fox 2026-05-21: (1) use REAL API token usage, not len//4; (2) the
substrate prefills a large retrieved CONTEXT as INPUT while solo feeds
~nothing, so per-completion-token over-charges the substrate — and per-
TOTAL-token UNDER-charges it (its mix is ~98% cheap prefill tokens).
Measured n=30 qwen-nothink/4090: substrate prefills ~6.6k input tok/query
(claim_lattice) vs solo ~52 — ~127x. Neither single per-token denominator
is honest; prefill (parallel, cheap/tok) and decode (autoregressive,
dear/tok) must be costed separately.
- OpenAICompatibleClient stashes data['usage'] as .last_usage (non-
invasive; return type unchanged).
- watt_bench captures real prompt_tokens + completion_tokens per call
(both arms), aggregates per cell, and energy_cogs reports gross +
marginal per BOTH 1k-total-tok and 1k-completion-tok plus the context
size. Prints the prompt/completion split.
- 12 tests incl. the prompt-context artifact (per-total cheap, per-
completion dear). Full suite 2540 passed.
The clean per-input-tok / per-output-tok split rides bench/watt_calibrate
(slope calibration; separate commit once validated live).
russell@unturf.com
459060c774