diff --git a/app/Http/Requests/Inventory/UpdateStockEntryRequest.php b/app/Http/Requests/Inventory/UpdateStockEntryRequest.php
index 90affa5..62c9b28 100644
--- a/app/Http/Requests/Inventory/UpdateStockEntryRequest.php
+++ b/app/Http/Requests/Inventory/UpdateStockEntryRequest.php
@@ -3,6 +3,7 @@
 namespace App\Http\Requests\Inventory;
 
 use App\Models\Ingredient;
+use App\Models\StockEntry;
 use Illuminate\Foundation\Http\FormRequest;
 use Illuminate\Validation\Rule;
 use Illuminate\Validation\Validator;
@@ -72,6 +73,12 @@ class UpdateStockEntryRequest extends FormRequest
                 // AP-42: ml-Erfassung nur mit hinterlegter Dichte.
                 if ($this->input('ordered_unit') === 'ml') {
                     $density = Ingredient::query()->whereKey($this->input('ingredient_id'))->value('density');
+                    // N-06: bei unverändertem Rohstoff gilt der Dichte-Snapshot der Bestellung als Rückfall.
+                    $entry = $this->route('stock_entry');
+                    if (($density === null || (float) $density <= 0) && $entry instanceof StockEntry
+                        && (int) $entry->ingredient_id === (int) $this->input('ingredient_id') && (float) $entry->density_used > 0) {
+                        $density = $entry->density_used;
+                    }
                     if ($density === null || (float) $density <= 0) {
                         $validator->errors()->add('ordered_quantity', __('Für diesen Rohstoff ist keine Dichte hinterlegt — bitte in Gramm erfassen oder zuerst die Dichte pflegen.'));
                     }
diff --git a/app/Repositories/StockEntryRepository.php b/app/Repositories/StockEntryRepository.php
index 652bd71..35565b9 100644
--- a/app/Repositories/StockEntryRepository.php
+++ b/app/Repositories/StockEntryRepository.php
@@ -30,6 +30,13 @@ class StockEntryRepository
     {
         if (array_key_exists('entry_type', $data)) {
             $data['unit'] = ($data['entry_type'] ?? '') === 'ingredient' ? 'gram' : 'piece';
+            // N-06: Dichte-Snapshot nur bei unverändertem Rohstoff als Rückfall mitgeben —
+            // eine fremde alte Dichte darf bei Rohstoffwechsel nicht übernommen werden.
+            if (($data['ordered_unit'] ?? null) === 'ml'
+                && (int) ($data['ingredient_id'] ?? 0) === (int) $stockEntry->ingredient_id
+                && (float) $stockEntry->density_used > 0) {
+                $data['density_used'] = (float) $stockEntry->density_used;
+            }
             $data = $this->applyPurchaseUnit($data);
         }
 
diff --git a/resources/views/admin/inventory/stock-entries/_form.blade.php b/resources/views/admin/inventory/stock-entries/_form.blade.php
index 2a999b6..7499b37 100644
--- a/resources/views/admin/inventory/stock-entries/_form.blade.php
+++ b/resources/views/admin/inventory/stock-entries/_form.blade.php
@@ -21,7 +21,8 @@
         <select name="ingredient_id" id="ingredient_id" class="w-100"
             data-search-url="{{ route('admin.inventory.api.ingredients.search') }}">
             @if ($model->ingredient_id && $model->ingredient)
-                <option value="{{ $model->ingredient_id }}" data-density="{{ $model->ingredient->density }}" selected>{{ $model->ingredient->name }}@if ($model->ingredient->inci)
+                {{-- N-06: fehlt die Stammdaten-Dichte inzwischen, gilt der Dichte-Snapshot der Bestellung --}}
+                <option value="{{ $model->ingredient_id }}" data-density="{{ $model->ingredient->density ?? $model->density_used }}" selected>{{ $model->ingredient->name }}@if ($model->ingredient->inci)
                         ({{ $model->ingredient->inci }})
                     @endif
                 </option>
diff --git a/tests/Feature/IngredientDensityTest.php b/tests/Feature/IngredientDensityTest.php
index 8823b2b..f377ab1 100644
--- a/tests/Feature/IngredientDensityTest.php
