#Json Schema

TypeSafe launched Jev, the first System One model: it doesn't complete text, it takes your program's state and returns a typed decision in a single parallel pass. No parser, no retries, no broken JSON. In this post: what Jev actually is, why it can't hallucinate (and why that doesn't mean it can't be wrong), the real math on $0.042 per million tokens with free output, the three primitives with running Python code, and the 5 traps the docs themselves admit to.

If your code has a try/catch wrapped around a json_decode of the model's response, you don't have a contract. You have hope. How to get truly guaranteed structured output from an LLM: constrained decoding at the provider, a schema the model can satisfy, semantic validation and retry with a fixed budget, with no infinite loop and no defensive parser.