Responsiveness
This proof gives the tree host height: 100% and does not rely on an initial row-budget hint. Drag the right edge or the bottom edge to see whether the file tree tracks its container like a full explorer pane.
Pane size: 620 × 420pxFlatten empty dirs: on
Content pane placeholder
Resize the surrounding workspace
In real apps the tree usually sits beside editor or detail content. This filler pane keeps the demo honest without needing a full-page layout.
What to watch
The tree viewport should grow and shrink with this container instead of staying stuck at its initial height.
Current setup
Width changes come from the right edge. Height changes come from the bottom edge. The explorer keeps the same model while the host box resizes around it.