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Ethereum ships Prysm 7.2.1 hours before Glamsterdam's 200M-gas Sepolia test
A last-minute Prysm patch switches the validator default to 200M gas so Sepolia's October 6 Glamsterdam activation actually tests the higher capacity target.
Prysm, one of Ethereum's two production consensus clients, published v7.2.1 late on October 5, hours before Glamsterdam activates on Sepolia at approximately 13:53 UTC on October 6, 2026, CoinDesk reports. The patch flips the client's default proposer gas-limit preference to 200 million gas so Sepolia's capacity test is not undermined by validators silently proposing 60M-gas blocks.
What the patch changes
The initial Glamsterdam-compatible releases from both Prysm and Teku shipped the fork rules but left validators defaulting to the pre-fork 60 million gas proposer preference. Operators who had not manually set gas_limit: "200000000" in their proposer settings — or pushed the value through the keymanager API — would have continued producing 60M-gas blocks on Sepolia even after Glamsterdam activation, defeating the point of the testnet rehearsal.
Prysm v7.2.1 raises the default so the gas-limit bump happens without validator intervention. The release notes and binary diffs are at the OffchainLabs/prysm releases page.
Why 200M matters
Sepolia's post-Glamsterdam gas target of 200 million is roughly 3.3x the pre-fork 60M. The purpose is to measure, under non-trivial load, how clients, provers and the public mempool handle blocks that large before the capacity jump moves to mainnet. State growth, witness size for stateless provers, and worst-case EL execution time are the three failure modes operators are watching.
The schedule for the activation epoch on Sepolia — 353024 — was fixed in the earlier Prysm 7.2.0 release in late September; 7.2.1 only adjusts the proposer default, not the fork timing.
Context
Glamsterdam's capacity jump is the headline change of this upgrade cycle, and client-default parameters have repeatedly been the choke point when a scheduled bump needs validator cooperation. The pattern — fork rules ship, operators do not update proposer config, measured gas on the testnet stays flat — is the same one that forced opt-in prompts around earlier gas-limit bumps on mainnet. Shipping the default change inside the client release removes the human-in-the-loop step.
Mainnet activation of Glamsterdam remains gated on a clean Sepolia pass. A silent fallback to 60M blocks today would have meant a second Sepolia rehearsal before Ethereum Foundation sign-off.
What to watch
- Observed median gas on Sepolia blocks in the hours after 13:53 UTC — the 200M target holds only if a working majority of validators are on 7.2.1 (or Teku's equivalent) by activation.
- Reorg and missed-slot rate at the higher gas ceiling — the main risk is EL execution timing out before CL deadlines on 200M-gas blocks.
- Teku's own patch: the other client that shipped the lower default has to match for the test to be meaningful across the validator set.
- Prover and witness-size numbers out of the zk and stateless-client teams running Sepolia under the new target.