BAP-578 Logic Contracts

Use this skill to design, build, deploy, and bind logic contracts that define on-chain agent behavior for BAP-578 Non-Fungible Agents. Logic contracts are the behavioral extension layer — they give agents the ability to perform autonomous actions, execute strategies, respond to events, and interact with other contracts.

---

When to use this skill

• Designing autonomous behavior for a BAP-578 agent.
• Building a logic contract from scratch.
• Binding or unbinding a logic contract to an existing agent.
• Reviewing the security of a logic contract before binding.
• Understanding the relationship between the NFA contract and logic contracts.
• Creating logic contract templates for common use cases.
• Planning a logic contract marketplace.

---

The Four Identity Questions (Logic View)

1) Who are you?

The logic contract is the behavioral layer of a BAP-578 agent. While the main NFA contract defines identity (who the agent is) and state (what it remembers), the logic contract defines action (what it does). A logic contract is a separate smart contract deployed independently, then bound to an agent via the logicAddress field.

The binding creates a relationship:

• NFA contract = identity + state + ownership
• Logic contract = behavior + strategy + automation

Think of it as: the NFA contract is the agent's brain (memory and identity), and the logic contract is the agent's hands (actions and capabilities).

2) What do you remember?

Logic contracts can maintain their own state variables, giving agents additional memory beyond what the NFA contract stores. This could include:

• Strategy parameters (thresholds, targets, limits)
• Execution history (last action timestamp, cumulative results)
• Configuration (enabled features, permissions)
• Relationships (other agents or contracts it interacts with)

The logic contract can also read the agent's on-chain state from the NFA contract by calling view functions like getAgentState and getAgentMetadata.

3) What can you do?

Logic contracts enable agents to perform actions autonomously. Capabilities depend entirely on what the logic contract implements:

• Execute strategies — DeFi yield farming, rebalancing, arbitrage
• Respond to events — react to price changes, governance proposals, or external triggers
• Route requests — forward incoming calls to specialized handler contracts
• Manage resources — allocate agent balance to different protocols
• Interact with other agents — agent-to-agent communication and coordination
• Provide services — answer queries, generate outputs, process requests

4) How can I trust it?

Logic contract trust must be established independently of the NFA contract:

• Source verification — the logic contract source code should be verified on a block explorer
• Audit — critical logic contracts should undergo security review
• Permissions analysis — understand exactly what the logic contract can and cannot do
• Immutability assessment — determine if the logic contract is upgradeable
• Separation of concerns — the logic contract should not be able to drain agent funds unless explicitly designed to do so

---

Architecture

How logic binding works

┌──────────────────────────┐
│      NFA Contract         │
│                           │
│  Agent #17                │
│  ├── owner: 0xABC         │
│  ├── balance: 1.5 BNB     │
│  ├── active: true         │
│  ├── metadata: {...}      │
│  └── logicAddress: 0xDEF  │◄──── binding
│                           │
└──────────────────────────┘
              │
              │ calls / reads
              ▼
┌──────────────────────────┐
│    Logic Contract (0xDEF) │
│                           │
│  - execute()              │
│  - getStatus()            │
│  - configure()            │
│                           │
│  Can read NFA state via:  │
│  - nfa.getAgentState(17)  │
│  - nfa.getAgentMetadata() │
│                           │
└──────────────────────────┘

Binding rules

1. Only the token owner can set the logic address for their agent.
2. The logic address must be a contract, not an externally owned account (EOA). The contract checks address.code.length > 0.
3. Setting to address(0) unbinds the logic contract (removes behavior).
4. Binding is reversible — the owner can change or remove the logic contract at any time.
5. The logic contract has no special permissions on the NFA contract. It cannot withdraw agent funds, transfer the token, or modify metadata unless explicitly delegated.

