From 2fa000bbf296fd49105e60e27f274a821b187132 Mon Sep 17 00:00:00 2001
From: Dong-Ha Kim <dongha.kim210@gmail.com>
Date: Mon, 9 Jun 2025 13:03:30 +0200
Subject: [PATCH] fix: do not charge lp fee for ultra lite

---
 api/_utils.ts         |  1 +
 api/limits.ts         | 13 +++++++------
 api/suggested-fees.ts | 21 ++++++++++++++-------
 3 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/api/_utils.ts b/api/_utils.ts
index 75cf0ad9c..245c07536 100644
--- a/api/_utils.ts
+++ b/api/_utils.ts
@@ -987,6 +987,7 @@ export const getCachedLimits = async (
     gasFeePercent: string;
     gasFeeTotal: string;
   };
+  routeInvolvesUltraLiteChain: boolean;
 }> => {
   return (
     await axios(`${resolveVercelEndpoint()}/api/limits`, {
diff --git a/api/limits.ts b/api/limits.ts
index f96d12cab..0d0caf592 100644
--- a/api/limits.ts
+++ b/api/limits.ts
@@ -294,12 +294,12 @@ const handler = async (
     const routeInvolvesLiteChain =
       originChainIsLiteChain || destinationChainIsLiteChain;
 
-    const originChainIsUltraLightChain =
+    const originChainIsUltraLiteChain =
       poolRebalanceRouteOrigin === ethers.constants.AddressZero;
-    const destinationChainIsUltraLightChain =
+    const destinationChainIsUltraLiteChain =
       poolRebalanceRouteDestination === ethers.constants.AddressZero;
-    const routeInvolvesUltraLightChain =
-      originChainIsUltraLightChain || destinationChainIsUltraLightChain;
+    const routeInvolvesUltraLiteChain =
+      originChainIsUltraLiteChain || destinationChainIsUltraLiteChain;
 
     // Base every amount on the input token decimals.
     let liquidReserves = ConvertDecimals(
@@ -345,7 +345,7 @@ const handler = async (
       ...transferRestrictedBalances
     ); // balances on destination chain + mainnet
 
-    if (!routeInvolvesLiteChain && !routeInvolvesUltraLightChain) {
+    if (!routeInvolvesLiteChain && !routeInvolvesUltraLiteChain) {
       const _lpCushion = ethers.utils.parseUnits(
         getLpCushion(l1Token.symbol, computedOriginChainId, destinationChainId),
         l1Token.decimals
@@ -446,7 +446,7 @@ const handler = async (
       bufferedMaxDepositShortDelay,
       limitsBufferMultiplier,
       chainHasMaxBoundary,
-      routeInvolvesLiteChain || routeInvolvesUltraLightChain
+      routeInvolvesLiteChain || routeInvolvesUltraLiteChain
     );
 
     if (
@@ -496,6 +496,7 @@ const handler = async (
             tokenGasCost: tokenGasCost.toString(),
           }
         : undefined,
+      routeInvolvesUltraLiteChain,
     };
     logger.debug({
       at: "Limits",
diff --git a/api/suggested-fees.ts b/api/suggested-fees.ts
index 0bb381712..e9b79388c 100644
--- a/api/suggested-fees.ts
+++ b/api/suggested-fees.ts
@@ -237,8 +237,13 @@ const handler = async (
       ),
       getFillDeadline(destinationChainId),
     ]);
-    const { maxDeposit, maxDepositInstant, minDeposit, relayerFeeDetails } =
-      limits;
+    const {
+      maxDeposit,
+      maxDepositInstant,
+      minDeposit,
+      relayerFeeDetails,
+      routeInvolvesUltraLiteChain,
+    } = limits;
     const quoteTimestamp = parseInt(_quoteTimestamp.toString());
 
     const amountInUsd = amount
@@ -264,11 +269,13 @@ const handler = async (
     const rateModel =
       validL1TokenConfig.routeRateModel?.[routeRateModelKey] ||
       validL1TokenConfig.rateModel;
-    const lpFeePct = sdk.lpFeeCalculator.calculateRealizedLpFeePct(
-      rateModel,
-      currentUt,
-      nextUt
-    );
+    const lpFeePct = routeInvolvesUltraLiteChain
+      ? 0 // Ultra lite routes do not have an LP fee
+      : sdk.lpFeeCalculator.calculateRealizedLpFeePct(
+          rateModel,
+          currentUt,
+          nextUt
+        );
     const lpFeeTotal = amount.mul(lpFeePct).div(ethers.constants.WeiPerEther);
 
     const isAmountTooLow = BigNumber.from(amountInput).lt(minDeposit);