diff --git a/.changeset/header-get-is-pinned.md b/.changeset/header-get-is-pinned.md
new file mode 100644
index 0000000000..2d08d9968e
--- /dev/null
+++ b/.changeset/header-get-is-pinned.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/table-core': minor
+---
+
+Add `header.getIsPinned()`, which reads the pinned region of a header's own leaf columns. A group column split across pinned regions renders one header per region, and `header.column.getIsPinned()` reported the same region for all of them (#4906).
diff --git a/docs/framework/alpine/guide/column-pinning.md b/docs/framework/alpine/guide/column-pinning.md
index e82ae63317..633839eeb7 100644
--- a/docs/framework/alpine/guide/column-pinning.md
+++ b/docs/framework/alpine/guide/column-pinning.md
@@ -140,6 +140,7 @@ There are a handful of useful Column API methods to help you implement column pi
 - `column.getCanPin`: Use to determine if a column can be pinned.
 - `column.pin`: Use to pin a column to the start or end. Or use to unpin a column.
 - `column.getIsPinned`: Use to determine where a column is pinned.
+- `header.getIsPinned`: Use to determine where a header is pinned. A group header split across pinned regions reports the region it is rendered in, which `header.column.getIsPinned` cannot.
 - `column.getPinnedIndex`: Use to read the column's index within its pinned column group.
 - `column.getStart`: Use to provide the correct `start` CSS value for a pinned column.
 - `column.getAfter`: Use to provide the correct `end` CSS value for a pinned column.
@@ -214,19 +215,16 @@ Because Alpine does not initialize directives inside content set with `x-html`,
   <template x-if="!header.isPlaceholder && header.column.getCanPin()">
     <div class="pin-actions">
       <button
-        x-show="header.column.getIsPinned() !== 'start'"
+        x-show="header.getIsPinned() !== 'start'"
         @click="header.column.pin('start')"
       >
         &lt;=
       </button>
-      <button
-        x-show="header.column.getIsPinned()"
-        @click="header.column.pin(false)"
-      >
+      <button x-show="header.getIsPinned()" @click="header.column.pin(false)">
         X
       </button>
       <button
-        x-show="header.column.getIsPinned() !== 'end'"
+        x-show="header.getIsPinned() !== 'end'"
         @click="header.column.pin('end')"
       >
         =&gt;
diff --git a/docs/framework/angular/guide/column-pinning.md b/docs/framework/angular/guide/column-pinning.md
index 8f9a6af3e3..115cecc5fd 100644
--- a/docs/framework/angular/guide/column-pinning.md
+++ b/docs/framework/angular/guide/column-pinning.md
@@ -139,6 +139,7 @@ There are a handful of useful Column API methods to help you implement column pi
 - `column.getCanPin`: Use to determine if a column can be pinned.
 - `column.pin`: Use to pin a column to the start or end. Or use to unpin a column.
 - `column.getIsPinned`: Use to determine where a column is pinned.
+- `header.getIsPinned`: Use to determine where a header is pinned. A group header split across pinned regions reports the region it is rendered in, which `header.column.getIsPinned` cannot.
 - `column.getPinnedIndex`: Use to read the column's index within its pinned column group.
 - `column.getStart`: Use to provide the correct `start` CSS value for a pinned column.
 - `column.getAfter`: Use to provide the correct `end` CSS value for a pinned column.
diff --git a/docs/framework/ember/guide/column-pinning.md b/docs/framework/ember/guide/column-pinning.md
index 75313e4660..7b0ae0fa6b 100644
--- a/docs/framework/ember/guide/column-pinning.md
+++ b/docs/framework/ember/guide/column-pinning.md
@@ -139,6 +139,7 @@ There are a handful of useful Column API methods to help you implement column pi
 - `column.getCanPin`: Use to determine if a column can be pinned.
 - `column.pin`: Use to pin a column to the start or end. Or use to unpin a column.
 - `column.getIsPinned`: Use to determine where a column is pinned.
+- `header.getIsPinned`: Use to determine where a header is pinned. A group header split across pinned regions reports the region it is rendered in, which `header.column.getIsPinned` cannot.
 - `column.getPinnedIndex`: Use to read the column's index within its pinned column group.
 - `column.getStart`: Use to provide the correct `start` CSS value for a pinned column.
