Hands-on with Fable 5.1: taking over a 5+ day math problem across Codex and CC threads

DimitrisPapail · x · 2026-09-02

A user shares hands-on experience with Fable 5.1 in Claude Code: far better than F5, more creative than Sol, and Opus 5 doesn't compare. He used 5.1 to take over a hard math problem running 5+ days across multiple Codex and Claude Code threads, and notes it talks less Claudish. He jokes this is an expensive long-shot attempt at a ridiculously hard information theory problem.

Related event: Anthropic's Fable 5.1 Fixes the "Claude-speak" Tone, Drawing Positive Early Reviews(5 posts)→

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