> 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/speth.md).

# spETH

Custom price feed for Spark Savings ETH (spETH).

Custom price feed for **Spark Savings ETH (spETH)**. spETH is an ERC-4626 vault share that accrues value as savings yield accumulates. The price is derived from the vault's current share-to-asset conversion rate multiplied by the NAV's WETH/USD price.

**Source:** [`spETH_CustomPriceFeed.sol`](https://github.com/karpatkey/onchain-accounting/blob/main/src/prices/protocols/spETH_CustomPriceFeed.sol)

***

## Approach

`spETH.convertToAssets(1 spETH)` × WETH/USD (from the NAV's primary feed)

{% hint style="info" %}
The WETH/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 %}

{% hint style="danger" %}
**Spark shipped this savings family twice — pin the vault by address, never by `symbol()`.** A dead earlier generation answers the same `symbol()` at a different address with `totalSupply == 0`. An empty ERC-4626 answers `convertToAssets` at the **1:1 default instead of reverting**, so wiring the dead one prices plausibly and wrongly. Note that `spETH` is 18-decimal in *both* generations, so decimals alone does not disambiguate it — only the address does.
{% endhint %}

***

## Price calculation

```
decimals = spETH.decimals()                     // vault share decimals
rate     = spETH.convertToAssets(10^decimals)   // WETH per 1 spETH
price    = rate × WETH_USD / 10^assetDecimals
```

| Input               | Source                                              | Description                                                |
| ------------------- | --------------------------------------------------- | ---------------------------------------------------------- |
| `convertToAssets()` | `IERC4626(spETH)`                                   | WETH backing per 1 spETH share at the current accrued rate |
| `WETH_USD`          | NAV base — `getPriceDataNoDivergence(WETH)` (8 dec) | the NAV's primary WETH/USD price                           |

The divisor is `10^assetDecimals` (the **underlying's** decimals), not the share decimals — they differ whenever a vault uses a decimals offset. Result carries the feed's **8 decimals**.

***

## Constructor

```solidity
constructor(
    address vault_,
    address nav_,
    address baseAsset_
)
```

| Parameter    | Description                                                                                                                            |
| ------------ | -------------------------------------------------------------------------------------------------------------------------------------- |
| `vault_`     | The spETH vault address (also used to read vault decimals)                                                                             |
| `nav_`       | NAVCalculator (proxy) — supplies the base asset's USD price via `getPriceDataNoDivergence`                                             |
| `baseAsset_` | The registered base asset whose USD price is read (WETH); **must equal the vault's `asset()`** — reverts `BaseAssetMismatch` otherwise |

***

## Staleness

The price is stale if the NAV reports the base asset (WETH) stale — all its feeds stale. The base leg's `updatedAt` comes from the NAV's selected WETH feed. The `convertToAssets` rate has no heartbeat — it is a live view on the ERC-4626 vault.

***

## Chains

Deployed on **Ethereum mainnet** only.

Unlike the other members of this family the base is **WETH**, not a stablecoin, so the share price tracks ETH rather than $1.


---

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