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← Back to the day · June 28, 2026

GPT-5.6 Beats Claude Mythos and Fable in Benchmarks

The GPT-5.6 Soul Ultra model outperformed Claude Mythos on Stanford's terminals benchmark and beat Claude Fable 5 by a significant margin. A separate model, Terra, also surpassed Fable 5 in cybersecurity tests.

The GPT-5.6 Soul Ultra model outperformed Claude Mythos on Stanford's terminals benchmark.

It also beat Claude Fable 5 by a significant margin in that benchmark.

In addition, the Terra model surpassed Fable 5 in cybersecurity tests.

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