.container-header had position:relative which overrode .sticky-top's position:sticky due to CSS source order (container-header appeared later). Removed the conflicting rule. Added .container-header.sticky-top with z-index:1020 to keep header above all content. Mobile media query now only disables sticky when the sticky class is present. Fixes #115 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>