Pick Your Coding-Agent Model by Opportunity Cost — Why I Run Fable 5 Low and Codex 5.6 Sol Light for Speed

Lately I've deliberately defaulted to light, fast settings: Fable 5 at the Low reasoning level in Claude Code, and 5.6 Sol at the Light reasoning level and the Fast speed level in Codex. Today's high-intelligence models fail with the same shape of mistakes whether you spend a lot of reasoning tokens or a few. If the failure mode is the same, review effort doesn't change, and what matters isn't token cost but wait time, which is opportunity cost. Hard to see, but its dominance is obvious once you accept that humans are the bottleneck.