> For the complete documentation index, see [llms.txt](https://rootwood.gitbook.io/rootwood-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://rootwood.gitbook.io/rootwood-docs/erc-7420.md).

# ERC-7420

```solidity
/// @title ERC-7420: Swap-Native Non-Fungible Token
interface IERC7420 {
    /// Emitted when an NFT swaps into its bonded token allocation.
    event SwapToTokens(address indexed holder, uint256 indexed tokenId, uint256 amount);

    function bondToken()    external view returns (address); // the fungible ROOT
    function tokensPerNFT() external view returns (uint256); // 500e18
    function launched()     external view returns (bool);    // swaps open?

    /// Burn tokenId, receive tokensPerNFT of ROOT. One-way, irreversible.
    function swapToTokens(uint256 tokenId) external;
}
```

The implementation is three small contracts:

| Contract       | Role                                                                     |
| -------------- | ------------------------------------------------------------------------ |
| `Rootwood.sol` | ERC-721 · mint sale · one-way swap · constant-product curve — all in one |
| `Root.sol`     | ROOT (ERC-20) · fixed supply · minted exactly once, at launch            |
| `IERC7420.sol` | The interface + ERC-165 id                                               |

Built with **Foundry**. **19 tests green**, including a solvency fuzz that hammers the pool with random buy/sell sequences. Compiled with the `via-ir` optimizer. Every ETH path is reentrancy-guarded.

***

The full lifecycle was driven by **real on-chain transactions**, each leg a separate tx:

```
mint ×3
   → launch (seed 0.001 ETH)
      → swap NFT#0 → 500 ROOT
         → buy  (spot 2.86 → 6.39 gwei/ROOT, fee accrued)
            → sell (price falls back)
               → withdraw creator revenue
```

The accounting invariant held **to the wei**:

```
contract balance  =  poolReserve  +  accruedFees  +  mintProceeds
```

…and withdrawing creator revenue **never touched the pool reserve.**

***

### Security & trust model

What the contract can and cannot do, stated plainly.

**Guaranteed by the code:**

* ROOT supply is **fixed** — minted once at launch, no `mint` afterward, no hidden inflation.
* The swap bucket is **locked** — those 499,500 tokens are reachable only by burning an NFT.
* The pool is **solvent** — constant-product math means sells are always honorable.
* Creator withdrawals **cannot touch the pool reserve** — proceeds and fees are separate buckets.
* Every ETH-moving function is **reentrancy-guarded**.

**Trust you still extend to the creator:**

* They choose the **seed depth** — thin depth means a volatile market.
* They hold **15% of supply** and control the **team address**.
* They set the **base URI** for metadata.
* Launch timing is **their call**.

None of this is hidden — it's all on-chain and visible. But it's honest to name it: this is a launch with a real team allocation, and the market should price that in.


---

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