> For the complete documentation index, see [llms.txt](https://docs.rome.builders/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rome.builders/use-cases/defi-protocols.md).

# DeFi Protocols

Rome enables EVM DeFi protocols to compose with Solana's native DeFi ecosystem atomically. This page covers common integration patterns. Several are already live on Rome — Aave v3, Compound v3 (Aerarium), Uniswap V2/V3/V4, and Rome DEX — see [Apps on Rome](/apps-on-rome/apps.md).

The code below is illustrative; interface names for third-party Solana programs are examples, not shipped SDK interfaces.

## Why DeFi on Rome?

* **Access Solana liquidity** — Jupiter, Kamino, Drift, Meteora, Raydium, Orca
* **Atomic composability** — multi-step DeFi operations in a single transaction
* **Solidity tooling** — familiar development and audit ecosystem
* **Shared state** — EVM and Solana users share the same pools

## Pattern 1: Lending Protocol with Solana Oracles

```solidity
import {IAggregatorV3Interface} from "@rome-protocol/rome-solidity/contracts/oracle/IAggregatorV3Interface.sol";

contract RomeLending {
    IAggregatorV3Interface public priceFeed;

    constructor(address _priceFeed) {
        priceFeed = IAggregatorV3Interface(_priceFeed);
    }

    function getCollateralValue(uint256 amount) public view returns (uint256) {
        (, int256 price,,,) = priceFeed.latestRoundData();
        // Pyth/Switchboard price via Oracle Gateway
        // Same interface as Chainlink on Ethereum
        return (amount * uint256(price)) / 1e8;
    }
}
```

## Pattern 2: DEX Aggregator via CPI

```solidity
contract RomeSwap {
    function swap(
        bytes32 fromMint,
        bytes32 toMint,
        uint256 amount,
        uint256 minOut
    ) external {
        // CPI to Jupiter/Raydium/Meteora
        // All Solana DEX liquidity accessible from Solidity
        CpiProgram.invoke(JUPITER_PROGRAM, accounts, swapData);
    }
}
```

## Pattern 3: Yield Vault

```solidity
contract YieldVault {
    function deposit(uint256 amount) external {
        // Accept USDC deposit
        // CPI → Jupiter: swap to optimal tokens
        // CPI → Kamino: supply as collateral
        // CPI → Drift: open delta-neutral hedge
        // All atomic — one tx, all-or-nothing
    }
}
```

## Pattern 4: Cross-Protocol Arbitrage

Using `RemusTx` (atomic cross-rollup transactions):

1. Buy on DEX A in rollup 1
2. Sell on DEX B in rollup 2
3. Both atomically — zero execution risk

## Reference implementations

Fork a working Rome app instead of starting from a blank page:

* [**rome-dex**](https://github.com/rome-protocol/rome-dex) — dual-lane AMM; bring a new idea and deploy it for both Solana and EVM users over one pool.
* [**aerarium**](https://github.com/rome-protocol/aerarium) — dual-lane Compound v3 lending UI.
* [**cardo**](https://github.com/rome-protocol/cardo) — CPI app-distribution portal (swap / lend / perps / compose).
* [**rome-aave-v3-demo**](https://github.com/rome-protocol/rome-aave-v3-demo) — Aave v3 lending UI.
* [**compound-on-rome-comet**](https://github.com/rome-protocol/compound-on-rome-comet) — the Comet money-market contracts.
* [**rome-oracle-gateway**](https://github.com/rome-protocol/rome-oracle-gateway) — a greenfield cross-VM app: reads Solana price accounts (Pyth, Switchboard), posts them on EVM, and serves them to Solidity through the standard Chainlink `AggregatorV3Interface`.

## Related

* [Oracle Gateway](/products/oracle-gateway.md) — Chainlink-compatible price feeds
* [Rome SDK](/products/rome-sdk.md) — typed interfaces for DeFi protocols


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