 - `column.getAfter`: Use to provide the correct `end` CSS value for a pinned column.
@@ -202,20 +203,26 @@ Use `table.getIsSomeColumnsPinned()` to check if any columns are pinned, or pass
 Because Ember templates extract method references without binding them, wrap these Column and Table method calls in small module-scope helper functions (or getters), then call the helpers from your markup:
 
 ```ts
-import { type Column, type ColumnPinningPosition } from '@tanstack/ember-table'
+import {
+  type Column,
+  type ColumnPinningPosition,
+  type Header,
+} from '@tanstack/ember-table'
 
 const getCanPin = (column: Column<typeof features, Person>): boolean =>
   column.getCanPin()
 
+// Read pin state from the header, so a group split across pinned regions
+// reports the region this header is rendered in
 const getIsPinned = (
-  column: Column<typeof features, Person>,
-): ColumnPinningPosition => column.getIsPinned()
+  header: Header<typeof features, Person>,
+): ColumnPinningPosition => header.getIsPinned()
 
-const isPinnedStart = (column: Column<typeof features, Person>): boolean =>
-  column.getIsPinned() === 'start'
+const isPinnedStart = (header: Header<typeof features, Person>): boolean =>
+  header.getIsPinned() === 'start'
 
-const isPinnedEnd = (column: Column<typeof features, Person>): boolean =>
-  column.getIsPinned() === 'end'
+const isPinnedEnd = (header: Header<typeof features, Person>): boolean =>
+  header.getIsPinned() === 'end'
 
 const pin = (
   column: Column<typeof features, Person>,
@@ -228,19 +235,19 @@ const pin = (
 ```hbs
 {{#if (getCanPin header.column)}}
   <div class='pin-actions'>
-    {{#unless (isPinnedStart header.column)}}
+    {{#unless (isPinnedStart header)}}
       <button
         class='pin-button'
         {{on 'click' (pin header.column 'start')}}
       >◀</button>
     {{/unless}}
-    {{#if (getIsPinned header.column)}}
+    {{#if (getIsPinned header)}}
       <button
         class='pin-button'
         {{on 'click' (pin header.column false)}}
       >✕</button>
     {{/if}}
-    {{#unless (isPinnedEnd header.column)}}
+    {{#unless (isPinnedEnd header)}}
       <button
         class='pin-button'
         {{on 'click' (pin header.column 'end')}}
diff --git a/docs/framework/lit/guide/column-pinning.md b/docs/framework/lit/guide/column-pinning.md
index 6afb6eda89..f8f9e184c4 100644
--- a/docs/framework/lit/guide/column-pinning.md
+++ b/docs/framework/lit/guide/column-pinning.md
@@ -147,6 +147,7 @@ There are a handful of useful Column API methods to help you implement column pi
 - `column.getCanPin`: Use to determine if a column can be pinned.
 - `column.pin`: Use to pin a column to the start or end. Or use to unpin a column.
 - `column.getIsPinned`: Use to determine where a column is pinned.
+- `header.getIsPinned`: Use to determine where a header is pinned. A group header split across pinned regions reports the region it is rendered in, which `header.column.getIsPinned` cannot.
 - `column.getPinnedIndex`: Use to read the column's index within its pinned column group.
 - `column.getStart`: Use to provide the correct `start` CSS value for a pinned column.
 - `column.getAfter`: Use to provide the correct `end` CSS value for a pinned column.
diff --git a/docs/framework/octane/guide/column-pinning.md b/docs/framework/octane/guide/column-pinning.md
index a947903be3..ef84d38fa1 100644
--- a/docs/framework/octane/guide/column-pinning.md
+++ b/docs/framework/octane/guide/column-pinning.md
@@ -129,6 +129,7 @@ There are a handful of useful Column API methods to help you implement column pi
 - `column.getCanPin`: Use to determine if a column can be pinned.
 - `column.pin`: Use to pin a column to the start or end. Or use to unpin a column.
 - `column.getIsPinned`: Use to determine where a column is pinned.
+- `header.getIsPinned`: Use to determine where a header is pinned. A group header split across pinned regions reports the region it is rendered in, which `header.column.getIsPinned` cannot.
 - `column.getPinnedIndex`: Use to read the column's index within its pinned column group.
