From ce3becea310258381313e3752b9fbc55d4d5a4f3 Mon Sep 17 00:00:00 2001
From: Timo <gasda@amazon.com>
Date: Wed, 17 Jun 2026 09:31:40 +0200
Subject: [PATCH 1/2] feat(space-between): Add `stretch` option to space
 between's `alignItems` property

---
 .../alignment.permutations.page.tsx           |  2 +-
 pages/space-between/styles.scss               |  2 ++
 .../__tests__/space-between.test.tsx          | 23 +++++++++++++++++++
 src/space-between/interfaces.ts               |  2 +-
 src/space-between/styles.scss                 |  4 ++++
 5 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/pages/space-between/alignment.permutations.page.tsx b/pages/space-between/alignment.permutations.page.tsx
index 0d5b71ad7c..287add1515 100644
--- a/pages/space-between/alignment.permutations.page.tsx
+++ b/pages/space-between/alignment.permutations.page.tsx
@@ -49,7 +49,7 @@ const permutations = createPermutations<Pick<SpaceBetweenProps, 'direction' | 'a
   {
     children: [ExampleChildren, NestedExample],
     direction: ['vertical', 'horizontal'],
-    alignItems: [undefined, 'center', 'start', 'end'],
+    alignItems: [undefined, 'center', 'start', 'end', 'stretch'],
   },
 ]);
 
diff --git a/pages/space-between/styles.scss b/pages/space-between/styles.scss
index 1106f593aa..7e88b4232c 100644
--- a/pages/space-between/styles.scss
+++ b/pages/space-between/styles.scss
@@ -7,11 +7,13 @@
 
 .border-box-outer,
 .box {
+  block-size: 100%;
   border-block: 1px solid tokens.$color-border-status-info;
   border-inline: 1px solid tokens.$color-border-status-info;
 }
 
 .border-box-inner {
+  block-size: 100%;
   border-block: 1px solid tokens.$color-border-status-error;
   border-inline: 1px solid tokens.$color-border-status-error;
 }
diff --git a/src/space-between/__tests__/space-between.test.tsx b/src/space-between/__tests__/space-between.test.tsx
index 4f1c0f1127..071fa0a236 100644
--- a/src/space-between/__tests__/space-between.test.tsx
+++ b/src/space-between/__tests__/space-between.test.tsx
@@ -85,6 +85,29 @@ describe('SpaceBetween', () => {
     expect(content[0].getElement()).toHaveAttribute('id', 'button-one');
     expect(content[1].getElement()).toHaveAttribute('id', 'button-two');
   });
+
+  it.each(['center', 'start', 'end', 'stretch'] as const)('applies align-%s class', alignItems => {
+    const { container } = render(
+      <SpaceBetween size="s" alignItems={alignItems}>
+        <button />
+        <button />
+      </SpaceBetween>
+    );
+    expect(container.firstChild).toHaveClass(styles[`align-${alignItems}`]);
+  });
+
+  it('does not apply an alignment class when alignItems is undefined', () => {
+    const { container } = render(
+      <SpaceBetween size="s">
+        <button />
+        <button />
+      </SpaceBetween>
+    );
+    expect(container.firstChild).not.toHaveClass(styles['align-center']);
+    expect(container.firstChild).not.toHaveClass(styles['align-start']);
+    expect(container.firstChild).not.toHaveClass(styles['align-end']);
+    expect(container.firstChild).not.toHaveClass(styles['align-stretch']);
+  });
 });
 
 describe('native attributes', () => {
diff --git a/src/space-between/interfaces.ts b/src/space-between/interfaces.ts
index 3be285cfd9..2883c10af9 100644
--- a/src/space-between/interfaces.ts
+++ b/src/space-between/interfaces.ts
@@ -45,5 +45,5 @@ export namespace SpaceBetweenProps {
 
   export type Size = 'xxxs' | 'xxs' | 'xs' | 's' | 'm' | 'l' | 'xl' | 'xxl';
 
-  export type AlignItems = 'center' | 'start' | 'end';
+  export type AlignItems = 'center' | 'start' | 'end' | 'stretch';
 }
diff --git a/src/space-between/styles.scss b/src/space-between/styles.scss
index 18544b66da..9966bb7a43 100644
--- a/src/space-between/styles.scss
+++ b/src/space-between/styles.scss
@@ -80,3 +80,7 @@ $sizes-vertical: (
 .align-end {
   align-items: end;
 }
+
+.align-stretch {
+  align-items: stretch;
+}

From 0b58a6c1fa8c73a8d900406c7393a23a988e5a41 Mon Sep 17 00:00:00 2001
From: Timo <gasda@amazon.com>
Date: Wed, 17 Jun 2026 10:10:54 +0200
Subject: [PATCH 2/2] Update documenter

---
 .../snapshot-tests/__snapshots__/documenter.test.ts.snap         | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/__tests__/snapshot-tests/__snapshots__/documenter.test.ts.snap b/src/__tests__/snapshot-tests/__snapshots__/documenter.test.ts.snap
index 09c5b8aae0..2ddd4b9183 100644
--- a/src/__tests__/snapshot-tests/__snapshots__/documenter.test.ts.snap
+++ b/src/__tests__/snapshot-tests/__snapshots__/documenter.test.ts.snap
@@ -26931,6 +26931,7 @@ exports[`Components definition for space-between matches the snapshot: space-bet
           "center",
           "end",
           "start",
+          "stretch",
         ],
       },
       "name": "alignItems",