AVS Node Interface Specification

The AVS Node Interface is the canonical on-chain API contract that bridges EigenLayer's restaking core with Actively Validated Services (AVSs). It standardizes how AVSs register with the protocol, receive operator commitments, distribute task definitions, and process operator responses. For any service to inherit cryptoeconomic security from EigenLayer, its smart contracts must conform to this interface, making it the single most critical specification for AVS developers and the middleware maintainers who ensure protocol-wide compatibility.

The interface defines a strict set of functions for operator registration, deregistration, and signature verification, often leveraging BLS signature aggregation for scalable attestations. It also encodes the hooks through which slashing conditions are enforced, linking operator misbehavior to the penalty logic in the core protocol. A breaking change to this specification can invalidate existing AVS deployments, requiring coordinated upgrades across all dependent services. The specification is versioned and tracked through the EigenLayer Improvement Proposal (ELIP) process, with ELIP-0001 and ELIP-0002 providing foundational standards for the slashing API and operator set architecture that build upon this base interface.

For AVS developers, strict compliance with the current interface version is a non-negotiable requirement for mainnet activation. Operator clients must implement the corresponding off-chain logic to watch for new task events and submit responses according to the defined API. A mismatch between an AVS's deployed interface and an operator's client version leads to silent failures, missed rewards, and potential slashing. Chainscore Labs can provide an interface compliance review and migration planning to help teams navigate breaking changes, ensuring that AVS contracts and operator software remain compatible with the evolving EigenLayer middleware.

The AVS Node Interface Specification defines the mandatory on-chain and off-chain API contract that an Actively Validated Service must expose to participate in the EigenLayer protocol. This specification is the primary integration surface between the core middleware contracts and the heterogeneous set of AVS logic. It standardizes how an AVS declares its service, registers operators, distributes tasks, accepts operator attestations, and triggers slashing requests. The interface is versioned, and breaking changes to its methods, event signatures, or expected state transitions can force coordinated upgrades across all operators serving that AVS and any middleware that routes messages to it.

The specification covers several critical interaction domains. For operator lifecycle management, it defines the registerOperator, deregisterOperator, and associated event emissions that the core DelegationManager calls to notify an AVS of stake allocation changes. For task distribution, it standardizes the off-chain API surface—often a gRPC or REST endpoint—that operator nodes query to fetch new work, alongside the on-chain commitment and proof verification methods that validate operator responses. The slashing interface, formalized in ELIP-0001, is a core component: it specifies how an AVS calls freezeOperator and presents a slashing request to the SlashingManager, including the required evidence format and dispute window parameters. The specification also defines the AVS's metadata endpoint, which returns its service name, software version, and a cryptographic hash of its current implementation, enabling operators to detect mismatches.

For AVS developers, strict adherence to this specification is a liveness and security requirement. A non-compliant registerOperator implementation can prevent operators from opting in, while an incorrect slashing interface can make penalties unenforceable, undermining the service's attributable security. Operator client maintainers must map this specification to their internal node logic, handling version negotiation and graceful degradation when an AVS upgrades. Middleware and indexing services parse the standard events to track operator commitments across the ecosystem. Chainscore Labs can provide interface compliance review against the canonical specification, assess the impact of version migrations on operator sets, and plan upgrade paths that minimize downtime and slashing risk.