 - `column.getStart`: Use to provide the correct `start` CSS value for a pinned column.
 - `column.getAfter`: Use to provide the correct `end` CSS value for a pinned column.
diff --git a/docs/framework/preact/guide/column-pinning.md b/docs/framework/preact/guide/column-pinning.md
index 6a57f46fb0..1746925291 100644
--- a/docs/framework/preact/guide/column-pinning.md
+++ b/docs/framework/preact/guide/column-pinning.md
@@ -129,6 +129,7 @@ There are a handful of useful Column API methods to help you implement column pi
 - `column.getCanPin`: Use to determine if a column can be pinned.
 - `column.pin`: Use to pin a column to the start or end. Or use to unpin a column.
 - `column.getIsPinned`: Use to determine where a column is pinned.
+- `header.getIsPinned`: Use to determine where a header is pinned. A group header split across pinned regions reports the region it is rendered in, which `header.column.getIsPinned` cannot.
 - `column.getPinnedIndex`: Use to read the column's index within its pinned column group.
 - `column.getStart`: Use to provide the correct `start` CSS value for a pinned column.
 - `column.getAfter`: Use to provide the correct `end` CSS value for a pinned column.
diff --git a/docs/framework/react/guide/column-pinning.md b/docs/framework/react/guide/column-pinning.md
index 740c9a8d35..7a4047f953 100644
--- a/docs/framework/react/guide/column-pinning.md
+++ b/docs/framework/react/guide/column-pinning.md
@@ -129,6 +129,7 @@ There are a handful of useful Column API methods to help you implement column pi
 - `column.getCanPin`: Use to determine if a column can be pinned.
 - `column.pin`: Use to pin a column to the start or end. Or use to unpin a column.
 - `column.getIsPinned`: Use to determine where a column is pinned.
+- `header.getIsPinned`: Use to determine where a header is pinned. A group header split across pinned regions reports the region it is rendered in, which `header.column.getIsPinned` cannot.
 - `column.getPinnedIndex`: Use to read the column's index within its pinned column group.
 - `column.getStart`: Use to provide the correct `start` CSS value for a pinned column.
 - `column.getAfter`: Use to provide the correct `end` CSS value for a pinned column.
diff --git a/docs/framework/solid/guide/column-pinning.md b/docs/framework/solid/guide/column-pinning.md
index 79d0a75b81..620c1380e4 100644
--- a/docs/framework/solid/guide/column-pinning.md
+++ b/docs/framework/solid/guide/column-pinning.md
@@ -135,6 +135,7 @@ There are a handful of useful Column API methods to help you implement column pi
 - `column.getCanPin`: Use to determine if a column can be pinned.
 - `column.pin`: Use to pin a column to the start or end. Or use to unpin a column.
 - `column.getIsPinned`: Use to determine where a column is pinned.
+- `header.getIsPinned`: Use to determine where a header is pinned. A group header split across pinned regions reports the region it is rendered in, which `header.column.getIsPinned` cannot.
 - `column.getPinnedIndex`: Use to read the column's index within its pinned column group.
 - `column.getStart`: Use to provide the correct `start` CSS value for a pinned column.
 - `column.getAfter`: Use to provide the correct `end` CSS value for a pinned column.
diff --git a/docs/framework/svelte/guide/column-pinning.md b/docs/framework/svelte/guide/column-pinning.md
index 3926d47955..bd7387b8d5 100644
--- a/docs/framework/svelte/guide/column-pinning.md
+++ b/docs/framework/svelte/guide/column-pinning.md
@@ -136,6 +136,7 @@ There are a handful of useful Column API methods to help you implement column pi
 - `column.getCanPin`: Use to determine if a column can be pinned.
 - `column.pin`: Use to pin a column to the start or end. Or use to unpin a column.
 - `column.getIsPinned`: Use to determine where a column is pinned.
+- `header.getIsPinned`: Use to determine where a header is pinned. A group header split across pinned regions reports the region it is rendered in, which `header.column.getIsPinned` cannot.
 - `column.getPinnedIndex`: Use to read the column's index within its pinned column group.
 - `column.getStart`: Use to provide the correct `start` CSS value for a pinned column.
