Ethereum Beacon Chain experiences 7 block reorg: What’s going on?

Ahead of the Merge tentatively penciled in for August, Ethereumโ€™s Beacon Chain experienced a seven-block reorganization (reorg) yesterday.

According to data from Beacon Scan, on May 25 seven blocks from number 3,887,075 to 3,887,081 were knocked out of the Beacon Chain between 08:55:23 to 08:56:35 AM UTC.

The term reorg refers to an event in which a block that was part of the canonical chain, such as the Beacon Chain, gets knocked off the chain due to a competing block beating it out.

It can be the result of a malicious attack from a miner with high resources or a bug. Such incidents see the chain unintentionally fork or duplicate.

On this occasion, developers believe that the issue is due to circumstance rather than something serious such as a security issue or fundamental flaw, with a โ€œproposer boost forkโ€ being highlighted in particular. This term refers to a method in which specific proposers are given priority for selecting the next block in the blockchain.

Core Ethereum developer Preston Van Loon suggested the reorg was due to a โ€œnon-trivial segmentationโ€ of new and old client node software, and was not necessarily anything malicious. Ethereum co-founder Vitalik Buterin labeling the theory a โ€œgood hypothesis.โ€

Block reorg: Beacon Scan

Martin Kรถppelmann, the co-founder of EVM compatible Gnosis chain was one of the first to highlight the occurrence via Twitter yesterday morning, noting that it โ€œshows that the current attestation strategy of nodes should be reconsidered to hopefully result in a more stable chain! (proposals already exist).โ€

In response to Kรถppelmann, Van Loon tentatively attributed the reorg to the proposer boost fork which hadnโ€™t fully been implemented yet:

โ€œWe 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 This reorg is not an indicator of a flawed fork choice, but a non-trivial segmentation of updated vs out of date client software.โ€

โ€œAll of the details will be made public once we have a high degree of confidence regarding the root cause. Expect a post-mortem from the client development community!โ€ he added.

Earlier today, another developer Terence Tsao echoed this hypothesis to his 11,900 Twitter followers, noting that the reorg seemed to be caused by โ€œboosted vs. non boosted nodes in the network and the timing of a really late arriving block.โ€

โ€œGiven that the proposer boost is a non-consensus-breaking change. With the asynchronicity of the client release schedule, the roll-out happened gradually. Not all nodes updated the proposer boost simultaneously.โ€

Related: OpenEthereum support ends with the Merge fast approaching

Van Loon spoke at the Permissionless conference last week and said that the Merge and switch to Proof-of-Stake (PoS) could come in August โ€œif everything goes to plan.โ€

While the reorg is sure to raise questions of this potential timeline, Van Loon and the other developers have not yet outlined whether it will have any impact at all.