Filament allows you to add attachments to a record, but doesn’t delete them when you delete the record.

In order to solve this issue, we have two alternatives:

Listen to model’s deleting event

When a model it’s about to be deleted, it fires the deleting event. We can listen to this event to trigger the functionality responsible to delete any attachements before the model no longer exists.

Inside the model class we can add the booted method to register new event listeners to the model.

class Project extends Model
{
    protected $fillable = [
        'title', 'slug', 'repository', 'description', 'thumbnail',
    ];

    /**
     * The "booted" method of the model.
     */
    protected static function booted(): void
    {
        static::deleting(function ($project) {
            Storage::disk('public')->delete($project->thumbnail);
        });
    }
}

This code will delete the thumbnail attachment before deleting the model.

You can read more about this in the Laravel documentation https://laravel.com/docs/11.x/eloquent#events-using-closures

Modify Filament’s delete action

Another option is to change the behaviour of the delete action.

protected function getActions(): array
{
    return [
        Actions\DeleteAction::make()
            ->after(function (Project $project) {
                // delete single
                if ($project->thumbnail) {
                    Storage::disk('public')->delete($project->thumbnail);
                }
            })
    ];
}

You can use the option better fits your requirements, but you should keep in mind that adding an event listener will delete the attachment when your model is deleted, whenever has occured by a Filament action or another part of code in your app.

This is important because probably will determine whenever option you should choose.