Sky LitePSM

Introduction

The Sky LitePSM is Ethereum mainnet stablecoin swap infrastructure for fixed-rate USDC swaps. The core DssLitePsm swaps USDC against DAI, while Sky's UsdsPsmWrapper exposes the USDS-facing USDC ↔ USDS interface most integrators should use. Today the public fees are zero, but tin and tout are governance-controlled parameters and should be read on-chain before quoting.

Architecturally, the LitePSM minimizes per-swap gas overhead by keeping a pre-minted DAI balance in the core PSM instead of touching the Maker core accounting contract (Vat) on every user trade. USDC custody sits in a separate immutable pocket address, and live route capacity must be read from the core PSM's DAI balance and the pocket's USDC balance.

For contract-level integrations on Ethereum mainnet, this is the canonical Sky USDC ↔ USDS fixed-rate route. It provides deterministic pricing without AMM curve math, but it still has mutable fees, halt states, finite per-block liquidity, and external token dependencies that integrators need to handle.

Role in Spark

The LitePSM is an important piece of infrastructure for Spark because it makes USDS highly liquid against USDC on Ethereum mainnet. By connecting USDS to billions of dollars of USDC liquidity in the Sky PSM pocket, it gives Spark products access to a deep fixed-rate USDS ↔ USDC conversion path.

Spark uses this liquidity in the Swap product for USDS and USDC conversion, and in SparkLend for the USDC via USDS market.

Key Contracts

Integrators swapping between USDS and USDC should call the UsdsPsmWrapper. The wrapper internally routes through the DAI-denominated core LitePSM and uses the Maker DaiJoin/UsdsJoin adapters to convert between external DAI/USDS balances and internal Vat balances, while exposing a USDS-native sellGem/buyGem interface.

What's Next

• How It Works — the swap mechanism, pre-minted buffer, immutable pocket model, and fee parameters.
• Contract Reference — deployment addresses, ABI, state variables, and events.
• Integration Guide — step-by-step swap flows with Solidity examples and liquidity checks.