Quote from: ETFbitcoin on May 28, 2021, 12:04:18 PM

Quote from: gmaxwell on May 27, 2021, 10:22:00 PM

Pre-taproot nodes (and miners) will not relay or mine taproot spends.

I forget the detail of backward compatibility, so i'll just ask it. Why pre-taproot won't relay taproot-transaction? Is it because the transaction missing witness and the (empty ?) script automatically treated as valid script?

Pre-Taproot nodes that support SegWit see the new witness version (version 1) and because by default they have a flag acalled SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM that acts as a standard rule and makes the node reject any transaction containing version 1+ that comes to their mempool. This flag doesn't exist when verifying blocks so they don't reject the transactions but they also don't verify everything about the said transaction.
After Taproot (core v0.21.1+) they will do the same with witness version 2+.