What happened?
When Prefab renders inside an MCP App iframe, opening a Popover with many items (e.g. a series picker with 200+ checkboxes) causes the host page to grow vertically. The popover content also can't scroll, so items below the fold are unreachable.
Expected: Popover floats over the chart; list scrolls inside ~18rem; iframe/document height unchanged.
Actual: Host scroll area expands when popover opens; long lists overflow with no scroll.
Proposed fix
App-level fixed overlay portal (position:fixed, pointer-events:none host + PortalContainerProvider).
Popover: positionMethod="fixed", pointer-events-auto on popup, max-height + internal overflow-y-auto.
PrefabPopover: scrollable body region below title.
This is a targeted bug fix — no new public API.
Example Code
Version Information
What happened?
When Prefab renders inside an MCP App iframe, opening a Popover with many items (e.g. a series picker with 200+ checkboxes) causes the host page to grow vertically. The popover content also can't scroll, so items below the fold are unreachable.
Expected: Popover floats over the chart; list scrolls inside ~18rem; iframe/document height unchanged.
Actual: Host scroll area expands when popover opens; long lists overflow with no scroll.
Proposed fix
App-level fixed overlay portal (position:fixed, pointer-events:none host + PortalContainerProvider).
Popover: positionMethod="fixed", pointer-events-auto on popup, max-height + internal overflow-y-auto.
PrefabPopover: scrollable body region below title.
This is a targeted bug fix — no new public API.
Example Code
Version Information