lists.linuxfoundation.org/pipermail/bitcoin-dev/2023-October/022042.html [bitcoin-dev] OP_Expire and Coinbase-Like Behavior: Making HTLCs Safer by Letting Transactions Expire Safely tl;dr: this proposal would fix the recent lightning exploit Antoine found by making disabling the preimage branch of HTLCs once the timeout is reached. Traditionally we've been dubious about making it possible for transactions to become invalid in the future. But in the post I argue that it is acceptable if we treat them similar to coinbase outputs, preventing outputs that may expire from being spent until they have 100 confirmations.