resolve asynchronously on one host and synchronously on another, or an adapter blocks where the design assumed it would not. These are not syntax errors. They are execution differences, and they are the real portability problem.