Remove support for claiming remote anchor output #3062
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We previously included support for spending the remote anchor output. This created some confusion: is this the anchor output using our key but in the remote commitment? Or is it the anchor output using our peer's key in our local commitment? It is actually the former: the anchor output that uses our peers' key. There is no reason to claim this output: it cannot be claimed while the commitment tx is unconfirmed, and even after it is confirmed, we must add wallet inputs to be able to claim this 330 sat output, which is something we've never implemented (since it would be an economic loss). It is only useful to spend those outputs when they pollute the utxo set after commit txs have confirmed. For it to be economical, it only makes sense when we're batching a lot of those outputs. This isn't something we support, so we should simply remove that code for simplicity.
sstone
approved these changes
Apr 15, 2025
eclair-core/src/main/scala/fr/acinq/eclair/wire/internal/channel/version4/ChannelCodecs4.scala
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We previously included support for spending the remote anchor output. This created some confusion: is this the anchor output using our key but in the remote commitment? Or is it the anchor output using our peer's key in our local commitment?
It is actually the former: the anchor output that uses our peers' key. There is no reason to claim this output: it cannot be claimed while the commitment tx is unconfirmed, and even after it is confirmed, we must add wallet inputs to be able to claim this 330 sat output, which is something we've never implemented (since it would be an economic loss).
It is only useful to spend those outputs when they pollute the utxo set after commit txs have confirmed. For it to be economical, it only makes sense when we're batching a lot of those outputs. This isn't something we support, so we should simply remove that code for simplicity.