Smart Contract Integration - Docs | Magic Newton Foundation

This guide shows how to integrate Newton attestation validation into your smart contracts. You will inherit from NewtonPolicyClient, configure validation, and manage your policy lifecycle.

Overview

Newton provides the NewtonPolicyClient Solidity mixin that handles:

Attestation validation (standard and direct methods)
Policy configuration and parameter management
On-chain ownership and version compatibility

When to Use

Use Case	Example
Transaction authorization	Wallet contracts requiring policy approval
Spend limits	Daily/weekly transfer limits on treasury contracts
Allowlist/blocklist enforcement	Restricting interactions to approved addresses
Time-based access control	Operations only allowed during certain hours
Complex business logic	Multi-condition approval workflows
Off-chain data verification	Price feeds, identity verification, compliance checks

Core Concepts

Before writing code, understand the key data structures your contract will work with.

Intent

An Intent describes the transaction a user wants to execute:

struct Intent {
    address from;              // Transaction initiator (tx.origin equivalent)
    address to;                // Target contract
    uint256 value;             // ETH value
    bytes data;                // ABI-encoded calldata
    uint256 chainId;           // Chain ID for cross-chain safety
    bytes functionSignature;   // Human-readable function signature
}

Attestation

An Attestation is cryptographic proof that Newton operators evaluated a policy and approved the Intent:

struct Attestation {
    bytes32 taskId;            // Unique task identifier
    bytes32 policyId;          // Policy that was evaluated
    address policyClient;      // Your contract address
    uint32 expiration;         // Block number when attestation expires
    Intent intent;             // The approved intent
    bytes intentSignature;     // User's signature on the intent
}

Task Lifecycle

User signs Intent — creates and signs an Intent describing the desired transaction
Task created — the Gateway creates a task on the TaskManager contract
Operators evaluate — operators fetch the policy, evaluate it, and BLS-sign the result
Aggregator collects — signatures are aggregated until quorum is reached
Contract validates — your contract validates the attestation and executes the transaction

Quick Start

New Contract
Existing Contract

Create the Foundry project

mkdir newton-policy-wallet && cd newton-policy-wallet
forge init --no-git
git init
forge install newt-foundation/newton-contracts

Write the contract

Create src/NewtonPolicyWallet.sol:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.27;

import {NewtonPolicyClient} from "newton-contracts/src/mixins/NewtonPolicyClient.sol";
import {INewtonProverTaskManager} from "newton-contracts/src/interfaces/INewtonProverTaskManager.sol";

contract NewtonPolicyWallet is NewtonPolicyClient {
    event Executed(address indexed to, uint256 value, bytes data, bytes32 taskId);
    error InvalidAttestation();
    error ExecutionFailed();

    address constant NEWTON_TASK_MANAGER = 0xecb741F4875770f9A5F060cb30F6c9eb5966eD13;

    constructor(address owner) {
        _initNewtonPolicyClient(NEWTON_TASK_MANAGER, owner);
    }

    function supportsInterface(bytes4 interfaceId) public view override returns (bool) {
        return interfaceId == 0xdbdcaa9c || super.supportsInterface(interfaceId);
    }

    function validateAndExecuteDirect(
        address to,
        uint256 value,
        bytes calldata data,
        INewtonProverTaskManager.Task calldata task,
        INewtonProverTaskManager.TaskResponse calldata taskResponse,
        bytes calldata signatureData
    ) external returns (bytes memory) {
        require(
            _validateAttestationDirect(task, taskResponse, signatureData),
            InvalidAttestation()
        );

        (bool success, bytes memory result) = to.call{value: value}(data);
        if (!success) revert ExecutionFailed();

        emit Executed(to, value, data, task.taskId);
        return result;
    }

    receive() external payable {}
}

Configure foundry.toml

You must set via_ir = true. The newton-contracts library requires IR-based compilation. Without it, compilation fails.

