Claude Fable 5.1 improves on Claude Fable 5 across the board, with the biggest gains in agentic coding, long-running agentic workflows, and knowledge work: long code refactors, front-end and visual...

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idanthropic/claude-fable-5.1
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context_length1000000
max_output_tokens128000
knowledge_cutoff2026-06
release_date2026-09-01
is_open_weightsno
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Claude Fable 5.1