Developers acted fast and the network recovered, but the event raised new questions about client diversity.
Ethereum Validator Drop After Fusaka
Ethereum hit a sudden 25% drop in voting participation right after the Fusaka upgrade.
The fall happened due to a flaw in Prysm version v7.0.0. The client produced old states when it processed outdated attestations, and this caused nodes to stop working as expected.
Prysm developers shared a temporary fix and told validators to start the client with a special flag.
However, Beaconcha.in data showed the hit clearly. At epoch 411448, sync participation dropped to 75% and voting participation reached about 74.7%.
Notably, Ethereum needs at least two-thirds of stakers to vote to keep finality. That means the network sat only a few percentage points away from losing that safety line.
Ethereum Client Diversity Brings Fresh Worries
Ethereum saw a fast recovery. At epoch 411712, voting participation climbed close to 99% and sync participation reached 97%. Before the issue, the network usually saw more than 99% of votes.
The recovery proved that the issue stayed tied to one client group.
Validator data lined up with the scale of the drop. Prysm had about 22.7% of validators before the bug. That number dropped to 18% after the event. This matched the fall in voting participation and showed that the failure stayed focused on Prysm users.
A similar problem happened in 2022. Ethereum lost finality twice due to older attestation bugs in both Prysm and Teku. Back then, Prysm ran on most Ethereum consensus nodes.
That created a higher risk because one client error could push the entire network into trouble.
Ethereum still has uneven client usage. Current MigaLabs data shows Lighthouse holds 52.55% of nodes while Prysm holds around 18%.
Developers want no single client above 33% and that limit keeps the network safe, even if one client breaks.
Thus, the recent event proved that the network still needs more balance.
Ethereum Faces Finality Challenge
Ethereum finality plays a major role in keeping the chain stable. If voting participation drops below two-thirds, the chain loses finality.
Blocks can still appear, but they do not count as finalised. That creates real problems because bridges can freeze and rollups can halt withdrawals. Exchanges can also raise confirmation limits and users may face delays and higher risks during that period.
Prysm developers warned that the bug made nodes produce old states. This blocked proper voting and caused the sudden drop.
The quick recovery, helped by the workaround, kept the chain safe. Yet the event served as a reminder.
The network needs strong client diversity to protect itself from single-point failures.
Related Reading: Ethereum Rallies Strongly Past $3,000 Before the Upcoming Fusaka Upgrade
Ethereum Gains From Fusaka Despite Setback
The Fusaka upgrade still brought clear gains for Ethereum. It added PeerDAS through EIP-7594.
This upgrade reduces bandwidth use and prepares Ethereum for higher throughput. It also supports more activity and lowers pressure on the base layer. In sum, the upgrade helps rollups scale and lowers costs for users.
Fusaka also increases blob capacity, which helps layer 2 networks. This means cheaper operations and smoother performance during heavy usage. It also makes Ethereum more suitable for large applications that need fast and cheap transactions.
Overall, the next months will show how validators respond and how fast the ecosystem builds on the upgrade.