Contracts

Four contracts plus a helper, Solidity 0.8.28, EVM cancun, on Monad Testnet (chain 10143). None has an owner, admin, pauser or upgrade path. Configuration is immutable or constant, set once at construction. Every state change emits an event. Custom errors only.

Deployed on Monad Testnet (4 Oct 2026, block 68082112, rpId grounded.sajal.sbs). Addresses are in deployments/10143.json and are the SDK's defaults:

Contract	Address
ReviewerRegistry	0xFb38DcB72C222d3943579b4F2c4C91ebcBE4eBa6
ReceiptRegistry	0xa89b76Ea9AcEA12A66Fb23d318219b9119362301
ReceiptRouter	0xab442c3cbc2997a6218FEA0DD253c3717edfc62e
GroundedReputation	0xaDDd1f2F876CD253C57177b675905Bdb0061bF82

They sit on top of two contracts we did not write and do not control: the ERC-8004 Identity and Reputation registries, and USDC (see Threat model).

Existing contracts we use (Monad Testnet)

ReceiptRouter

• pay(agentId, token, value) -> receiptId: transfers value from the caller to the agent's payout wallet (getAgentWallet), then issues a receipt with the caller as payer.
• payWithAuthorization(agentId, token, from, value, validAfter, validBefore, salt, signature) -> receiptId: the payer signs an EIP-3009 ReceiveWithAuthorization naming the router as payee. Anyone may relay it; the receipt's payer is from, never the relayer. Only the payee can redeem a receive-authorization, so it cannot be front-run into the token (money moved, no receipt). Its nonce is authorizationNonce(agentId, salt) = keccak256(abi.encode(agentId, salt)), so it cannot be replayed against a different agent. Funds pass through the router within the call; it holds nothing afterwards.
• Allowed tokens are fixed at construction. Minimum payment is 0.01 USDC (MIN_AMOUNT_6DP = 10_000).
• Errors: TokenNotAllowed(token), AmountBelowMinimum(normalised6dp), AmountTooLarge(value) (more than uint96), NoAgentWallet(agentId), BadSignatureLength(length), NoTokens(), InvalidRecipient(to) (a payout wallet that is the router itself, which would lock funds).

ReceiptRegistry

• issue(receipt) -> id (router only). Ids are sequential from 1.
• consume(id) (GroundedReputation only). Requires status Issued and age at most RECEIPT_TTL (30 days).
• get(id) returns { agentId, payer, token, amount, paidAt, status }; isValid(id) is a boolean.
• Expiry is evaluated on read: nobody has to run a job to age a receipt out.
• Events: ReceiptIssued(id, agentId, payer, token, amount), ReceiptConsumed(id, agentId, payer).
• Errors: NotRouter(), NotGrounded(), ReceiptNotIssued(id), ReceiptExpired(id).

ReviewerRegistry

• bind(qx, qy, proof): the passkey (qx, qy) signs an EIP-712 Bind(reviewer, qx, qy, nonce) challenge, verified through the P-256 precompile with user verification required. A key can belong to one reviewer only.
• Calling bind again rotates the key. Only the new key signs the proof: the old key is not asked. See the threat model.
• Views: keyOf(reviewer) -> (qx, qy), reviewerOf(keyHash), nonces(reviewer), bindDigest(...).
• Constructor takes rpIdHash = sha256(rpId), the WebAuthn relying party the passkey is scoped to. Changing the domain means redeploying, and reviewer bindings do not carry over.
• Event: ReviewerBound(reviewer, keyHash, qx, qy). Errors: BadSignature(), KeyAlreadyBound(keyHash).

GroundedReputation

• ground(receiptId, feedbackIndex, deadline, sig): the one write. Checks, cheapest first: deadline, receipt, payer, exclusions, ERC-8004 feedback, passkey, signature. Then it consumes the receipt, weights the rating by what was paid, and updates the histogram. See the scoring spec.
• sweepRevoked(agentId, reviewer): permissionless. Removes a rating whose feedback was revoked after it was grounded.
• Views: scoreOf, meets, liveRating, disputeCount, lastOwnerOf.
• Events: Grounded(agentId, reviewer, receiptId, feedbackIndex, score, weight, isDispute), Swept(agentId, reviewer, feedbackIndex), OwnerChanged(agentId, previousOwner, newOwner).
• Errors: Expired(), BadReceipt(receiptId), NotPayer(payer), ExcludedReviewer(), BadFeedback(feedbackIndex), NoPasskey(), BadSignature(), NothingToSweep(), StillValid().

Two behaviours to expect from the live ERC-8004 registry: feedback indices are 1-based, and reading an index that does not exist reverts (index must be > 0 / index out of bounds) rather than returning empty, so ground on a bad index surfaces the registry's message, not BadFeedback. The SDK's rate dry-runs first for exactly this reason.

GroundedGate

contract TrustedHiring is GroundedGate {
    constructor(IGroundedReputation g) GroundedGate(g, 70, 5) {}   // minScore 70, minReviewers 5, immutable

    function hire(uint256 agentId) external onlyTrusted(agentId) { /* ... */ }
}

onlyTrusted(agentId) reverts with AgentNotTrusted(agentId) unless meets(agentId, minScore, minReviewers). A worked example is in contracts/src/examples/TrustedHiring.sol.

Gas

Measured on a fork with the live precompile and registries:

Monad charges the gas limit, so the SDK sets each limit from an estimate times 1.15. About a third of ground is exclusion and feedback reads into the ERC-8004 proxies. The full table, and how to reproduce it, is in docs/gas.md.