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Claude Opus 5.5 is $4 in and $20 out, and the model Anthropic now recommends first

2026/09/28

Anthropic's comparison table now lists four current models: Claude Fable 5.1, Claude Opus 5.5, Claude Sonnet 5 and Claude Haiku 4.5⁠[1]. Claude Opus 5 has moved to the list of legacy models, which are still available⁠[1]. A migration guide covers moving from Opus 5 or earlier⁠[1].

The model id for Opus 5.5 is claude-opus-5-5⁠[1]. Anthropic describes it as built for long-running agentic coding and knowledge work⁠[1].

For anyone unsure which model to use, Anthropic says to start with Opus 5.5 for most workloads⁠[1]. Fable 5.1 is for demanding reasoning and long-horizon agentic work, or for when evals on Opus 5.5 at higher effort still fall short⁠[1].

Per million tokens it is $4 input and $20 output, exactly twice Sonnet 5 and two fifths of Fable 5.1⁠[1]. Batch API requests are half price on every model⁠[1].

Prompt cache reads cost 10 percent of the input price on most Claude models, but 5 percent on Opus 5.5, which is $0.20 per million tokens⁠[1]. Fable 5.1 and Mythos 5.1 are lower still, at 2.5 percent⁠[1].

Thinking is adaptive and always on, and the default effort is medium⁠[1]. Fable 5.1 and Sonnet 5 default to high⁠[1].

The context window is 1 million tokens, and one response can run to 128K tokens⁠[1]. On the Message Batches API, a beta header raises that to 300K⁠[1].

The reliable knowledge cutoff and the training data cutoff are both June 2026, the same as Fable 5.1⁠[1]. The retirement commitment is not sooner than 22 September 2027⁠[1].

On Amazon Bedrock the model id is anthropic.claude-opus-5-5, and on Google Cloud it is claude-opus-5-5⁠[1]. Microsoft Foundry and Claude Platform on AWS use the same id as the Claude API⁠[1].