400 LoRA steps on Gemma 4 31B beat dedicated decision model Jev

vanstriendaniel · x · 2026-10-24

'System One' decision models like Jev return calibrated decisions at a fraction of LLM cost. The team shows you don't need specialized architectures: attach a decision head (softmax over LM-head rows) to an open LLM's last hidden state and train only LoRA adapters plus head correction, one forward pass per decision.

On OpenDecisions, closed-API Jev 1.13 scores 80.1 and Gemma 4 31B out-of-the-box 79.6; after just 400 LoRA steps (5 GPU-hours) it reaches 84.4, beating the dedicated model. Paper: arxiv.org/abs/2610.17205.

Related event: Open Replication Matches Specialized Jev Decision Model with Simple LoRA Fine-tuning(2 posts)→

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