Bitcoin SV (BSV) performed a planned upgrade with the name Genesis on February. 3. Since most nodes have not been updated yet, this resulted in a small chain split where two versions of BSV exist.
As reported by BitMEX Research, the upgrade took place at block height 620,538, or about 8:30 PM EST. The following block was considered invalid by old rules, indicating the hard fork.
About a quarter of all blockchain nodes are still in the old version, which means that they cannot be synchronized with the main chain.
Moreover, a chain break occurred a few hours later. The old chain was expanded by one block, which means that some miners were also unable to upgrade to the new rules.
This does not seem like a premeditated attempt to create a new chain. With only one block added in more than 10 hours, only a very small minority of miners remain behind the old chain.
Genesis changes many of the consensus rules for Bitcoin SV to remove all remaining restrictions. The block size is now effectively unlimited. Instead of being hard coded in the node software, the block size is now a parameter that miners can manually shrink.
This can lead to problems if not all miners agree with a certain value. A block larger than the maximum size allowed for a certain group of users would be considered invalid by them. By default, this setting is unlimited.
Many other limits were also increased, such as the maximum size of a transaction or the number of owners for a multisig wallet.
The Bitcoin Script language now has a formalized grammar that will be checked by consensus participants. The upgrade has also restored OP_RETURN, an instruction for saving custom data on the blockchain.
Although the changes are apparently small, a hard fork is always needed for every change to the consensus rules.