Benchmarks

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11 min read

Claude Fable 5: what the official demos don't tell you

Fable 5 migrates 50 million lines of Ruby in a day. That's true. But while prepping a training module, I ran into the flip side the announcements skip: 500k to 1M tokens per session, 19 timeouts out of 33 tasks, and guardrails that trip at the faintest hint — to the point that Anthropic had to publicly apologize 48 hours after launch. The real manual for a model you commission instead of steer.