From ed14849cdc3d3362b8b1c7435a09fd42d8f54322 Mon Sep 17 00:00:00 2001
From: VC-Semih <55637588+VC-Semih@users.noreply.github.com>
Date: Fri, 27 Mar 2026 16:29:22 -0400
Subject: [PATCH 1/2] fix(selection): prevent group row ID from leaking into
 rowSelection when grouping

TanStack's toggleSelected() on a group row correctly propagates to leaf rows
but also writes the synthetic group row ID (ex: "city:Paris": true) into rowSelection
as a side effect.

After the toggle, removing the group row ID from rowSelection via setRowSelection,
leaving only the leaf row IDs.

Fixes #1226
---
 .../src/utils/row.utils.ts                    | 24 ++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/packages/material-react-table/src/utils/row.utils.ts b/packages/material-react-table/src/utils/row.utils.ts
index 576bc0060..bc17dddea 100644
--- a/packages/material-react-table/src/utils/row.utils.ts
+++ b/packages/material-react-table/src/utils/row.utils.ts
@@ -175,6 +175,16 @@ export const getMRT_RowSelectionHandler =
 
     const wasCurrentRowChecked = getIsRowSelected({ row, table });
 
+    // Fix: toggleSelected() on a group row also writes its own ID into rowSelection 
+    // Removing it, keeping only the leaf row IDs
+    if (row.getIsGrouped()) {
+      table.setRowSelection((prev) => {
+        const next = { ...prev };
+        delete next[row.id];
+        return next;
+      });
+    }
+
     // toggle selection of this row
     row.toggleSelected(value ?? !wasCurrentRowChecked);
 
@@ -250,9 +260,17 @@ export const getMRT_SelectAllHandler =
       refs: { lastSelectedRowId },
     } = table;
 
-    selectAllMode === 'all' || forceAll
-      ? table.toggleAllRowsSelected(value ?? (event as any).target.checked)
-      : table.toggleAllPageRowsSelected(value ?? (event as any).target.checked);
+    // Fix: replaces toggleAllPageRowsSelected() / toggleAllRowsSelected() which
+    // include group rows in flatRows, causing group IDs to pollute rowSelection.
+    const checked = value ?? (event as any).target.checked;
+    const rows = (selectAllMode === 'all' || forceAll
+      ? table.getPrePaginationRowModel().flatRows
+      : table.getPaginationRowModel().flatRows
+    ).filter((row) => !row.getIsGrouped());
+    rows.forEach((row) => {
+      if (row.getCanSelect()) row.toggleSelected(checked);
+    });
+    
     if (enableRowPinning && rowPinningDisplayMode?.includes('select')) {
       table.setRowPinning({ bottom: [], top: [] });
     }

From 6471515b610cdb0e1c65433ca259daff29dfd248 Mon Sep 17 00:00:00 2001
From: VC-Semih <55637588+VC-Semih@users.noreply.github.com>
Date: Fri, 27 Mar 2026 16:32:21 -0400
Subject: [PATCH 2/2] fix(selection): recalculate header checkbox state from
 leaf rows only when grouping

getIsAllPageRowsSelected(), getIsAllRowsSelected(), and getIsSomeRowsSelected()
include group rows in their denominator, so the header checkbox checked and
indeterminate states couldn't resolve correctly when grouping was active.

Replaced all three with a leaf-only helper that filters flatRows with
getIsGrouped().

Fixes #1226
---
 .../src/components/inputs/MRT_SelectCheckbox.tsx   | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/packages/material-react-table/src/components/inputs/MRT_SelectCheckbox.tsx b/packages/material-react-table/src/components/inputs/MRT_SelectCheckbox.tsx
index 03c3f53d6..346c14673 100644
--- a/packages/material-react-table/src/components/inputs/MRT_SelectCheckbox.tsx
+++ b/packages/material-react-table/src/components/inputs/MRT_SelectCheckbox.tsx
@@ -43,10 +43,15 @@ export const MRT_SelectCheckbox = <TData extends MRT_RowData>({
 
   const selectAll = !row;
 
+  const getLeafRows = () => (
+    selectAllMode === 'page'
+    ? table.getPaginationRowModel().flatRows
+    : table.getPrePaginationRowModel().flatRows
+  ).filter((r) => !r.getIsGrouped());
+
+  // Fix: getIsAllPageRowsSelected() / getIsAllRowsSelected() include group rows
   const allRowsSelected = selectAll
-    ? selectAllMode === 'page'
-      ? table.getIsAllPageRowsSelected()
-      : table.getIsAllRowsSelected()
+    ? getLeafRows().every((r) => r.getIsSelected())
     : undefined;
 
   const isChecked = selectAll
@@ -122,7 +127,8 @@ export const MRT_SelectCheckbox = <TData extends MRT_RowData>({
         <Checkbox
           indeterminate={
             !isChecked && selectAll
-              ? table.getIsSomeRowsSelected()
+              ? // Fix: getIsSomeRowsSelected() includes group rows, use leaf-only filter
+                getLeafRows().some((r) => r.getIsSelected())
               : row?.getIsSomeSelected() && row.getCanSelectSubRows()
           }
           {...commonProps}