Binding flow

// Token owner binds a logic contract
nfa.setLogicAddress(tokenId, logicContractAddress);

// Emits event for tracking
// event LogicAddressChanged(uint256 indexed tokenId, address logicAddress);

// Token owner unbinds
nfa.setLogicAddress(tokenId, address(0));

---

Building a Logic Contract

Minimal interface

Logic contracts don't need to implement a specific interface, but a recommended pattern is:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

interface INonFungibleAgents {
    struct AgentState {
        uint256 balance;
        bool active;
        address logicAddress;
        uint256 createdAt;
        address owner;
    }

    struct AgentMetadata {
        string persona;
        string experience;
        string voiceHash;
        string animationURI;
        string vaultURI;
        bytes32 vaultHash;
    }

    function getAgentState(uint256 tokenId) external view returns (AgentState memory);
    function getAgentMetadata(uint256 tokenId) external view returns (AgentMetadata memory);
}

Pattern: Simple Greeter

A minimal logic contract that reads agent metadata and returns a greeting:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import "./INonFungibleAgents.sol";

contract GreeterLogic {
    INonFungibleAgents public immutable nfa;

    event GreetingGenerated(uint256 indexed tokenId, string greeting);

    constructor(address _nfa) {
        nfa = INonFungibleAgents(_nfa);
    }

    function greet(uint256 tokenId) external view returns (string memory) {
        INonFungibleAgents.AgentMetadata memory meta = nfa.getAgentMetadata(tokenId);
        return string(abi.encodePacked(
            "Hello! I am an agent with experience in: ",
            meta.experience
        ));
    }

    function getAgentInfo(uint256 tokenId) external view returns (
        bool active,
        uint256 balance,
        string memory experience
    ) {
        INonFungibleAgents.AgentState memory state = nfa.getAgentState(tokenId);
        INonFungibleAgents.AgentMetadata memory meta = nfa.getAgentMetadata(tokenId);
        return (state.active, state.balance, meta.experience);
    }
}

Pattern: Strategy Executor

A logic contract that executes a defined action when triggered by a keeper or automation service:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import "./INonFungibleAgents.sol";

contract StrategyLogic {
    INonFungibleAgents public immutable nfa;

    struct StrategyConfig {
        uint256 threshold;
        uint256 lastExecuted;
        uint256 executionCount;
        bool enabled;
    }

    mapping(uint256 => StrategyConfig) public strategies;

    event StrategyExecuted(uint256 indexed tokenId, uint256 timestamp);
    event StrategyConfigured(uint256 indexed tokenId, uint256 threshold);

    constructor(address _nfa) {
        nfa = INonFungibleAgents(_nfa);
    }

    modifier onlyAgentOwner(uint256 tokenId) {
        INonFungibleAgents.AgentState memory state = nfa.getAgentState(tokenId);
        require(msg.sender == state.owner, "Not agent owner");
        _;
    }

    function configure(uint256 tokenId, uint256 threshold) external onlyAgentOwner(tokenId) {
        strategies[tokenId] = StrategyConfig({
            threshold: threshold,
            lastExecuted: 0,
            executionCount: 0,
            enabled: true
        });
        emit StrategyConfigured(tokenId, threshold);
    }

    function execute(uint256 tokenId) external {
        INonFungibleAgents.AgentState memory state = nfa.getAgentState(tokenId);
        require(state.active, "Agent not active");

        StrategyConfig storage config = strategies[tokenId];
        require(config.enabled, "Strategy not enabled");
        require(
            block.timestamp >= config.lastExecuted + config.threshold,
            "Too soon"
        );

        // Execute strategy logic here
        // This is where you'd interact with DeFi protocols, oracles, etc.

        config.lastExecuted = block.timestamp;
        config.executionCount++;

        emit StrategyExecuted(tokenId, block.timestamp);
    }

    function disable(uint256 tokenId) external onlyAgentOwner(tokenId) {
        strategies[tokenId].enabled = false;
    }
}