 - `column.getAfter`: Use to provide the correct `end` CSS value for a pinned column.
diff --git a/docs/framework/vue/guide/column-pinning.md b/docs/framework/vue/guide/column-pinning.md
index 8113e557ca..767b695d78 100644
--- a/docs/framework/vue/guide/column-pinning.md
+++ b/docs/framework/vue/guide/column-pinning.md
@@ -136,6 +136,7 @@ There are a handful of useful Column API methods to help you implement column pi
 - `column.getCanPin`: Use to determine if a column can be pinned.
 - `column.pin`: Use to pin a column to the start or end. Or use to unpin a column.
 - `column.getIsPinned`: Use to determine where a column is pinned.
+- `header.getIsPinned`: Use to determine where a header is pinned. A group header split across pinned regions reports the region it is rendered in, which `header.column.getIsPinned` cannot.
 - `column.getPinnedIndex`: Use to read the column's index within its pinned column group.
 - `column.getStart`: Use to provide the correct `start` CSS value for a pinned column.
 - `column.getAfter`: Use to provide the correct `end` CSS value for a pinned column.
diff --git a/examples/react/column-pinning-split/src/main.tsx b/examples/react/column-pinning-split/src/main.tsx
index 747de17796..70a6b33651 100644
--- a/examples/react/column-pinning-split/src/main.tsx
+++ b/examples/react/column-pinning-split/src/main.tsx
@@ -164,7 +164,7 @@ function App() {
                     </div>
                     {!header.isPlaceholder && header.column.getCanPin() && (
                       <div className="pin-actions">
-                        {header.column.getIsPinned() !== 'start' ? (
+                        {header.getIsPinned() !== 'start' ? (
                           <button
                             className="pin-button"
                             onClick={() => {
@@ -174,7 +174,7 @@ function App() {
                             {'<='}
                           </button>
                         ) : null}
-                        {header.column.getIsPinned() ? (
+                        {header.getIsPinned() ? (
                           <button
                             className="pin-button"
                             onClick={() => {
@@ -184,7 +184,7 @@ function App() {
                             X
                           </button>
                         ) : null}
-                        {header.column.getIsPinned() !== 'end' ? (
+                        {header.getIsPinned() !== 'end' ? (
                           <button
                             className="pin-button"
                             onClick={() => {
@@ -233,7 +233,7 @@ function App() {
                     </div>
                     {!header.isPlaceholder && header.column.getCanPin() && (
                       <div className="pin-actions">
-                        {header.column.getIsPinned() !== 'start' ? (
+                        {header.getIsPinned() !== 'start' ? (
                           <button
                             className="pin-button"
                             onClick={() => {
@@ -243,7 +243,7 @@ function App() {
                             {'<='}
                           </button>
                         ) : null}
-                        {header.column.getIsPinned() ? (
+                        {header.getIsPinned() ? (
                           <button
                             className="pin-button"
                             onClick={() => {
@@ -253,7 +253,7 @@ function App() {
                             X
                           </button>
                         ) : null}
-                        {header.column.getIsPinned() !== 'end' ? (
+                        {header.getIsPinned() !== 'end' ? (
                           <button
                             className="pin-button"
                             onClick={() => {
@@ -302,7 +302,7 @@ function App() {
                     </div>
                     {!header.isPlaceholder && header.column.getCanPin() && (
                       <div className="pin-actions">
-                        {header.column.getIsPinned() !== 'start' ? (
+                        {header.getIsPinned() !== 'start' ? (
                           <button
                             className="pin-button"
                             onClick={() => {
@@ -312,7 +312,7 @@ function App() {
                             {'<='}
                           </button>
                         ) : null}
-                        {header.column.getIsPinned() ? (
+                        {header.getIsPinned() ? (
                           <button
                             className="pin-button"
                             onClick={() => {
@@ -322,7 +322,7 @@ function App() {
                             X
                           </button>
                         ) : null}
-                        {header.column.getIsPinned() !== 'end' ? (
+                        {header.getIsPinned() !== 'end' ? (
                           <button
                             className="pin-button"
                             onClick={() => {
diff --git a/examples/react/column-pinning-split/tests/e2e/smoke.spec.ts b/examples/react/column-pinning-split/tests/e2e/smoke.spec.ts
index c101c0ca57..935eb83643 100644
--- a/examples/react/column-pinning-split/tests/e2e/smoke.spec.ts
+++ b/examples/react/column-pinning-split/tests/e2e/smoke.spec.ts
@@ -195,6 +195,36 @@ test('returns a column to the centre table when unpinned', async ({ page }) => {
   expect(errors).toEqual([])
 })
 
+test('offers pin buttons for the region a split group header is in', async ({
+  page,
+}) => {
+  const errors = await openExample(page)
+
+  await pinButton(page, CENTER_TABLE, 'firstName', '<=').click()
+  await expect.poll(() => leafCount(page, START_TABLE)).toBe(1)
+  await pinButton(page, CENTER_TABLE, 'Last Name', '=>').click()
+  await expect.poll(() => leafCount(page, END_TABLE)).toBe(1)
+
+  // The "Name" group is split, so the start and end tables each render a
+  // "Name" header for the same group column. Each must act on its own region.
