Building a local Jev-style System One model: fine-tune 300M or build a custom decision engine?

AbbreviationsLoud182 · reddit · 2026-10-02

A Reddit poster weighs strategies for building Jev-style "System One" models for structured decisions — classification, routing, scoring, confidence estimation, agent action selection.

Three paths analyzed: (1) fine-tune a small decision model like Laya (300M) — cheap, fast, small footprint, but architecture-limited and the author's zero-shot domain classification tests fell short; (2) fine-tune/distill a larger CLM-8B — better generalization but VRAM and serving costs feel excessive for "which intent?" tasks; (3) build a custom 300M-500M decision engine mapping state + question + allowed options to a calibrated probability distribution, with uncertainty and abstention as first-class objectives — more data and harder debugging required. The favored middle ground: pretrained multilingual encoder → general decision training → domain decision data → optional adaptation.

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