The launch of Fusaka Devnet 2 was meant to test the upcoming Fusaka upgrade. In this analysis we examine three major issues from the testing phase, explore their root causes, & outline the steps client teams are taking to resolve each one.
- Fork ID Miscalculation & Non Finality Stalls
- Race Conditions in Transaction Pool & Spammer Failures
- Blob Inclusion & Relay Payload Inconsistencies
- Conclusion
Fork ID Miscalculation & Non Finality Stalls
During testing clients such as Teku & Nethermind failed to finalize blocks for extended periods because the execution consensus handshake used an outdated Fork ID. After the cleanup of the Fusaka branch the code still referenced legacy identifiers so nodes treated valid payloads as belonging to an unknown fork.
Consensus logic then refused to finalize blocks until the discrepancy was corrected. Client teams have responded by adding targeted unit tests around each fork transition to ensure identifiers update automatically with future upgrades & by expanding spec test coverage across all clients to detect mismatches before network launches.
Race Conditions in Transaction Pool & Spammer Failures
A custom “spammer” tool was developed to deploy twelve thousand large contracts over eight thousand blocks. Under heavy load this exposed a race condition in the transaction pool’s blob indexing.
When two large contract submissions arrived at the same moment, a pointer that was one position out of range corrupted the pool’s state. As a result some transactions were lost or malformed during block proposals, leading to consensus timeouts.
To address this, developers are adding locks around the blob indexing routines and validating pointer positions before use. They are also integrating full performance tests into the continuous integration pipeline that mimic high-volume contract deployments.
This approach will catch similar race conditions early and ensure the transaction pool remains consistent under stress.
Blob Inclusion & Relay Payload Inconsistencies
Testing of Flashbots & Fulu style relay workflows exposed that the new MEVBoost relay library failed to tag empty blob commitments correctly. As a result relay builders generated incomplete bundles which downstream nodes then rejected blocking MEV relay transactions.
The remedy involves merging the corrected MEVBoost relay code to ensure all blob commitments (even when empty) are properly encoded & adding relay specific integration tests that replay known blob bundle sequences through both the legacy code path & the updated library.
Conclusion
The [Fusaka Devnet 2]((/2025/06/19/eips-included-in-fusaka-devnet-2-what-to-expect/) testing cycle underscores how essential comprehensive, cross-client validation is for protocol upgrades. By expanding unit test coverage around fork transitions, stress-testing transaction pooling under realistic loads, & formalizing end-to-end relay integration checks, client teams can identify & resolve subtle incompatibilities before they impact network stability.
If you find any issues in this blog or notice any missing information, please feel free to reach out at yash@etherworld.co for clarifications or updates.
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- History Expiry Moves Forward in Ethereum’s Fusaka Upgrade
- A Closer Look at What’s Coming in Fusaka Devnet 2
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