Source conditionThe fixed-height panel clips overflow; its vertical nav list has no bounded height and no overflow-y.

Trace the clipping owner.

800px / viewport.paneloverflow: hidden
→
188px rail.navflex-direction: column
→
unbounded rows.navListno scroll owner

Make the list the scrollport.

.navList {
  flex: 1;
  min-height: 0;
  overflow-y: auto;
}
Allocateflex: 1

Take the height left below the fixed title.

Shrinkmin-height: 0

Permit a flex child below its min-content size.

Reachoverflow-y: auto

Expose excess rows through a real scrollport.

Test behavior, not decoration.

Last row scrolls into viewKeyboard focus stays visibleTitle never scrolls awayContent scroll is independentFew rows show no scrollbar200% zoom remains usable

Avoid the tempting patches.

Do not unclip the whole panelDo not scroll the titleDo not hide plugin rowsDo not patch hashed CSS

Primary evidence.

Keep the full regression plan.

The canonical guide adds a DevTools proof, installed-build containment, keyboard semantics, responsive cases, partial-fix routing, and twenty regression gates.

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