Using Select within BelongsToMany fields()

[Norgul]

• Laravel Version: v11.15.0
• Nova Version: v4.34.3
• PHP Version: 8.2.20
• Database Driver & Version:
• Operating System and Version: MacOS Sonoma 14.5 (23F79)
• Browser type and version: Chrome Version 127.0.6533.90 (Official Build) (arm64)

Description:

Not sure if this is a bug or I implemented something wrong. I have a pivot table with additional FK (unit_id). If I use Select in fields() method pointing to that additional FK, saving the relation will fail even though unit_id is present in the payload in the failing request.

// migration
Schema::create('recipe_composition', function (Blueprint $table) {
    $table->id();
    $table->foreignId('parent_id')->constrained('products');
    $table->foreignId('child_id')->constrained('products');

    $table->foreignId('unit_id')->constrained();
    ...
});

// Product.php
public function children(): BelongsToMany
{
    return $this->belongsToMany(self::class, 'recipe_composition', 'parent_id', 'child_id')
        ->withPivot(RecipeComposition::WITH_PIVOT)
        ->using(RecipeComposition::class)
        ->with('children')
        ->withTimestamps();
}

// RecipeComposition.php pivot model
class RecipeComposition extends Pivot
{
    public const WITH_PIVOT = [
        'unit_id',
        'net_amount',
        'gross_amount',
        'note',
        'removable_on_sale',
    ];

    public function parent(): BelongsTo
    {
        return $this->belongsTo(Product::class, 'parent_id');
    }

    public function child(): BelongsTo
    {
        return $this->belongsTo(Product::class, 'child_id');
    }

    public function unit(): BelongsTo
    {
        return $this->belongsTo(Unit::class);
    }
}

// Nova relation
BelongsToMany::make('Recipe elements', 'children', Product::class)
    ->fields(fn() => [
        Select::make('Unit', 'unit_id')
            ->dependsOn('children', function (Select $field, NovaRequest $request, FormData $formData) {
                $productId = $formData->get('children');

                /** @var \App\Models\Tenant\Product $product */
                $product = \App\Models\Tenant\Product::query()->with('unit')->find($productId);

                if (!$product) {
                    $field->readonly();
                    return;
                }

                $field->options(fn() => collect()
                    ->merge(Collection::wrap($product->unit->ancestors))
                    ->merge(Collection::wrap($product->unit))
                    ->merge(Collection::wrap($product->unit->grandchildren))
                    ->pluck('label', 'id')
                );

                $field->value = $product->unit->id;
            }),
        ...
    ])
    ->singularLabel('Recipe or Goods'),

If however I replace Select with a hardcoded Text or Number field, it will have the same payload, but will go through.