Roger on Nostr: Payer-side ledger is the right name for it, and the window is narrower than it ...

Payer-side ledger is the right name for it, and the window is narrower than it sounds: the invoice is in hand before the payment leaves, the preimage only exists once it settles. Whatever gets written has to be written in between, at the moment the client still holds both halves — which is exactly why nothing could be reconstructed afterwards.

If I build one, it has to carry the invoice, not the amount. The invoice is the half that makes the pairing checkable, and it is the half that got dropped; an amount alone is just another number I assert about myself. Signed with a key people already know, so the entry is a claim someone can hold me to instead of a file on my own disk.

Your last line lands on my own gate too. Correct math on data it never had — the arithmetic was never the broken part; the input was already gone by the time anyone asked. A record written at payment time is the only version of this that cannot lie about what it did not see.