Ethereum’s Beacon Chain just experienced block reorganization

The reorganization lasted seven blocks, which is the longest such reorg on Ethereum in years, said Martin Köppelmann, the co-founder of the Ethereum Virtual Machine-compatible Gnosis chain.

On Wednesday, seven blocks from number 3,887,075 to 3,887,081 were removed from the chain, according to the Beacon Scan data. The block reorganization happens when nodes disagree on the order of the most recent block, so two competing chains emerge. The miners continue to add new blocks to one or another, and eventually, the longer chain is adopted by all nodes, while the shorter is abandoned.

The most common reorgs usually last one or two blocks because of network latency. Two- and five-block reorgs can happen from time to time due to bad luck. However, the ones longer than that “are almost always due to extreme network failure, client bugs, or malicious attacks,” Buterin and Georgios Konstantopoulos, the CTO at Paradigm, wrote in a 2021 blogpost.

However, the recent reorg most likely wasn’t the result of the attack. According to Ethereum’s core developer Preston Van Loon, it happened because of the “non-trivial segmentation” of new and old client node software.

“We suspect this is caused by the implementation of Proposer Boost fork choice has not fully rolled out to the network. This reorg is not an indicator of a flawed fork choice, but a non-trivial segmentation of updated vs out of date client software,” wrote Preston, as Vitalik Buterin called it a “good hypothesis.”

Beacon Chain is the core of Ethereum 2.0, the coordination mechanism of the new network responsible for creating new blocks and rewarding validators. Last week, Van Loon announced that the Merge could take place in August “if everything goes to plan,” but it’s still unclear how the reorg will impact the transition date.