Opus 4.8 vs Sonnet vs Haiku: How I Route Work in 2026

Flat 5/25 price, a 3x cheaper Fast mode, and abstention reset the routing math in 2026 I reach for Opus 4.8 when a silent wrong answer is expensive, citing SWE-Bench Pro 69.2 Sonnet wins on well-scoped, high-volume, latency-sensitive jobs at mid relative cost Haiku takes the cheapest, fastest work like classification and rough drafts Fast mode runs about 2.5x faster and effort scales from low to max For two years the rule was simple. Reach for the cheap tier by default, escalate to the top tier only when the cheap one failed. In 2026 I flipped that for hard work.