TypeSafe AI introduced Jev—a model that takes text as input and returns numbers: a category, a probability, or a yes/no answer with a confidence level. Simon Willison and Maggie
Text as an interface is the bottleneck
Appleton suggests calling these “decision models”—a more precise term than the marketing label System One.
For businesses, this is a signal: the next layer of LLM systems will make decisions without passing through text.
Most business systems with an LLM inside are poorly designed:
- the model writes prose
- and then an engineer builds a parser on top
- regex or JSON mode
- to extract “approve/reject” from this prose
- a number from 0 to
Each such layer introduces errors and delays.
The model may change the format, add a polite introduction, or break the JSON with an extra comma.
The model responds quickly on its own
TTU—the time from a request to a ready decision—increases during text parsing after the response.


