## Software

Arbitrum One runs **Arbitrum Nitro**, maintained by Offchain Labs ([repository](https://github.com/OffchainLabs/nitro)). Nitro integrates go-ethereum code as a library with Arbitrum-specific execution and rollup components; it is the Nitro stack, rather than unmodified upstream node software ([Nitro architecture](https://docs.arbitrum.io/how-arbitrum-works/inside-arbitrum-nitro), [repository](https://github.com/OffchainLabs/nitro)). Node roles use the `nitro` binary; the optional split validator is `nitro-val`, and the `prover` binary generates and verifies fraud proofs. The docs identify these as binaries built from Nitro ([node roles](https://docs.arbitrum.io/run-a-node/assign-node-roles), [binary catalog](https://docs.arbitrum.io/run-a-node/nitro/docker-and-cli-binaries)).

Pages checked **27 October 2026 UTC**.

## Newest node release

- **Repository:** [OffchainLabs/nitro](https://github.com/OffchainLabs/nitro/releases)
- **Tag:** `v3.12.1` ([release page](https://github.com/OffchainLabs/nitro/releases/tag/v3.12.1))
- **Release title:** Arbitrum Nitro v3.12.1 ([release page](https://github.com/OffchainLabs/nitro/releases/tag/v3.12.1))
- **Published date shown:** `02 Oct 22:54` (GitHub’s release display does not show a year) ([release page](https://github.com/OffchainLabs/nitro/releases/tag/v3.12.1)). The release notes’ version heading separately says `2026-09-29` ([release list and notes](https://github.com/OffchainLabs/nitro/releases)).
- **Change:** Adds REST-backed sequencer-feed backfill and related feed backfill endpoints; changes Stylus activation defaults and fixes tracing calls on chains collecting tips ([release notes](https://github.com/OffchainLabs/nitro/releases)).
- **Pre-release:** No; the page marks it **Latest**, with no pre-release label ([release page](https://github.com/OffchainLabs/nitro/releases/tag/v3.12.1)). The release list’s newest displayed entry is this stable release; it also lists older `v3.11.0-rc.3` and `v3.11.0-rc.2` entries ([release list](https://github.com/OffchainLabs/nitro/releases)).

## Newest prover release

**Same repository as node:** Nitro packages the `nitro-val` validation server and `prover` fraud-proof binary, and the docs say these binaries are built from the Nitro repository ([binary catalog](https://docs.arbitrum.io/run-a-node/nitro/docker-and-cli-binaries)). Its newest listed stable release is therefore the Nitro `v3.12.1` release above ([Nitro releases](https://github.com/OffchainLabs/nitro/releases), [release page](https://github.com/OffchainLabs/nitro/releases/tag/v3.12.1)).

I also checked the proposed separate [BOLD repository’s Releases page](https://github.com/OffchainLabs/bold/releases): its latest entry is `BOLD Research Specification + Documentation Release`, tag `v0.0.2`, displayed as released `15 Apr 16:25` (year not shown). Its notes describe research and documentation, not a current prover software release; GitHub marks the repository archived ([release page](https://github.com/OffchainLabs/bold/releases/tag/v0.0.2)). Nitro’s release page is the current public software release source for the node and its included validator/prover binaries.

## Operator docs version

The project’s “Prepare to run a node” page says to use a release version, not beta or release candidate, and gives the latest Docker image as `offchainlabs/nitro-node:v3.12.1-70fa99a` ([Recommended Nitro version](https://docs.arbitrum.io/run-a-node/start-here)). The docs’ full-node guide uses the same image ([run a full node](https://docs.arbitrum.io/run-a-node/run-full-node)).

## Not found

- GitHub’s Nitro and BOLD Tags-page URLs were attempted, but the pages could not be fetched during this check ([Nitro tags](https://github.com/OffchainLabs/nitro/tags), [BOLD tags](https://github.com/OffchainLabs/bold/tags)). The release pages themselves show tag names and release histories.
- Nitro’s GitHub page shows its release publication as `02 Oct 22:54`, while the release notes heading dates `v3.12.1` `2026-09-29`; GitHub did not display a year alongside the publication time ([release page](https://github.com/OffchainLabs/nitro/releases/tag/v3.12.1), [release notes](https://github.com/OffchainLabs/nitro/releases)). Both page displays are reported without reconciling the difference.
- BOLD’s latest release display gives `15 Apr 16:25` without a year ([BOLD release](https://github.com/OffchainLabs/bold/releases/tag/v0.0.2)).