Sepolia Is the First Ethereum Testnet to Get a Post-Merge Upgrade

Sepolia, an Ethereum test network (testnet) chain had a post-merge update on Aug. 22 at 03:01 UTC – the first of its kind on any of the Ethereum proof-of-stake testnets. The update was originally slated for Aug. 17, but was postponed for four days to allow some offline validators to rejoin the network.

While the effects of the upgrade aren’t of the “user-facing” variety, the upgrade itself is worth understanding from a technical point of view, as it has implications for the future success of Ethereum's main blockchain after it transitions from a proof-of-work to a proof-of stake consensus protocol.

In preparation for the Ethereum Merge forecast for mid-September, a series of test networks (testnets) have run through the merge process and transitioned from proof-of-work to proof-of-stake. One of these testnets, Sepolia, successfully merged with its proof-of-stake beacon chain on July 6.

Read more: Merge Testing on Ethereum: What Is It and Why Does It Matter?

The Sepolia testnet went through an upgrade on its Execution Layer (EL), at block 1,735,371. This caused EL clients to disconnect from any peers that did not transition to proof-of-stake, a process which helps maintain a healthy network for Ethereum. The Ethereum Foundation noted that the upgrade will not add additional functionality to the chain.

Parithosh Jayanthi, a DevOps engineer at the Ethereum Foundation, told CoinDesk that “the upgrade is there just to clear up any dead nodes in the system. This is sort of a cleanup, and we wouldn’t really expect to see any change.” Jayanthi also noted that this is something they have to do every time a network merges.

The Ropsten testnet did not upgrade because that chain is considered to be deprecated. On the Aug. 18 All Core Developers call, Ethereum developers discussed deprecating the Kiln testnet as well, ahead of the Merge (a bit earlier than anticipated), given that not many transactions are taking place on it, and participants have moved most of their testing over to the Goerli tesnet. Goerli, which transitioned to proof-of-stake last week, will still see network upgrades even after the Merge on Ethereum’s mainnet.

Alex Stokes, a researcher working on the Merge with the Ethereum Foundation, told CoinDesk that the upgrade isn’t that significant but it can be used as an identifier to help with peer discovery, or finding other nodes in the network. He also said that, ultimately, developers just want the upgrade to go well. They will “do something similar on other networks, but ultimately it will have similarly low fanfare.”

Read more: Ethereum’s After the Merge: What Comes Next?