diff --git a/packages/super-editor/src/extensions/comment/comments-marks.js b/packages/super-editor/src/extensions/comment/comments-marks.js
index 9da39361c6..a42c387569 100644
--- a/packages/super-editor/src/extensions/comment/comments-marks.js
+++ b/packages/super-editor/src/extensions/comment/comments-marks.js
@@ -8,6 +8,8 @@ export const CommentsMark = Mark.create({
 
   excludes: '',
 
+  inclusive: false,
+
   addOptions() {
     return {
       htmlAttributes: { class: 'sd-editor-comment' },
diff --git a/tests/behavior/tests/comments/comment-mark-non-inclusive.spec.ts b/tests/behavior/tests/comments/comment-mark-non-inclusive.spec.ts
new file mode 100644
index 0000000000..04c181972f
--- /dev/null
+++ b/tests/behavior/tests/comments/comment-mark-non-inclusive.spec.ts
@@ -0,0 +1,86 @@
+import { test, expect } from '../../fixtures/superdoc.js';
+import { addCommentByText, assertDocumentApiReady } from '../../helpers/document-api.js';
+
+test.use({ config: { toolbar: 'full', comments: 'on' } });
+
+test.describe('comment mark non-inclusive boundary', () => {
+  test('typing after commented text does not extend the comment mark', async ({ superdoc }) => {
+    await assertDocumentApiReady(superdoc.page);
+
+    // 1. Type initial text
+    await superdoc.type('Commented');
+    await superdoc.waitForStable();
+    await superdoc.assertTextContains('Commented');
+
+    // 2. Add a comment on the word "Commented"
+    const commentId = await addCommentByText(superdoc.page, {
+      pattern: 'Commented',
+      text: 'Test comment',
+    });
+    await superdoc.waitForStable();
+    await superdoc.assertCommentHighlightExists({ text: 'Commented', commentId, timeoutMs: 20_000 });
+
+    // 3. Place cursor right after the commented text and type new text
+    const pos = await superdoc.findTextPos('Commented');
+    await superdoc.setTextSelection(pos + 'Commented'.length);
+    await superdoc.waitForStable();
+
+    await superdoc.type(' after');
+    await superdoc.waitForStable();
+
+    // 4. Verify the new text exists
+    await superdoc.assertTextContains('Commented after');
+
+    // 5. Verify the comment mark stays only on "Commented", not " after"
+    // Check that "Commented" has the comment mark
+    const commentedMarks = await superdoc.getMarksAtPos(await superdoc.findTextPos('Commented'));
+    expect(commentedMarks).toContain('commentMark');
+
+    // Check that " after" does NOT have the comment mark
+    const afterPos = await superdoc.findTextPos(' after');
+    const afterMarks = await superdoc.getMarksAtPos(afterPos);
+    expect(afterMarks).not.toContain('commentMark');
+
+    await superdoc.snapshot('comment-mark-non-inclusive');
+  });
+
+  test('typing before commented text does not extend the comment mark', async ({ superdoc }) => {
+    await assertDocumentApiReady(superdoc.page);
+
+    // 1. Type initial text
+    await superdoc.type('Commented');
+    await superdoc.waitForStable();
+
+    // 2. Add a comment on the word "Commented"
+    const commentId = await addCommentByText(superdoc.page, {
+      pattern: 'Commented',
+      text: 'Test comment',
+    });
+    await superdoc.waitForStable();
+    await superdoc.assertCommentHighlightExists({ text: 'Commented', commentId, timeoutMs: 20_000 });
+
+    // 3. Place cursor right before the commented text and type new text
+    const pos = await superdoc.findTextPos('Commented');
+    await superdoc.setTextSelection(pos);
+    await superdoc.waitForStable();
+
+    await superdoc.type('before ');
+    await superdoc.waitForStable();
+
+    // 4. Verify the new text exists
+    await superdoc.assertTextContains('before Commented');
+
+    // 5. Verify the comment mark stays only on "Commented", not "before "
+    // Check that "before " does NOT have the comment mark
+    const beforePos = await superdoc.findTextPos('before ');
+    const beforeMarks = await superdoc.getMarksAtPos(beforePos);
+    expect(beforeMarks).not.toContain('commentMark');
+
+    // Check that "Commented" still has the comment mark
+    const commentedPos = await superdoc.findTextPos('Commented');
+    const commentedMarks = await superdoc.getMarksAtPos(commentedPos);
+    expect(commentedMarks).toContain('commentMark');
+
+    await superdoc.snapshot('comment-mark-non-inclusive-before');
+  });
+});