Article
CommunityJev Practices & Patterns
Typed Decision Models: Jev and Laya in Agentic AI
A comparative review of Jev and the open-source Laya encoder: interfaces, deployment, disclosed internals, calibration claims, and the limits of agreement-based workflow evals.
- Format
- Article
- Reading time
- 2 min
- Published by
- Community
- Author
- Michał Chromiak
- Last verified
- Sep 2026
Highlights
- Notes that TypeSafe's workflow evals measure agreement with other models rather than ground truth.
- Details Laya: a 421M ModernBERT encoder with a typed-option head and open weights.
- Reports 67.8% mean agreement at $0.0004 per case versus 67.9% at $0.0304 for the comparison model.
Questions about this entry
Short answers drawn from the linked project or page.
Same task shape, different products. Both expose Noul, Choice and Score style typed questions, but their internals, training evidence and deployment choices differ and the implementations are not interchangeable. Typed decision model is a description of the interface, not the name of one architecture.
Not ground truth. TypeSafe's workflow evals measure agreement with other models rather than verified labels, and the post labels its own illustrative numbers as examples rather than measured responses. A bounded answer set is a type guarantee, not a correctness guarantee: if fraud is missing from your list, the model can pick billing confidently.
The post reports 67.8% mean agreement at roughly $0.0004 per case against 67.9% at roughly $0.0304, so near-identical agreement across a seventy-fold price gap. The captured text does not restate which figure belongs to which model, so read the comparison section before drawing a conclusion from it.
TypeSafe documents up to 255 Choice options, two to ten Score levels, a 64k combined request limit, and 32k for state plus the longest question. The design rule is one semantic judgment per question: if question B needs A's answer, put it in a later request or compute the dependency in code.
A Noul returns a probability for yes, and 0.5 means yes and no are equally likely, not a medium intensity. To represent intensity, use a Score over explicit ordered levels: a probability-weighted position, so 0.25, 0.50, and 0.25 over three levels returns 1.0.
The article says TypeSafe calls Jev a System One Model and describes a new architecture, a parallel sampler, and post-training called Reinforcement Learning for Calibrated Decisions. It has not published the neural topology, parameter count, training recipe, or loss, so the article describes documented behavior, not hidden layers.
A Choice assumes the valid outcomes form a fixed set, and the model cannot name an option outside the list you supplied. That is a type guarantee, not a correctness guarantee: if the right answer is missing, it may confidently choose the least-wrong declared option, so include other or none_of_the_above.
Reactions & coverage
Posts, threads, and videos about this entry from around the web.
X: How the agent stack moved in Jev's first three days
YouTube: Diogo Almeida tells swyx what System One is, why RLHF failed his automation goal, and why AI should eventually disappear.
X: The 10-step roadmap, summarised
X: Giving your agents a decision brain
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