PosterVisor is a control framework for generating scientific posters that shifts from transient prompts to persistent control. It uses Semantic-Geometric Contracts (SGCs) to bind claims and sources to required visuals, budgets, and spatial commitments, and Recursive Contract Enforcement (RCE) to dynamically trigger checks across stages as evidence emerges. PosterVisor improves poster-grounded QA accuracy and is preferred by human judges in pairwise comparisons.