Claude Opus 5.5 fast mode leaves research preview with default API rate limits
Anthropic's October 15 release notes say fast mode for Claude Opus 5.5 is out of research preview. It no longer needs an access request or beta header, and every usage tier now has a default fast mode rate limit. Fast mode for Opus 5 and Opus 4.8 stays in preview.
SessionWatcher editorial · Published · Updated · Source announcement: 2026-10-15
What changed on October 15
Anthropic's release notes dated October 15, 2026 say fast mode is out of research preview for Claude Opus 5.5. You no longer need to request access before using it.
Every usage tier now has a default fast mode rate limit for Claude Opus 5.5, so fast mode capacity no longer depends on a separate access approval.
Requests to Claude Opus 5.5 no longer need the fast-mode-2026-02-01 beta header. Requests that still send the header keep working, so existing integrations do not break.
Sources: Anthropic release notes: 2026-10-15
Opus 5 and Opus 4.8 stay in research preview
The change covers only Claude Opus 5.5. Fast mode for Claude Opus 5 and Claude Opus 4.8 is still in research preview, and Anthropic says to keep sending the beta header with fast mode requests to those models.
Sources: Anthropic release notes: 2026-10-15
What the note does not say
The release note gives no figures for the new default fast mode rate limits in each usage tier, and it does not mention any change to fast mode pricing. It covers the Claude API and does not say whether fast mode access changes in Claude Code or claude.ai subscription plans.
Sources: Anthropic release notes: 2026-10-15
AI assisted reporting, checked against the linked official sources. Source pages checked 2026-10-15. Editorial process and corrections.