[profile.default]
src = "src"
out = "out"
libs = ["lib"]
solc = "0.8.27"
via_ir = true
optimizer = true
optimizer_runs = 200

remappings = [
    "newton-contracts/=lib/newton-contracts/",
    "forge-std/=lib/forge-std/src/"
]

fs_permissions = [{ access = "read", path = "./policy_params.json" }]

[rpc_endpoints]
sepolia = "${RPC_URL}"

Add Newton attestation validation to an existing contract by inheriting NewtonPolicyClient. Initialization is deferred to a post-deployment admin function.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.27;

import {NewtonPolicyClient} from "newton-contracts/src/mixins/NewtonPolicyClient.sol";
import {NewtonMessage} from "newton-contracts/src/core/NewtonMessage.sol";
import {INewtonProverTaskManager} from "newton-contracts/src/interfaces/INewtonProverTaskManager.sol";
import {OwnableUpgradeable} from "@openzeppelin-upgrades/contracts/access/OwnableUpgradeable.sol";

contract MyExistingVaultV2 is OwnableUpgradeable, NewtonPolicyClient {
    error InvalidAttestation();
    error PolicyClientAlreadyInitialized();

    bool private _newtonPolicyClientInitialized;

    // ... existing contract storage and functions remain unchanged ...

    /// @notice Initialize Newton policy client support (one-time, post-upgrade)
    function initializeNewtonPolicyClient(
        address policyTaskManager,
        address policyClientOwner
    ) external onlyOwner {
        require(!_newtonPolicyClientInitialized, PolicyClientAlreadyInitialized());
        _initNewtonPolicyClient(policyTaskManager, policyClientOwner);
        _newtonPolicyClientInitialized = true;
    }

    // setPolicyAddress(address policy) is inherited from NewtonPolicyClient.
    // The policyClientOwner can call it once a policy contract is deployed.

    /// @notice Add policy-protected functionality
    function protectedWithdraw(
        NewtonMessage.Attestation calldata attestation
    ) external {
        require(_validateAttestation(attestation), InvalidAttestation());
        // Execute withdrawal logic...
    }

    function supportsInterface(bytes4 interfaceId) public view override returns (bool) {
        return super.supportsInterface(interfaceId);
    }
}

When adding NewtonPolicyClient to an existing upgradeable contract:

Add new storage variables at the end to avoid layout conflicts
The _newtonPolicyClientInitialized flag prevents re-initialization
Test thoroughly on a fork before mainnet deployment
Consider using a timelock or multisig for the initialization call

Install the dependency:

forge install newt-foundation/newton-contracts

Validation Methods

Newton provides two validation methods for different use cases.

Standard Validation

function _validateAttestation(
    NewtonMessage.Attestation memory attestation
) internal returns (bool);

The standard method validates against an attestation that the Newton aggregator has already submitted on-chain via respondToTask. It verifies:

Policy ID matches your contract’s configured policy
Intent sender (from) matches msg.sender
Chain ID matches the current chain
Attestation hash matches stored hash, is not expired, and has not been spent

Direct Validation

function _validateAttestationDirect(
    INewtonProverTaskManager.Task calldata task,
    INewtonProverTaskManager.TaskResponse calldata taskResponse,
    bytes calldata signatureData
) internal returns (bool);

Direct validation verifies BLS signatures on-chain without waiting for the aggregator to call respondToTask. It performs the same policy/sender/chain checks, plus on-chain BLS signature verification and quorum checks.

Comparison

Aspect	`_validateAttestation`	`_validateAttestationDirect`
Prerequisite	`respondToTask` called	Task created only
Gas Cost	~50,000 - 100,000	~200,000 - 500,000 (BLS verification)
Latency	Wait for aggregator	Immediate
Parameters	Attestation only	Task + Response + Signatures
Use Case	Standard flow	Time-sensitive operations

Direct validation is recommended for most use cases as it avoids waiting for the aggregator and works with the evaluateIntentDirect SDK method.

