Walnut Labs is partnering with Offchain Labs—the team behind Arbitrum—to improve the debugging experience across the Arbitrum stack. This effort is part of our broader mission to bring modern debugging and monitoring tools to emerging rollup ecosystems.
Debugging smart contracts is hard—especially with custom VMs and execution models. We’ve seen this firsthand across the chains we support. Without good tooling, developers face slower iteration, higher risk of bugs, and friction when building complex apps. Many blockchain projects introduce their own VMs or languages that aren’t compatible with web2 tooling. Some, like Starknet, Miden, or Fuel, use entirely custom architectures. Others—like Arbitrum’s MultiVM, zkSync, Scroll, or Gravity—build on the foundations of the EVM.
Why Focus on MultiVM?
Most existing debugging tools are commercial and gated, which slows down experimentation and limits growth. Offchain Labs saw the need for more open and accessible options.
Arbitrum’s MultiVM (previously called EVM+) adds a second virtual machine alongside the EVM, allowing developers to write smart contracts in both Solidity and languages that compile to WebAssembly (WASM), such as Rust or C. This approach enables faster, more memory-efficient execution while maintaining full compatibility with the Ethereum development model.
While this flexibility unlocks significant development potential, it also introduces new complexity to the debugging process. To address this, Walnut Labs is building an open-source, CLI-based debugger tailored for the MultiVM environment. Open-source makes it ideal for chains that need custom tooling and deep integration. Over the next year, our team will focus on supporting both Solidity and Rust contracts running on Arbitrum Orbit chains, giving developers deeper visibility into their execution paths and transaction behavior.
We’re excited to help make development on Arbitrum easier—and to support the next wave of builders on Orbit.
🔧 What’s Next
Over the coming months, we’ll be rolling out early versions of the MultiVM debugger for Arbitrum, starting with support for Solidity and Rust contracts on Orbit chains. Our goal is to make debugging seamless across both VMs—so developers can focus on building, not digging through logs.
If you’re building on Arbitrum, experimenting with MultiVM, or working on your own rollup and need help with debugging or monitoring, reach out. Walnut Labs works closely with teams to deliver custom devtools and observability infrastructure tailored to new VMs, languages, or runtime environments.