Claude Fable 5 vs Opus 4.8: Should You Actually Switch? (Mythos-Class, Benchmarked)
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Claude Fable 5 hits 80.3% on SWE-Bench Pro against Opus 4.8's 69.2%, costs $10/$50 per million tokens, and falls back to Opus 4.8 on high-risk queries. Here's the benchmark breakdown, the worked cost-per-task math, and an honest framework for whether you should switch.