# Cross-Chain Layer

CurveYield 2.0 uses a Frax-style LayerZero V2 OFT/adapter bridge design for yield-bearing vault assets.

CurveYield did not fork LayerZero core contracts. The bridge architecture follows the Frax LayerZero V2 pattern because it fits multi-token OFT bridging and remote messaging for vault assets better than a narrow single-token bridge path.

## Bridge model

The bridge model uses:

* **Origin chain vault token:** an adapter-style contract for the original vault token;
* **Remote chain representation:** an OFT-style token on the destination chain;
* **Deployment pattern:** one adapter/OFT pair per supported vault token;
* **Endpoint:** LayerZero V2 Endpoint on Ethereum/Base at `0x1a44076050125825900e736c501f859c50fE728c`;
* **Ethereum EID:** `30101`;
* **Base EID:** `30184`.

CurveYield wrapper contracts add fee logic and ownership/configuration controls without rewriting the underlying Frax/LayerZero design.

## Bridge fees

The bridge fee model has three parts:

1. LayerZero V2 native messaging fee from `quoteSend`.
2. Extra owner-configurable native ETH fee.
3. Owner-configurable token-denominated basis-point fee.

Prepared default values:

| Fee                  | Default            | Hard cap          |
| -------------------- | ------------------ | ----------------- |
| Extra native ETH fee | `0.001 ETH`        | `0.0025 ETH`      |
| Token fee            | `15 bps` / `0.15%` | `50 bps` / `0.5%` |

The fee recipient is configurable and belongs in DAO-approved treasury infrastructure for production routes.

## Security configuration

CurveYield's prepared LayerZero V2 ULN configuration uses a 3-of-4 DVN threshold.

Selected DVNs:

* LayerZero Labs;
* Google Cloud;
* Polyhedra zkBridge;
* Nethermind.

This means messages require agreement from three of the four selected verification networks. The selected DVNs use different operators and validation approaches, which reduces reliance on a single provider or a single security domain. Exact pathway configuration should be checked against public deployment references before using any live bridge route.

## Rate publishing for yield-bearing assets

CurveYield vault assets are not flat ERC20s. Their value depends on vault PPS and underlying asset pricing.

The bridge design includes a cross-chain oracle messaging layer:

1. The origin-chain oracle reads live vault PPS and underlying asset value.
2. The origin-chain publisher sends rate snapshots through LayerZero.
3. The remote-chain oracle stores the latest received value.
4. Remote-chain contracts can consume origin-chain PPS/value without reproducing every pricing route locally.

This allows remote chains to understand the value of bridged vault assets such as `cysdCRV`, `cysdFXN`, `cycvxCRV`, and `cysdSPECTRA` without duplicating every Ethereum or Base pricing dependency.

## Initial vault scope

Prepared bridge scope includes:

| Vault         | Planned origin direction                      |
| ------------- | --------------------------------------------- |
| `cysdCRV`     | Ethereum-origin, bridged to Base              |
| `cysdFXN`     | Ethereum-origin, bridged to Base              |
| `cycvxCRV`    | Ethereum-origin, bridged to Base              |
| `cysdSPECTRA` | Base-origin, bridged to Ethereum if activated |

## Current status

The Frax-style LayerZero V2 bridge architecture, fee-enabled wrappers, oracle messaging design, Ethereum/Base pathway configuration, and 3-of-4 DVN configuration have been prepared.

The final public bridge deployment for renamed CurveYield vault assets is marked **Designed / Pending** unless the relevant adapter/OFT pair, pathway configuration, ownership path, fee recipient, and rate oracle are listed in the public contract references.


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