JACK

JACK (Just-in-time Autonomous Cross-chain Kernel) is an intent-based execution engine that lets users and applications express high-level DeFi goals instead of manual transactions, and have autonomous agents route, bridge and execute those actions across EVM and non-EVM ecosystems. JACK is asset-agnostic and protocol-agnostic: it turns a single intent (for example, “obtain a target amount of a token under specific constraints”) into a cross-chain execution plan, and settles the final trade on the destination chain through specialized adapters. In this submission, JACK’s first live execution module routes cross-chain liquidity into a Uniswap v4 pool protected by a custom hook that enforces market and policy constraints. This demonstrates how Uniswap v4 can act as a programmable settlement layer for autonomous agents, enabling new classes of cross-chain DeFi applications such as regional currencies, FX routing, and policy-aware liquidity execution.

JACK is built as a modular execution kernel composed of an intent layer, solver/agent execution, cross-chain routing, privacy protection, and settlement adapters. User intents are created through Yellow’s Fusion+ protocol, allowing solvers to interpret and execute cross-chain objectives instead of single swaps. Routing and bridge selection are handled using the LI.FI SDK to compute optimal paths from source chains into the destination EVM chain. Sensitive execution parameters and constraints are encrypted using Fhenix, allowing private intent handling and reducing information leakage before settlement. The final execution leg is performed on Uniswap v4, where a custom hook acts as an on-chain policy and stabilization agent that validates market conditions and enforces execution rules during swaps. The system is implemented using TypeScript and React for the frontend, Foundry and Solidity for smart contracts, and viem/wagmi for wallet and RPC integration. A notable hack is using Uniswap v4 hooks as an autonomous execution policy layer controlled by an off-chain agent workflow, effectively combining intent-based execution with on-chain programmable market logic.