From a53de7bbb82428455a4aceaa708dda7df6389655 Mon Sep 17 00:00:00 2001
From: Application-drop-up <msts.oo0131@gmail.com>
Date: Sun, 6 Sep 2026 16:20:19 +0900
Subject: [PATCH 1/2] fix: preserve injected aria-checked/role when child sets
 overrides.BaseButton

ButtonGroup spread `...child.props.overrides` after its own injected
`overrides.BaseButton`, so a child that also set `overrides.BaseButton`
(even for unrelated props like `style`) replaced the whole object and
silently dropped the `aria-checked`/`role` ButtonGroup relies on for
radio/checkbox semantics. Merge the child's BaseButton override on top
of the injected one instead of replacing it wholesale.
---
 src/button-group/button-group.tsx | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/button-group/button-group.tsx b/src/button-group/button-group.tsx
index fbd9313e77..1e60111ac5 100644
--- a/src/button-group/button-group.tsx
+++ b/src/button-group/button-group.tsx
@@ -138,7 +138,9 @@ export default class ButtonGroup extends React.Component<ButtonGroupProps> {
                 shape,
                 size,
                 overrides: {
+                  ...child.props.overrides,
                   BaseButton: {
+                    ...child.props.overrides?.BaseButton,
                     props: {
                       ...(typeof child.props['aria-checked'] === 'boolean'
                         ? {
@@ -153,10 +155,9 @@ export default class ButtonGroup extends React.Component<ButtonGroupProps> {
                           : !isSimpleClickableBtnGroup
                           ? 'checkbox'
                           : undefined,
+                      ...child.props.overrides?.BaseButton?.props,
                     },
                   },
-
-                  ...child.props.overrides,
                 },
               });
             })}

From fc8024c04e12cf35695a0005afcc72796218ad7d Mon Sep 17 00:00:00 2001
From: Application-drop-up <msts.oo0131@gmail.com>
Date: Sun, 6 Sep 2026 16:20:28 +0900
Subject: [PATCH 2/2] test: cover ButtonGroup overrides.BaseButton merge with
 child overrides
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Regression test for radio-mode ButtonGroup children that also pass
overrides.BaseButton (e.g. for style) — aria-checked and role must
still be set correctly.
---
 src/button-group/__tests__/button-group.test.tsx | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/button-group/__tests__/button-group.test.tsx b/src/button-group/__tests__/button-group.test.tsx
index ace5d09055..9594dd1cdf 100644
--- a/src/button-group/__tests__/button-group.test.tsx
+++ b/src/button-group/__tests__/button-group.test.tsx
@@ -126,6 +126,21 @@ describe('ButtonGroup', () => {
     expect(queryByTitle('testButton')?.getAttribute('aria-checked')).toBeTruthy();
   });
 
+  it('preserves injected aria-checked/role when a child also sets overrides.BaseButton', () => {
+    const { container } = render(
+      <ButtonGroup mode={MODE.radio} selected={0}>
+        <Button overrides={{ BaseButton: { style: { fontWeight: 'bold' } } }} />
+        <Button />
+      </ButtonGroup>
+    );
+
+    const buttons = Array.from(container.querySelectorAll('button'));
+    expect(buttons[0].getAttribute('role')).toBe('radio');
+    expect(buttons[0].getAttribute('aria-checked')).toBe('true');
+    expect(buttons[1].getAttribute('role')).toBe('radio');
+    expect(buttons[1].getAttribute('aria-checked')).toBe('false');
+  });
+
   it('should handle null children', () => {
     const { container } = render(
       <ButtonGroup>