Usage preserves reported token presence

Context

Adapters replaced missing token measurements with zero. Pricing those zeros made unmeasured calls look free, including on per-call telemetry.

Decision

Preserve input and output presence independently through normalization and serialization. Keep the existing integer counters for consumer compatibility. Add optional presence arguments to UsageStatistics, with legacy inference when omitted, and read presence through isPromptTokensReported() and isCompletionTokensReported(); the arguments are not public properties, so the legacy rule lives in one place. A normalized explicit zero is known; an absent or invalid field is unknown. Local split-token pricing requires both measurements. An independently reported monetary amount remains known without token counts. A sum has known presence only when both operands have it.

This is an additive public constructor change. Existing positional and named arguments keep their meaning. Legacy all-zero objects remain unmeasured; callers requiring an explicit zero measurement supply presence or fromArray.

Consequences

Daily aggregates retain their existing integer storage and request counting. Per-call telemetry preserves nullability; aggregated zero alone does not prove free usage. UsagePresenceTest checks both telemetry and tracker inputs.