Run-scoped budgets for agent calls
The agent budget RFC treats cost as a pre-call authorization decision. It proposes estimating worst-case spend before each provider request, reserving that amount atomically across run, user, key, and other scopes, then committing actual usage after the call. The design targets loops that resend growing context; the RFC says one run can pass 50K input tokens by step 20.
The useful detail is the failure path. Agents receive budget state through headers and RFC 9457 problem-detail errors, so they can choose a cheaper model, shorten context, or stop cleanly. The RFC cites reported cost incidents, including a $4,200 weekend bill and an $87K monthly team bill, but it does not report latency, savings, false-block, or adoption results.