The VuePress->VitePress migration replaced the `themeConfig.mode === 'dev'` gate with a heuristic on `site.title`. CI overrides version with a short SHA (dev) or git tag (prod), so the title never contains "edge"/"dev" and the banner never renders on live deploys. Surface `meta.mode` in `themeConfig` and check it directly, mirroring the original behaviour. Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>