The Valid constraint default group is no Default but null.

If we defined something like:

  class User
  {
    #[Assert\NotBlank(groups: ['create'])]
    #[Assert\Length(min: 4, groups: ['create'])]
    protected $firstName;

    #[Assert\NotBlank(groups: ['create'])]
     protected $lastName;

    #[Assert\Valid]
    private Collection $addresses;
  }

  class Address
  {
    #[Assert\NotBlank]
    protected $street;

    #[Assert\NotBlank]
    #[Assert\Length(max: 5)]
    protected $zipCode;
  }

When we validate the User with the create validation groups, it also validate Address, because the Valid constraint define the validation groups to null instead of Default.

To have something that work as attended we must define Default in Valid constraint:

       #[Assert\Valid(groups: ['Default'])]
        private Collection $addresses;
  }

It appear that this behavior is attended because there is a test to check that the Valid default group is null instead of Default.

There is no info about that behavior in the documentation, and why this specific constraint do not have Default as default group. I don't know why null is the default value here, just pass some times to find why the behavior is not the attended one (expect Default group like others).

Maybe @xabbuh you can help us about it (symfony/symfony#21111) ?