# We’ve deprecated fast mode for Claude Opus 4.8, with removal on November 30, 2026

By Steven Van · 2026-10-30

Requests to claude-opus-4-8 with speed "fast" will error after removal, and Claude Opus 5.5 supports fast mode with no beta header.

Fast mode for Claude Opus 4.8 is deprecated, and [Anthropic will remove it on November 30, 2026](<https://platform.claude.com/docs/en/models/opus-5-5/migration-guide#migrating-from-claude-opus-4-8>). After that date, requests to claude-opus-4-8 with speed: "fast" will return an error.

## Keeping fast mode

Fast mode continues on Claude Opus 5.5, which Anthropic names as the migration target. On Claude Opus 5.5, fast mode is set with speed: "fast" on the request and needs no beta header. Fast mode is not available on Claude Opus 4.7, where such requests return an error.

## Other differences when moving from Opus 4.8

The migration guide lists several changes between [Anthropic](<https://creatorstoolbox.com/tools/anthropic>)'s Opus 4.8 and Opus 5.5:

- A request with no thinking field now runs with thinking. On Opus 4.8, thinking is off unless requested.

- The minimum cacheable prompt length drops from 1,024 tokens to 512 tokens.

- Priority Tier is not supported on Opus 5.5, while Opus 4.8 keeps it. Organisations with a Priority Tier commitment need to plan capacity separately.

The guide also suggests, as optional, trying task budgets (beta, with the task-budgets-2026-03-13 header) for agentic workloads and mid-conversation tool changes (beta) to keep prompt cache hits when tools change.

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Sources

[Original source](<https://platform.claude.com/docs/en/release-notes/overview#october-30-2026>)

[Read We’ve deprecated fast mode for Claude Opus 4.8, with removal on November 30, 2026 on Creators Toolbox](<https://creatorstoolbox.com/blog/anthropic-we-ve-deprecated-fast-mode-for-claude-opus-4-8-with-removal>)

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Canonical source: https://creatorstoolbox.com/blog/anthropic-we-ve-deprecated-fast-mode-for-claude-opus-4-8-with-removal