Is the pre-finality double-spend race intrinsic to single-owner coins?

The issue discussed revolves around the challenge of preventing double-spending in transactions without relying on existing punitive models like those used in Lightning Network channels or requiring soft forks for implementation. The primary concern is to ensure that Alice, the payer, cannot pre-broadcast a transaction an instant before completing a payment to Bob, thereby causing Bob's subsequent transaction to be recognized as a double-spend. This is critical because it impacts the security and reliability of the transaction process, where the goal is to ensure that funds remain under the exclusive control of their owner until the moment they are spent.

The current solutions involve channel-based approaches like the 2-of-2 model, which are not ideal due to their punitive nature in scenarios such as loss of device or outdated backup states, potentially leading to a complete loss of funds when an old state is broadcasted. This problem introduces a significant risk, particularly in consumer product applications where ease of recovery is crucial. The proposed alternative, using eltoo, aligns better with user-friendly recovery processes by allowing the latest state to prevail without penalties. However, eltoo depends on the activation of BIP-118 and still necessitates additional mechanisms like watchtowers to monitor offline parties, adding complexity and dependency on external components.

The overarching goal is to find a solution that allows users to retain full custody of their funds without needing locked unspent transaction outputs (UTXOs) or shared ownership via funding channels. The ideal system would change hands only at the exact time of payment, hence eliminating any window where preemptive actions by the payer could compromise the transaction. Unfortunately, all explored solutions thus far have only been able to reduce, but not eliminate, the vulnerability window provided to Alice, without fully solving the pre-finality race issue.

The inquiry extends into whether the pre-finality race is an intrinsic property of single-owner coins and if there exists a structural solution that circumvents both the challenges posed by the 2-of-2 model and the race itself. It also seeks to identify if there are ongoing research efforts aimed at developing a viable solution that meets these criteria, suggesting a broader interest and need within the community to address these fundamental challenges in cryptocurrency transactions.