Claude Opus 5.5 now available on AI Gateway

Claude Opus 5.5 from Anthropic is now available on AI Gateway as anthropic/claude-opus-5.5.

Opus 5.5 is Anthropic’s strongest Opus model for agentic coding, long-running agent tasks, and professional knowledge work. It communicates progress, findings, and next steps clearly, making extended work easier to supervise.

It has a 1M-token context window and supports up to 128K output tokens. Compared with Opus 5, Anthropic has stated that Opus 5.5 performs at a similar level to Fable 5.1, but is ~30% faster and ~40% cheaper per task than Opus 5.

The new model includes two API changes that can turn previously valid requests into HTTP 400 errors:

• Thinking is always adaptive. Requests that disable thinking or set a fixed thinking budget are rejected. Use an effort level and prompting to control reasoning depth.

• Forced tool choice is unsupported. Requests cannot require a tool call or force a specific tool. Use automatic tool selection and prompt the model when it should call a tool. If you previously forced a tool call to return JSON, use structured outputs instead.

To use Claude Opus 5.5:

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import { streamText } from 'ai';
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const result = streamText({
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  model: 'anthropic/claude-opus-5.5',
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  reasoning: 'medium',
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  prompt: 'Investigate the failing tests, implement a fix, and report what changed.',
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  providerOptions: {
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    gateway: {
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      speed: 'fast',
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      inferenceRegion: { scope: 'zone', geoRegion: 'us' },
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    },
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  },
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});

For lower latency, enable fast mode with speed: 'fast' or use anthropic/claude-opus-5.5-fast. In Claude Code, run /fast to toggle it for the session.

Opus 5.5 also supports regional inference and Zero Data Retention through AI Gateway. Try it in the model playground.