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GPT-5.6, Fable 5, and Grok 4.5 rebuild Basecamp from the same spec
The author evaluated GPT-5.6 Sol, Fable 5, Grok 4.5, and other AI models on a benchmark called Basecamp Bench, testing their ability to build a frontend and backend from the same specification. Fable 5 won both tracks, while Grok 4.5 offered the best speed-cost tradeoff. Results show significant differences in polish and completeness, especially in the final 10% of work.
- Fable 5 scored highest on both frontend and backend, closely matching the real Basecamp implementation.
- Grok 4.5 completed the build in 37 minutes at a cost of $9.30, offering the best speed and cost tradeoff.