Arbos 51 notices and release

docs/launch-arbitrum-chain/02-configure-your-chain/common-configurations/13-arbos-upgrade.mdx

@@ -16,7 +16,7 @@ The specific upgrade requirements for each ArbOS release are located under each
 
 #### Step 1: Update Nitro on nodes and validators
 
-Refer to the [requirements for the targeted ArbOS release](/run-arbitrum-node/arbos-releases/01-overview.mdx) to identify the specific [Nitro release](https://github.com/OffchainLabs/nitro/releases/) that supports the ArbOS version that you're upgrading to. For example, if your upgrade targets ArbOS 50, you'd use Nitro `v3.9.0` (Docker image: `offchainlabs/nitro-node:v3.9.0-cca645a`) or higher. This is the version of the Nitro stack that needs to be running on each of your Arbitrum chain's nodes. A list of [all Nitro releases can be found on Github](https://github.com/OffchainLabs/nitro/releases).
+Refer to the [requirements for the targeted ArbOS release](/run-arbitrum-node/arbos-releases/01-overview.mdx) to identify the specific [Nitro release](https://github.com/OffchainLabs/nitro/releases/) that supports the ArbOS version that you're upgrading to. For example, if your upgrade targets ArbOS 51, you'd use Nitro `v3.9.3` (Docker image: `offchainlabs/nitro-node:v3.9.3-8bc5554`) or higher. This is the version of the Nitro stack that needs to be running on each of your Arbitrum chain's nodes. A list of [all Nitro releases can be found on Github](https://github.com/OffchainLabs/nitro/releases).
 
 Begin by upgrading your validator node(s) to the specified Nitro version, then update each remaining Arbitrum chain node to match this version.
 
@@ -26,7 +26,7 @@ Note that upgrading your node version _must occur_ before the deadline establish
 
 While every ArbOS upgrade will require an update to the WASM module root, not every ArbOS upgrade will require an upgrade to the chain's `nitro-contracts` version.
 
-If necessary, as defined in the release notes for each ArbOS release ([example of ArbOS 50](/run-arbitrum-node/arbos-releases/arbos50.mdx)), you may need to deploy new versions of some (or all) of the Nitro contracts to the parent chain of your Arbitrum chain. These contracts include the rollup logic, bridging logic, fraud-proof contracts, and interfaces for interacting with Nitro precompiles. To verify the current version of your Nitro contracts, follow [these instructions](https://github.com/OffchainLabs/orbit-actions/blob/main/README.md#check-version-and-upgrade-path) while replacing the inbox contract address and network name with that of your Arbitrum chain. This information will allow you to find the correct upgrade path for your Nitro contracts.
+If necessary, as defined in the release notes for each ArbOS release ([example of ArbOS 51](/run-arbitrum-node/arbos-releases/arbos51.mdx)), you may need to deploy new versions of some (or all) of the Nitro contracts to the parent chain of your Arbitrum chain. These contracts include the rollup logic, bridging logic, fraud-proof contracts, and interfaces for interacting with Nitro precompiles. To verify the current version of your Nitro contracts, follow [these instructions](https://github.com/OffchainLabs/orbit-actions/blob/main/README.md#check-version-and-upgrade-path) while replacing the inbox contract address and network name with that of your Arbitrum chain. This information will allow you to find the correct upgrade path for your Nitro contracts.
 
 To update the WASM module root and deploy your chain's Nitro contracts to the parent chain for the most recent ArbOS release, you will need the following inputs (obtained from the [requirements for the targeted ArbOS release](/run-arbitrum-node/arbos-releases/01-overview.mdx)):
 
@@ -35,7 +35,7 @@ To update the WASM module root and deploy your chain's Nitro contracts to the pa
 
 Once you have the WASM module root and have identified the required `nitro-contracts` version for the target ArbOS release, if any, [please follow the instructions in this guide](https://github.com/OffchainLabs/orbit-actions?tab=readme-ov-file#nitro-contracts-upgrades) for specific actions based on the `nitro-contracts` version you are deploying. Note that each ArbOS release will require performing this step with a different WASM module root and may require a different version of `nitro-contracts`. The guide linked above will be kept updated with the instructions for each specific ArbOS release.
 
