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Ethereum developers have set an Oct. 6 Glamsterdam activation for the Sepolia testnet while warning that valueless test ETH could let malicious builders repeatedly win block auctions and withhold execution payloads.
The concern centers on EIP-7732, which introduces enshrined proposer-builder separation, or ePBS. The mechanism moves the relationship between validators and specialized block builders into Ethereum’s protocol rather than relying mainly on external infrastructure.
Free Test ETH Could Let Malicious Builders Submit Inflated Bids
Under ePBS, builders compete for the right to supply an execution payload after committing a bid to the protocol.
Ethereum consensus developer Potuz warned during the Sept. 17 All Core Developers Consensus call that Sepolia’s economics could make malicious behavior unusually cheap. An attacker could use disposable builder identities, submit oversized bids and then withhold the promised execution payload after winning.
Clients can identify and reject problematic builders, but an attacker could return under a new identity and repeat the behavior.
The specific Sepolia abuse is amplified by test ETH having no meaningful monetary value and does not represent a direct threat to mainnet user funds. EIP-7732 nevertheless treats payload withholding itself as a protocol behavior that implementations must handle safely.
Sepolia Glamsterdam Activation Set for October 6
Ethereum has scheduled Glamsterdam to activate on Sepolia at epoch 353024 on Oct. 6. Hoodi is tentatively planned to follow on Oct. 27, while a mainnet activation date remains unset.
The public-testnet move follows Glamsterdam Devnet-11, which completed its Gloas transition and raised its block gas limit from 60 million to 200 million during the controlled rehearsal. The 200 million setting remains a test parameter rather than a confirmed mainnet limit.
Sepolia will provide a longer-lived public environment for testing the upgrade before developers decide whether to proceed with Hoodi and later mainnet deployment.
Client Teams Get Seven Days Between Releases and Sepolia Fork
Consensus and execution client teams were asked to publish Sepolia-ready releases by Sept. 29, leaving seven days before the Oct. 6 activation.
Ethereum’s normal upgrade process generally aims for roughly 14 days between release-ready software and a public testnet fork to allow additional security review and bug testing. Developers accepted the shorter window partly because Sepolia has a more controlled validator environment and is easier to recover if testing encounters problems.
The Oct. 6 fork will give developers a public environment to test both ordinary Glamsterdam operation and adversarial builder behavior before the upgrade moves to later testnets and, eventually, Ethereum mainnet.
