diff --git a/tools/ui/src/lib/components/app/misc/CollapsibleRegion.svelte b/tools/ui/src/lib/components/app/misc/CollapsibleRegion.svelte
new file mode 100644
index 0000000000..4a7a2ffbcc
--- /dev/null
+++ b/tools/ui/src/lib/components/app/misc/CollapsibleRegion.svelte
@@ -0,0 +1,87 @@
+<script lang="ts">
+	import type { Snippet } from 'svelte';
+
+	interface Props {
+		children: Snippet;
+		open: boolean;
+	}
+
+	let { children, open }: Props = $props();
+
+	// rows stay mounted through the collapse transition so it can play
+	const EXPAND_TRANSITION_MS = 200;
+	// the initial state only: the effect below owns it afterwards
+	// svelte-ignore state_referenced_locally
+	let contentMounted = $state(open);
+
+	$effect(() => {
+		if (open) {
+			contentMounted = true;
+
+			return;
+		}
+
+		const timer = setTimeout(() => (contentMounted = false), EXPAND_TRANSITION_MS);
+
+		return () => clearTimeout(timer);
+	});
+</script>
+
+<div class="collapsible-region" data-expanded={open}>
+	{#if contentMounted}
+		<div class="collapsible-region-content">
+			{@render children()}
+		</div>
+	{/if}
+</div>
+
+<style>
+	/*
+	 * The region animates between height 0 and height auto. `interpolate-size`
+	 * lets the auto keyword take part in the interpolation, so the content needs
+	 * no measured height to stay in sync with. Browsers without it fall back to
+	 * an interpolating grid row, which snaps only in the oldest engines.
+	 */
+	.collapsible-region {
+		height: 0;
+		/* clip, not hidden: hidden would make the region a scrollport, and the
+		   sticky rows inside it would then never leave their opening position */
+		overflow: clip;
+		visibility: hidden;
+		interpolate-size: allow-keywords;
+		transition:
+			height 200ms cubic-bezier(0.23, 1, 0.32, 1),
+			visibility 200ms;
+	}
+
+	.collapsible-region[data-expanded='true'] {
+		height: auto;
+		visibility: visible;
+	}
+
+	@supports not (interpolate-size: allow-keywords) {
+		.collapsible-region {
+			display: grid;
+			/* minmax(0, 1fr) pins the column to the region width: a plain auto
+			   column would size to the content and push wide rows out of the list */
+			grid-template-columns: minmax(0, 1fr);
+			grid-template-rows: 0fr;
+			/* the row owns the height here: leaving height: 0 in place would snap
+			   the region shut before the row could interpolate */
+			height: auto;
+			transition:
+				grid-template-rows 200ms cubic-bezier(0.23, 1, 0.32, 1),
+				visibility 200ms;
+		}
+
+		.collapsible-region[data-expanded='true'] {
+			grid-template-rows: 1fr;
+		}
+
+		.collapsible-region-content {
+			min-height: 0;
+			min-width: 0;
+			overflow: clip;
+		}
+	}
+</style>
diff --git a/tools/ui/src/lib/components/app/misc/CollapsibleSection.svelte b/tools/ui/src/lib/components/app/misc/CollapsibleSection.svelte
index 25a65d1812..2e9202cf29 100644
--- a/tools/ui/src/lib/components/app/misc/CollapsibleSection.svelte
+++ b/tools/ui/src/lib/components/app/misc/CollapsibleSection.svelte
@@ -1,4 +1,5 @@
 <script lang="ts">
+	import CollapsibleRegion from './CollapsibleRegion.svelte';
 	import { ChevronDown, ChevronUp } from '@lucide/svelte';
 	import * as DropdownMenu from '$lib/components/ui/dropdown-menu';
 	import { ICON_CLASS_DEFAULT } from '$lib/constants';
@@ -11,7 +12,10 @@
 		trigger: Snippet;
 		/** Render the trigger as a dropdown menu item, so menu keyboard navigation reaches it. */
 		inMenu?: boolean;
-		/** Start expanded. */
+		/** Start expanded. The section owns the state, so a parent rebuild cannot
+		 *  snap it back open. Bind `open` instead to control it from outside. */
+		defaultOpen?: boolean;
+		/** Controlled open state, for a caller that binds it. */
 		open?: boolean;
 		/** Hide the chevron while expanded, until the trigger is hovered. */
 		revealChevronOnHover?: boolean;
@@ -23,33 +27,15 @@
 