+  const groupPinButton = (tableIndex: number, label: '<=' | 'X' | '=>') =>
+    tableAt(page, tableIndex)
+      .locator('thead tr')
+      .first()
+      .locator('th')
+      .filter({ hasText: 'Name' })
+      .getByRole('button', { name: label, exact: true })
+
+  await expect(groupPinButton(START_TABLE, '<=')).toHaveCount(0)
+  await expect(groupPinButton(START_TABLE, 'X')).toHaveCount(1)
+  await expect(groupPinButton(START_TABLE, '=>')).toHaveCount(1)
+  await expect(groupPinButton(END_TABLE, '<=')).toHaveCount(1)
+  await expect(groupPinButton(END_TABLE, 'X')).toHaveCount(1)
+  await expect(groupPinButton(END_TABLE, '=>')).toHaveCount(0)
+
+  expect(errors).toEqual([])
+})
+
 test('keeps every table showing the same rows', async ({ page }) => {
   const errors = await openExample(page)
 
diff --git a/packages/table-core/src/features/column-pinning/columnPinningFeature.ts b/packages/table-core/src/features/column-pinning/columnPinningFeature.ts
index bb2fb5bce4..7131145b7e 100644
--- a/packages/table-core/src/features/column-pinning/columnPinningFeature.ts
+++ b/packages/table-core/src/features/column-pinning/columnPinningFeature.ts
@@ -11,6 +11,7 @@ import {
   column_getPinnedIndex,
   column_pin,
   getDefaultColumnPinningState,
+  header_getIsPinned,
   row_getCenterVisibleCells,
   row_getEndVisibleCells,
   row_getStartVisibleCells,
@@ -83,6 +84,14 @@ export const columnPinningFeature: TableFeature = {
     })
   },
 
+  assignHeaderPrototype: (prototype, table) => {
+    assignPrototypeAPIs('columnPinningFeature', prototype, table, {
+      header_getIsPinned: {
+        fn: (header) => header_getIsPinned(header),
+      },
+    })
+  },
+
   assignRowPrototype: (prototype, table) => {
     assignPrototypeAPIs('columnPinningFeature', prototype, table, {
       row_getCenterVisibleCells: {
diff --git a/packages/table-core/src/features/column-pinning/columnPinningFeature.types.ts b/packages/table-core/src/features/column-pinning/columnPinningFeature.types.ts
index 15e3bdce7b..b2a24a1e07 100644
--- a/packages/table-core/src/features/column-pinning/columnPinningFeature.types.ts
+++ b/packages/table-core/src/features/column-pinning/columnPinningFeature.types.ts
@@ -77,6 +77,16 @@ export interface Column_ColumnPinning {
   pin: (position: ColumnPinningPosition) => void
 }
 
+export interface Header_ColumnPinning {
+  /**
+   * Reads the logical pinned position shared by this header's own leaf
+   * columns: `'start'`, `'end'`, or `false` when unpinned or mixed. Unlike
+   * `header.column.getIsPinned()`, a group header split across regions
+   * reports the region it is rendered in.