Pattern: Request Router

A logic contract that forwards incoming requests to specialized handlers:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import "./INonFungibleAgents.sol";

contract RouterLogic {
    INonFungibleAgents public immutable nfa;

    mapping(bytes4 => address) public handlers;
    address public admin;

    event RequestRouted(uint256 indexed tokenId, bytes4 selector, address handler);

    constructor(address _nfa) {
        nfa = INonFungibleAgents(_nfa);
        admin = msg.sender;
    }

    function registerHandler(bytes4 selector, address handler) external {
        require(msg.sender == admin, "Not admin");
        require(handler.code.length > 0, "Handler must be contract");
        handlers[selector] = handler;
    }

    function route(uint256 tokenId, bytes4 selector, bytes calldata data) external returns (bytes memory) {
        INonFungibleAgents.AgentState memory state = nfa.getAgentState(tokenId);
        require(state.active, "Agent not active");

        address handler = handlers[selector];
        require(handler != address(0), "No handler registered");

        (bool success, bytes memory result) = handler.call(data);
        require(success, "Handler execution failed");

        emit RequestRouted(tokenId, selector, handler);
        return result;
    }
}

---

Deployment and Binding Workflow

Step 1: Develop the logic contract

Write the logic contract in Solidity. Test thoroughly using Hardhat.

cd non-fungible-agents-BAP-578
# Create logic contract in contracts/logic/
# Write tests in test/logic/
npm test

Step 2: Deploy the logic contract

Deploy separately from the NFA contract:

const GreeterLogic = await ethers.getContractFactory("GreeterLogic");
const logic = await GreeterLogic.deploy(NFA_CONTRACT_ADDRESS);
await logic.waitForDeployment();
console.log("Logic deployed at:", await logic.getAddress());

Step 3: Verify on block explorer

Verify the logic contract source code so anyone can review it:

npx hardhat verify --network bscTestnet LOGIC_ADDRESS NFA_CONTRACT_ADDRESS

Step 4: Bind to agent

The token owner calls setLogicAddress:

const nfa = await ethers.getContractAt("NonFungibleAgents", NFA_ADDRESS);
await nfa.setLogicAddress(tokenId, LOGIC_ADDRESS);

Step 5: Interact with the logic

const logic = await ethers.getContractAt("GreeterLogic", LOGIC_ADDRESS);
const greeting = await logic.greet(tokenId);
console.log(greeting);

---

Security Considerations

What logic contracts CAN do

• Read agent state and metadata from the NFA contract (public view functions)
• Maintain their own state
• Interact with other contracts (DeFi protocols, oracles, etc.)
• Emit events
• Receive and send ETH/BNB (if designed to)

What logic contracts CANNOT do (by default)

• Withdraw from agent balance (only token owner via NFA contract)
• Transfer the agent token (only token owner or approved)
• Modify agent metadata (only token owner via NFA contract)
• Pause or unpause the NFA contract (only contract owner)

Security checklist for logic contracts

• [ ] Source code is verified on block explorer
• [ ] No external calls to untrusted contracts without validation
• [ ] No self-destruct pattern (prevents permanent loss)
• [ ] Ownership checks reference the NFA contract's token ownership
• [ ] No hidden admin functions that could manipulate state
• [ ] Events emitted for all state-changing actions
• [ ] Reentrancy guards on functions that send BNB
• [ ] No upgradeable proxy unless explicitly required and documented
• [ ] Gas limits considered for all loops and external calls

Risk assessment framework

Before binding a logic contract, evaluate:

1. Source availability — is the code open and verified?
2. Audit status — has it been reviewed by security professionals?
3. Permissions — what can this contract actually do?
4. Upgadeability — can the logic contract be changed after binding?
5. Dependencies — does it call other contracts that could be compromised?
6. Fund exposure — can it move BNB or tokens on behalf of the agent?

