Glamsterdam Roadmap: Why ePBS & BAL Testing Won’t Be Rushed

Ethereum’s upcoming Glamsterdam upgrade has ignited deep technical discussions around its headline features: Enshrined Proposer-Builder Separation (ePBS) & Block Access Lists (BALs). Developers are signaling caution, preferring a staged rollout rather than merging both features prematurely.

• The Debate: Merged vs Sequential Testing
• Why Prysm Leads BAL Testing
• Technical Dependencies Between ePBS & BALs

The Debate: Merged vs Sequential Testing

During ACDC #165, contributors debated whether combining ePBS & BAL testing in a single devnet would accelerate Ethereum’s roadmap. While the idea promised efficiency, most developers agreed that merging both would strain client teams, complicate testing, and amplify risks.

Instead, the community leaned toward sequential devnets, giving each feature the attention it requires without overwhelming contributors.

Why Prysm Leads BAL Testing

The phased roadmap begins with BAL-only devnets, initially run with Prysm. This approach limits disruption by isolating BAL testing, while other Consensus Layer clients remain focused on ePBS.

The split prevents bottlenecks, balances workload across teams, and ensures that progress continues on both fronts. Once stable, BAL features will later align with ePBS for a unified implementation.

Technical Dependencies Between ePBS & BALs

BALs depend heavily on ePBS. Without ePBS, implementing BALs requires state changes to the beacon chain, which increases complexity & long-term maintenance overhead.

By contrast, when BALs run on top of ePBS, they integrate seamlessly without additional state modifications. Developers therefore agreed to start with a BAL-only branch for near-term testing, then move to a BAL-on-ePBS model as soon as minimal ePBS support is available.

By opting for sequenced testing of ePBS & BALs, developers reduce risks, distribute workload efficiently, and ensure governance stability. Glamsterdam’s scope will only be finalized after Fusaka’s mainnet launch, proving once again that Ethereum values resilience over reckless speed in its evolution.

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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