Tutorials, deep dives and product notes — built for developers.
Anthropic's new Mythos-class Fable 5 (80.3% SWE-bench Pro, $50/1M) vs the outgoing flagship Opus 4.8 (69.2%, $25/1M). Fable 5 dominates every benchmark — but costs 2× more, hallucinates more, and sometimes falls back to Opus 4.8 anyway. Full 30-benchmark comparison.
Which frontier AI model tells the truth? 🆕 Claude Fable 5 debuts at #1 on AA-Omniscience (40, 61% accuracy) but with accuracy-driven strategy — higher hallucination than Opus 4.8. GPT-5.4 Mini leads Vectara (5.5%). The reasoning paradox: thinking mode amplifies hallucination 2-3×. Full 19-model ranking.