diff --git a/packages/@sanity/portable-text-editor/src/editor/plugins/__tests__/withEditableAPISelectionsOverlapping.test.tsx b/packages/@sanity/portable-text-editor/src/editor/plugins/__tests__/withEditableAPISelectionsOverlapping.test.tsx
new file mode 100644
index 000000000000..e7532fdb3f18
--- /dev/null
+++ b/packages/@sanity/portable-text-editor/src/editor/plugins/__tests__/withEditableAPISelectionsOverlapping.test.tsx
@@ -0,0 +1,162 @@
+import {describe, expect, it, jest} from '@jest/globals'
+import {type PortableTextBlock} from '@sanity/types'
+import {render, waitFor} from '@testing-library/react'
+import {createRef, type RefObject} from 'react'
+
+import {PortableTextEditorTester, schemaType} from '../../__tests__/PortableTextEditorTester'
+import {PortableTextEditor} from '../../PortableTextEditor'
+
+const INITIAL_VALUE: PortableTextBlock[] = [
+  {
+    _key: 'a',
+    _type: 'block',
+    children: [
+      {
+        _key: 'a1',
+        _type: 'span',
+        marks: [],
+        text: 'This is some text in the block',
+      },
+    ],
+    markDefs: [],
+    style: 'normal',
+  },
+]
+
+describe('plugin:withEditableAPI: .isSelectionsOverlapping', () => {
+  it('returns true if the selections are partially overlapping', async () => {
+    const editorRef: RefObject<PortableTextEditor> = createRef()
+    const onChange = jest.fn()
+    render(
+      <PortableTextEditorTester
+        onChange={onChange}
+        ref={editorRef}
+        schemaType={schemaType}
+        value={INITIAL_VALUE}
+      />,
+    )
+    const selectionA = {
+      focus: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 4},
+      anchor: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 8},
+    }
+
+    const selectionB = {
+      focus: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 2},
+      anchor: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 6},
+    }
+
+    await waitFor(() => {
+      if (editorRef.current) {
+        const isOverlapping = PortableTextEditor.isSelectionsOverlapping(
+          editorRef.current,
+          selectionA,
+          selectionB,
+        )
+
+        expect(isOverlapping).toBe(true)
+      }
+    })
+  })
+
+  it('returns true if the selections are fully overlapping', async () => {
+    const editorRef: RefObject<PortableTextEditor> = createRef()
+    const onChange = jest.fn()
+    render(
+      <PortableTextEditorTester
+        onChange={onChange}
+        ref={editorRef}
+        schemaType={schemaType}
+        value={INITIAL_VALUE}
+      />,
+    )
+    const selectionA = {
+      focus: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 4},
+      anchor: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 8},
+    }
+
+    const selectionB = {
+      focus: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 4},
+      anchor: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 8},
+    }
+
+    await waitFor(() => {
+      if (editorRef.current) {
+        const isOverlapping = PortableTextEditor.isSelectionsOverlapping(
+          editorRef.current,
+          selectionA,
+          selectionB,
+        )
+
+        expect(isOverlapping).toBe(true)
+      }
+    })
+  })
+
+  it('return true if selection is fully inside another selection', async () => {
+    const editorRef: RefObject<PortableTextEditor> = createRef()
+    const onChange = jest.fn()
+    render(
+      <PortableTextEditorTester
+        onChange={onChange}
+        ref={editorRef}
+        schemaType={schemaType}
+        value={INITIAL_VALUE}
+      />,
+    )
+    const selectionA = {
+      focus: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 2},
+      anchor: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 10},
+    }
+
+    const selectionB = {
+      focus: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 4},
+      anchor: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 6},
+    }
+
+    await waitFor(() => {
+      if (editorRef.current) {
+        const isOverlapping = PortableTextEditor.isSelectionsOverlapping(
+          editorRef.current,
+          selectionA,
+          selectionB,
+        )
+
+        expect(isOverlapping).toBe(true)
+      }
+    })
+  })
+
+  it('returns false if the selections are not overlapping', async () => {
+    const editorRef: RefObject<PortableTextEditor> = createRef()
+    const onChange = jest.fn()
+    render(
+      <PortableTextEditorTester
+        onChange={onChange}
+        ref={editorRef}
+        schemaType={schemaType}
+        value={INITIAL_VALUE}
+      />,
+    )
+    const selectionA = {
+      focus: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 4},
+      anchor: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 8},
+    }
+
+    const selectionB = {
+      focus: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 10},
+      anchor: {path: [{_key: 'a'}, 'children', {_key: 'a1'}], offset: 12},
+    }
+
+    await waitFor(() => {
+      if (editorRef.current) {
+        const isOverlapping = PortableTextEditor.isSelectionsOverlapping(
+          editorRef.current,
+          selectionA,
+          selectionB,
+        )
+
+        expect(isOverlapping).toBe(false)
+      }
+    })
+  })
+})