Sei Completes v6.7 Mainnet Upgrade, Halving WebSocket Limit to 5MiB

Sei v6.7 Goes Live on Mainnet

The mandatory v6.7 upgrade is now live on the Sei mainnet, completing a release the project's own GitHub notes had marked as compulsory for every node operator and validator. Confirmation came in a post from the official Sei Network account dated October 8. The changes themselves were spelled out in release notes published on October 5, and they cut deep into legacy surfaces. Inter-blockchain communication through IBC, the messaging layer that lets Sei talk to other chains, has been removed. The feegrant module is gone as well; it previously allowed one account to pay transaction fees on behalf of another. Sei's custom JSON-RPC methods are deprecated with only a handful of exceptions, and developers are directed to the Ethereum-standard eth_* set. Applications that query the chain, from wallets to indexers, had to rework those calls before the activation block arrived. Any service still calling a retired endpoint gets an error rather than data, so the cleanup lands immediately. Two hard limits were tightened at the same time. The WebSocket payload ceiling, the maximum a single connection can send or receive, drops from 10MiB to 5MiB under default settings. API routes that return large volumes of data now face restrictions of their own, part of a broader effort to keep node load predictable. Validators, the operators who verify transactions and produce blocks, were told the upgrade was not optional; a node left on the older version would fall out of consensus once the activation block passed. The direction of travel matches the v6.x line so far: fewer legacy modules to maintain, a smaller surface for the core team to defend, and interfaces that match what Ethereum developers already run. The market's read has been cool so far: the SEI price slipped roughly 10.6% over the past 24 hours.

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From memIAVL to FlatKV

v6.7 is only half of the work scheduled this week. A separate migration now under way moves the storage layer that holds EVM smart contract state from the legacy memIAVL structure to a new design called FlatKV. The protocol's own account framed it as the largest migration the network has undertaken since January 2024. Timing came from the release notes for v6.7.1, published on October 8: the switch was set for roughly 17:00 UTC on October 9, and a testnet rehearsal had already run between October 1 and 2. The patch itself matters for a second reason. Unlike the compulsory v6.7 activation, it fixed bugs tied to the migration without requiring a network-wide halt, so operators applied it while blocks kept flowing. The storage work runs under the Eidos program, whose first features shipped in v6.6 this August and have been extended step by step since. Storage sits at the center of the scaling plan because every transaction execution generates reads and writes against state, and that throughput caps how fast blocks can close. Sei's design brief has always been trading speed: the network was built so market makers and liquidity pools could operate with minimal latency, which is why read and write performance carries so much weight. The chain started life as a finance-focused network before adding EVM compatibility, which let it run smart contracts and tooling written for Ethereum; a primer on how to use Ethereum covers the workflow those teams lean on. Everything above feeds one target: Giga, the next-generation upgrade at the heart of the Sei ecosystem, which aims for 200,000 transactions per second while preserving EVM compatibility. The team is pursuing that goal across three areas at once: consensus, the execution layer that processes smart contracts, and storage.

What the Cuts Buy Giga

Read together, the release and the migration amount to one bet: that storage, not consensus or execution, is the binding constraint on Sei's throughput. Stripping out IBC, feegrant and the custom JSON-RPC methods shrinks the code the core team has to maintain, while the FlatKV switch attacks the read and write path every executed transaction touches. The 200,000 transactions per second target depends on all three layers improving at once, and storage was the least developed of the three until Eidos began shipping in August. Among altcoin infrastructure projects racing to scale, Sei rebuilt its state layer before promising headline numbers. Nothing in v6.7 moves the levels our SEI technical analysis tracks; what it changes is the code base those levels will eventually price.