 	let {
 		children,
+		defaultOpen = true,
 		inMenu = false,
-		open = $bindable(true),
+		open = $bindable(defaultOpen),
 		revealChevronOnHover = false,
 		trigger,
 		triggerClass = '',
 		triggerPosition = 'top',
 		triggerStyle = ''
 	}: Props = $props();
-
-	// rows stay mounted through the collapse transition so it can play; after it
-	// they unmount - mounted rows are menu items and would pollute the arrow-key
-	// navigation
-	// the region animates between height 0 and auto; see the component styles
-	const EXPAND_TRANSITION_MS = 200;
-	let contentMounted = $state(open);
-
-	$effect(() => {
-		if (open) {
-			contentMounted = true;
-
-			return;
-		}
-
-		const timer = setTimeout(() => (contentMounted = false), EXPAND_TRANSITION_MS);
-
-		return () => clearTimeout(timer);
-	});
 </script>
 
 {#snippet chevron()}
@@ -107,13 +93,11 @@
 {#snippet region()}
 	<!-- Custom expand region instead of bits-ui Collapsible (whose conditional
 	     rendering kills the transition). -->
-	<div class="collapsible-region" data-expanded={open}>
-		{#if contentMounted}
-			<div class="collapsible-region-content">
-				{@render children()}
-			</div>
-		{/if}
-	</div>
+	{#snippet body()}
+		{@render children()}
+	{/snippet}
+
+	<CollapsibleRegion {open}>{@render body()}</CollapsibleRegion>
 {/snippet}
 
 {#if triggerPosition === 'top'}
@@ -125,54 +109,3 @@
 
 	{@render triggerButton()}
 {/if}
-
-<style>
-	/*
-	 * The region animates between height 0 and height auto. `interpolate-size`
-	 * lets the auto keyword take part in the interpolation, so the content needs
-	 * no measured height to stay in sync with. Browsers without it fall back to
-	 * an interpolating grid row, which snaps only in the oldest engines.
-	 */
-	.collapsible-region {
-		height: 0;
-		/* clip, not hidden: hidden would make the region a scrollport, and the
-		   sticky rows inside it would then never leave their opening position */
-		overflow: clip;
-		visibility: hidden;
-		interpolate-size: allow-keywords;
-		transition:
-			height 200ms cubic-bezier(0.23, 1, 0.32, 1),
-			visibility 200ms;
-	}
-
-	.collapsible-region[data-expanded='true'] {
-		height: auto;
-		visibility: visible;
-	}
-
-	@supports not (interpolate-size: allow-keywords) {
-		.collapsible-region {
-			display: grid;
-			/* minmax(0, 1fr) pins the column to the region width: a plain auto
-			   column would size to the content and push wide rows out of the list */
-			grid-template-columns: minmax(0, 1fr);
-			grid-template-rows: 0fr;
-			/* the row owns the height here: leaving height: 0 in place would snap
-			   the region shut before the row could interpolate */
-			height: auto;
-			transition:
-				grid-template-rows 200ms cubic-bezier(0.23, 1, 0.32, 1),
-				visibility 200ms;
-		}
-
-		.collapsible-region[data-expanded='true'] {
-			grid-template-rows: 1fr;
-		}
-
-		.collapsible-region-content {
-			min-height: 0;
-			min-width: 0;
-			overflow: clip;
-		}
-	}
-</style>
diff --git a/tools/ui/src/lib/components/app/misc/GroupedList.svelte b/tools/ui/src/lib/components/app/misc/GroupedList.svelte
index 752797a159..fb6f609f44 100644
--- a/tools/ui/src/lib/components/app/misc/GroupedList.svelte
+++ b/tools/ui/src/lib/components/app/misc/GroupedList.svelte
@@ -8,6 +8,7 @@
 </script>
 
