Haiku Burned More Tokens Than Sonnet. Spec It in Code.
A controlled 90-trial experiment found Claude Haiku 4.5 spent 735K tokens where Sonnet 4.6 spent 640K, for a result 1.9 points worse. Downgrading a coding agent to a cheap tier saves less than the rate card implies, varies fivefold by vendor, and only holds up if you replace prose design docs with machine-checkable contracts.
August 25, 2026 · 12 min read