Holesky Testnet Chain Split Causes Prolonged Non-Finalization

The Holesky testnet experienced a chain split on February 24, 2025, due to incorrect deposit contract addresses used by some clients. This caused validators who attested to the invalid chain to face slashing if they tried to switch to the correct network, creating a massive negative feedback loop.

Clients using Besu, Nethermind, and go-ethereum accepted an invalid block at slot 3711006 with a deposit transaction containing an empty requests list. In contrast, Erigon and Reth rejected this block. The invalid chain reached justified status in epoch 115968, making it difficult for validators to switch.

PandaOps attempted coordination to reach the 66% threshold of validators on the correct chain but failed. This resulted in a prolonged period of non-finalization, causing inactivity leaks and filling the validator exit queue for 1.5 years. The Ethereum Foundation plans to discontinue Holesky by September 30, 2025.

The issue has been fixed, but network performance remains degraded. To mitigate this, developers plan to move testing to the Hoodi testnet. This allows for immediate testing of Pectra features and enables better management of validator credentials.