The general replay potential of APO style sighashing was discussed quite a bit in 2018 when eltoo came out. For example here's GMax suggesting to call it "SIGHASH_WEAK_REPLAYABLE" :) [1] . It's not hard to deduce that of all the various and sundry op_code proposals we've had over the years, this is one that has the least solid foundation of "users cannot footgun themselves". By any measure, they can.
To be clear, I haven't bothered to read these new proposals, but I get that your point is: because they offer more powerful templating, the risk is no longer just 'replay the payment' but 'replay the coin-spending into an actually different payment'. Very clearly a bigger risk, agreed.
Presumably the obvious counter-arguments apply: the contract outputs are 'special', they'll never be presented as addresses you can spend into and etc etc. The counter-counter argument is operational fallbility etc. I guess. I don't really have strong opinions, but I think I agree that this at least a point of controversy in terms of what should be added to consensus rules. That style of argument has been made before.
[1] https://gnusha.org/pi/bitcoindev/CAAS2fgS-_D7aBcDf_nAbuREBxv65zYMr60-1YqCnx-esvRVfEg@mail.gmail.com/
waxwing
npub1va…knuu7
2026-10-12 17:31:02 UTC
in reply to nevent1q…685w
Author Public Key
npub1vadcfln4ugt2h9ruwsuwu5vu5am4xaka7pw6m7axy79aqyhp6u5q9knuu7Published at
2026-10-12 17:31:02 UTCEvent JSON
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"content": "The general replay potential of APO style sighashing was discussed quite a bit in 2018 when eltoo came out. For example here's GMax suggesting to call it \"SIGHASH_WEAK_REPLAYABLE\" :) [1] . It's not hard to deduce that of all the various and sundry op_code proposals we've had over the years, this is one that has the least solid foundation of \"users cannot footgun themselves\". By any measure, they can.\n\nTo be clear, I haven't bothered to read these new proposals, but I get that your point is: because they offer more powerful templating, the risk is no longer just 'replay the payment' but 'replay the coin-spending into an actually different payment'. Very clearly a bigger risk, agreed.\n\nPresumably the obvious counter-arguments apply: the contract outputs are 'special', they'll never be presented as addresses you can spend into and etc etc. The counter-counter argument is operational fallbility etc. I guess. I don't really have strong opinions, but I think I agree that this at least a point of controversy in terms of what should be added to consensus rules. That style of argument has been made before.\n\n[1] https://gnusha.org/pi/bitcoindev/CAAS2fgS-_D7aBcDf_nAbuREBxv65zYMr60-1YqCnx-esvRVfEg@mail.gmail.com/",
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