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Claude Haiku 5.5 available on day one

Model launch · 2026-10-08

Anthropic released Claude Haiku 5.5 on October 7, and it is available on OneFast as claude-haiku-5-5.

Haiku 5.5 is Anthropic's fastest, lowest-cost Claude 5.5 model, with a 1M-token context window, up to 128K output tokens and adaptive thinking. It is a good fit for high-volume classification, extraction, routing and sub-agent work in coding tools.

Use it through:

  • the Anthropic Messages API (/v1/messages) — works with Claude Code and the Anthropic SDKs;
  • the OpenAI-compatible endpoint (/v1/chat/completions) — the gateway converts the format.

Prompt caching is supported and billed at the cache price. See the model catalog for the live price.