> For the complete documentation index, see [llms.txt](https://docs.kpk.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.kpk.io/funds/infrastructure/onchain-accounting/price-feeds/cross-rate.md).
# stETH, lsETH & OETH (CrossRate)
Generic custom price feed for an asset **Y** that has no direct Y/USD feed but is quoted in a base asset **X** that does. The price is the cross-rate of the NAV's own X/USD base price and a Chainlink Y/X feed. The shared `CrossRateCustomPriceFeed` base is instantiated as one **named per-token contract** for each asset that needs it. On Ethereum mainnet the **primary** instances are **lsETH** (`lsETH_CustomPriceFeed`, Liquid Collective — Y/X is Chainlink's *LsETH/ETH Exchange Rate*) and **OETH** (`OETH_CustomPriceFeed`) — each `Y/USD = ETH/USD × Y/ETH`, where the cross-rate is the asset's sole pricing feed.
{% hint style="info" %}
**stETH is not priced by a cross-rate.** Its primary is a [fundamental](/funds/infrastructure/onchain-accounting/price-feeds.md#custom-price-feeds) unit-rate feed (`1.0 × ETH/USD`), matching wstETH and eETH; the market `stETH/ETH` cross-rate is registered as a **monitor** (`stETHCrossRate`), deployed from the generic base rather than a named per-token subclass. This page describes how that monitor computes its price — it does not set stETH's NAV value.
{% endhint %}
**Source:** [`CrossRateCustomPriceFeed.sol`](https://github.com/karpatkey/onchain-accounting/blob/main/src/prices/protocols/CrossRateCustomPriceFeed.sol)
The same base also backs **divergence monitors** for the fundamental LST/LRT primaries — **ezETH**, **ETHx**, **osETH**, and **rETH**, where the `Y/ETH` leg is an independent market feed. Three of the four have a named per-token subclass (`ezETH_CrossRateCustomPriceFeed`, `ETHx_CrossRateCustomPriceFeed`, `osETH_CrossRateCustomPriceFeed`); **rETH's monitor is deployed from the generic base** under the config key `rETHCrossRate`, as stETH's is. Those assets are priced by a fundamental protocol-rate primary ([ezETH](/funds/infrastructure/onchain-accounting/price-feeds/ezeth.md), [ETHx](/funds/infrastructure/onchain-accounting/price-feeds/ethx.md), [osETH](/funds/infrastructure/onchain-accounting/price-feeds/ostoken.md), [rETH](/funds/infrastructure/onchain-accounting/price-feeds/reth.md)); the cross-rate is registered as a [monitor feed](/funds/infrastructure/onchain-accounting/price-feeds.md#primary-feed-and-divergence-monitors), so a market depeg makes it diverge from the fundamental primary and NAV flags the asset `irregular` — it never prices NAV. The L2 deployments use the same pattern (e.g. `weETHCrossRate`, `rsETHCrossRate` monitors on Arbitrum/Base).
***
## Approach
NAV base X/USD (`getPriceDataNoDivergence(WETH)`) × Chainlink Y/X
{% hint style="info" %}
The base/USD term is sourced from the NAV's own selector — see [Base/USD from the NAV's own selector](/funds/infrastructure/onchain-accounting/price-feeds.md#base-usd-from-the-navs-own-selector).
{% endhint %}
stETH, lsETH & OETH (CrossRate) price feed — how its oracle inputs compose into a USD price, with the staleness gate.
***
## Price calculation
```
price = (X/USD) × (Y/X) / 10^(Y/X decimals)
```
| Input | Source | Description |
| ------- | --------------------------------------------------- | ------------------------------- |
| `X/USD` | NAV base — `getPriceDataNoDivergence(WETH)` (8 dec) | the NAV's primary ETH/USD price |
| `Y/X` | Chainlink Y/X feed (`latestRoundData`) | Underlying Y quoted in X |
The Y/X leg is a Chainlink feed; the X/USD (ETH/USD) leg is the NAV's primary base price. The divisor is `10 ** yToX.decimals()`, which cancels the Y/X feed's decimals so the result keeps the X/USD leg's scale. Output is **8 decimals** (inherited from the X/USD leg via `_decimals`).
For the mainnet instances, X is ETH (ETH/USD via the NAV base) and Y is stETH, lsETH, or OETH respectively (a stETH/ETH, LsETH/ETH, or OETH/ETH feed).
***
## Constructor
```solidity
constructor(
address underlyingAsset_,
address yToXFeed_,
uint256 yToXHeartbeat_,
address nav_,
address baseAsset_
)
```
| Parameter | Description |
| ------------------ | ------------------------------------------------------------------------------------------ |
| `underlyingAsset_` | The asset Y whose USD price is returned (stETH, lsETH, or OETH) |
| `yToXFeed_` | Chainlink Y/X aggregator (e.g. stETH/ETH or OETH/ETH) |
| `yToXHeartbeat_` | Staleness window (seconds) for the Y/X feed |
| `nav_` | NAVCalculator (proxy) — supplies the base asset's USD price via `getPriceDataNoDivergence` |
| `baseAsset_` | The registered base asset whose USD price is read (WETH) |
***
## Staleness
The Y/X heartbeat is checked directly. `getLatestPrice()` returns `stale = true` if the Y/X feed satisfies `block.timestamp − updatedAt ≥ heartbeat`, if either leg's answer is `≤ 0`, if the Y/X `updatedAt` is in the future (clamped to `block.timestamp`), or if the NAV reports the base asset (WETH) primary feed stale. The base leg's `updatedAt` comes from the NAV's selected feed. The reported `updatedAt` is the **older** of the two legs.
***
## Chains
On **Ethereum**, as **primary** feeds: `lsETH` and `OETH`, each configured with the matching Y/X feed. As **monitor** feeds (same base contract, market Y/ETH leg), watching their fundamental primaries: `stETHCrossRate`, `ezETHCrossRate`, `ezETHCrossRateMarket`, `ETHxCrossRate`, `osETHCrossRate`, and `rETHCrossRate` — [ezETH carries two](/funds/infrastructure/onchain-accounting/price-feeds/ezeth.md) because its original monitor's rate leg stopped being a market feed.
On the L2s, all monitors: `weETHCrossRate`, `ezETHCrossRate` and `rsETHCrossRate` on **Arbitrum**, and `weETHCrossRate` on **Base**. Gnosis has no cross-rate instance.
Every one of these takes an external `yToXFeed`, so each is covered by the pre-deploy [rate-feed guard](/funds/infrastructure/onchain-accounting/price-feeds.md#custom-price-feeds) — pair identity where the provider's `description()` names the pair, and a declared `$UNVERIFIABLE` exemption plus a plausibility band where it does not.
---
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