Claude Opus 4.8 fast mode is deprecated and ends Nov 30, 2026; those requests will error instead of falling back to standard speed, and Anthropic directs users to Opus 5.5.

Anthropic’s fast-mode API documentation warning that Opus 4.8 fast mode ends November 30, 2026, above its model availability table.

Published 31 Oct 2026 · 01:30 UTC

Anthropic Claude Code 2.1.316 release notes ↗ · Source dated 31 Oct 2026

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