Arbitrum Nitro rc.3 moves ArbOS 61 into code. The warning matters more.
Operator-facing defaults are changing, but Offchain Labs is also telling node runners not to treat this like a live upgrade.
CryptoVibe Desk · arbitrum · nitro · arbos
- →Offchain Labs published Nitro v3.11.0-rc.3 as pre-release software, after rc.2 and a separate consensus-v61-rc.2 tag.
- →The code adds ArbOS 60 and 61 support, but the consensus release warns node operators not to run it.
- →Watch the next stable Nitro release for a non-RC consensus build and a clean activation path.
- Nitro → Nitro is the software Arbitrum node operators run to follow the chain and check its state.
- ArbOS → ArbOS is Arbitrum's chain operating system, the layer that defines how transactions and system rules work.
- WASM fraud proof → A WASM fraud proof is code that lets Arbitrum check a disputed result by replaying it in a small virtual machine.
- release candidate → A release candidate is a test build that might become stable if no serious issue appears.
Arbitrum's new Nitro candidate changes operator behavior.
Offchain Labs tagged Nitro v3.11.0-rc.3 as a pre-release in its GitHub release notes. The code does what the roadmap implied, plus one operator-facing warning: ArbOS 61 is moving into downloadable builds, not production comfort.
That makes this a preparation signal, not a deployment story. Arbitrum operators are seeing the next ArbOS work land in flags, defaults, and proof code. Offchain Labs has not turned this into a mainnet activation notice in the cited releases. If you're running Arbitrum infra, treating rc.3 like production means reading past the label.
The rc.2 notes added support for ArbOS 60 and 61. They also changed a default: `--node.transaction-streamer.shutdown-on-blockhash-mismatch` is now true. When a feed block hash and the local block hash disagree, the node shuts down gracefully. That is better than persisting or rebroadcasting a mismatch.
rc.3 is more cleanup, but not trivial cleanup. Offchain Labs says it replaced `sha3` and `digest` keccak with `tiny-keccak` across `prover` and `caller-env`. It also fixed invalid Prometheus metric names, removed the legacy validator, and made `GuestPtr` addition checked instead of silently wrapping. That last change is the boring safety fix you want in code that handles pointers.
And that's the catch. Offchain Labs calls the separate consensus-v61-rc.2 tag a WASM fraud proof consensus version for ArbOS v61 RC 2. The same release says it is "not a good version to run a node on." It also lists WAVM Module Root `0xc10cd7ec6acaf1c441a3f6bd0900ad20f15855ba775a96f1939118cbc629dc97`.
This is a release-management problem, not a consensus win yet. The code path is visible, but the operator instructions are not final. Read the release tag, not the roadmap. ArbOS 61 is officially closer, but the safe read is still waiting for the build Offchain Labs says is node-ready.
Offchain Labs would be reckless to let v61 RC builds enter operator runbooks before a stable Nitro tag. Its own consensus tag says this build is not a good version to run a node on.
By the next stable Nitro release, watch for a non-RC consensus-v61 tag that removes the node warning and lists a final WAVM module root.
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