-The `WASM module root` is a 32-byte hash created from the Merkelized Go replay binary and its dependencies. When ArbOS is upgraded, a new WASM module root is generated due to modifications in the State Transition Function (STF). This new WASM module root must be set in the rollup contract on the parent chain. For example, the WASM module root for ArbOS 50 Dia is `0x2c54f6e9e378ba320ed9c713a1d9f067a572b1437e4f1c40b1a915d3066c04f2`.
+The `WASM module root` is a 32-byte hash created from the Merkelized Go replay binary and its dependencies. When ArbOS is upgraded, a new WASM module root is generated due to modifications in the State Transition Function (STF). This new WASM module root must be set in the rollup contract on the parent chain. For example, the WASM module root for ArbOS 51 Dia is `0x8a7513bf7bb3e3db04b0d982d0e973bcf57bf8b88aef7c6d03dba3a81a56a499`.
 
 To set the WASM module root manually (i.e., not using the above guide), use the `Rollup proxy` contract's [`setWasmModuleRoot`](https://github.com/OffchainLabs/nitro-contracts/blob/38a70a5e14f8b52478eb5db08e7551a82ced14fe/src/rollup/RollupAdminLogic.sol#L321) method. Note that the `upgrade executor` contract on the parent chain is the designated owner of the Rollup contract, so the **chain owner account** needs to initiate a call to the `upgrade executor` contract in order to perform the upgrade. This call should include the correct calldata for setting the new WASM module root.
 
@@ -49,7 +49,7 @@ WASM module roots are backward compatible, so upgrading them before an ArbOS ver
 
 To schedule an ArbOS version upgrade for your Arbitrum chain, [follow this guide](https://github.com/OffchainLabs/orbit-actions/tree/main/scripts/foundry/arbos-upgrades/at-timestamp). In addition to the upgrade action contract address and the account address for the chain owner account, you will need the following inputs:
 
-1. **`newVersion`**: Specify the ArbOS version you wish to upgrade to (e.g., `50`).
+1. **`newVersion`**: Specify the ArbOS version you wish to upgrade to (e.g., `51`).
 2. **`timestamp`**: Set the exact UNIX timestamp at which you want your Arbitrum chain (Orbit) to transition to the new ArbOS version.
 
 If you would prefer to do this manually, simply call the [`scheduleArbOSUpgrade`](https://github.com/OffchainLabs/nitro-precompile-interfaces/blob/fe4121240ca1ee2cbf07d67d0e6c38015d94e704/ArbOwner.sol#L116) function on the `ArbOwner` precompile of the Arbitrum chain(s) you're upgrading. Because this is an administrative action (similar to upgrading your Wasm module root), the **chain owner account** must call the target chain's `upgrade executor` contract with the appropriate calldata in order to invoke the `scheduleArbOSUpgrade` function of the ArbOwner precompile. This will schedule the ArbOS upgrade using the specified version and timestamp.
@@ -64,14 +64,14 @@ To upgrade immediately (without scheduling), set the timestamp to `0`.
 
 You can obtain the current ArbOS version of your chain by calling `ArbSys.ArbOSVersion()`. Keep in mind that this function adds `55` to the current ArbOS version. For example, if your chain is running on ArbOS 10, calling this function will return `65`.
 
-When scheduling the ArbOS upgrade through `ArbOwner.scheduleArbOSUpgrade` you must use the actual ArbOS version you're upgrading to. For example, if you're upgrading to ArbOS 50, you will pass `50` when calling this function.
+When scheduling the ArbOS upgrade through `ArbOwner.scheduleArbOSUpgrade` you must use the actual ArbOS version you're upgrading to. For example, if you're upgrading to ArbOS 51, you will pass `51` when calling this function.
 
 </VanillaAdmonition>
 
 #### Step 4: Enable ArbOS specific configurations or feature flags (not always required)
 
-For some ArbOS upgrades, such as [ArbOS 50 Dia](/run-arbitrum-node/arbos-releases/arbos50.mdx), there may be additional requirements or steps that need to be satisfied to ensure your Arbitrum chain can use all of the new features and improvements made available in that particular ArbOS release.
+For some ArbOS upgrades, such as [ArbOS 51 Dia](/run-arbitrum-node/arbos-releases/arbos51.mdx), there may be additional requirements or steps that need to be satisfied to ensure your Arbitrum chain can use all of the new features and improvements made available in that particular ArbOS release.
 