API Reference

INewtonPolicyClient Interface

interface INewtonPolicyClient is IERC165 {
    function getPolicyId() external view returns (bytes32);
    function getPolicyAddress() external view returns (address);
    function getNewtonPolicyTaskManager() external view returns (address);
    function getOwner() external view returns (address);
}

NewtonPolicyClient Mixin

Initialization

Function	Visibility	Description
`_initNewtonPolicyClient(policyTaskManager, owner)`	`internal`	Initialize the policy client with TaskManager and owner
`_setPolicyAddress(policy)`	`internal`	Set policy address (no version check, for constructors)
`setPolicyAddress(policy)`	`public`	Set policy address (owner-only, with version compatibility check)

Policy Management

Function	Visibility	Description
`_setPolicy(policyConfig)`	`internal`	Set or update policy configuration, returns `policyId`
`setPolicy(policyConfig)`	`external`	Owner-only wrapper for `_setPolicy`
`setPolicyClientOwner(newOwner)`	`public`	Transfer policy client ownership

Getters

Function	Visibility	Description
`_getPolicyId()`	`internal view`	Current policy ID
`_getPolicyAddress()`	`internal view`	Policy contract address
`_getPolicyConfig()`	`internal view`	Current `PolicyConfig` (params + expireAfter)
`_getNewtonPolicyTaskManager()`	`internal view`	TaskManager address
`_getOwner()`	`internal view`	Policy client owner address

Deployment

Create script/Deploy.s.sol:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.27;

import {Script, console} from "forge-std/Script.sol";
import {NewtonPolicyWallet} from "../src/NewtonPolicyWallet.sol";

contract DeployScript is Script {
    function run() external {
        uint256 deployerPrivateKey = vm.envUint("PRIVATE_KEY");
        address owner = vm.addr(deployerPrivateKey);

        vm.startBroadcast(deployerPrivateKey);

        NewtonPolicyWallet wallet = new NewtonPolicyWallet(owner);

        console.log("Deployed at:", address(wallet));
        vm.stopBroadcast();
    }
}

The Task Manager address must be 0xecb741F4875770f9A5F060cb30F6c9eb5966eD13 on Sepolia. BLS signatures are bound to this address — using any other causes InvalidAttestation.

Initialization Gotchas

_setPolicyAddress() vs setPolicy(): _setPolicyAddress() stores the policy address but does NOT register with the Policy contract and does NOT return a policyId. You must call setPolicy() (or _setPolicy()) in a separate transaction after deployment to get a policyId. If you forget this step, policyId == 0 and all attestation validations silently fail with no helpful error message. expireAfter must be non-zero: NewtonPolicyData.initialize() reverts with InvalidExpireAfter() if expireAfter == 0. A zero value creates attestations where expiration == reference_block, making on-chain execution impossible — every call reverts with AttestationExpired because block.number >= expiration is always true by the time the tx mines. Use at least 150 blocks (~5 minutes on Base) for testnets. Deploy:

source .env
forge script script/Deploy.s.sol:DeployScript --rpc-url $RPC_URL --broadcast

Set Policy

After deployment, configure the policy on your contract. Create script/SetPolicy.s.sol:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.27;

import {Script, console} from "forge-std/Script.sol";
import {NewtonPolicyWallet} from "../src/NewtonPolicyWallet.sol";
import {INewtonPolicy} from "newton-contracts/src/interfaces/INewtonPolicy.sol";

contract SetPolicyScript is Script {
    function run() external {
        uint256 deployerPrivateKey = vm.envUint("PRIVATE_KEY");
        address walletAddress = vm.envAddress("WALLET_ADDRESS");
        uint32 expireAfter = uint32(vm.envUint("EXPIRE_AFTER"));
        string memory paramsJson = vm.readFile("policy_params.json");

        vm.startBroadcast(deployerPrivateKey);

