[combobox] Shift+Home / Shift+End does not extend text selection when Input is inside Popup

[hungnm-kaopiz]

Bug report

Current behavior

When Combobox.Input is rendered inside Combobox.Popup ("input inside popup" pattern, e.g. a button-triggered searchable dropdown), pressing Shift+Home (or Shift+End) while the input has text does not extend the native text selection from the caret to the start/end of the input value.

Shift+ArrowLeft / Shift+ArrowRight work correctly and do extend the selection one character at a time in the same input.

This reproduces in the official shadcn/ui docs demo for the base-ui Combobox "Popup" pattern (button trigger + ComboboxInput moved inside ComboboxContent), which is functionally the same "input inside popup" layout as this repo's input-inside-popup demo:

https://ui.shadcn.com/docs/components/base/combobox#popup

Steps to reproduce there:

1. Open the "Popup" example on the page above.
2. Click the trigger button to open the popup.
3. Type some text into the search input (e.g. "united").
4. Press Home — caret correctly moves to the start (no selection), as expected.
5. Now type again and press Shift+Home — expected: text from the caret to position 0 becomes selected. Actual: nothing gets selected (caret just moves, or nothing visibly happens), while Shift+ArrowLeft/Shift+ArrowRight correctly extend the selection one character at a time.

Expected behavior

Shift+Home / Shift+End should extend the native browser text selection in the input, exactly like a plain <input> outside of any Combobox, and exactly like Shift+ArrowLeft/Shift+ArrowRight already do inside this same Combobox input.

Notes from investigation

We use this pattern in our own app (a button Combobox.Trigger/ComboboxSelectTrigger + Combobox.Input inside Combobox.Popup, multiple selection mode) and traced the relevant keydown handling across:

• combobox/input/ComboboxInput.mjs — its own inline onKeyDown for Home/End (caret-positioning / RTL support) explicitly bails out early when any modifier (ctrlKey || shiftKey || altKey || metaKey) is held, before reaching the Home/End branches.
• internals/composite/root/useCompositeRoot.js — its keydown handler also explicitly bails ("return to native textbox behavior") when event.shiftKey is true and the event target is a native input.
• floating-ui-react/hooks/useListNavigation.mjs — the commonOnKeyDown's Home/End branch is gated by !typeableComboboxReference, so it should not apply when the reference is a typeable combobox input either.

All three layers we found appear to correctly defer to native browser selection behavior when Shift is held, so we weren't able to pin down from static source reading alone which handler (if any) is still intercepting the event, or whether this is a mergeProps ordering/interaction issue between these layers when the input is rendered inside a popup specifically (as opposed to being the trigger itself, e.g. the async-multiple chips-input-as-trigger demo, which does not exhibit this issue).

Reproducible example

Any "input inside popup" Combobox with multiple (our case) or single-select (the shadcn docs "Popup" example, single-select) reproduces it. Minimal repro is the official input-inside-popup demo pattern:

<Combobox.Root items={items}>
  <Combobox.Trigger>
    <Combobox.Value placeholder="Select..." />
  </Combobox.Trigger>
  <Combobox.Portal>
    <Combobox.Positioner>
      <Combobox.Popup>
        <Combobox.Input placeholder="Search..." />
        <Combobox.List>{/* ... */}</Combobox.List>
      </Combobox.Popup>
    </Combobox.Positioner>
  </Combobox.Portal>
</Combobox.Root>

Type text into Combobox.Input, then press Shift+Home.

Base UI version

@base-ui/react 1.6.0

Which browser are you using?

Reproduced on Windows/Linux with a physical Home key (not a Fn+arrow laptop substitute), so this isn't an OS/keyboard-hardware quirk. Exact browser/version not captured on our end, but also reproduces on the public shadcn docs demo above — happy to confirm exact browser/version if needed.

Which OS are you using?

Windows / Linux

Which assistive tech are you using (if applicable)?

N/A