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Fast mode on Claude Opus 4.8 ends on 30 November; on Opus 5.5 it costs $8 input and $40 output

2026/11/02

Anthropic deprecated fast mode for Claude Opus 4.8 on 30 October 2026⁠[1]. It will be removed on 30 November, and after that, requests to claude-opus-4-8 with speed: "fast" will return an error⁠[1,2].

To keep using fast mode, Anthropic says to migrate to Claude Opus 5.5⁠[1,2]. The steps are in its guide to migrating from Opus 4.8 to Opus 5.5⁠[2].

Fast mode runs the same model with a faster inference configuration, with no change to intelligence or capabilities⁠[2]. Output tokens per second are up to 2.5 times higher⁠[2].

Per million tokens, fast mode costs $10 input and $50 output on Opus 4.8 and Opus 5, and $8 input and $40 output on Opus 5.5⁠[2]. The price is a multiplier on standard rates across the full context window, including requests over 200k input tokens⁠[2]. Prompt caching and data residency multipliers apply on top⁠[2].

Fast mode on Opus 4.8 and Opus 5 is in research preview and available only on the Claude API⁠[2]. Requests need the fast-mode-2026-02-01 beta header, and access to fast mode on Opus 5 requires contacting an account manager or joining the waitlist⁠[2].

Fast mode on Opus 5.5 needs no beta header and runs on the Claude API, Claude Models on Google Cloud (Anthropic managed) and Microsoft Foundry hosted on Azure⁠[2]. Its rate limit is granted by default in the Start, Build and Scale usage tiers⁠[2].

Fast mode is not available with the Batch API or with a Priority Tier commitment⁠[2]. A request that exceeds the rate limit can be retried at standard speed, but requests at different speeds do not share cached prefixes, so the prompt cache misses⁠[2].