OP Stack Migration

On this page, you’ll learn what changes when Immutable Chain migrates to the OP Stack, who is affected, and what to do. Accounts, balances, contracts, approvals, the chain ID, and IMX as the gas token all carry over. In almost all cases, no user or developer action is required; see Who is affected for exceptions.

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Why Immutable Chain is migrating

Immutable Chain currently runs as a custom fork of Geth with a single validator producing a block every 2 seconds. Its native bridge relies on an external cross-chain messaging network (Axelar). Migrating to the OP Stack makes Immutable Chain an Ethereum rollup, which:

• Replaces the existing bridge with withdrawals verified directly against state commitments posted to Ethereum
• Starts with permissioned fault proofs, with zk-validity proofs to follow
• Lets Immutable adopt protocol upgrades, EVM upgrades, and security patches more quickly

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What changes

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Bridging

Bridged tokens keep their addresses on Immutable Chain. The assets that back them on Ethereum move from the current bridge to the OP Stack native bridge, so they stay backed. Native withdrawals will take about 7 days, across three steps: start the withdrawal on Immutable Chain, prove it on Ethereum, then finalize it once the challenge period ends. The upcoming migration guide will cover which of these steps Immutable’s tools handle. Deposits arrive somewhat faster. Liquidity bridges such as Layerswap and Squid remain available for faster transfers. See Bridging.

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Fees

Fees stay in IMX and increase slightly, because they now cover posting data to Ethereum as well as execution.

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Who is affected

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Migration day

The cutover is the switch from Immutable Geth to the OP Stack. Bridging pauses first, then block production; the length of the pause will be confirmed closer to the date. When block production resumes, the chain runs on the OP Stack.

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For infrastructure providers

If you run Immutable Chain nodes directly or provide RPC services, you need to replace your Geth-based node with the OP Stack node stack. This applies to both public and private nodes.

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What to change

op-reth and op-node start from state exported at the cutover, so they can’t run before it. Start them from Immutable’s snapshot, or from your own node’s state using migration tooling in an upcoming, optional Immutable Geth release, then switch your RPC traffic to them.

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Using RPC providers

If you use an ecosystem RPC partner, they handle the node migration. Check with your provider that they support the OP Stack migration timeline.

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Testnet deprecation

The current Immutable testnet will be deprecated for game usage by the end of 2026. Gas on Immutable Chain is cheap and the testnet has few third-party integrations, so most games test against local chains or mainnet. Infrastructure providers and integration partners, such as exchanges, indexers, and apps that bridge with Immutable’s SDKs or widgets, keep access to the testnet through its migration and the trial period that follows, so nodes, SDK upgrades, and the new bridge flow can be tested before the mainnet migration.

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Timeline

Dates depend on testing and integrity checks at each stage and may move. Contact your Immutable account manager for support during the migration.

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Next steps