# DeFi Composer

DeFi Composer enables Yearn-style multi-protocol vaults written in Solidity that compose across multiple Solana DeFi protocols atomically via CPI.

## Overview

A single Solidity function can orchestrate operations across Jupiter, Kamino, Drift, Meteora, and other Solana protocols — all atomically. If any step fails, the entire transaction reverts.

```solidity
function executeStrategy(uint256 amount) external {
    // 1. Swap 50% USDC to SOL via Jupiter
    IJupiter(JUPITER).swap(USDC, SOL, amount / 2, minSolOut);

    // 2. Deposit SOL as collateral on Kamino
    IKamino(KAMINO).deposit(SOL, solAmount);

    // 3. Borrow USDC against SOL collateral
    IKamino(KAMINO).borrow(USDC, borrowAmount);

    // 4. Open SOL-PERP short on Drift (delta hedge)
    IDrift(DRIFT).placeOrder(SOL_PERP, SHORT, size, leverage);

    // All atomic. One Solidity function. Four CPI hops.
}
```

## Why Solidity for DeFi Composition?

* **Familiar tooling** — Solidity devs don't need to learn Rust/Anchor
* **Mature ecosystem** — leverage OpenZeppelin, existing audit tooling, Hardhat/Foundry workflows
* **Composability** — Solidity's `try/catch`, modifiers, and inheritance work naturally
* **Atomic execution** — Solana's transaction model guarantees all-or-nothing

## Reference Strategies (Planned)

| Strategy            | Protocols              | Description                                      |
| ------------------- | ---------------------- | ------------------------------------------------ |
| SOL Yield Optimizer | Kamino, Drift          | Supply SOL, borrow stables, delta-hedge on perps |
| Stablecoin Yield    | Kamino, Orca           | LP stablecoins across pools, auto-rebalance      |
| Delta-Neutral       | Jupiter, Kamino, Drift | Swap + supply + hedge for yield without exposure |
| LST Arbitrage       | Jupiter, Marinade      | Exploit LST price differentials                  |

## Status

**Designed** — depends on Rome SDK Phase 2 (IJupiter, IDrift, IKamino interfaces). Core CPI infrastructure is live; protocol-specific typed interfaces are in progress.

## What's Next

* [Rome SDK](/products/rome-sdk.md) — typed Solidity interfaces for Solana programs
* [Call Solana from EVM](/developer-guides/call-solana-from-evm.md) — CPI guide
* [Constraints](/core-concepts/constraints.md) — CPI depth limits and compute budget


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