Vitalik Buterin defined heavy nodes as nodes trusted on a 1-of-n basis and responsible for block construction and proof generation

Quotes that support claims

I will define three types of nodes: Light node: sufficient to (i) verify the chain, including correctness and availability, and (ii) access any needed data privately, assuming the existence of at least 1 honest heavy node (for liveness; safety is unconditional) Medium node: any type of node that Ethereum has a n/2-of-n trust assumption in (eg. attesters in staking, FOCIL) Heavy node: any type of node that Ethereum has a 1-of-n assumption in (eg. optimal block building, proving)

Vitalik Buterin outlined a framework categorizing nodes into three types based on their roles and trust assumptions: Light nodes, which are capable of verifying chain correctness and availability, and accessing necessary data privately—assuming at least one honest heavy node exists to maintain liveness, while safety remains unconditional; Medium nodes, which Ethereum relies on with an n/2-of-n trust model, such as attesters in staking and FOCIL participants; and Heavy nodes, which the protocol trusts on a 1-of-n basis for functions like optimal block construction or proof generation.