I think there's another thing I'd like to change, and it seems like it's "just" an implementation detail.  In _Py_HashRandomization_Init(), if use_hash_seed is 0, then we directly inject the random bits into the buffer, and then there's no hash_seed.  I'd like to change that so that if use_hash_seed is 0, then we create a random hash seed first, and then call lcg_urandom() for the hash secret.  That way, even if Python itself uses a random hash seed, we'll have a record of that in the runtime that can be used to reproduce the hashing.  In this case, I'd still leave use_hash_seed == 0, and that would tell you what combinations of env vars were used.