feat: mobile drag-to-trash to remove draft starter chips

Lift both starter groups into one DndContext so a trash drop-zone is reachable from either group's drag. On mobile the trash replaces the + button while dragging (color-only over feedback, no resize); dropping a chip on it removes that starter. Hide the hover-x on mobile since there is no hover. Desktop keeps the hover-x + add button unchanged.

packages/ui/src/components/chat/DraftPresetChips.tsx

@@ -5,7 +5,9 @@ import {
     TouchSensor,
     useSensor,
     useSensors,
+    useDroppable,
     closestCenter,
+    MeasuringStrategy,
     type DragEndEvent,
 } from '@dnd-kit/core';
 import { SortableContext, useSortable, rectSortingStrategy } from '@dnd-kit/sortable';
@@ -28,13 +30,13 @@ import {
 } from '@/components/ui/dialog';
 import { useI18n } from '@/lib/i18n';
 import { useThemeSystem } from '@/contexts/useThemeSystem';
+import { useDeviceInfo } from '@/lib/device';
 import { cn } from '@/lib/utils';
 import {
     useDraftStarters,
     type ResolvedStarter,
     type PinnableItem,
     type PinnableSection,
-    type StarterGroup,
 } from './useDraftStarters';
 
 type DraftPresetChipsProps = {
@@ -44,6 +46,17 @@ type DraftPresetChipsProps = {
     className?: string;
 };
 
+// Droppable id for the mobile "drag a chip here to delete" target. Kept distinct
+// from any chip id (which are `group:type:name`) so collisions never alias.
+const TRASH_DROPPABLE_ID = '__draft-starter-trash__';
+
+// Shared box for the round icon buttons in the "+" slot (add picker and the
+// mobile trash drop-zone). Identical so swapping one for the other never shifts
+// layout or changes the circle size. shrink-0 keeps it from being compressed by
+// the wrapping flex row.
+const ROUND_ICON_BUTTON_CLASS =
+    'inline-flex h-7 w-7 shrink-0 items-center justify-center rounded-full border transition-colors';
+
 const PICKER_SECTIONS: { key: PinnableSection; headingKey: 'chat.draftStarters.sectionBuiltIn' | 'chat.draftStarters.sectionCommands' | 'chat.draftStarters.sectionSkills' }[] = [
     { key: 'built-in', headingKey: 'chat.draftStarters.sectionBuiltIn' },
     { key: 'command', headingKey: 'chat.draftStarters.sectionCommands' },
@@ -54,7 +67,9 @@ const SortableChip: React.FC<{
     item: ResolvedStarter;
     onSubmit: (text: string) => void;
     onRemove: () => void;
-}> = ({ item, onSubmit, onRemove }) => {
+    /** Hide the per-chip hover "x" (mobile uses the trash drop-zone instead). */
+    hideRemove?: boolean;
+}> = ({ item, onSubmit, onRemove, hideRemove }) => {
     const { t } = useI18n();
     const { currentTheme } = useThemeSystem();
     const { attributes, listeners, setNodeRef, transform, transition, isDragging } = useSortable({ id: item.id });
@@ -82,6 +97,7 @@ const SortableChip: React.FC<{
                 <Icon name={item.icon} className="h-3.5 w-3.5 shrink-0 opacity-70 transition-opacity group-hover:opacity-100" />
                 <span className="whitespace-nowrap">{item.label}</span>
             </button>
+            {hideRemove ? null : (
                 <button
                     type="button"
                     onClick={(e) => { e.stopPropagation(); onRemove(); }}
@@ -92,42 +108,59 @@ const SortableChip: React.FC<{
                 >
                     <Icon name="close" className="h-2.5 w-2.5" />
                 </button>
+            )}
         </div>
     );
 };
 
-const StarterGroupRow: React.FC<{
+const StarterGroup: React.FC<{
-    group: StarterGroup;
     items: ResolvedStarter[];
     onSubmit: (text: string) => void;
-    onRemove: (group: StarterGroup, ref: ResolvedStarter['ref']) => void;
+    onRemove: (item: ResolvedStarter) => void;
-    onReorder: (group: StarterGroup, fromId: string, toId: string) => void;
+    hideRemove?: boolean;
-}> = ({ group, items, onSubmit, onRemove, onReorder }) => {
+}> = ({ items, onSubmit, onRemove, hideRemove }) => (
-    const sensors = useSensors(
-        // Desktop: start dragging after a small move so a click still submits.
-        useSensor(MouseSensor, { activationConstraint: { distance: 8 } }),
-        // Touch: long-press to drag (tap submits, a quick swipe scrolls instead).
-        useSensor(TouchSensor, { activationConstraint: { delay: 200, tolerance: 6 } }),
-    );
-    const handleDragEnd = (event: DragEndEvent) => {
-        const { active, over } = event;
-        if (over && active.id !== over.id) {
-            onReorder(group, String(active.id), String(over.id));
-        }
-    };
-    return (
-        <DndContext sensors={sensors} collisionDetection={closestCenter} onDragEnd={handleDragEnd}>
     <SortableContext items={items.map((i) => i.id)} strategy={rectSortingStrategy}>
         {items.map((item) => (
             <SortableChip
                 key={item.id}
                 item={item}
                 onSubmit={onSubmit}
-                        onRemove={() => onRemove(group, item.ref)}
+                onRemove={() => onRemove(item)}
+                hideRemove={hideRemove}
             />
         ))}
     </SortableContext>
-        </DndContext>
+);
+
+/**
+ * Mobile delete target. Sits in the "+" slot and is only mounted while a chip is
+ * being dragged; dropping a chip on it removes that starter. Styled to match the
+ * add ("+") button so the swap reads as the same affordance toggling purpose.
+ */
+const TrashDropZone: React.FC = () => {
+    const { t } = useI18n();
+    const { currentTheme } = useThemeSystem();
+    const { setNodeRef, isOver } = useDroppable({ id: TRASH_DROPPABLE_ID });
+
+    return (
+        <button
+            type="button"
+            ref={setNodeRef}
+            aria-label={t('chat.draftStarters.remove')}
+            title={t('chat.draftStarters.remove')}
+            // Same box as the "+" button so the swap never shifts layout; on-hover
+            // feedback is color-only (no resize).
+            className={cn(
+                ROUND_ICON_BUTTON_CLASS,
+                isOver ? 'border-destructive text-destructive' : 'text-muted-foreground',
+            )}
+            style={{
+                backgroundColor: currentTheme?.colors?.surface?.elevated,
+                borderColor: isOver ? undefined : currentTheme?.colors?.interactive?.border,
+            }}
+        >
+            <Icon name="delete-bin" className="h-4 w-4" />
+        </button>
     );
 };
 