-If there are additional requirements for the targeted ArbOS release you're attempting to upgrade to; the additional requirements will be listed on the reference pages for [the targeted ArbOS release](/run-arbitrum-node/arbos-releases/01-overview.mdx#list-of-available-arbos-releases). For example, the additional requirements for Arbitrum chains upgrading to ArbOS 50 can be found [here on the ArbOS 50 docs](/run-arbitrum-node/arbos-releases/arbos50.mdx).
+If there are additional requirements for the targeted ArbOS release you're attempting to upgrade to; the additional requirements will be listed on the reference pages for [the targeted ArbOS release](/run-arbitrum-node/arbos-releases/01-overview.mdx#list-of-available-arbos-releases). For example, the additional requirements for Arbitrum chains upgrading to ArbOS 51 can be found [here on the ArbOS 51 docs](/run-arbitrum-node/arbos-releases/arbos51.mdx).
 
 Congratulations! You've upgraded your Arbitrum chain(s) to the specified ArbOS version.

docs/notices/arbos51-arbsepolia-upgrade-notice.mdx

@@ -0,0 +1,23 @@
+---
+title: 'ArbOS 51 activation on ArbSepolia'
+description: Upgrade notices for ArbOS 51 activation on ArbSepolia
+user_story: As an Arbitrum chain owner or node operator, I want to configure my chain/nodes to run on ArbSepolia.
+content_type: notice
+---
+
+On Monday, December 1, 2025 at 17:00 UTC, ArbOS 51 will activate on the Arbitrum Sepolia chain.
+
+:::warning Action required
+
+Arbitrum Sepolia node operators **must upgrade** to Nitro **`v3.9.3`** ahead of this activation to continue syncing the chain.
+
+- **Docker image:** `offchainlabs/nitro-node:v3.9.3-8bc5554`
+- **Release notes:** https://github.com/OffchainLabs/nitro/releases/tag/v3.9.3
+
+:::
+
+### **Context**
+
+ArbOS 51 is a follow-up to ArbOS 50 that fixes issues with the Pricing Framework. ArbOS 50 was previously activated on Sepolia, but the Gas Target & Pricing Framework changes remained disabled pending this fix. ArbOS 51 now completes that work.
+
+Upstream governance items (ArbOS 50 + Gas Target & Pricing Framework) are being bundled into a single on-chain vote. Both components have passed Snapshot temperature checks, with the Tally vote expected to open on or around **December 4, 2025**.

docs/notices/fusaka-upgrade-notice.mdx

@@ -7,7 +7,7 @@ content_type: notice
 
 :::danger 🛑 IMPORTANT 🛑
 
-Arbitrum chain operators must ensure that their nodes are properly configured before or shortly after the parent chain upgrades to Fusaka or the child chain upgrades to [ArbOS 50](docs/run-arbitrum-node/arbos-releases/arbos50.mdx).
+Arbitrum chain operators must ensure that their nodes are properly configured before or shortly after the parent chain upgrades to Fusaka or the child chain upgrades to [ArbOS 51](docs/run-arbitrum-node/arbos-releases/arbos51.mdx).
 
 :::
 
@@ -23,8 +23,8 @@ The following dates are relevant for Arbitrum chain operators.
 
 | Date                                     | Network upgrade                                                                            | Affected audience                                                                              |
 | ---------------------------------------- | ------------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------------------- |
-| `Nov 20th 2025, 17:00:00 UTC`            | Arbitrum Sepolia upgrade to [ArbOS 50](docs/run-arbitrum-node/arbos-releases/arbos50.mdx)  | Node operators for Arbitrum Sepolia                                                            |
-| `Jan 8th, 2026, 17:00:00 UTC (proposed)` | Arbitrum One/Nova upgrade to [ArbOS 50](docs/run-arbitrum-node/arbos-releases/arbos50.mdx) | Node operators for Arbitrum One/Nova                                                           |
+| `Nov 20th 2025, 17:00:00 UTC`            | Arbitrum Sepolia upgrade to [ArbOS 51](docs/run-arbitrum-node/arbos-releases/arbos51.mdx)  | Node operators for Arbitrum Sepolia                                                            |
+| `Jan 8th, 2026, 17:00:00 UTC (proposed)` | Arbitrum One/Nova upgrade to [ArbOS 51](docs/run-arbitrum-node/arbos-releases/arbos51.mdx) | Node operators for Arbitrum One/Nova                                                           |
 | `Oct 14th 2025, 07:36:00 UTC`            | Ethereum Sepolia Fusaka hard fork                                                          | Node operators for Arbitrum chains settling on Ethereum Sepolia (Orbit L2s, Arbitrum Sepolia)  |
 | `Dec 3rd 2025, 21:49:11 UTC`             | Ethereum Mainnet Fusaka hard fork                                                          | Node operators for Arbitrum chains settling on Ethereum Mainnet (Orbit L2s, Arbitrum One/Nova) |
 
