Arbitrum launches the first L3 XAI to declare war on Optimism, initiating vertical transformation

Original Title: “Arbitrum's Vertical L3 Revolution: XAI Declares War on Optimism”

Original Author: yyy

Focusing on the Rollup track, the battle between Arbitrum and Optimism is indeed exciting. Optimism expands horizontally with its OP Stack, while Arbitrum takes a different approach by launching the vertical L3 revolution with Arbitrum Orbit. The Arbitrum team has personally launched the first L3 based on Arbitrum Orbit - XAI, officially declaring war on Optimism.

In my opinion, the launch of XAI holds significant strategic importance for Arbitrum, representing a direct declaration of war against OP. OP has leveraged strong B-end resources to successively promote Binance and Coinbase to build L2 chains based on its OP Stack, significantly expanding the L2 ecological landscape; during this time, Arbitrum appeared to be relatively quiet, with no major actions. The rapid launch of XAI amidst OP's flourishing development feels like more than just coincidence.

Arbitrum Orbit

Before discussing XAI, we must talk about Arbitrum Orbit. Arbitrum Orbit is a general modular L3 stack that allows developers to build dedicated L3 chains based on it, with transactions on L3 being settled through Arbitrum L2 (Arbitrum One or Nova). XAI is built on Arbitrum Orbit and focuses on gaming scenarios.

Arbitrum Nova vs. XAI

Nova is a general L2 focused on gaming scenarios, which should theoretically meet the needs of gaming scenarios, so why launch XAI? The reason is simple: compared to Nova's positioning as a public chain for games, XAI, as a dedicated gaming L3, can achieve higher performance with dedicated computing and storage resources. This makes resource-intensive use cases on-chain possible, such as compute-intensive AI models.

XAI natively benefits from Arbitrum's technology stack: Nitro + BOLD + Stylus. Nitro is an upgrade of the One technology stack. It directly compiles the core of Geth through the base layer of client software, with Geth being the mainstream Ethereum client, thus achieving higher Ethereum compatibility. Regarding the differences between Arbitrum Nitro/One/Nova, I have discussed them separately before and will not elaborate here. (Related Link)

BOLD

BOLD is a permissionless verification mechanism proposed by the Arbitrum team, aimed at minimizing the delay of settlement states. In simple terms, for optimistic Rollups, there is generally a challenge period of one week, during which users must wait a week for withdrawals from L2 to L1; if validators discover issues with the submitted L2 transactions during the challenge period, they can initiate a challenge.

There are two questions regarding challenges: 1. Who has the right to challenge? 2. Why can't anyone challenge?

Currently, the fraud proof challenge mechanism is not permissionless; it is performed by specific roles acting as challengers. If challenges were permissionless, malicious challengers could continuously prevent the settlement state from being confirmed through DDoS attacks.

For example, a normal withdrawal might take a week to arrive, but in reality, it could take longer.

By introducing the BOLD mechanism, it can achieve permissionless verification, aligning more with the decentralized philosophy of blockchain; on the other hand, it minimizes the delay of settlement states. BOLD allows a single honest validator to win disputes against any number of opponents on Ethereum, rendering DDoS attacks ineffective.

Stylus

Stylus is an open-source SDK developed by Arbitrum that supports building applications in multiple languages. It is a product that achieves EVM+ compatibility. In short, developers can use both traditional Solidity language and WASM-compatible languages, such as Rust, C, and C++, to build applications on Arbitrum. Additionally, Stylus makes the execution of Dapps more efficient, significantly reducing gas costs.

Stylus is not limited to supporting Rust, C, and C++; it also supports languages like Move, Sway, Cairo, and Go. Imagine in the future, dApps on Aptos/Fuel/StarkNet could be migrated to Arbitrum with one click. It is even possible to achieve one-click L3 chain migration through Arbitrum Orbit.

Interestingly, both BOLD and Stylus are general modular components;

Developers can launch specific use case L3s based on Arbitrum Orbit, integrating BOLD and Stylus natively;

They can also decide to integrate the aforementioned modular components through decentralized DAO governance after the L3 is launched and running smoothly.

XAI has already fired the first shot in the defense of Arbitrum L2, and this battle with Optimism may just be beginning.