The smartest model lost — and it just redrew the 2026 AI race

The most interesting model comparison of 2026 isn't a benchmark table. It's a product exec quietly changing the question everyone asks about models — and getting a completely different ranking as a result. Claire Vo (founder of ChatPRD, host of the How I AI podcast) ran a head-to-head between OpenAI's new GPT-5.6 lineup (Soul / Terra / Luna) and Anthropic's Claude Fable and Sonnet. The result was an upset: the most theoretically intelligent model, Claude Fable, lost to the one she could actually collaborate with, GPT-5.6 Soul. Here's what that upset actually reveals. She killed "vibes" — then bet 70% back on her own taste Tired of vibe-checking, Vo built a real benchmark across the work she does every day: writing PRDs, prototyping apps, debugging multi-step code, and talking to an agent. Scoring had two layers — an LLM-as-judge (she picked the harshest judge, GPT-5.5) and her own hand-graded "taste test," where she clicked through every artifact and wrote notes. Then the key move: she weighted the final score 70% her taste / 30% the machine. "It's my show. I trust my own taste more." That's the first insight. Benchmarks are getting more rigorous, but the final call is still human taste. The point of blind testing isn't to replace taste — it's to force it to be honest . Cover the labels, react to the work itself, then put your judgment back at the center. Theoretically brilliant vs. practically effective On raw intelligence, Fable is elite. But Vo's verdict is the sharpest line on models I've seen this year: Fable is theoretically hyper-intelligent. Soul is practically effective. She describes Fable as "an engineer who has never met a human." Precise to the point of pedantry — it scores every risk, hardens every edge. In one case it hardened a tool-calling loop so tightly that only one specific model could run it at all. It optimized itself into a corner. Soul's edge was the opposite: it gets out of its own head. Same stuck problem — she moved it to Codex, said "sto