Blockchain networks periodically ship hard-fork upgrades that change client software and consensus or execution rules. On 28 September 2026, the Ronin blog said the Karst upgrade would go live on Ronin mainnet on 7 October 2026 at 16:00:01 UTC (17:00 London), after running on the Saigon testnet since 2 September 2026. [1]
This piece is written for readers after that scheduled window. It follows Ronin’s published activation clock and exchange notices that supported the fork—not a separate post-activation post-mortem from the project.
What was Karst meant to change?
Per the Ronin blog, Karst brings Ronin in line with Ethereum’s Fusaka hard fork on the execution layer, plus a new system for managing Ronin’s core contracts. Named pieces include: [1]
- An L2 Contract Manager, described as allowing upgrades to Ronin’s core contracts in a single block, rather than relying on Ethereum multisig transactions or client-level changes.
- An upgrade of Ronin’s L1 contracts to op-contracts/v7.0.0, framed as aligning bridge and rollup mechanics with newer Optimism standards.
Optimism documentation also lists a Karst hardfork in the OP Stack hardfork series—useful cross-reference for the shared stack name, not a substitute for Ronin’s own activation clock. [2]
What should users, builders and node operators have done?
Users: the blog said no action is required, expected no downtime, and said people can continue using Ronin as usual. [1]
Builders: most applications should continue to work, but the blog flagged changes to test on Saigon before mainnet activation, including: [1]
- A new transaction gas cap of about 16.8 million gas after Karst (Ethereum deposit transactions exempt); the blog said everyday DEX swaps are far below that limit.
- Higher costs for P256VERIFY (roughly twice as expensive) and MODEXP, with a new 1024-byte input limit on MODEXP.
- bn256Pairing accepting up to 300 pairs per call (down from 427).
- A new CLZ opcode (additive; tooling that parses bytecode or estimates gas may need updates).
Node operators: had to upgrade before activation. The blog said nodes that were not upgraded would stop following the chain. Steps named include upgrading op-node with the stated Karst override timestamps, upgrading to op-reth v2.2.3, refreshing genesis files, and migrating off op-geth—described as end-of-support and no longer working after Karst. [1]
Binance said it would suspend Ronin-network deposits and withdrawals around 15:00 UTC on 7 October to support the upgrade and hard fork at about 16:00 UTC, with trading unaffected and deposits/withdrawals to reopen once the upgraded network was deemed stable. [3]
Why label the clock carefully?
The primary Ronin source is a pre-activation blog with an explicit 16:00:01 UTC clock. This explainer does not invent a separate “all clear” post from Ronin. It treats the upgrade as having reached its scheduled mainnet time, and leaves room for any later official confirmation or incident note. [1]
What this does not prove
- That every validator and application saw a perfectly smooth transition; a schedule and an exchange support notice are not a full post-mortem. [1][3]
- That every dapp is unaffected; builders were told to test gas, crypto-op and pairing changes. [1]
- That op-geth nodes can lag and catch up later; the blog said unupgraded nodes stop following the chain. [1]
- Any token price implication for RON or ecosystem assets.
No investment advice is offered here.
The Bottom Line
Ronin set Karst for 7 October 2026, 16:00:01 UTC, bringing Fusaka-aligned execution-layer changes, an L2 Contract Manager, and op-contracts v7.0.0, with no user action and a hard requirement that node operators move to op-reth v2.2.3. Read this as coverage after the published activation window—grounded in Ronin’s schedule and exchange support notices, not as a substitute for a formal post-activation report.
Sources
- Ronin blog, The Karst Upgrade goes LIVE October 7th — 28 September 2026 — https://blog.roninchain.com/p/the-karst-upgrade-goes-live-october
- Optimism docs, Karst hardfork (OP Stack) — https://docs.optimism.io/op-stack/protocol/hardforks/karst
- Binance announcement (via Tree of Alpha preview), Ronin network upgrade & hard fork support — dated for 7 October 2026 — https://www.treeofalpha.com/preview_article?id=1790733600000