@@ -34,8 +34,8 @@ Outlined below are different types of Arbitrum chains, along with node software
 
 | Layer  | Data Availability    | Fallback to blobs enabled? | Required Nitro node version                                                                                                                                                                                                                                 | Configurations for the Ethereum Consensus Layer client                                                                              |
 | ------ | -------------------- | -------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------- |
-| **L2** | **Rollup**           | N/A                        | Update to [`3.9.0`](https://github.com/OffchainLabs/nitro/releases/tag/v3.9.0) (ArbOS 50); [`3.8.0`](https://github.com/OffchainLabs/nitro/releases/tag/v3.8.0) or [`3.7.6`](https://github.com/OffchainLabs/nitro/releases/tag/v3.7.6) (ArbOS 40 or older) | Requires all [historical blob data](#how-to-ensure-your-node-has-access-to-all-historical-blob-data-and-blob-data-from-all-subnets) |
-| **L2** | **AnyTrust / AltDA** | Enabled                    | Update to [`3.9.0`](https://github.com/OffchainLabs/nitro/releases/tag/v3.9.0) (ArbOS 50); [`3.8.0`](https://github.com/OffchainLabs/nitro/releases/tag/v3.8.0) or [`3.7.6`](https://github.com/OffchainLabs/nitro/releases/tag/v3.7.6) (ArbOS 40 or older) | Requires all [historical blob data](#how-to-ensure-your-node-has-access-to-all-historical-blob-data-and-blob-data-from-all-subnets) |
+| **L2** | **Rollup**           | N/A                        | Update to [`3.9.3`](https://github.com/OffchainLabs/nitro/releases/tag/v3.9.3) (ArbOS 51); [`3.8.0`](https://github.com/OffchainLabs/nitro/releases/tag/v3.8.0) or [`3.7.6`](https://github.com/OffchainLabs/nitro/releases/tag/v3.7.6) (ArbOS 40 or older) | Requires all [historical blob data](#how-to-ensure-your-node-has-access-to-all-historical-blob-data-and-blob-data-from-all-subnets) |
+| **L2** | **AnyTrust / AltDA** | Enabled                    | Update to [`3.9.3`](https://github.com/OffchainLabs/nitro/releases/tag/v3.9.3) (ArbOS 51); [`3.8.0`](https://github.com/OffchainLabs/nitro/releases/tag/v3.8.0) or [`3.7.6`](https://github.com/OffchainLabs/nitro/releases/tag/v3.7.6) (ArbOS 40 or older) | Requires all [historical blob data](#how-to-ensure-your-node-has-access-to-all-historical-blob-data-and-blob-data-from-all-subnets) |
 | **L2** | **AnyTrust / AltDA** | Disabled                   | No nitro update required                                                                                                                                                                                                                                    | Doesn't require historical blob data                                                                                                |
 | **L3** | **Rollup**           | N/A                        | No nitro update required                                                                                                                                                                                                                                    | Doesn't require historical blob data                                                                                                |
 | **L3** | **AnyTrust / AltDA** | Enabled or Disabled        | No nitro update required                                                                                                                                                                                                                                    | Doesn't require historical blob data                                                                                                |

docs/run-arbitrum-node/arbos-releases/01-overview.mdx

@@ -31,7 +31,7 @@ Visit [How Arbitrum works](/how-arbitrum-works/01-inside-arbitrum-nitro.mdx) to
 
 ## List of available ArbOS releases
 
-- [Dia (ArbOS 50)](/run-arbitrum-node/arbos-releases/arbos50.mdx)
+- [Dia (ArbOS 51)](/run-arbitrum-node/arbos-releases/arbos51.mdx)
 - [Callisto (ArbOS 40)](/run-arbitrum-node/arbos-releases/arbos40.mdx)
 - [Bianca (ArbOS 32)](/run-arbitrum-node/arbos-releases/arbos32.mdx)
 - [Atlas (ArbOS 20)](/run-arbitrum-node/arbos-releases/arbos20.mdx)