Input-triggered transaction expiry

The exploration of coin-height introspection as a potential solution to the double-delay problem in LN-Symmetry presents a nuanced discussion on the mechanics of Bitcoin transaction delays and timelocks. The issue at hand involves scenarios where a participant, such as Alice, has not received a fully signed update transaction. In this scenario, if Alice needs to initiate an on-chain transaction before receiving the final signature from Bob, it triggers a classical relative timelock that effectively doubles the waiting period (notated as U*2) before settlement can be finalized.

This delay complication arises because once Alice goes on-chain due to the absence of Bob's final transaction during the U-1 blocks period, Bob’s eventual submission of the transaction resets the timeout, leading to the extended wait. The question raised concerns whether the proposed coin-height introspection could allow for immediate settlement or offer a way to circumvent this delay, thus mitigating the layered complexity associated with timelock semantics in Bitcoin validation.

Furthermore, the discourse also references a transformation from CSV (Check Sequence Verify) to CLTV (Check Locktime Verify), which is significant in the context of timelock management. This transformation is critical for understanding how different types of timelocks influence transaction validation and settlement times in blockchain operations. For those interested in a deeper dive into how these transformations impact Bitcoin scripting and transaction delays, more information can be found in a detailed thread linked within the original discussion.