HAI CurveStableSwapNG Oracle Review

_adjustForOracleRates() computes _price.wmul(_baseOracleRate).wdiv(_quoteOracleRate), which introduces an avoidable rounding step.

The expression _price.wmul(_baseOracleRate).wdiv(_quoteOracleRate) expands to:

((_price * _baseOracleRate / WAD) * WAD) / _quoteOracleRate

The intermediate division by WAD in wmul() truncates before the subsequent multiplication in wdiv(). This can be simplified to _price * _baseOracleRate / _quoteOracleRate, which avoids the intermediate truncation and preserves more precision. Since all three values are in WAD scale, the single division by _quoteOracleRate (1e18-denominated) produces the correct WAD-scaled result.

Low.

Replace the chained wmul/wdiv with a single multiplication and division:

return _price * _baseOracleRate / _quoteOracleRate;

Acknowledged. This is the same pattern used throughout the codebase.

CurveStableSwapNGRelayerFactory stores deployed relayers in an EnumerableSet.AddressSet and exposes curveStableSwapNGRelayersList() to retrieve all entries, but provides no way to check whether a specific address belongs to the set.

The factory uses OpenZeppelin's EnumerableSet which natively supports contains(), but this function is never exposed. Consumers that need to verify whether a given oracle was deployed by the factory must iterate over the full list returned by curveStableSwapNGRelayersList(), which is gas-inefficient and impractical for on-chain callers.

Informational.

Add a public view that wraps _curveStableSwapNGRelayers.contains():

function isCurveStableSwapNGRelayer(address _relayer) external view returns (bool) {
  return _curveStableSwapNGRelayers.contains(_relayer);
}

Fixed in commit fa1dff9fa41bd77c32201bced3a35ba661731a8d.

CurveStableSwapNGRelayer.getResultWithValidity() calls pool.stored_rates(), which depending on the pool's asset types may query an external oracle or invoke an ERC4626 convertToAssets() call. Either of these can revert, violating the IBaseOracle requirement that getResultWithValidity() should never revert.

Curve StableSwap-NG pools support multiple asset types. For type 1 (oracle) assets, stored_rates() queries an external price oracle; for type 3 (ERC4626) assets, it calls convertToAssets() on the vault. If the external oracle is paused, deprecated, or the ERC4626 vault reverts (e.g., due to a paused state), the entire stored_rates() call will revert. This causes getResultWithValidity() to revert instead of returning (0, false), breaking the contract specified by IBaseOracle which states that this method should never revert.

Informational.

Consider returning (0, false) instead of bubbling the error if an external call reverts.

Fixed in commit 19ad26fe2d15e04c377531e76de3b9ec8ebbb2b7.

The relayer uses Curve's manipulation-resistant EMA but adjusts it with current rates from external oracles, which can change suddenly.

The relayer combines two data sources (CurveStableSwapNGRelayer.sol#L82-94):

• price_oracle(): EMA of historical prices (slow-moving, manipulation-resistant)
• stored_rates(): Current rates via external calls (can change instantly)

For pools on Optimism with asset_type 1 (custom rate providers) or asset_type 3 (ERC4626 vaults), stored_rates() makes external calls to fetch current rates. The relayer multiplies the EMA by the current rate ratio.

Example: wstETH / ETH pool

• EMA shows 1.0 (balanced pool in xp space)
• Historical wstETH rate: 1.15
• Current wstETH rate: 1.20 (sudden increase from staking rewards or oracle update)
• Relayer immediately reports adjusted price using rate 1.20

While this gives the correct current execution price, the EMA's manipulation resistance is partially bypassed since rates can spike instantly (e.g., ERC4626 donation inflation, or sudden oracle updates).

Informational. Low risk in most situation with battle-tested rate providers / high TVL ERC4626 vaults.

No ideal fix (can't dynamically bound rates without storing history). Consider:

• Setting hardcoded boundaries, to restrict how high/low a rate can go
• Only deploying relayers on pools with well-established ERC4626 vaults and robust rates manipulation protection

Acknowledged. This is mitigated through the selection of assets.

All state variables in CurveStableSwapNGRelayer are set once in the constructor and never modified, but are not marked as immutable.

The following variables at CurveStableSwapNGRelayer.sol#L21-40 can be immutable:

• pool
• baseToken
• quoteToken
• symbol
• baseIndex
• quoteIndex
• baseRateMultiplier
• quoteRateMultiplier

Gas.

Consider making all variables immutable.

Acknowledged.

Originally I had these marked as immutable but if they are immutable we cannot use .runtimeCode in our unit tests.