Ethereum’s testnet launch of the Istanbul hard fork arrived two days earlier than expected, which caught Ropsten miners by surprise.
Originally expected to activate on 2 October, Istanbul arrived two days earlier, and was released on 30 September at 3:40 A.M. UTC.
The reason behind the sudden activation of the system-wide upgrade was due to unusually fast block confirmation times, the Community manager of the Ethereum Foundation, Hudson Jameson explained.
He further said in a tweet that some miners are still relying on the old Ropsten testnet, while others are already mining on the new one, which caused a split in the network.
The arrival of the hard fork caught many developers off guard, which resulted in miners on the Ropsten blockchain not upgrading to the latest software, which miners on a proof-of-work blockchain are required to do manually in order to ensure the continuation of a single chain.
Jameson further added in his tweet that “this is what testnets are for”, and that the test network will be unstable until “this all plays out”.
It is still unknown if this temporary chain split will affect the activation of Istanbul on the main Ethereum network, though Jameson has reportedly said that the issues with the Ropsten network appear to be the result of poor communication and not flaws in the code.