## Software Pages read: 2026-10-27 UTC (research observation date; applies to all sources below). OP Mainnet uses the upstream OP Stack maintained by the Optimism Collective, rather than a separately maintained OP Mainnet fork. The [Optimism monorepo README](https://github.com/ethereum-optimism/optimism#what-is-optimism) identifies that stack as powering OP Mainnet. The primary supported node pair is **op-node** (rollup consensus client) plus **op-reth** (execution client built on Reth), both now in [ethereum-optimism/optimism](https://github.com/ethereum-optimism/optimism). The [operator overview](https://docs.optimism.io/node-operators/overview) also offers kona-node as an alternative consensus client; the [source tutorial](https://docs.optimism.io/node-operators/tutorials/run-node-from-source) specifies op-node plus op-reth and gives OP Mainnet settings. This reports the primary supported pair, not a claim to have inspected the sequencer's running binaries. For proofs, [L2BEAT](https://l2beat.com/layer2s/projects/op-mainnet#state-validation) identifies interactive fraud proofs and Cannon/Kona. The maintained software is op-challenger (dispute agent), Cannon (fault-proof VM), kona-client (fault-proof program), and kona-host (preimage server), rather than a ZK prover. Their relationship is described in the [Cannon component docs](https://docs.optimism.io/op-stack/components/cannon). The [deprecation notice](https://docs.optimism.io/notices/archive/op-geth-deprecation) says op-program has been replaced by kona-client and op-geth by op-reth. ## Newest node release Selection: opened both [Optimism Releases](https://github.com/ethereum-optimism/optimism/releases) and [Tags](https://github.com/ethereum-optimism/optimism/tags), plus [op-geth Releases](https://github.com/ethereum-optimism/op-geth/releases) and [Tags](https://github.com/ethereum-optimism/op-geth/tags). The monorepo has independent component releases: the top overall stable release is op-challenger, so the newest stable entries for the two node components are reported individually. Tags were read through direct GitHub HTML after the browser fetch failed. Tag timestamps are not used as release publication dates. - **Consensus node:** repository [ethereum-optimism/optimism](https://github.com/ethereum-optimism/optimism). Tag `op-node/v1.19.11` ([release](https://github.com/ethereum-optimism/optimism/releases/tag/op-node%2Fv1.19.11)); title **op-node v1.19.11** ([release](https://github.com/ethereum-optimism/optimism/releases/tag/op-node%2Fv1.19.11)). Published **22 Oct 02:51**, HTML timestamp **2026-10-22T02:51:39Z** ([release](https://github.com/ethereum-optimism/optimism/releases/tag/op-node%2Fv1.19.11)). Not marked pre-release; marked Latest. Changes: certificate-trust and Go security fixes, sequencer L1-origin correction, beacon slot-duration compatibility, and startup handling for pruned L1 history. [Release notes](https://github.com/ethereum-optimism/optimism/releases/tag/op-node%2Fv1.19.11). - **Execution node:** repository [ethereum-optimism/optimism](https://github.com/ethereum-optimism/optimism). Tag `op-reth/v2.6.1` ([release](https://github.com/ethereum-optimism/optimism/releases/tag/op-reth%2Fv2.6.1)); title **op-reth v2.6.1** ([release](https://github.com/ethereum-optimism/optimism/releases/tag/op-reth%2Fv2.6.1)). Published **22 Oct 02:51**, HTML timestamp **2026-10-22T02:51:23Z** ([release](https://github.com/ethereum-optimism/optimism/releases/tag/op-reth%2Fv2.6.1)). Not marked pre-release. Changes: removes trust in compromised eMudhra intermediates and roots through TLS dependencies and container CA updates. [Release notes](https://github.com/ethereum-optimism/optimism/releases/tag/op-reth%2Fv2.6.1). - **Legacy candidate, not today's supported execution node:** repository [ethereum-optimism/op-geth](https://github.com/ethereum-optimism/op-geth). Tag and title `v1.101702.3` ([release](https://github.com/ethereum-optimism/op-geth/releases/tag/v1.101702.3)). Published **31 Aug 12:30**, HTML timestamp **2026-08-31T12:30:36Z** ([release](https://github.com/ethereum-optimism/op-geth/releases/tag/v1.101702.3)). Not marked pre-release; marked Latest. Changes: library maintenance including Pion STUN/DTLS security updates. The notes explicitly state that running op-geth from this release is unsupported and op-geth is deprecated. [Release notes](https://github.com/ethereum-optimism/op-geth/releases/tag/v1.101702.3). The newest visible entry on each default Releases page is stable, but the Tags pages contain newer release candidates: the top Optimism tag is `op-dispute-mon/v1.6.4-rc.1` ([Tags](https://github.com/ethereum-optimism/optimism/tags)); the top op-geth tag is `v1.101702.4-rc.1` ([Tags](https://github.com/ethereum-optimism/op-geth/tags)). These are RC tags, not substituted for published stable node releases. ## Newest prover release **Same repository as node:** [ethereum-optimism/optimism](https://github.com/ethereum-optimism/optimism). Latest stable fault-proof component releases found on its [Releases page](https://github.com/ethereum-optimism/optimism/releases), cross-checked against [Tags](https://github.com/ethereum-optimism/optimism/tags): - **op-challenger:** tag `op-challenger/v1.11.0` ([release](https://github.com/ethereum-optimism/optimism/releases/tag/op-challenger%2Fv1.11.0)); title **op-challenger v1.11.0** ([release](https://github.com/ethereum-optimism/optimism/releases/tag/op-challenger%2Fv1.11.0)). Published **26 Oct 19:49**, HTML timestamp **2026-10-26T19:49:27Z** ([release](https://github.com/ethereum-optimism/optimism/releases/tag/op-challenger%2Fv1.11.0)). Not marked pre-release. Changes: fixes resolved-game progress metrics, improves catching-up logs and super-root CLI handling, and updates bundled kona-host. [Release notes](https://github.com/ethereum-optimism/optimism/releases/tag/op-challenger%2Fv1.11.0). - **kona-client (fault-proof program):** tag `kona-client/v1.9.0` ([release](https://github.com/ethereum-optimism/optimism/releases/tag/kona-client%2Fv1.9.0)); title **kona-client v1.9.0** ([release](https://github.com/ethereum-optimism/optimism/releases/tag/kona-client%2Fv1.9.0)). Published **23 Oct 21:05**, HTML timestamp **2026-10-23T21:05:25Z** ([release](https://github.com/ethereum-optimism/optimism/releases/tag/kona-client%2Fv1.9.0)). Not marked pre-release. Changes: optional image CA trust-store update; notes explicitly say no change to proof execution for existing chains. [Release notes](https://github.com/ethereum-optimism/optimism/releases/tag/kona-client%2Fv1.9.0). - **kona-host (companion):** tag `kona-host/v1.9.0` ([release](https://github.com/ethereum-optimism/optimism/releases/tag/kona-host%2Fv1.9.0)); title **kona-host v1.9.0** ([release](https://github.com/ethereum-optimism/optimism/releases/tag/kona-host%2Fv1.9.0)). Published **23 Oct 21:05**, HTML timestamp **2026-10-23T21:05:09Z** ([release](https://github.com/ethereum-optimism/optimism/releases/tag/kona-host%2Fv1.9.0)). Not marked pre-release. Changes: validates dependency-set configuration more strictly, supports beacon slot-duration changes, and updates TLS security. [Release notes](https://github.com/ethereum-optimism/optimism/releases/tag/kona-host%2Fv1.9.0). Newest release does **not** establish the deployed prestate: L2BEAT currently identifies the OP Kona interop absolute prestate as `v1.7.0-rc.2` ([L2BEAT program hashes and discovery update](https://l2beat.com/layer2s/projects/op-mainnet#state-validation)). Its discovery update identifies SUPER CANNON KONA as the respected game type and says proposing/challenging remain permissionless. The [project's program docs](https://docs.optimism.io/op-stack/components/kona-client) explain that the chain's absolute prestate commits to the particular program executed by Cannon. ## Operator docs version The [source-build tutorial](https://docs.optimism.io/node-operators/tutorials/run-node-from-source) tells operators to select a recent release using GitHub, rather than declaring one fixed current version. Its illustrative checkout is `op-node/v1.18.2` ([tutorial](https://docs.optimism.io/node-operators/tutorials/run-node-from-source)), described as co-tagged with `op-reth/v2.2.4` ([tutorial](https://docs.optimism.io/node-operators/tutorials/run-node-from-source)). The Docker tutorial literally pins op-node `v1.18.2` ([Docker tutorial](https://docs.optimism.io/node-operators/tutorials/node-from-docker)) and op-reth `v2.2.5` ([Docker tutorial](https://docs.optimism.io/node-operators/tutorials/node-from-docker)), but says those image tags were latest **as of writing** and directs readers to GitHub for current tags. These examples differ from the newest releases above; they are not evidence that those older pins are today's recommended production versions. The migration notice gives op-reth `v2.2.3 or later` ([notice](https://docs.optimism.io/notices/archive/op-geth-deprecation)) as the historical-proof-store migration minimum. The current node release notes above strongly recommend their respective releases. No single fixed, synchronized "run this version today" pin was found in the readable operator tutorials. ## Not found - A separately confirmed version actually running on OP Mainnet's sequencer: NOT FOUND in the [operator overview](https://docs.optimism.io/node-operators/overview), [source tutorial](https://docs.optimism.io/node-operators/tutorials/run-node-from-source), or release pages above. Public release availability is reported separately from deployment. - A standalone newest Cannon release/date: NOT established. The [Cannon docs](https://docs.optimism.io/op-stack/components/cannon) link release tags and say there is no Cannon page under the docs' Releases section. The [monorepo Releases](https://github.com/ethereum-optimism/optimism/releases) and first [Tags page](https://github.com/ethereum-optimism/optimism/tags) did not expose a newest stable standalone Cannon release; no version or date is guessed. The maintained fault-proof program and challenger releases are reported above. - The docs' release catalog and component release histories were not readable through the browser: tried [release index](https://docs.optimism.io/releases/index), [index Markdown](https://docs.optimism.io/releases/index.md), [op-node history](https://docs.optimism.io/releases/op-node.md), and [op-reth history](https://docs.optimism.io/releases/op-reth.md). The [documentation index](https://docs.optimism.io/llms.txt) lists them, but their contents could not be verified. GitHub release pages were reachable and supplied all release dates; no blog or package-registry dates were substituted.