+   */
+  getIsPinned: () => ColumnPinningPosition
+}
+
 export interface Row_ColumnPinning<
   in out TFeatures extends TableFeatures,
   in out TData extends RowData,
diff --git a/packages/table-core/src/features/column-pinning/columnPinningFeature.utils.ts b/packages/table-core/src/features/column-pinning/columnPinningFeature.utils.ts
index 51d1ed23a8..666b2bfa46 100644
--- a/packages/table-core/src/features/column-pinning/columnPinningFeature.utils.ts
+++ b/packages/table-core/src/features/column-pinning/columnPinningFeature.utils.ts
@@ -189,6 +189,48 @@ export function column_getPinnedIndex<
     : 0
 }
 
+// Header APIs
+
+/**
+ * Reads the pinned region of this header's own leaf columns.
+ *
+ * A group column split across regions renders one header per region, so its
+ * column reports a single position. Each header reads only the leaf columns
+ * it renders: returns their shared position, or `false` when they are
+ * unpinned or mixed.
+ *
+ * @example
+ * ```ts
+ * const position = header_getIsPinned(header)
+ * ```
+ */
+export function header_getIsPinned<
+  TFeatures extends TableFeatures,
+  TData extends RowData,
+  TValue extends CellData = CellData,
+>(header: Header<TFeatures, TData, TValue>): ColumnPinningPosition {
+  const leafHeaders = header.getLeafHeaders()
+  let position: ColumnPinningPosition | undefined
+
+  for (let i = 0; i < leafHeaders.length; i++) {
+    const leafHeader = leafHeaders[i]!
+    // getLeafHeaders() also returns the group headers themselves, whose
+    // shared column would report every region its leaves are pinned to
+    if (leafHeader.subHeaders.length) {
+      continue
+    }
+
+    const leafPosition = column_getIsPinned(leafHeader.column)
+    if (position === undefined) {
+      position = leafPosition
+    } else if (leafPosition !== position) {
+      return false
+    }
+  }
+
+  return position ?? false
+}
+
 // Row APIs
 
 /**
diff --git a/packages/table-core/src/types/Header.ts b/packages/table-core/src/types/Header.ts
index 2a85f694ee..31a3a56794 100644
--- a/packages/table-core/src/types/Header.ts
+++ b/packages/table-core/src/types/Header.ts
@@ -3,6 +3,7 @@ import type { CellData, RowData } from './type-utils'
 import type { ExtractFeatureMapTypes, TableFeatures } from './TableFeatures'
 import type { Header_Header } from '../core/headers/coreHeadersFeature.types'
 import type { Header_ColumnResizing } from '../features/column-resizing/columnResizingFeature.types'
+import type { Header_ColumnPinning } from '../features/column-pinning/columnPinningFeature.types'
 
 export interface Header_Core<
   in out TFeatures extends TableFeatures,
@@ -11,6 +12,7 @@ export interface Header_Core<
 > extends Header_Header<TFeatures, TData, TValue> {}
 
 export interface Header_FeatureMap {
+  columnPinningFeature: Header_ColumnPinning
   columnSizingFeature: Header_ColumnSizing
   columnResizingFeature: Header_ColumnResizing
 }
diff --git a/packages/table-core/tests/unit/features/column-pinning/columnPinningFeature.utils.test.ts b/packages/table-core/tests/unit/features/column-pinning/columnPinningFeature.utils.test.ts
index 59bebfb324..a64184ff95 100644
--- a/packages/table-core/tests/unit/features/column-pinning/columnPinningFeature.utils.test.ts
+++ b/packages/table-core/tests/unit/features/column-pinning/columnPinningFeature.utils.test.ts
@@ -12,6 +12,7 @@ import {
   column_getPinnedIndex,
   column_pin,
   getDefaultColumnPinningState,
+  header_getIsPinned,
   row_getCenterVisibleCells,
   row_getStartVisibleCells,
   row_getEndVisibleCells,
@@ -281,6 +282,136 @@ describe('column_getIsPinned', () => {
   })
 })
 
+describe('header_getIsPinned', () => {
+  function makeSplitGroupTable() {
+    const columns: Array<ColumnDef<typeof features, Person, any>> = [
+      {
+        id: 'identity',
+        columns: [
+          { accessorKey: 'firstName', id: 'firstName' },
+          { accessorKey: 'age', id: 'age' },
+          { accessorKey: 'lastName', id: 'lastName' },
+        ],
+      },
+    ]
+    return constructTable<typeof features, Person>({
+      features,
+      columns,
+      data: generateTestData(1),
+      initialState: {
+        columnPinning: {
+          start: ['firstName'],
+          end: ['lastName'],
+        },
+      },
+    })
+  }
+
+  it('should report the region each split group header is rendered in', () => {
+    const table = makeSplitGroupTable()
+    const startGroup = table_getStartHeaderGroups(table)[0]!.headers[0]!