@@ -187,7 +220,7 @@ const AddStarterPicker: React.FC<{
                     type="button"
                     aria-label={t('chat.draftStarters.add')}
                     title={t('chat.draftStarters.add')}
-                    className="inline-flex h-7 w-7 items-center justify-center rounded-full border text-muted-foreground transition-colors hover:bg-[var(--interactive-hover)] hover:text-foreground"
+                    className={cn(ROUND_ICON_BUTTON_CLASS, 'text-muted-foreground hover:bg-[var(--interactive-hover)] hover:text-foreground')}
                     style={{
                         backgroundColor: currentTheme?.colors?.surface?.elevated,
                         borderColor: currentTheme?.colors?.interactive?.border,
@@ -215,19 +248,86 @@ const AddStarterPicker: React.FC<{
  * global group then the project group (each reorderable within itself), plus a
  * "+" picker to pin existing commands/skills. The surface owns how a chip click
  * is submitted via `onSubmit`.
+ *
+ * Both groups share a single DndContext so the mobile trash drop-zone (which
+ * replaces the "+" while dragging) is reachable from either group's drag.
+ * Reorder is constrained to within a chip's own group; cross-group hovers are
+ * ignored.
  */
 export const DraftPresetChips: React.FC<DraftPresetChipsProps> = ({ onSubmit, className }) => {
     const { global, project, pinnable, ensureLoaded, addStarter, removeStarter, reorder } = useDraftStarters();
+    const { isMobile } = useDeviceInfo();
+    const [isDragging, setIsDragging] = React.useState(false);
+
+    const sensors = useSensors(
+        // Desktop: start dragging after a small move so a click still submits.
+        useSensor(MouseSensor, { activationConstraint: { distance: 8 } }),
+        // Touch: long-press to drag (tap submits, a quick swipe scrolls instead).
+        useSensor(TouchSensor, { activationConstraint: { delay: 200, tolerance: 6 } }),
+    );
+
+    const chipById = React.useCallback(
+        (id: string): ResolvedStarter | undefined =>
+            global.find((i) => i.id === id) ?? project.find((i) => i.id === id),
+        [global, project],
+    );
+
+    const handleDragStart = () => setIsDragging(true);
+    const handleDragCancel = () => setIsDragging(false);
+    const handleDragEnd = (event: DragEndEvent) => {
+        setIsDragging(false);
+        const { active, over } = event;
+        if (!over) return;
+        const activeId = String(active.id);
+        const chip = chipById(activeId);
+        if (!chip) return;
+        if (String(over.id) === TRASH_DROPPABLE_ID) {
+            removeStarter(chip.group, chip.ref);
+            return;
+        }
+        const overId = String(over.id);
+        if (activeId === overId) return;
+        const overChip = chipById(overId);
+        // Reorder only within the same group; ignore cross-group hovers.
+        if (overChip && overChip.group === chip.group) {
+            reorder(chip.group, activeId, overId);
+        }
+    };
 
     return (
+        <DndContext
+            sensors={sensors}
+            collisionDetection={closestCenter}
+            // The trash drop-zone mounts on drag start, so re-measure droppables
+            // while dragging or it never registers a rect to drop onto.
+            measuring={{ droppable: { strategy: MeasuringStrategy.Always } }}
+            onDragStart={handleDragStart}
+            onDragCancel={handleDragCancel}
+            onDragEnd={handleDragEnd}
+        >
             <div className={cn('flex flex-wrap items-center justify-center gap-2', className)}>
                 {global.length > 0 ? (
-                <StarterGroupRow group="global" items={global} onSubmit={onSubmit} onRemove={removeStarter} onReorder={reorder} />
+                    <StarterGroup
+                        items={global}
+                        onSubmit={onSubmit}
+                        onRemove={(item) => removeStarter('global', item.ref)}
+                        hideRemove={isMobile}
+                    />
                 ) : null}
                 {project.length > 0 ? (
-                <StarterGroupRow group="project" items={project} onSubmit={onSubmit} onRemove={removeStarter} onReorder={reorder} />
+                    <StarterGroup
+                        items={project}
+                        onSubmit={onSubmit}
+                        onRemove={(item) => removeStarter('project', item.ref)}
+                        hideRemove={isMobile}
+                    />
                 ) : null}
+                {isMobile && isDragging ? (
+                    <TrashDropZone />
+                ) : (
                     <AddStarterPicker pinnable={pinnable} onOpen={ensureLoaded} onAdd={addStarter} />
+                )}
             </div>
+        </DndContext>
     );
 };