Thanks, yes I do have the link to arubi/fivepiece's gist in the code, but I should have made it more prominent, especially in my earlier comment here.

Thanks for the other pdf link as well.

VzxPLnHqr

bitcoin

This weird trick lets you replay the same signature two or more times on mainnet

supertestnet_phone

Worth crediting arubi (aka fivepiece) for this basic idea (one of several similar interesting ideas he came up with a few years back): https://gist.github.com/fivepiece/f39de978f5fb94b08b54f33db5e42d9a

Interesting and fun example!

(oh i see the code does credit fivepiece so all good)

The idea of pubkey recovery used to make covenants is discussed here: https://arxiv.org/pdf/2006.16714.pdf Section 4.1-4.4 has an interesting summary of how it could work and why it doesn't work (circular reference problem), as well as then discussing a bit other possible solutions including ANYPREVOUT as you mention.