Thank you so much @ricardoV94 and @cluhmann! I thought this was the case when I read the tutorial on how to create custom Distributions in PyMC. However, the pytensor code seems to enforce a check to ensure that rng is a RandomGeneratorType or a RandomStateType (see https://github.com/pymc-devs/pytensor/blob/a6e7722f16c49eea208891c02940ff16bd3e3482/pytensor/tensor/random/op.py#L328-L333). Can I just ignore and assume that PyMC will use either Generator or RandomState for rng?