What is Fast mode for Claude Opus 5?

Fast mode is a research-preview option for Claude Opus 5 that trades higher per-token pricing for roughly 2.5 times faster output, aimed at exploration, drafting, and lower-risk loops where speed matters more than squeezing out maximum cost efficiency.

It's currently available only through the Claude API directly, not through Amazon Bedrock, Google Cloud, or Microsoft Foundry, so teams relying on those platforms don't yet have access to it for Opus 5.

It continues a pattern from earlier Opus versions (4.6 through 4.8), which also shipped with their own fast-mode sibling at premium pricing, rather than being a brand-new capability introduced specifically with Opus 5.

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