Opus 5.5 fast mode no longer requires an access request

15 October 2026AnthropicAPIs and performance

The move out of research preview applies to Opus 5.5, not every Opus model.

General availability for Opus 5.5

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Opus 5.5 no longer requires the `fast-mode-2026-02-01` beta header; requests still sending it remain compatible.
Default rate limits exist in Start, Build and Scale tiers; fast mode also arrives on Claude in Microsoft Foundry for Azure-hosted deployments.
Opus 5 and Opus 4.8 remain in research preview and retain the beta-header requirement.

Header migration depends on the precise model version.

Remove the beta header only for Opus 5.5 calls.

Belgium/EEA: the source specifies no explicit regional exclusion; availability depends on the account, plan and service region.

Fast mode is a service mode for the same model, not a new model or a constant-latency guarantee. Check pricing before enabling it.