Core Architecture

Foundation is modular by design, consisting of two primary layers working in unison.

The Two-Layer Architecture

Layer	Component	Description
Base Layer	USD' (USD Prime)	Backed by fiat stablecoins and RWAs. The shared liquidity layer.
Strategy Layer	PrimeUSD, ApolloUSD, OrdUSD	Yield strategies built on top of USD'.

Base Layer: USD' (USD Prime)

USD' is the stable base asset of the Foundation ecosystem—the shared liquidity layer that all strategies are built upon.

Property	Description
Backing	Fiat stablecoins (USDC, USDT) and RWA tokens
Peg	Soft-pegged 1:1 to the US Dollar
Function	Shared liquidity layer for all strategy swaps
Standard	ERC20-compatible

When you move capital from one strategy to another, USD' is the internal settlement layer that enables instant swaps—without requiring external DEX trades or waiting for settlement.

The Foundation Vault

The Core Accounting Engine

The Vault is the immutable ledger that holds all collateral backing USD' and maintains the master map of solvency.

Key Properties

Property	Benefit
Collateral Custody	Holds USDC, USDT, and RWA tokens that back USD'
Asset Isolation	Strategy contracts cannot access collateral directly
Virtual Settlement	Strategy swaps are ledger updates—no costly token transfers
Real-Time Solvency	Maintains global Asset ↔ Liability mapping at all times

Collateral Types Backing USD'

• Fiat Stablecoins: USDC, USDT, FRAX

• RWA Tokens: Tokenized T-Bills, private credit

Strategy Layer: Yield Strategies (ERC4626)

Strategy dollars like PrimeUSD, ApolloUSD, and OrdUSD are built on top of USD' as standardized ERC4626 Tokenized Vaults.

How Strategies Work

1. Deposit: Users deposit USD' to mint strategy shares

2. Deploy: The strategy deploys capital to external yield venues (Aave, Orderly, Acred)

3. Yield: Profits flow back and increase share value

4. Withdraw: Burn shares to receive USD' plus accrued yield

Why ERC4626?

The ERC4626 standard ensures:

• Composability — Strategies work across all DeFi protocols

• Standardization — Consistent interface for deposits, withdrawals, and share accounting

• Transparency — Share prices and total assets are always queryable on-chain