 <script generics="G, E" lang="ts">
+	import CollapsibleRegion from './CollapsibleRegion.svelte';
 	import type { Snippet } from 'svelte';
 	import { SvelteMap, SvelteSet } from 'svelte/reactivity';
 
@@ -120,7 +121,7 @@
 			</div>
 		{/if}
 
-		{#if expanded}
+		<CollapsibleRegion open={expanded}>
 			{#each entry.rows as row (keyOf(row))}
 				{@render item({ depth: 1, entry: row })}
 			{/each}
@@ -132,7 +133,7 @@
 					unit: 'entries'
 				})}
 			{/if}
-		{/if}
+		</CollapsibleRegion>
 	{/each}
 
 	{#if windowed.length < (groups?.length ?? 0) && more}
diff --git a/tools/ui/src/lib/components/app/models/ModelsManager/ModelsManagerModelsTable.svelte b/tools/ui/src/lib/components/app/models/ModelsManager/ModelsManagerModelsTable.svelte
index 325521eaa6..dfb565eb3b 100644
--- a/tools/ui/src/lib/components/app/models/ModelsManager/ModelsManagerModelsTable.svelte
+++ b/tools/ui/src/lib/components/app/models/ModelsManager/ModelsManagerModelsTable.svelte
@@ -548,9 +548,9 @@
 				<ModelsSection
 					backendId={group.kind === 'provider' ? (group.backendId ?? undefined) : undefined}
 					count={group.items.length}
+					defaultOpen={group.kind !== 'hidden'}
 					icon={group.kind === 'provider' ? undefined : groupIcon}
 					label={group.label}
-					open={group.kind !== 'hidden'}
 					sticky
 					stickyClass="sticky z-10 bg-muted/90 backdrop-blur-lg"
 				>
diff --git a/tools/ui/src/lib/components/app/models/ModelsSection.svelte b/tools/ui/src/lib/components/app/models/ModelsSection.svelte
index f4e6f51958..0efb436410 100644
--- a/tools/ui/src/lib/components/app/models/ModelsSection.svelte
+++ b/tools/ui/src/lib/components/app/models/ModelsSection.svelte
@@ -20,7 +20,7 @@
 		/** Renders the back control, for a drilled-in provider. */
 		onBack?: () => void;
 		/** Start expanded; the manager collapses its hidden block. */
-		open?: boolean;
+		defaultOpen?: boolean;
 		revealChevronOnHover?: boolean;
 		sectionHeaderClass?: string;
 		/** Sticky class of the header, so a surface can shade it differently. */
@@ -33,12 +33,12 @@
 		backendId,
 		children,
 		count,
+		defaultOpen = true,
 		error = false,
 		icon,
 		label,
 		loading = false,
 		onBack,
-		open = true,
 		revealChevronOnHover = false,
 		sectionHeaderClass = 'm-0 px-2 py-2 text-[13px] font-semibold text-muted-foreground select-none',
 		sticky = false,
@@ -52,7 +52,7 @@
 	let triggerStyle = $derived(sticky ? 'top: var(--dropdown-sticky-height, 0px)' : '');
 </script>
 
-<CollapsibleSection {open} {revealChevronOnHover} {triggerClass} {triggerStyle}>
+<CollapsibleSection {defaultOpen} {revealChevronOnHover} {triggerClass} {triggerStyle}>
 	{#snippet trigger()}
 		{#if onBack}
 			<button