What is Claude Haiku 5.5? Anthropic's fastest, cheapest small model

Claude Haiku 5.5 is a small model Anthropic released on October 7, 2026, built for speed and low cost on high-volume work such as subagents, summaries, classification and browser use.

Anthropic released Claude Haiku 5.5 on October 7, 2026, describing it as the cheapest, fastest and most capable small model it has shipped. It is designed for high-volume, cost-sensitive work such as summaries, compactions, database queries and classification. Anthropic says it pairs well with Opus 5.5 and Sonnet 5.5 as a subagent on coding work, and its speed suits live customer support and browser use.

According to the Claude Platform documentation, Haiku 5.5 has a 1M token context window, up to 128K output tokens and adaptive thinking. It is the first Haiku-class model with an adjustable effort setting, so users can trade cost against intelligence. The API model ID is claude-haiku-5-5, and it is also available on Amazon Bedrock, Google Cloud and Microsoft Foundry. Anthropic also added computer use and browser use in beta to its Python and TypeScript SDKs.

Official pricing for prompts up to 100K tokens is 0.10 dollars per million input tokens and 0.50 dollars per million output tokens, rising to 0.50 and 2.50 dollars for longer prompts. Anthropic says Haiku 5.5 costs around 75 percent less to run than Haiku 4.5 on average. On the same day it halved the price of cache reads on Sonnet 5.5, which it estimates makes most agentic work about 20 percent cheaper.

In Anthropic's published results, Haiku 5.5 scores 72.4 percent on the OSWorld 2.1 offline subset and 39.2 percent on Terminal-Bench 4.0, where Haiku 4.5 scored 0.0 percent. Anthropic notes that Sonnet 5.5 and Opus 5.5 remain the better choice for complex agentic coding, while Haiku 5.5 fits narrowly scoped tasks like compaction, summarization and subagent work.