Ethereum developers have postponed the Glamsterdam hard fork on the Hoodi testnet after security researchers raised concerns about how the upgrade could affect existing smart contracts. The activation had been scheduled for October 26, 2026, but was canceled during a coordination meeting held on October 22, giving researchers additional time to investigate potential vulnerabilities before the network upgrade proceeds.

For Glamsterdam, the Hoodi activation was positioned as the final rehearsal before mainnet — the stage where client teams, node operators, and validators confirm an upgrade behaves correctly under live network conditions before the same rules reach Ethereum's production chain. That positioning is why a cancellation at this point carries directly into the broader rollout timeline.

The decision follows an analysis by smart contract security firm ChainSecurity, which identified risks tied to proposed changes in Ethereum's gas accounting system. According to the firm, researchers uncovered 13 real-world cases involving contracts that could be affected. ChainSecurity is coordinating responsible disclosures with the relevant projects while the Ethereum Foundation assesses the broader security implications.

Security Researchers Flag Potential Contract Vulnerabilities

The concerns center on EIP-8037 and EIP-8038, two proposals that modify Ethereum's gas pricing and state management. Gas is the unit that prices computation on Ethereum, which is why even technical accounting changes can surface hidden dependencies in deployed contracts. Under the proposed rules, existing smart contracts could behave differently when transactions run into insufficient gas.

ChainSecurity's technical analysis indicates that certain failed operations could produce unexpected outcomes. In some circumstances, contracts might permanently record failed transactions that previously would have reverted, potentially blocking users from retrying legitimate operations.

The researchers have urged development teams to review their smart contracts for dependencies on existing gas behavior. The affected projects and contract addresses have not been publicly identified, and no confirmed financial losses have been disclosed in connection with the findings. Because the issues surfaced during testnet testing, the responsible-disclosure process gives affected teams time to adapt their contracts before any mainnet activation.

Developers Reassess Glamsterdam Deployment Plans

Glamsterdam is part of Ethereum's broader push to improve scalability, transaction processing, and network efficiency. Its headline features include enshrined proposer-builder separation and block-level access lists, both designed to improve block production and validation.

Ethereum activated Glamsterdam on the Sepolia testnet on October 6. Developers then scheduled the Hoodi deployment for October 26, along with an increase in the testnet's gas limit to 200 million, as outlined in the official Hoodi announcement. The latest decision removes both the scheduled activation and the accompanying gas-limit adjustment.

Hoodi node operators and validators must now review their software configurations to ensure compatibility with the revised schedule.

Mainnet Timeline Remains Uncertain

The postponement clouds Glamsterdam's path to Ethereum mainnet. Developers had weighed early December activation dates, contingent on successful Hoodi testing. The Ethereum Foundation has not announced a replacement testnet activation date or confirmed a mainnet launch schedule.

The next milestone for Glamsterdam is a revised Hoodi activation, which would allow the testing sequence to resume; until the Foundation sets that date, the mainnet timeline remains open.

In the meantime, developers continue to investigate the security findings and to evaluate whether additional protocol changes are needed. The episode underscores the importance of testing protocol upgrades against existing applications before changes reach Ethereum's production network.