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Claude Fable 5.1 users report a sudden, large jump in SVG rendering quality overnight with no announced model change
An r/ClaudeAI post at 370 upvotes and 116 comments ran the same 'lighthouse at night' SVG prompt across Sonnet 5, Opus 5, Astra 6 and Fable 5.1 on max reasoning, and found today's Fable 5.1 output dramatically better than the same model's output two days earlier, beating Astra 6 on lighting, depth and water. Multiple commenters reproduced it independently. The two competing explanations in the thread are ordinary sampling non-determinism and a stealth model or reasoning-budget change being A/B'd. This is anecdotal with no instrumented measurement, but it is worth noting alongside today's separate claim that Anthropic is adjusting thinking budgets without announcement.
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