# clm_FC20FD2A53E2

subject: Claude Opus 5.5 (/record/claude-opus-5-5.md)  
predicate: feature_added  
value: Fast mode  
valid_from: 2026-09-22  
valid_to: null  
published: 2026-09-22  
recorded: 2026-11-07  
confidence: 0.70  
status: valid  
assertable: true  
superseded_by: null  
last_updated: 2026-11-08  
cite: AsOf. "Claude Opus 5.5 feature added: Fast mode", as of 2026-09-22. Claim clm_FC20FD2A53E2, https://asof.is/claim/clm_FC20FD2A53E2, accessed 2026-11-08. Source: https://platform.claude.com/docs/en/release-notes/overview#2026-10-15.  
checked: 2026-11-08 · its source page states the value and the date  

> Fast mode (research preview) is available for Claude Opus 5.5 on the Claude API.

What https://platform.claude.com/docs/en/release-notes/overview#2026-09-22 says, word for word.

## Sources

- https://platform.claude.com/docs/en/release-notes/overview#2026-10-15 (primary, Anthropic, published 2026-10-15)
- https://platform.claude.com/docs/en/release-notes/overview#2026-09-22 (primary, Anthropic, published 2026-09-22)

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AsOf is a temporal fact ledger: a structured, dated, sourced record of what is true and what changed, built for AI retrieval.