OptionalcachedWhole-turn prefix-cache hits.
OptionalchatOptionalcompletionWhole-turn completion tokens (inclusive of reasoningTokens).
OptionalmemoryOptionalmodelThe served model of the final billed hop (fallback-aware), when known.
OptionalpromptWhole-turn prompt tokens (sum across hops).
OptionalreasoningReasoning tokens — a subset of completionTokens, not additive; present
only when the served model reports it.
Optionalvoice
Payload of a
control.usageevent — a per-turn metering echo the host can surface in a usage/billing view. Emitted after a companion input turn that billed tokens, carrying the same whole-turn totals as the input done frame'susageblock; subscribe viaclient.onUsage(...). All fields optional.