Screenshot prompting has a ceiling. You paste the design, the model makes a plausible approximation, you correct it, and on the next turn it drifts again. Nothing is anchored. The model has no source of truth to check itself against between turns. A context bundle changes the contract. Instead of a pixel reference the model has to interpret every time, you get a structured, referenceable set of files — design tokens, layout IR, component inventory, UI strings — that stay in the session and st...