Two bugs: 1. [data-theme="dark"] block was defined BEFORE :root in source CSS, so :root cascade overrode it. Moved to AFTER :root and bumped specificity to html[data-theme="dark"] to beat plain :root. 2. Theme toggle button only existed in the topbar, which is hidden on landing/login/sso-callback scenes. Added a ThemeToggle to the Landing header so users can flip theme from the home page. Confidence: high Scope-risk: narrow