error code. The HTTP status identifies the broad failure class; the code explains the specific refusal. Foreign resources are treated as unavailable without disclosing whether they exist.
A request timeout does not prove that the server rejected the operation. A dispatch timeout does not prove that the effect did not happen. Keep those uncertainties separate: server retries use the same operation identity; an executor retains its durable launch fence and never repeats an uncertain effect.
Unsupported protocol or profile versions require an explicit compatibility decision. Do not remove required profiles or change purpose to make a refused request pass. Any material change needs a new request and, where required, fresh human review.
The SDK error guide shows how to handle these responses without automatic unsafe retries.