Zenny

Zenny is a non-custodial stablecoin yield engine that enables users to passively earn returns (~3.65% APY) without losing custody of their funds. Once activated, a single signature from the user assigns a session key with scoped permissions to an automated backend engine, allowing it to place and execute multiple limit orders directly from the user’s wallet.

The core design leverages a hook-based integration with the 1inch router. Every swap request is first routed through a custom pre-hook contract that enforces a minimum profit check (e.g. only execute if 100 USDT returns at least 101 USDC). This ensures that users only participate in profitable trades, removing downside risk entirely. Profitable arbitrage opportunities across stablecoins are identified and executed automatically, using smart contracts and the authorized session key, all while the funds remain in the user’s wallet.

This system provides a passive, low-risk return stream, especially appealing to users who hold stablecoins but don't want to engage in active strategies or face protocol risk from lending markets. With “Zen-mode” activated, the system operates in the background, continuously compounding micro-arbitrage profits without further interaction.

On the taker side, users benefit from access to 1:1 stablecoin swaps at better-than-market rates, with zero protocol fees and execution at the user-defined limit price.

Zenny uses a combination of Privy, Porto, ZeroDev, and 7702 smart accounts to power session-key-based execution directly from the user's wallet. When a user signs up, their embedded Privy wallet is checked for bytecode — if it's not upgraded, it is automatically upgraded to support the 7702 spec via ZeroDev.

This upgrade allows us to generate a session key and assign it restricted permissions (e.g. call rights to specific contracts and functions, valid for a time window). The backend engine holds this session key and uses it to place and manage multiple orders on behalf of the user, without ever touching custody or private keys.

We use the 1inch SDK for routing and quoting, but every swap passes through a custom pre-hook contract. This hook acts as a validation layer before execution and ensures that the output stablecoin meets or exceeds a predefined threshold. If the expected return falls below that, the order reverts. This guarantees that every trade is profitable and enforces a strict no-loss policy. Using EIP1271, the signatures generated by the session key are validated for the smart account.

Our backend engine continuously scans for arbitrage opportunities between stablecoins (e.g. USDT → USDC → USDT) and dispatches calls to the user wallet using the authorized session key when valid opportunities arise. All execution is gasless for the user, powered by integrated paymasters, making the experience seamless and requiring only one signature to get started.

The result is a fully automated, non-custodial yield layer for stablecoin holders with no protocol interaction beyond a one-time opt-in.