fix: avoid fees in intent based swaps sent amount calculation

packages/bridge-controller/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Fix `calcSentAmount` double-counting fees for intent-based swap quotes ([#8845](https://github.com/MetaMask/core/pull/8845))
+
 ## [73.0.0]
 
 ### Added

packages/bridge-controller/src/utils/quote.test.ts

@@ -254,6 +254,41 @@ describe('Quote Metadata Utils', () => {
       expect(result.valueInCurrency).toBe('2.2');
       expect(result.usd).toBe('1.65');
     });
+
+    it('should not add feeData fees for intent-based quotes', () => {
+      // For intent-based swaps (e.g. CoW Protocol), srcTokenAmount is already
+      // the total fixed commitment including protocol fees. Adding feeData fees
+      // on top would double-count them.
+      const intentQuote = {
+        srcTokenAmount: '10000000', // 10 USDT (6 decimals), fee already included
+        srcAsset: {
+          decimals: 6,
+          assetId: 'eip155:1/erc20:0xdAC17F958D2ee523a2206206994597C13D831ec7',
+        },
+        feeData: {
+          metabridge: {
+            amount: '500000', // 0.5 USDT protocol fee — already inside srcTokenAmount
+            asset: {
+              assetId:
+                'eip155:1/erc20:0xdAC17F958D2ee523a2206206994597C13D831ec7',
+              address: '0xdAC17F958D2ee523a2206206994597C13D831ec7',
+              decimals: 6,
+            },
+          },
+        },
+        intent: { protocol: 'cow', order: {} },
+      } as unknown as Quote;
+
+      const result = calcSentAmount(intentQuote, {
+        exchangeRate: '1',
+        usdExchangeRate: '1',
+      });
+
+      // Should be exactly 10 USDT — not 10.5 (which would double-count the fee)
+      expect(result.amount).toBe('10');
+      expect(result.valueInCurrency).toBe('10');
+      expect(result.usd).toBe('10');
+    });
   });
 
   describe('calcNonEvmTotalNetworkFee', () => {

packages/bridge-controller/src/utils/quote.ts

@@ -141,17 +141,24 @@ export const calcToAmount = (
 };
 
 export const calcSentAmount = (
-  { srcTokenAmount, srcAsset, feeData }: Quote,
+  { srcTokenAmount, srcAsset, feeData, intent }: Quote,
   { exchangeRate, usdExchangeRate }: ExchangeRate,
 ) => {
-  // Find all fees that will be taken from the src token
-  const srcTokenFees = Object.values(feeData).filter(
-    (fee) => fee && fee.amount && fee.asset?.assetId === srcAsset.assetId,
-  );
-  const sentAmount = srcTokenFees.reduce(
-    (acc, { amount }) => acc.plus(amount),
-    new BigNumber(srcTokenAmount),
-  );
+  // For intent-based swaps (e.g. CoW Protocol), srcTokenAmount is the total
+  // fixed commitment the user makes to the protocol — the protocol fee is
+  // already baked in. Adding feeData fees on top would double-count them.
+  // For conventional swaps, srcTokenAmount is the net routing amount (fees
+  // excluded), so the src-token fees must be added to get the wallet deduction.
+  const sentAmount = intent
+    ? new BigNumber(srcTokenAmount)
+    : Object.values(feeData)
+        .filter(
+          (fee) => fee && fee.amount && fee.asset?.assetId === srcAsset.assetId,
+        )
+        .reduce(
+          (acc, { amount }) => acc.plus(amount),
+          new BigNumber(srcTokenAmount),
+        );
   const normalizedSentAmount = calcTokenAmount(sentAmount, srcAsset.decimals);
   return {
     amount: normalizedSentAmount.toString(),