Points of focus

• Opinions that WASM beats RISC-V as Ethereum L1’s delivery ISA due to flexibility, hardware compatibility, and mature tools.  
• Researchers propose splitting roles. WASM for contracts, RISC-V as a backend for ZK proofs.  
• ZK costs $0.025 per block to reduce urgency for RISC-V on L1.

In a post on Ethereum Research forum, four Offchain Labs contributors: Mario Alvarez, Matteo Campanelli, Tsahi Zidenberg, and Daniel Lumi, challenged a proposal from Vitalik Buterin to replace Ethereum Virtual Machine bytecode with RISC-V instructions. Buterin’s plan, as proposed in April 2025, wanted to cut on-chain ZK proving costs by up to 100 times by optimizing for hardware-efficient proofs.

The researchers support ZK enhancements but “question Vitalik’s implicit assumption that one ISA can optimally serve both ZK-proving and smart contract delivery”.

WASM as the ‘Internet Protocol’ for Contracts

Offchain Labs advocates WASM as the “delivery ISA,” or dISA, the format for uploading and storing contracts on-chain. Key advantages include:

• Structure and Modifiability: WASM’s design allows tweaks for optimization without breaking existing contracts.
• Hardware Fit: Runs natively on most Ethereum nodes, avoiding RISC-V’s emulation overhead on non-specialized CPUs.
• Ecosystem Maturity: Battle-tested across billions of executions, with tools for type safety that prevent vulnerabilities.
• Backend Flexibility: Acts as a neutral layer between source languages and diverse proving backends.

Not only did the researchers present their arguments, but they also demonstrated feasibility with a prototype. Arbitrum blocks that run WASM contracts (via Stylus) are compiled into RISC-V code for zero-knowledge proving, a move that shows Ethereum can keep WASM for developers while using RISC-V only where it matters most; fast proofs.

“We can ZK-prove real-world blocks today in a blockchain that uses WASM as a dISA, by using a RISC-V-based ZK-VM as a backend,” the post states.

RISC-V’s Limits

RISC-V is viable for current ZK proofs but risks locking Ethereum into outdated tech as proving shifts from 32-bit to 64-bit variants and beyond. Offchain Labs notes ZK costs have plunged to $0.025 per Ethereum block, minimizing the need for L1-level proving tweaks. “Even if L1 were to require multiple ZK proofs per block, this cost would be minimal compared to the gas fees and MEV a builder could receive from a block.”

The summary is that one side wants to hard-code RISC-V into Ethereum’s core, while the other wants it as a plug-in behind a more versatile WASM layer.

Ethereum traded at $3,033 on November 21, down 5.31% amid broader market weakness.