Jev vs JSON mode
JSON mode (and cousins: “return JSON only,” YAML fences, markdown tables) is a prompt-plus-parser contract. Failure modes are familiar: truncated objects, extra keys, strings where you wanted enums, retries.
The TypeSafe HTTP response is JSON because HTTP APIs use JSON. The model is not being asked to author that document as a completion. Your client unmarshals a stable schema: model, answers, usage.
If you find yourself writing json.loads(completion) after a Jev call, you are on the wrong endpoint.
Independent projects that read option logits instead of generating JSON are exploring a related idea on open weights. They are not Jev. See OpenJev.
Sources
Public TypeSafe or adjacent documentation only. No private claims.