An `effort_cost_index` table inside the Claude Code binary shows `max` costs almost nothing extra on Opus 5 and more than doubles on Sonnet 5.

Normalized so high = 1: opus-5 runs 0.67/0.76/1/1.60/1.70 across low through max, sonnet-5 runs 0.47/0.74/1/2.41/5.59. That makes xhigh to max +6% on Opus 5 and +132% on Sonnet 5. The poster ran 8 agents on Opus 5 across two real tasks and four effort levels in isolated clones; magnitudes were loose but the catalog correctly predicted xhigh and max would be near-identical, at 397,827 against 397,761 output tokens. r/ClaudeAI I've been defaulting to xhigh on Opus out of cost caution. Based on this I'm moving to max and leaving Sonnet where it is.