diff --git a/resources/boost/skills/livewire-material-development/SKILL.md b/resources/boost/skills/livewire-material-development/SKILL.md
index 74511648..56e114af 100644
--- a/resources/boost/skills/livewire-material-development/SKILL.md
+++ b/resources/boost/skills/livewire-material-development/SKILL.md
@@ -565,7 +565,7 @@ M3 text fields. `variant`: `outlined` or `filled`; without it, `config('livewire
 
 M3 selection controls on native inputs; the whole row is the label.
 
-- `<x-checkbox label hint right indeterminate />` — `indeterminate` for a "select all" whose items are partly ticked (bind it to a server expression; it follows every render).
+- `<x-checkbox label hint right indeterminate />` — `indeterminate` for a "select all" whose items are partly ticked (bind it to a server expression; it follows every render). Grouping is yours: from `expanded` (840px) M3 wants a set of related checkboxes gathered into a contained region rather than one long column, so wrap the set in `<div class="grid gap-4 expanded:grid-cols-2">` (or a card or side sheet) under a heading that names what the group asks.
 - `<x-radio label wire:model :options inline />` — options `['id', 'name', 'hint', 'disabled']` (`option-value`, `option-label`, `option-hint`); `value` checks an option without `wire:model`; `name` names an unbound group. M3 stacks radios and cautions against a row at any width, so reach for `inline` only for two or three short labels; it also wants five options or fewer and one of them chosen when the page loads.
 - `<x-toggle label hint right icons />` — M3 switch (`role="switch"`); `icons` puts a check and a cross on the handle, `icons="selected"` only the check. Without `label`, pass `aria-label`.
 
diff --git a/resources/views/components/checkbox.blade.php b/resources/views/components/checkbox.blade.php
index 150d0a28..9aaea1f8 100644
--- a/resources/views/components/checkbox.blade.php
+++ b/resources/views/components/checkbox.blade.php
@@ -10,7 +10,13 @@
      (resources/css/components/selection.css).
 
      Without a label — a "select all" in a table header, a row's tick — the row is only the 18px box,
-     so the box carries `touch-target` and catches presses over M3's 48px minimum. --}}
+     so the box carries `touch-target` and catches presses over M3's 48px minimum.
+
+     Grouping is the caller's, not this component's: M3 asks that from `expanded` (840px) a set of
+     related checkboxes be gathered into a contained region rather than left as one long column
+     (docs/reference/m3/components-navigation-selection-inputs.md § Checkbox, Behaviour). Lay the
+     group out yourself — `<div class="grid gap-4 expanded:grid-cols-2">` around the checkboxes, or a
+     `<x-card>` or side sheet holding them — and give the group a heading that names what it asks. --}}
 
 @props([
     'label' => null,
diff --git a/resources/views/showcase/sections/fields.blade.php b/resources/views/showcase/sections/fields.blade.php
index 8dba5072..0ae1bbed 100644
--- a/resources/views/showcase/sections/fields.blade.php
+++ b/resources/views/showcase/sections/fields.blade.php
@@ -92,6 +92,23 @@
                 </div>
             </div>
             BLADE,
+        'A checkbox group at expanded' => <<<'BLADE'
+            {{-- M3: from expanded (840px), gather related checkboxes into a contained region instead of one long column. --}}
+            <x-card variant="outlined" class="w-full max-w-2xl">
+                <fieldset>
+                    <legend class="mb-4 type-title-sm text-on-surface">Tell me about</legend>
+
+                    <div class="grid gap-4 expanded:grid-cols-2">
+                        <x-checkbox label="Downloads" name="notify[]" value="downloads" checked />
+                        <x-checkbox label="Comments" name="notify[]" value="comments" />
+                        <x-checkbox label="Expiring shares" name="notify[]" value="expiring" checked />
+                        <x-checkbox label="Failed uploads" name="notify[]" value="failed" />
+                        <x-checkbox label="New team members" name="notify[]" value="members" />
+                        <x-checkbox label="Weekly summary" name="notify[]" value="summary" />
+                    </div>
+                </fieldset>
+            </x-card>
+            BLADE,
         'Radio buttons' => <<<'BLADE'
             <div class="grid w-full gap-6 medium:grid-cols-2">
                 <x-radio label="Who can open the link" name="showcase-audience" value="password" :options="[['id' => 'anyone', 'name' => 'Anyone with the link'], ['id' => 'password', 'name' => 'Anyone with the password', 'hint' => 'Share the password separately'], ['id' => 'team', 'name' => 'My team only', 'disabled' => true]]" />
diff --git a/tests/Feature/Components/SelectionTest.php b/tests/Feature/Components/SelectionTest.php
index d25d5d85..b7e083e7 100644
--- a/tests/Feature/Components/SelectionTest.php
+++ b/tests/Feature/Components/SelectionTest.php
@@ -37,6 +37,29 @@ it('gives a selection control without a label a 48px target', function () {
         ->and((string) $this->blade('<x-radio :options="[[\'id\' => \'a\', \'name\' => \'A\']]" />'))->not->toContain('touch-target');
 });
 
+it('leaves a checkbox group to the caller and says how M3 wants it laid out', function () {
+    $html = (string) $this->blade(<<<'BLADE'
+        <fieldset>
+            <legend>Tell me about</legend>
+            <div class="grid gap-4 expanded:grid-cols-2">
+                <x-checkbox label="Downloads" name="notify[]" value="downloads" />
+                <x-checkbox label="Comments" name="notify[]" value="comments" />
+            </div>
+        </fieldset>
+        BLADE);
+
+    expect($html)
+        ->toContain('class="grid gap-4 expanded:grid-cols-2"')
+        ->toContain('Downloads')
+        ->toContain('Comments')
+        ->and(substr_count($html, 'data-checkbox'))->toBe(2);
+
+    // The rule is guidance, not markup, so the component's header has to carry it.
+    expect(file_get_contents(__DIR__.'/../../../resources/views/components/checkbox.blade.php'))
+        ->toContain('expanded')
+        ->toContain('contained region');
+});
+
 it('puts a checkbox at the end of its row on request', function () {
     expect((string) $this->blade('<x-checkbox label="Show" right />'))->toContain('flex-row-reverse justify-between');
 });