# clm_AA51DFB9B1B8

subject: Anthropic (/record/anthropic.md)  
predicate: model_release  
value: Claude Fable 5.1  
valid_from: 2026-09-01  
valid_to: null  
published: 2026-09-01  
recorded: 2026-10-31  
confidence: 0.70  
status: valid  
assertable: true  
superseded_by: null  
last_updated: 2026-10-31  
checked: 2026-10-31 · its source page states the value and the date  

> September 1, 2026 Claude Fable 5.1 and Claude Mythos 5.1 launch We just launched Claude Fable 5.1 and Claude Mythos 5.1, the world’s most advanced models for coding and knowledge work.

What https://support.claude.com/en/articles/12138966-release-notes#2026-09-01 says, word for word.

## Sources

- https://support.claude.com/en/articles/12138966-release-notes#2026-09-01 (primary, Anthropic, published 2026-09-01)

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