Bitcoin Optech Newsletter #409

A draft BIP has been proposed to replace testnet4 with testnet5 to address reliability issues caused by the difficulty exception rule, which allowed 'block storms'. The proposal suggests removing this exception to align testnet behavior more closely with mainnet. Additionally, updates were released for LND (0.21.0-beta) and Core Lightning (26.06.1), along with various technical improvements in Bitcoin Core, LDK, and BTCPay Server.