Fast mode for Opus 4.8 is deprecated and ends November 30

What changed

Claude Code 2.1.316 marks fast mode for Opus 4.8 as deprecated as of October 30, 2026, with removal on November 30, 2026. After that date, fast-mode requests on Opus 4.8 return an error and don’t fall back to standard Opus 4.8. Anthropic’s fast mode docs give the same date and point to Opus 5.5 instead.

Who it affects

Claude Code and Claude API users running Opus 4.8 with fast mode.

What to do

Move fast-mode work to Opus 5.5 before November 30, and remove speed: "fast" from any API calls to claude-opus-4-8.

Source: https://github.com/anthropics/claude-code/blob/main/CHANGELOG.md#21316