---

Logic Contract Marketplace (Future)

A marketplace for logic contracts would allow:

• Discovery — browse available logic contracts by category
• Verification — verified source, audit status, usage statistics
• One-click binding — bind a marketplace logic contract to your agent
• Reviews — user ratings and reviews of logic contracts
• Revenue sharing — logic contract developers earn fees

Categories:

• DeFi strategies (yield farming, rebalancing)
• Social (agent-to-agent messaging, reputation)
• Automation (scheduled tasks, event responses)
• Analytics (on-chain monitoring, alerts)
• Integration (bridge connectors, API proxies)

---

Common Patterns and Anti-Patterns

Do: Read-only logic for information agents

Logic contracts that only read state are inherently safe. They cannot modify anything and carry minimal risk.

Do: Use ownership checks that reference the NFA contract

modifier onlyAgentOwner(uint256 tokenId) {
    require(msg.sender == nfa.getAgentState(tokenId).owner, "Not owner");
    _;
}

Don't: Allow arbitrary external calls

// DANGEROUS — allows calling any contract with any data
function execute(address target, bytes calldata data) external {
    target.call(data);
}

Don't: Store agent funds in the logic contract

Agent funds should stay in the NFA contract. If the logic contract holds funds, a bug or exploit in the logic contract could cause loss.

Do: Emit events for every action

Events are the audit trail. Every meaningful action in the logic contract should emit an event with relevant parameters.

---

Method-Agnostic AI Integration via Logic Contracts

BAP-578's specification defines logic contracts as the learning module layer — the interface through which agents connect to AI systems. The standard provides infrastructure without prescribing specific implementations:

RAG (Retrieval-Augmented Generation) Pattern

The logic contract queries the agent's vault content to provide context for AI generation:

interface IRAGLogic {
    function retrieveContext(uint256 tokenId, string calldata query) external view returns (string memory);
    function generateWithContext(uint256 tokenId, string calldata query) external returns (string memory);
}

Implementation: Logic contract reads vaultURI from agent metadata, fetches relevant documents, and passes them as context to an AI model via oracle or off-chain service.

MCP (Model Context Protocol) Pattern

The logic contract routes agent interactions to different AI providers:

interface IMCPLogic {
    function routeToProvider(uint256 tokenId, string calldata input, string calldata provider) external returns (bytes memory);
    function getAvailableProviders() external view returns (string[] memory);
}

Implementation: Logic contract acts as a router, forwarding requests to registered AI service endpoints and returning structured responses.

Merkle Tree Learning Module

The logic contract manages the agent's learning tree and updates the on-chain Merkle root:

interface ILearningLogic {
    function processInteraction(uint256 tokenId, bytes calldata interactionData) external returns (bytes32 newLearningNode);
    function updateMerkleRoot(uint256 tokenId, bytes32 newRoot, bytes32[] calldata proof) external;
    function verifyLearning(uint256 tokenId, bytes32 leaf, bytes32[] calldata proof) external view returns (bool);
    function queryKnowledge(uint256 tokenId, string calldata query) external view returns (bytes memory);
}

The learning pipeline: interaction → learning extraction → tree building → Merkle root → on-chain update via updateAgentMetadata.

Reinforcement Learning Pattern

The logic contract stores reward signals and outcome data:

interface IRLLogic {
    function recordOutcome(uint256 tokenId, bytes32 actionId, int256 reward) external;
    function getRecommendation(uint256 tokenId, bytes calldata context) external view returns (bytes memory);
}

Hybrid Pattern

Combine multiple approaches in a single logic contract:

contract HybridLearningLogic is IRAGLogic, ILearningLogic, IRLLogic {
    // RAG for knowledge retrieval
    // Merkle tree for verifiable learning state
    // RL for action optimization
    // All behind the single logicAddress binding
}

---

Output Format

When asked for logic contract help, respond with:

1. Behavior goal (what should the agent do?)
2. Contract architecture (interfaces, state, functions)
3. Complete Solidity code (compilable, with comments)
4. Security constraints (what to check before binding)
5. Deployment steps (compile, deploy, verify, bind)
6. Testing guidance (what to test and expected outcomes)

---

Related Skills

• bap578
• bap578-security-audit
• bap578-upgrade