# U-Space: Uncovering When and Why Uncertainty Arises in Language Models [R][D] > Source: > Published: 2026-10-17 21:00:03+00:00 If you build on open-weight reasoning models, you have probably wanted a "how sure is the model about this answer?" signal that does not cost 5x sampling, a judge model, or a labeled dataset. Hence, we built the U-Lens. In one line: score = (how strongly the hidden state points toward different "dou