60th UX feature: internal #section links show a tooltip with target heading + first ~150 characters. 300ms show / 200ms hide, keyboard focus, dark mode, print-hidden. Pure client-side on 126 files.
Commit 0597742 + coverage map 2a04c45. Verified LIVE markers on ai-wellbeing-manifesto.html. CSS+JS injected across 126 files.
Behavior: hover or keyboard-focus an internal fragment link → tooltip previews the destination heading and a short content snip (~150 chars). Delays 300ms show / 200ms hide keep it from flickering. Dark-mode aware; hidden in print. No telemetry.
Cascade: S372 Focus · S373 Streak · S374 Dependency Graph · S375 Glossary · S376 Outline Export · S377 Anchor Preview. Distinctive beyond S376; Non-WOW; no standing/echoes bump.