Phase 9d · Tier B

RN-universal Combobox pilot

Scaffolded

Single-select picker with typeahead. Composes RnPopover + RnCommand — no new runtime dep. Mirrors the shadcn Combobox surface (options array + value/onChange) plus controlled-mode open/onOpenChange for A2UI agents.

Side-by-side: pick a fruit

shadcn (Popover + cmdk)

Selected: (none)

Search-text synonyms (RN)

Each option packs synonyms into searchText while the trigger displays a clean label. Try typing "vue", "shopify", or "universal".

Selected: (none)

Library decision

Per Phase 9 Q2, every Tier B primitive must record its library choice. RnCombobox ships with no new runtime dependency.

shadcn Combobox is itself a Popover + cmdk composition. The RN-universal substitutes (RnPopover 0.2.1, RnCommand 0.2.3) are already shipped, so this primitive is a thin composition shell — same code path on web and native.
Compared with downshift@9 (MIT, ~7M/wk): downshift solves the same combobox state machine but is DOM-coupled (uses document.activeElement, DOM event listeners, and focus rings) and would force a.web/.native split. Rejected for the same reason as cmdk.
Compared with react-native-paper Searchbar + Autocomplete (MIT): full UI kit; pulls Material Design styling and a Paper Provider. Out of scope for a single primitive.

Semantics

Aspect	shadcn (Popover + cmdk)	RN	Notes
Trigger	Button (variant=outline)	Pressable + chevron + label	Same compact, full-width-by-default visual
Filter	fuzzy + score	substring (case-insensitive)	Pass `filter` prop for custom ranking
Empty state	<CommandEmpty>	<RnCommandEmpty>	Shown only after the user has typed and 0 match
Synonyms	value + keywords	searchText overrides label	Trigger shows label; filter sees searchText
Controlled value	value + onChange	value + onValueChange	A2UI agents drive both modes
Controlled open	(via Popover)	open + onOpenChange	Exposed at the root for declarative agent UIs
Single-select	yes	yes	Multi-select is a 0.2.x candidate
Auto-flip	no	no	Same perf-budget call as RnPopover