+    const centerGroup = table_getCenterHeaderGroups(table)[0]!.headers[0]!
+    const endGroup = table_getEndHeaderGroups(table)[0]!.headers[0]!
+
+    // the shared group column can only report one region
+    expect(column_getIsPinned(endGroup.column)).toBe('start')
+
+    expect(header_getIsPinned(startGroup)).toBe('start')
+    expect(header_getIsPinned(centerGroup)).toBe(false)
+    expect(header_getIsPinned(endGroup)).toBe('end')
+    expect(endGroup.getIsPinned()).toBe('end')
+  })
+
+  it('should return false when a header spans leaves from different regions', () => {
+    const table = makeSplitGroupTable()
+    const groupHeader = table.getHeaderGroups()[0]!.headers[0]!
+
+    expect(groupHeader.subHeaders).toHaveLength(3)
+    expect(header_getIsPinned(groupHeader)).toBe(false)
+  })
+
+  it('should report the region of a group split start/end with no center leaves', () => {
+    const columns: Array<ColumnDef<typeof features, Person, any>> = [
+      {
+        id: 'name',
+        columns: [
+          { accessorKey: 'firstName', id: 'firstName' },
+          { accessorKey: 'lastName', id: 'lastName' },
+        ],
+      },
+      { accessorKey: 'age', id: 'age' },
+    ]
+    const table = constructTable<typeof features, Person>({
+      features,
+      columns,
+      data: generateTestData(1),
+      initialState: {
+        columnPinning: {
+          start: ['firstName'],
+          end: ['lastName'],
+        },
+      },
+    })
+    const startGroup = table_getStartHeaderGroups(table)[0]!.headers[0]!
+    const endGroup = table_getEndHeaderGroups(table)[0]!.headers[0]!
+
+    expect(startGroup.column.id).toBe('name')
+    expect(endGroup.column.id).toBe('name')
+    expect(header_getIsPinned(startGroup)).toBe('start')
+    expect(header_getIsPinned(endGroup)).toBe('end')
+  })
+
+  it('should read only leaf columns through nested group headers', () => {
+    const columns: Array<ColumnDef<typeof features, Person, any>> = [
+      {
+        id: 'outer',
+        columns: [
+          {
+            id: 'inner',
+            columns: [
+              { accessorKey: 'firstName', id: 'firstName' },
+              { accessorKey: 'lastName', id: 'lastName' },
+            ],
+          },
+          { accessorKey: 'age', id: 'age' },
+        ],
+      },
+    ]
+    const table = constructTable<typeof features, Person>({
+      features,
+      columns,
+      data: generateTestData(1),
+      initialState: {
+        columnPinning: {
+          start: ['firstName'],
+          end: ['lastName', 'age'],
+        },
+      },
+    })
+    const endGroups = table_getEndHeaderGroups(table)
+    const endOuter = endGroups[0]!.headers[0]!
+    const endInner = endGroups[1]!.headers[0]!
+
+    expect(endOuter.column.id).toBe('outer')
+    expect(endInner.column.id).toBe('inner')
+    expect(header_getIsPinned(endOuter)).toBe('end')
+    expect(header_getIsPinned(endInner)).toBe('end')
+    expect(
+      header_getIsPinned(table_getStartHeaderGroups(table)[0]!.headers[0]!),
+    ).toBe('start')
+  })
+
+  it('should match the column for leaf headers', () => {
+    const table = makeSplitGroupTable()
+    const leaf = (id: string) =>
+      table.getLeafHeaders().find((header) => header.column.id === id)!
+
+    expect(header_getIsPinned(leaf('firstName'))).toBe('start')
+    expect(header_getIsPinned(leaf('age'))).toBe(false)
+    expect(header_getIsPinned(leaf('lastName'))).toBe('end')
+  })
+})
+
 describe('table_setColumnPinning', () => {
   it('should call onColumnPinningChange with updater', () => {
     const onColumnPinningChange = vi.fn()