spUSDT

Custom price feed for Spark Savings USDT (spUSDT).

Custom price feed for Spark Savings USDT (spUSDT). spUSDT 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 USDT/USD price.

Source: spUSDT_CustomPriceFeed.sol

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Approach

spUSDT.convertToAssets(1 spUSDT) × USDT/USD (from the NAV's primary feed)

The USDT/USD term is sourced from the NAV's own selector — see Base/USD from the NAV's own selector.

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.

Registered at heartbeat 90000, not the 86400 its USDC-based siblings use. USDT/USD is itself registered at 86400, and a derived feed's updatedAt is its base feed's timestamp — so a tighter gate cannot prevent a stale price, only manufacture a stale verdict while the base is fresh. That is the failure sUSDS shipped at 82800, which priced $0 for ~23s a day on 97% of days. Keep this at or above USDT's own heartbeat.

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Price calculation

decimals = spUSDT.decimals()                     // vault share decimals
rate     = spUSDT.convertToAssets(10^decimals)   // USDT per 1 spUSDT
price    = rate × USDT_USD / 10^assetDecimals

Input	Source	Description
convertToAssets()	IERC4626(spUSDT)	USDT backing per 1 spUSDT share at the current accrued rate
USDT_USD	NAV base — getPriceDataNoDivergence(USDT) (8 dec)	the NAV's primary USDT/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.

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Constructor

constructor(
    address vault_,
    address nav_,
    address baseAsset_
)

Parameter	Description
vault_	The spUSDT 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 (USDT); must equal the vault's asset() — reverts BaseAssetMismatch otherwise

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Staleness

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

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Chains

Deployed on Ethereum mainnet only.