ERC-8004

As AI agents start acting autonomously on-chain, trading, hiring other agents, paying for API calls: a basic question becomes unanswerable by default: when you interact with an agent, who's actually behind it, and does it have any track record worth trusting? ERC-8004 is an Ethereum standard built to answer exactly that, on-chain, without requiring a central directory anyone has to trust.

It defines three registries a smart contract or another agent can query. An Identity Registry mints each agent a portable, ERC-721-based handle, an NFT whose tokenURI points to an off-chain "agent card" describing what the agent is and who controls it, so an agent's identity survives independent of any single platform. A Reputation Registry lets clients who've actually used an agent leave on-chain feedback about it. A Validation Registry lets a third party attach a cryptographic proof that a specific agent action was checked and found valid. Put together: instead of trusting an agent's self-description, another party can look up its registry entries and decide for itself.

Where it comes from

ERC-8004, titled "Trustless Agents," was formally proposed on Ethereum on August 13, 2025, co-authored by Marco De Rossi (MetaMask), Davide Crapis (Ethereum Foundation), Jordan Ellis (Google), and Erik Reppel (Coinbase), and refined with input from over 100 contributors across the ecosystem, including ENS, EigenLayer, and The Graph. Its core registries were deployed live on Ethereum mainnet on January 29, 2026. Solidus did not author any part of it, is not a co-author, and does not compete with it: Solidus is an integrator filling in a piece the standard deliberately leaves open: which issuer stands behind the DID a passport anchors to, and what evidence format backs a Validation Registry entry.

Solidus status

Solidus has anchored a real agent to the real ERC-8004 Identity Registry contracts, but on Base Sepolia, a public Ethereum L2 testnet, not Ethereum mainnet, where the ERC-8004 standard's own registries already run live. @solidus-network/agent-identity (the SDK) and agents.solidus.network (the service wrapping it) mint the passport, anchor a did:solidus identity alongside it, and issue a BBS+ capability credential, all currently running against Base Sepolia and Solidus's own public testnet, not either project's mainnet. The Validation Registry slot is not filled yet: it's gated on the upstream ERC-8004 standard publishing an actual Validation Registry contract address, which had not happened as of this writing.

Proof you can run yourself: verified live, 2026-07, eth_call for ownerOf(8064) against the Identity Registry at 0x8004A818…94BD9e on Base Sepolia's public RPC (sepolia.base.org) returns 0xcdcfa8a7…e3ede4; tokenURI(8064) on the same contract decodes to https://agents.solidus.network/v1/agents/.../card, which returns a JSON document naming a did:solidus:testnet:... identity as that token's linked identity. Anyone can run both calls against Base Sepolia's public RPC and get the same answer without trusting Solidus's account of it.