diff --git a/apps/www/src/content/docs/components/accordion/index.mdx b/apps/www/src/content/docs/components/accordion/index.mdx
index db12ac4fb..53cae5139 100644
--- a/apps/www/src/content/docs/components/accordion/index.mdx
+++ b/apps/www/src/content/docs/components/accordion/index.mdx
@@ -107,4 +107,5 @@ Every rendered part carries a stable `data-slot` attribute for [styling and test
 - Trigger elements use `aria-expanded` to indicate open/closed state
 - Supports keyboard navigation with Enter and Space to toggle items
 - Content panels use `aria-controls` and `aria-labelledby` for association
+- A disabled item's trigger has the native `disabled` attribute, so it is left out of the Tab order
 - Respects motion preferences: icon rotation and panel expand/collapse motion is enabled only when `prefers-reduced-motion: no-preference`
diff --git a/apps/www/src/content/docs/components/collapsible/index.mdx b/apps/www/src/content/docs/components/collapsible/index.mdx
index 694af2e68..009a11e2f 100644
--- a/apps/www/src/content/docs/components/collapsible/index.mdx
+++ b/apps/www/src/content/docs/components/collapsible/index.mdx
@@ -85,4 +85,5 @@ Every rendered part carries a stable `data-slot` attribute for [styling and test
 - The Trigger uses `aria-expanded` to indicate the open/closed state of the panel.
 - Supports keyboard interaction with Enter and Space to toggle the panel.
 - The Panel is automatically associated with the Trigger via `aria-controls`.
+- A disabled Trigger has the native `disabled` attribute, so it is left out of the Tab order.
 - Respects motion preferences: panel expand/collapse motion is enabled only when `prefers-reduced-motion: no-preference`
diff --git a/packages/react/CHANGELOG.md b/packages/react/CHANGELOG.md
index fa5ec7f72..63c0922fc 100644
--- a/packages/react/CHANGELOG.md
+++ b/packages/react/CHANGELOG.md
@@ -2,6 +2,26 @@
 
 ## Unreleased
 
+### Base UI 1.9.0
+
+Apsara uses `@base-ui/react` 1.9.0 and `@base-ui/utils` 0.5.0. The
+changes below are the ones an app can see.
+
+#### Changes
+
+- A disabled `Accordion` or `Collapsible` trigger has the native
+  `disabled` attribute. It is dimmed and left out of the Tab order.
+- A multiple `Combobox` or `Select` accepts a readonly array for `value`
+  and `defaultValue`. `onValueChange` still receives a mutable array.
+- In `Menu`, `ContextMenu` and `Menubar`, activating the trigger of an
+  open submenu closes it, and a submenu closes when focus leaves it
+  through its focus guard.
+- The `ScrollArea` viewport has no `role="presentation"`.
+- `Checkbox`, `Radio` and `Switch` take their accessible name from
+  `aria-label` when they also have an associated label.
+- A `Dialog`, `AlertDialog` or `Drawer` opened from code through a
+  handle is not linked to a trigger that did not open it.
+
 ### Icons — lucide replaces @radix-ui/react-icons (BREAKING)
 
 Apsara names every icon with a stable key that does not name a library —
diff --git a/packages/react/components/combobox/__tests__/combobox.test.tsx b/packages/react/components/combobox/__tests__/combobox.test.tsx
index be67e1770..4f6f53d35 100644
--- a/packages/react/components/combobox/__tests__/combobox.test.tsx
+++ b/packages/react/components/combobox/__tests__/combobox.test.tsx
@@ -605,6 +605,13 @@ describe('Combobox chips', () => {
     expect(screen.getByText('banana')).toBeInTheDocument();
   });
 
