# Errors and refusals

Platform API uses Problem Details for invalid requests, state conflicts, and governed refusals. Missing Evidence, unresolved authority, incompatible resource state, unavailable capability, exhausted budget, policy refusal, stale preconditions, and cancellation remain machine-readable outcomes rather than being translated into successful-looking prose.

Clients should branch on the Problem Details `type` and HTTP status, preserve the `instance`, and follow Receipt or operation links when present. A refusal is a valid terminal result when the governing conditions for the requested act are not satisfied.