Guide

Three questions

Objective

Pick a primitive by output shape, not by how hard the judgment feels. Know that Noul has no confidence field, and what happens when Choice has no other.

Three primitives (docs.typesafe.ai / systemonemodels.org / OpenTweet)
TypeQuestionReturnsLimits
ChoiceWhich of these?choice + probabilities + confidenceUp to 255 keys
ScoreWhere on this scale?Weighted score + legend + distribution + confidence2–10 levels, index from 0
NoulIs this statement true of the state?Only noul ∈ [0, 1]No confidence / probabilities

systemonemodels: Choice if you switch; Score if you compare to a cutoff; Noul if you gate one branch. A two-option Choice returns a pair plus confidence — heavier than a yes/no. OpenTweet: the common third-party bug is reading answers.*.confidence on a Noul (undefined). 0.97 and 0.03 are both sure; 0.5 means “cannot tell.” 0.5 is not “medium” — degree is a Score.

A Score is the probability-weighted mean of level indices, so it can sit between levels. The same 1.0 can mean all mass on 1, or half on 0 and half on 2 — read probabilities and confidence together. Docs: describe situations (“broken, workaround exists”), not intensifiers (“moderately severe”). The model does not see neighbors or level numbers. One Score, one dimension.

Exercise

The state is a browser snapshot. Lock TYPE_TEXT / CLICK / DONE as a Choice and leave an escape. See whether it invents hover.

Readings

Run