Ethereum core developers have placed the Glamsterdam upgrade on hold for the Hoodi testnet, pausing the network transition until security concerns tied to eight smart contract invariants are resolved. The Ethereum Foundation disclosed the decision in a blog post published on Nov. 6.

LATEST: ⚡ Ethereum developers say they are delaying the Glamsterdam hard fork process and won't fork the Hoodi testnet until gas-repricing issues flagged by ChainSecurity are resolved. pic.twitter.com/7HDv6dZDrc

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An invariant is a condition that a smart contract expects to hold true at all times. Gas is the unit Ethereum uses to meter computational work, and many deployed projects assume certain operations will cost a fixed amount of it. Two proposals scheduled for inclusion in Glamsterdam change how gas is charged, and those changes could invalidate such assumptions across existing contracts. This is why the repricing is being treated as a security matter rather than a routine fee adjustment: the amounts involved can determine whether certain code paths execute at all.

What ChainSecurity Found

The concerns stem from an Oct. 13 report by smart contract auditor ChainSecurity, which examined how Glamsterdam could affect contracts that continue running after an external call fails. The report covers EIP-8037, which changes the cost of creating new blockchain state, and EIP-8038, which adjusts the charges for accessing existing state. Both alter gas accounting for certain operations.

Under today's rules, some contracts rely on a failed operation leaving too little gas for the next steps to execute. Under the new rules, certain operations could finish even when developers expected the entire transaction to revert. That could weaken safeguards built into those contracts.

ChainSecurity provided one example. A contract marks an operation as failed after an external call runs out of gas. With the new rules, gas that was once out of reach could become available again, and the contract could record a permanent failure.

The Ethereum Foundation has published a GitHub repository documenting the eight affected invariants. It includes explanations, examples, and concrete steps developers can use to check their own code against the new gas rules. Fixed gas budgets and gas reserves are the most common issues found so far, meaning a protocol-level change can surface latent assumptions in deployed code without any modification to the contracts themselves.

Other risks involve contracts that assume gas use only moves in one direction, that fixed gas allowances will stay sufficient, or that a reverted call cannot return gas already spent on creating state.

Hoodi Fork on Hold

The Hoodi activation was first scheduled for Oct. 26 at 17:42:48 UTC. Hoodi is Ethereum's principal public testnet, where planned protocol changes are typically rehearsed before mainnet deployment. The postponement removed the Amsterdam execution-layer and Gloas consensus-layer activations from the schedule, along with a planned rise in the testnet gas limit to 200 million. No replacement date has been announced, and the Foundation said the Hoodi fork will not go ahead until the issues are resolved. With mainnet activation normally following public testnet rehearsals, Glamsterdam's path to mainnet is likewise left without a fixed schedule.

Developers are now assessing whether affected contracts can be updated on their own or whether the upgrade specifications must change. Ethereum Foundation developer Marius van der Wijden said the group is working with ChainSecurity and Dedaub, and is running internal audits to assess the effects on existing applications.

The Foundation said its reviews cannot cover every project, especially where contracts interact with off-chain systems. It has asked developers and independent auditors to review both on-chain contracts and off-chain tools, including wallets, relayers, and other infrastructure that may use hardcoded gas limits.

Findings should be submitted before the next All Core Developers discussions, the standing forum where Ethereum client teams and researchers coordinate protocol changes. Reports should list the affected contract, the invariant involved, possible fixes, and tests where available. They can be sent privately to glamsterdam@ethereum.org. Based on the feedback, developers may adjust EIP-8037 and EIP-8038, making those discussions the checkpoint to watch for specification changes that would shape when the Hoodi fork can be rescheduled.

Glamsterdam Background

Glamsterdam went live on the Sepolia testnet on Oct. 6, where developers began testing its scaling changes under a 200 million gas limit. The upgrade also adds enshrined proposer-builder separation through EIP-7732 and block-level access lists through EIP-7928. Testnet activations like this one allow developers to observe upgrade behavior in a live environment before mainnet deployment.

In an August assessment, the Foundation said replays of past transactions showed most smart contracts were unaffected by the pricing changes. A smaller group needed higher gas limits or larger changes to avoid unexpected failures.

On Oct. 26, developers also merged a validator deposit fix. It addressed a flaw that could have credited staking deposits to block builders sharing the same public key. Regression tests were added to the specifications.

The Foundation said work on the next upgrade, Hegota, continues in parallel and is not affected by the Glamsterdam delay.