On September 15, 2026, TypeSafe AI launched Jev, a new category of System One models that classify inputs by returning probabilities for provided options in a single forward pass, without token generation. Open-source alternatives like Laya, Lev, and CLM emerged within weeks, each using different architectures (ModernBERT or Qwen backbones) to achieve the same task. Analysis of these implementations' architectures enables researchers to infer properties of the closed Jev model through controlled experiments.