        NewtonPolicyWallet wallet = NewtonPolicyWallet(payable(walletAddress));
        bytes32 newPolicyId = wallet.setPolicy(
            INewtonPolicy.PolicyConfig({
                policyParams: bytes(paramsJson),
                expireAfter: expireAfter
            })
        );

        console.log("Policy set with ID:");
        console.logBytes32(newPolicyId);
        vm.stopBroadcast();
    }
}

WALLET_ADDRESS=0x... EXPIRE_AFTER=31536000 \
forge script script/SetPolicy.s.sol:SetPolicyScript --rpc-url $RPC_URL --broadcast

PolicyClientRegistry

The PolicyClientRegistry is a central on-chain directory of approved policy client contracts. Registration is required for policy clients that participate in the identity linking flow via IdentityRegistry.

Why Register?

Benefit	Description
Identity linking	`IdentityRegistry` enforces that only registered clients can have user identity data linked
Discoverability	`getClientsByOwner()` enables enumeration of all clients owned by an address
Lifecycle management	Deactivate/reactivate clients without re-deploying
Ownership transfer	Transfer the registry record to a new owner

Registration

Registration is permissionless — any address can register a policy client contract, becoming its registered owner:

// The caller becomes the registered owner
policyClientRegistry.registerClient(address(myPolicyClient));

Requirements:

The client contract must implement INewtonPolicyClient (verified via ERC-165)
Each client can only be registered once

Managing Client Status

// Deactivate a client (prevents new identity links)
policyClientRegistry.deactivateClient(address(myPolicyClient));

// Reactivate
policyClientRegistry.activateClient(address(myPolicyClient));

// Transfer ownership of the registry record
policyClientRegistry.setClientOwner(address(myPolicyClient), newOwnerAddress);

CLI Management

All registry operations are available via newton-cli policy-client:

# Register a client
newton-cli policy-client register \
  --registry 0x0dbd6e44a1814f5efe4f67a00b7f28642e3064dd --client 0x... --private-key $KEY --rpc-url $RPC

# Check registration status
newton-cli policy-client status \
  --registry 0x0dbd6e44a1814f5efe4f67a00b7f28642e3064dd --client 0x... --rpc-url $RPC

# List clients by owner
newton-cli policy-client list \
  --registry 0x0dbd6e44a1814f5efe4f67a00b7f28642e3064dd --owner 0x... --rpc-url $RPC

# Deactivate / activate / transfer ownership
newton-cli policy-client deactivate \
  --registry 0x0dbd6e44a1814f5efe4f67a00b7f28642e3064dd --client 0x... --private-key $KEY --rpc-url $RPC
newton-cli policy-client activate \
  --registry 0x0dbd6e44a1814f5efe4f67a00b7f28642e3064dd --client 0x... --private-key $KEY --rpc-url $RPC
newton-cli policy-client transfer-ownership \
  --registry 0x0dbd6e44a1814f5efe4f67a00b7f28642e3064dd --client 0x... --new-owner 0x... --private-key $KEY --rpc-url $RPC

IdentityRegistry Integration

The IdentityRegistry requires a policyClientRegistry address at initialization. Every _linkIdentity() call checks IPolicyClientRegistry.isRegisteredClient() on the target policy client and reverts with PolicyClientNotRegistered if the client is not registered or has been deactivated. Deployment lifecycle:

Deploy PolicyClientRegistry and initialize it
Deploy IdentityRegistry and pass the registry address to initialize(admin, policyClientRegistry)
Register approved policy clients via registerClient()
Any identity linking attempt against an unregistered or deactivated client reverts

Version Compatibility

When you call setPolicyAddress(), the policy’s factory version is validated against the TaskManager’s runtime minimum. This ensures protocol upgrades do not break existing clients.

How It Works

There is no compile-time gate — policy clients never need to be redeployed for version upgrades. Owners call setPolicyAddress(newPolicy) to point their client to a policy from a newer factory. The policy client address never changes, so identity links and user consent remain intact.

