Layout measurement excluded pill margin on some renderers, collapsing the intended gap above visible tracks. Keep the two-pill rail on one line and derive its complete tail clearance from shared geometry so chat switching and layout callbacks cannot change the result.
Keep agent and task pills as a transparent transcript overlay while measuring their rendered height for scroll-tail clearance. Share geometry and spacing with the import-session pill so borders, type, corners, and composer separation match across platforms.
Mohamed Boudra