Product chose A after the A/B: low cut answer-step reasoning tokens ~45% and answer time 34s -> 22s with no quality loss. Unset now means "low"; CONSULT_ANSWER_REASONING_EFFORT=off restores the pre-change request body, and the old "unset keeps the body" guarantee moves to "off". Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>