“…a compromise that will see an undisclosed number of hereditary members allowed to stay by being ‘recycled’ into life peers.”

What? Are the membership roles and the text of this law confidential?

Odd! I think this is the bill?

https://bills.parliament.uk/bills/3755/publications

It's rather hard to read because the amendments are written as a diff, but it seems to imply the undisclosed number is 87 peers. I guess they need to decide amongst themselves who the lucky 87 are?

https://publications.parliament.uk/pa/bills/cbill/59-01/0295... Bill 295 2024-25 (Lords Amendments)

    “1. (2) (2) No more than 87 people at any one time shall be excepted from section 1.”

Edit: Wow, is this ever hard to pin down. I think section 1 of the lord's amendments were dropped here: https://bills.parliament.uk/bills/3755/stages/20179/motionsa...

which I guess means that the text remains the same as the original text in HL-49 (https://bills.parliament.uk/publications/56858/documents/533...):

    # Exclusion of remaining hereditary peers
    Omit section 2 of the House of Lords Act 1999 (exception to exclusion of hereditary peers from membership of House of Lords).

Doesn't need to be in the text of the law. The Crown can appoint an arbitrary list of life peers - possibly at any time (see Chiltern Hundreds).

As the article points out, the life peers are arguably worse. People like Mandelson.

All primary legislation is published. But this needn't be in the primary legislation since there is no need to legislate to make it happen. It's a side deal, the government agrees to do this, the Lords agree not to get in their way.

Much, but not all secondary legislation is also published. A typical means by which Secondary Legislation is brought into existence is that a Law says there shall be some list or reference established by some particular minister, and that document is Secondary Legislation. For example maybe a Law concerning Clown Licensing says there shall be a list of Clown License Offices, and the Secretary of State for Hilarity shall write this list, that list isn't voted on by Parliament, the list gets written by some bureaucrats working for the current Secretary of State for Hilarity. This "undisclosed" list needn't be in secondary legislation either.

The idea is that some of the current hereditary peers will be given new life peerages under existing rules which would enable them to stay in the chamber. Granting new life peerages is mostly within the gift of the Prime Minister (although there are committees which vet appointments and conventions about allowing opposition parties to nominate some), so this is not part of the legislation but a back-room deal by which the votes were secured by the government.