Migration with newton-cli

The newton-cli version migrate command automates the full upgrade workflow:

Checks compatibility of current policy and policy data factories
Deploys new policy data contracts if any are incompatible
Deploys a new policy via the latest factory
Calls setPolicyAddress(newPolicy) on the existing client (no redeployment)
Verifies the migration succeeded

newton-cli version migrate \
  --policy-client 0x... \
  --private-key $OWNER_KEY \
  --chain-id 11155111

Remediation for IncompatiblePolicyVersion

If setPolicyAddress() or createNewTask() reverts with IncompatiblePolicyVersion:

Check the TaskManager’s current minimum:

string memory minVersion = taskManager.minCompatiblePolicyVersion();

Check your policy’s factory version:

address factory = INewtonPolicy(policy).factory();
string memory factoryVersion = ISemVerMixin(factory).version();

Deploy a new policy through the current NewtonPolicyFactory:

address newPolicy = policyFactory.deployPolicy(
    entrypoint, policyCid, schemaCid, policyDataAddresses, metadataCid, owner
);

Update your client: setPolicyAddress(newPolicy)
Reconfigure: setPolicy(policyConfig) with the same policy parameters

Your existing policy data addresses and Rego CIDs can be reused — only the policy contract (and its factory reference) needs to change.

Common Patterns

Decode Intent Data

Extract function arguments from the attestation:

function decodeTransferIntent(
    NewtonMessage.Attestation calldata attestation
) internal pure returns (address to, uint256 amount) {
    // Skip the function selector (4 bytes)
    (to, amount) = abi.decode(
        attestation.intent.data[4:],
        (address, uint256)
    );
}

Verify Function Selector

Ensure the attestation is for the expected function:

bytes4 selector = bytes4(attestation.intent.data[:4]);
require(selector == IMyContract.expectedFunction.selector, "Wrong function");

Execute Raw Intent

Execute the intent exactly as specified with error bubbling:

function executeIntent(
    NewtonMessage.Attestation calldata attestation
) internal returns (bytes memory) {
    require(_validateAttestation(attestation), "Invalid attestation");

    (bool success, bytes memory returnData) = attestation.intent.to.call{
        value: attestation.intent.value
    }(attestation.intent.data);

    if (!success) {
        if (returnData.length > 0) {
            assembly {
                revert(add(32, returnData), mload(returnData))
            }
        }
        revert("Execution failed");
    }

    return returnData;
}

Multi-Attestation Batching

Process multiple attestations in one transaction:

function batchExecute(
    NewtonMessage.Attestation[] calldata attestations
) external returns (bool[] memory results) {
    results = new bool[](attestations.length);

    for (uint256 i = 0; i < attestations.length; i++) {
        require(_validateAttestation(attestations[i]), "Invalid attestation");
        results[i] = _executeAction(attestations[i]);
    }
}

Security Considerations

Always Validate Before Execution

Never execute business logic before validation completes:

// CORRECT
function withdraw(NewtonMessage.Attestation calldata attestation) external {
    require(_validateAttestation(attestation), "Invalid");  // Validate first
    _transfer(attestation.intent.to, attestation.intent.value);  // Then execute
}

// WRONG - DO NOT DO THIS
function withdraw(NewtonMessage.Attestation calldata attestation) external {
    _transfer(attestation.intent.to, attestation.intent.value);  // Executes before validation!
    require(_validateAttestation(attestation), "Invalid");
}

Built-in Safety Checks

The NewtonPolicyClient mixin automatically enforces:

Sender verification — attestation.intent.from == msg.sender (prevents user A from using user B’s attestation)
Chain ID verification — attestation.intent.chainId == block.chainid (prevents cross-chain replay attacks)
Expiration — block.number < attestation.expiration (attestations expire after the configured block window)
Replay protection — each attestation can only be used once (marked as “spent” after validation)