+++ b/tests/Feature/IngredientDensityTest.php
@@ -196,3 +196,60 @@ test('F-16: wareneingang prueft „offen“ innerhalb der sperre — zweite buch
     expect((float) $entry->fresh()->received_quantity)->toBe(500.0)
         ->and($entry->fresh()->batch_number)->toBe('F16-1');
 });
+
+test('N-06: ml-kopie ohne stammdatendichte übersteht bearbeiten, speichern und wareneingang', function () {
+    [$admin, $ingredient, $location, $supplier, $quality] = densSetup(0.79);
+    $this->actingAs($admin, 'user');
+
+    $this->post(route('admin.inventory.stock-entries.store'), [
+        'entry_type' => 'ingredient', 'ingredient_id' => (string) $ingredient->id, 'supplier_id' => (string) $supplier->id,
+        'location_id' => (string) $location->id, 'quality_id' => (string) $quality->id, 'ordered_at' => '2026-08-01',
+        'ordered_quantity' => '100', 'ordered_unit' => 'ml', 'price_per_kg' => '10,00',
+    ])->assertRedirect();
+    $original = StockEntry::query()->latest('id')->firstOrFail();
+    $ingredient->forceFill(['density' => null])->save();
+
+    $this->post(route('admin.inventory.stock-entries.copy', $original))->assertRedirect();
+    $copy = StockEntry::query()->latest('id')->firstOrFail();
+
+    // Bearbeitungsformular: ml bleibt wählbar (Dichte-Snapshot als data-density), Menge 100,00 ml.
+    $this->get(route('admin.inventory.stock-entries.edit', $copy))->assertOk()
+        ->assertSee('data-density="0.79', false)
+        ->assertSee('value="100,00"', false);
+
+    // Unverändert speichern (wie die Kopiermeldung es verlangt).
+    $this->put(route('admin.inventory.stock-entries.update', $copy), [
+        'entry_type' => 'ingredient', 'ingredient_id' => (string) $ingredient->id, 'supplier_id' => (string) $supplier->id,
+        'location_id' => (string) $location->id, 'quality_id' => (string) $quality->id, 'ordered_at' => '2026-08-02',
+        'ordered_quantity' => '100', 'ordered_unit' => 'ml', 'price_per_kg' => '10,00',
+    ])->assertRedirect()->assertSessionHasNoErrors();
+
+    $copy->refresh();
+    expect($copy->purchase_unit)->toBe('ml')
+        ->and((float) $copy->density_used)->toBe(0.79)
+        ->and((float) $copy->ordered_quantity)->toBe(79.0);
+
+    $this->put(route('admin.inventory.stock-entries.receive', $copy), [
+        'received_at' => '2026-08-05', 'received_quantity' => '100', 'batch_number' => 'N06-1', 'best_before' => '2030-12-31',
+    ])->assertRedirect();
+    expect((float) $copy->fresh()->received_quantity)->toBe(79.0);
+});
+
+test('N-06: bei rohstoffwechsel wird keine fremde alte dichte übernommen', function () {
+    [$admin, $ingredient, $location, $supplier, $quality] = densSetup(0.79);
+    $other = Ingredient::query()->create(['name' => 'INCI-ohne-Dichte', 'active' => true, 'pos' => 0, 'density' => null]);
+    $this->actingAs($admin, 'user');
+
+    $this->post(route('admin.inventory.stock-entries.store'), [
+        'entry_type' => 'ingredient', 'ingredient_id' => (string) $ingredient->id, 'supplier_id' => (string) $supplier->id,
+        'location_id' => (string) $location->id, 'quality_id' => (string) $quality->id, 'ordered_at' => '2026-08-01',
+        'ordered_quantity' => '100', 'ordered_unit' => 'ml', 'price_per_kg' => '10,00',
+    ])->assertRedirect();
+    $entry = StockEntry::query()->latest('id')->firstOrFail();
+
+    $this->from(route('admin.inventory.stock-entries.edit', $entry))->put(route('admin.inventory.stock-entries.update', $entry), [
+        'entry_type' => 'ingredient', 'ingredient_id' => (string) $other->id, 'supplier_id' => (string) $supplier->id,
+        'location_id' => (string) $location->id, 'quality_id' => (string) $quality->id, 'ordered_at' => '2026-08-02',
+        'ordered_quantity' => '100', 'ordered_unit' => 'ml', 'price_per_kg' => '10,00',
+    ])->assertSessionHasErrors('ordered_quantity');
+});