Normalized token usage and pricing

Usage components are disjoint: input excludes cache reads and writes, while output includes any reported reasoning tokens. reasoning is an optional breakdown of output; it is never added to total a second time. The optional cache_write_1h value is a subset of cache_write.

Details

rho_price_usage() is the open pricing protocol. Its default Model method selects the highest matching long-context tier, prices every component, and returns a new Usage value. Model subclasses may provide methods for provider-specific pricing rules.