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Contract Layer

aztec-contract hosts the high-level surface for talking to deployed contracts: call construction, deployment, authwits, and public events.

Context

Given a wallet (W: Wallet), applications want to:

  • Point at a deployed contract and build calls against its ABI.
  • Deploy a new contract (class + instance) deterministically.
  • Set and look up public authorization witnesses.
  • Read public events.

All of these live in this crate.

Design

The crate is structured around four modules, each generic over a Wallet:

ModulePrimary types
contractContract<W>, ContractFunctionInteraction<'a, W>, BatchCall<'a, W>
deploymentContractDeployer<'a, W>, DeployMethod<'a, W>, DeployResult, DeployOptions, helpers
authwitSetPublicAuthWitInteraction<'a, W>, AuthWitValidity, lookup_validity
eventsPublicEvent<T>, PublicEventFilter, get_public_events

Implementation Notes

Call Construction

Contract::method(name, args) performs:

  1. Artifact lookup by function name.
  2. Arity validation against the AbiParameter list.
  3. Construction of a FunctionCall with type (Private / Public / Utility) and is_static flag from metadata.

The returned ContractFunctionInteraction is a builder with simulate(opts), profile(opts), send(opts), with(authwits, capsules), and request() producing the raw ExecutionPayload.

Deployment

ContractDeployer follows a builder pattern:

ContractDeployer::new(artifact, &wallet)
    .with_constructor_name("constructor")
    .with_public_keys(public_keys)
    .deploy(args)?
    .send(DeployOptions::default())
    .await?

Lower-level primitives — publish_contract_class, publish_instance, get_contract_instance_from_instantiation_params — let callers split deployment steps (e.g. to share a class across instances).

Addresses are deterministic in the constructor + salt + public keys tuple; get_contract_instance_from_instantiation_params returns the computed address without sending a tx.

Events

Public events are pulled from the node via get_public_events, with filtering by address + event selector + block range. Private events come from the wallet (Wallet::get_private_events) since they require PXE-side decryption.

Authwits

SetPublicAuthWitInteraction targets the AuthRegistry protocol contract. lookup_validity returns the still-consumable state of a witness from the current chain head.

Edge Cases

  • Utility vs public: calls with FunctionType::Utility MUST NOT be scheduled as on-chain calls — use Wallet::execute_utility or Contract::method(...).simulate(...).
  • Deployment replay: deploying with an identical salt + args re-derives the same address; DeployResult contains the TxReceipt so callers can distinguish inclusion success from idempotent no-ops.
  • Missing selector: artifacts occasionally omit selectors; Contract::method surfaces this with an Error::InvalidData rather than silently computing one.

Security Considerations

  • Artifact integrity SHOULD be verified against the expected class hash before use; once registered in PXE / on-chain, the class id is the authoritative reference.
  • Public event payloads are untrusted until decoded against the matching ABI type; the decoder enforces shape.
  • Authwits bound to the wrong intent or origin are rejected at consumption — but applications SHOULD validate shape before issuing a wit to avoid user confusion.

References