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Anthropic previews fast mode for Claude Opus 5.5

Anthropic Sep 22, 2026 Capability

Fast mode is available as a research preview for Claude Opus 5.5 on the Claude API.

Models: Claude Opus 5.5

Read on platform.claude.com

Source: Claude Developer Platform release notes, checked Sep 28, 2026. Summarized from the provider’s announcement.

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