Jev Can't Be Calibrated
Jev can't be calibrated September 23, 2026 · 3 mins · 617 words Share on: X · HN Unless you’ve been living under a rock, you’ve probably heard about Jev. Simon Willison’s post is a good overview, and this one shows how to implement it in a few lines of Python. In short, Jev is TypeSafe’s first “System One Model”: instead of generating text, it takes unstructured input and returns typed decisions from a set of outputs you define in advance, each with a probability attached.
- ▪Jev can't be calibrated September 23, 2026 · 3 mins · 617 words Share on: X · HN Unless you’ve been living under a rock, you’ve probably heard about Jev.
- ▪Simon Willison’s post is a good overview, and this one shows how to implement it in a few lines of Python.
- ▪In short, Jev is TypeSafe’s first “System One Model”: instead of generating text, it takes unstructured input and returns typed decisions from a set of outputs you define in advance, each with a probability attached.
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| Original publisher | Alexmolas |
| Canonical URL | https://www.alexmolas.com/2026/09/23/jev-cant-be-calibrated.html |
| Publication time | Wed, 23 Sep 2026 14:39:57 +0000 |
| Retrieval time | 2026-09-23T16:09:30.701Z |
| Last seen | 2026-09-23T16:09:30.701Z |
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Opening excerpt (first ~120 words) tap to expand
Jev can't be calibrated September 23, 2026 · 3 mins · 617 words Share on: X · HN Unless you’ve been living under a rock, you’ve probably heard about Jev. Simon Willison’s post is a good overview, and this one shows how to implement it in a few lines of Python. In short, Jev is TypeSafe’s first “System One Model”: instead of generating text, it takes unstructured input and returns typed decisions from a set of outputs you define in advance, each with a probability attached. One of its selling points is that “all answers are accompanied with calibrated probabilities and confidence scores”. In this post I argue that Jev is useful, but that the calibration claim can’t hold in general, and that you should treat its outputs as scores rather than probabilities.
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Excerpt limited to ~120 words for fair-use compliance. The full article is at Alexmolas.
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