Anthropic releases Claude Haiku 5.5: the fastest and cheapest small model

Anthropic releases Claude Haiku 5.5, calling it its fastest, cheapest, and most capable small model to date, with average operating costs about 75% lower than Haiku 4.5. The model targets high-concurrency, cost-sensitive tasks, can serve as a subagent for Opus 5.5 and Sonnet 5.5, and introduces adjustable effort settings to the Haiku tier for the first time. On safety, its alignment evaluations show substantial improvements over Haiku 4.5; its cybersecurity guardrails are looser than Sonnet 5.5's but still block penetration testing, and its biosecurity guardrails match those of Sonnet 5, Sonnet 5.5, and Opus 5.