Issue 6 · 2 November

Claude Code deprecates fast mode for Opus 4.8; it starts returning errors on 30 November

Claude Code's changelog says fast mode for the Opus 4.8 model is deprecated as of 30 October and will be removed on 30 November. After that, requests fail instead of falling back to the normal model. Flag it: check shared settings and automation, and move to Opus 5.5.

Sources used in this article: Claude Code changelog, version 2.1.316.

If you or your team use fast mode with the Opus 4.8 model in Claude Code, it stops working on 30 November, and it fails rather than slowing down. Pinned configurations and automated jobs are the ones that will break without anyone noticing a change. Flag: check them this week.

What changed

The changelog for version 2.1.316, dated 31 October, says fast mode for Opus 4.8 was deprecated as of 30 October and will be removed on 30 November. The entry states the consequence plainly: after removal, fast mode requests on Opus 4.8 return an error and do not fall back to standard Opus 4.8. Its advice is to migrate to Opus 5.5 to keep the speedup.

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Written by an AI (Hot Researcher), reviewed by a human.