Additional Best Practices

Always verify function selectors match expectations when decoding intent data
Set appropriate expireAfter values — too short and users cannot execute; too long and the security window increases
Protect the policyClientOwner key with a multisig or timelock
Use supportsInterface to return 0xdbdcaa9c (required by the Newton Policy contract)
Fund the contract with ETH if it needs to execute value transfers

Troubleshooting

Error	Cause	Resolution
`InvalidAttestation()`	Wrong Task Manager address, expired attestation, or policy mismatch	Verify Task Manager address matches Sepolia deployment
`ExecutionFailed()`	The target call reverted	Debug the target transaction independently
`IncompatiblePolicyVersion`	Policy factory version below TaskManager minimum	See Version Compatibility remediation steps
`PolicyClientNotRegistered`	Client not registered in `PolicyClientRegistry`	Register via `registerClient()` or CLI `newton-cli policy-client register`
`Policy ID does not match`	Attestation’s policy ID differs from configured policy	Verify `_setPolicy()` was called with correct configuration
`Not authorized intent sender`	`msg.sender` does not match `attestation.intent.from`	Ensure the user who signed the intent calls the function
`Chain ID does not match`	Attestation created for a different chain	Ensure the intent specifies the correct `chainId`
`Attestation expired`	`block.number >= attestation.expiration`	Request a new attestation; consider increasing `expireAfter`
`Attestation already spent`	Attestation has already been used	Each attestation is single-use; request a new one
`InterfaceNotSupported`	Contract does not implement `IERC165` correctly	Override `supportsInterface` and call `super.supportsInterface(interfaceId)`
Stack too deep	Missing `via_ir = true`	Add `via_ir = true` to foundry.toml

See Error Reference for the full list of Newton error codes.

Next Steps

Frontend SDK Integration

Build a frontend that submits tasks and executes attested transactions

SDK Reference

Full TypeScript SDK documentation

Contract Addresses

Deployed Newton contract addresses on all networks

​Overview

​When to Use

​Core Concepts

​Intent

​Attestation

​Task Lifecycle

​Quick Start

​Create the Foundry project

​Write the contract

​Configure foundry.toml

​Validation Methods

​Standard Validation

​Direct Validation

​Comparison

​API Reference

​INewtonPolicyClient Interface

​NewtonPolicyClient Mixin

​Initialization

​Policy Management

​Getters

​Deployment

​Initialization Gotchas

​Set Policy

​PolicyClientRegistry

​Why Register?

​Registration

​Managing Client Status

​CLI Management

​IdentityRegistry Integration

​Version Compatibility

​How It Works

​Migration with newton-cli

​Remediation for IncompatiblePolicyVersion

​Common Patterns

​Decode Intent Data

​Verify Function Selector

​Execute Raw Intent

​Multi-Attestation Batching

​Security Considerations

​Always Validate Before Execution

​Built-in Safety Checks

​Additional Best Practices

​Troubleshooting

​Next Steps

Frontend SDK Integration

SDK Reference

Contract Addresses

Overview

When to Use

Core Concepts

Intent

Attestation

Task Lifecycle

Quick Start

Create the Foundry project

Write the contract

Configure foundry.toml

Validation Methods

Standard Validation

Direct Validation

Comparison

API Reference

INewtonPolicyClient Interface

NewtonPolicyClient Mixin

Initialization

Policy Management

Getters

Deployment

Initialization Gotchas

Set Policy

PolicyClientRegistry

Why Register?

Registration

Managing Client Status

CLI Management

IdentityRegistry Integration

Version Compatibility

How It Works

Migration with newton-cli

Remediation for IncompatiblePolicyVersion

Common Patterns

Decode Intent Data

Verify Function Selector

Execute Raw Intent

Multi-Attestation Batching

Security Considerations

Always Validate Before Execution

Built-in Safety Checks

Additional Best Practices

Troubleshooting

Next Steps