+  it('accepts a readonly array as the value', () => {
+    const value = ['apple', 'banana'] as const;
+    render(<BasicCombobox multiple value={value} />);
+    expect(screen.getByText('apple')).toBeInTheDocument();
+    expect(screen.getByText('banana')).toBeInTheDocument();
+  });
+
   it('removes the last chip on Backspace in an empty input', async () => {
     const user = userEvent.setup();
     const handleValueChange = vi.fn();
diff --git a/packages/react/components/combobox/combobox-root.tsx b/packages/react/components/combobox/combobox-root.tsx
index 3c22bca55..cc40f1986 100644
--- a/packages/react/components/combobox/combobox-root.tsx
+++ b/packages/react/components/combobox/combobox-root.tsx
@@ -19,7 +19,7 @@ interface ComboboxContextValue<Value = string> {
   hasItems: boolean;
   inputId: string;
   inputContainerRef: RefObject<HTMLDivElement | null>;
-  value: Value | Value[] | null | undefined;
+  value: Value | readonly Value[] | null | undefined;
   getLabel: (value: Value) => string;
 }
 
@@ -58,8 +58,8 @@ export interface SingleComboboxProps<Value = string, Item = Value>
 export interface MultipleComboboxProps<Value = string, Item = Value>
   extends BaseComboboxRootProps<Value, Item> {
   multiple: true;
-  value?: Value[];
-  defaultValue?: Value[];
+  value?: readonly Value[];
+  defaultValue?: readonly Value[];
   onValueChange?: (value: Value[]) => void;
 }
 
@@ -95,7 +95,7 @@ export const ComboboxRoot = <Value extends unknown | unknown[], Item = Value>({
     state: 'inputValue'
   });
   const [computedValue, setValueUnwrapped] = useControlled<
-    Value | Value[] | null
+    Value | readonly Value[] | null
   >({
     controlled: providedValue,
     default: defaultValue ?? null,
diff --git a/packages/react/components/select/__tests__/select.test.tsx b/packages/react/components/select/__tests__/select.test.tsx
index 82647b7bd..ab45b93bc 100644
--- a/packages/react/components/select/__tests__/select.test.tsx
+++ b/packages/react/components/select/__tests__/select.test.tsx
@@ -291,6 +291,31 @@ describe('Select', () => {
       await flushMicrotasks();
       expect(handleValueChange).toHaveBeenCalledTimes(1);
     });
+
+    it('accepts a readonly array as the value', async () => {
+      const value = ['apple', 'banana'] as const;
+      const user = userEvent.setup();
+      render(
+        <Select multiple value={value}>
+          <Select.Trigger>{TRIGGER_TEXT}</Select.Trigger>
+          <Select.Content>
+            {FRUIT_OPTIONS.map(option => (
+              <Select.Item key={option.value} value={option.value}>
+                {option.label}
+              </Select.Item>
+            ))}
+          </Select.Content>
+        </Select>
+      );
+      await openSelect(user);
+      await flushMicrotasks();
+
+      const checked = screen
+        .getAllByRole('option')
+        .map(option => within(option).getByRole('checkbox'))
+        .map(checkbox => checkbox.getAttribute('aria-checked'));
+      expect(checked).toEqual(['true', 'true', 'false', 'false', 'false']);
+    });
   });
 
   describe('Keyboard Navigation', () => {
diff --git a/packages/react/components/select/select-root.tsx b/packages/react/components/select/select-root.tsx
index 5a0321ecf..5d78591f5 100644
--- a/packages/react/components/select/select-root.tsx
+++ b/packages/react/components/select/select-root.tsx
@@ -25,7 +25,7 @@ interface CommonProps {
 }
 
 interface SelectContextValue extends CommonProps {
-  value?: string | string[];
+  value?: string | readonly string[];
   registerItem: (item: ItemType) => void;
   unregisterItem: (value: string) => void;
   multiple: boolean;
@@ -79,9 +79,9 @@ export interface SingleSelectProps extends BaseSelectProps {
 
 export interface MultipleSelectProps extends BaseSelectProps {
   multiple: true;
-  value?: string[];
+  value?: readonly string[];
   onValueChange?: (value: string[]) => void;
-  defaultValue?: string[];
+  defaultValue?: readonly string[];
 }
 
 export type SelectRootProps = SingleSelectProps | MultipleSelectProps;
@@ -112,7 +112,7 @@ export const SelectRoot = (props: SelectRootProps) => {
   const resolvedRequired = required ?? fieldContext?.required;
 
   const [computedValue, setValueUnwrapped] = useControlled<
-    string | string[] | undefined
+    string | readonly string[] | undefined
   >({
     controlled: providedValue,
     default: defaultValue,