Ethereum developers are gearing up for the next major stage of testing with a planned shadow fork & large-scale public testnet. However, progress depends on resolving ongoing orphan block anomalies, validator onboarding issues, & client connectivity bugs first. These discussions formed a central focus of the All Core Devs Testing Call #46 on July 28, 2025.

Next Phase: Shadow Fork & Large Testnet

Ethereum’s upgrade process involves layered testing phases. After devnets like Fusaka 3, the network will transition to a shadow fork, where changes are tested against live mainnet conditions, followed by a large public testnet that mimics a mainnet-scale environment.

During ACDT #46, Parithosh Jayanthi confirmed that planning is already underway, but execution hinges on stabilizing current Devnet 3 anomalies.

Bottlenecks Before Scaling Up

Before moving ahead, developers flagged several roadblocks:

  1. Orphan Blocks: Higher-than-expected orphan rates observed randomly across clients, possibly linked to MEV workflows.
  2. Bootnode & Peering Issues: Nimbus EL/CL clients struggling to connect; Lodestar validator registration anomalies.
  3. Client-Specific Bugs: Networking issues identified in Geth & Nethermind, with active debugging underway (see Geth PR #32287).
  4. Validator Coverage: Manual top-ups needed in Devnet 3 to normalize stake distribution across clients.

These blockers must be addressed before scaling testing infrastructure.

Cautious Approach to Timelines

While some suggested pushing to a shadow fork as early as next week, consensus favored a more measured approach. Developers emphasized focusing first on orphan block investigation, connectivity fixes, and client-specific bug resolutions.

Parithosh noted:

“For now, it would be great if clients focus on the orphan issue as well as any client-specific bugs. Once those are stable, we can move as soon as possible to the next phase.”

Client teams agreed to coordinate asynchronously via the Interop Notes.

Strategic Importance

The shadow fork & large testnet represent critical checkpoints in preparing for Ethereum’s upcoming Glamsterdam upgrade. These phases will validate:

  • Blob propagation efficiency under varying loads
  • Validator fairness & stake normalization
  • Client resilience under large-scale stress conditions

Skipping or rushing these steps could expose the mainnet to untested risks, making careful sequencing vital.

Conclusion

Ethereum’s path to mainnet upgrades remains deliberate. While Fusaka Devnet 3 has delivered important insights, the priority now lies in debugging anomalies before escalating to larger-scale tests. The shadow fork & public testnet will mark the next milestones, reflecting Ethereum’s safety-first philosophy in protocol development.

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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