diff --git a/src/components/transactions/Swap/actions/DebtSwap/DebtSwapActionsViaCoW.tsx b/src/components/transactions/Swap/actions/DebtSwap/DebtSwapActionsViaCoW.tsx
index 1487130d56..60eed532bb 100644
--- a/src/components/transactions/Swap/actions/DebtSwap/DebtSwapActionsViaCoW.tsx
+++ b/src/components/transactions/Swap/actions/DebtSwap/DebtSwapActionsViaCoW.tsx
@@ -81,8 +81,11 @@ export const DebtSwapActionsViaCoW = ({
     [state.expiry]
   );
 
-  // Pre-compute instance address
+  // Pre-compute instance address.
+  // Skip recalculation while approval is in progress or succeeded to prevent in-flight quote
+  // responses from changing the adapter address and invalidating the user's signature.
   useEffect(() => {
+    if (approvalTxState.loading || approvalTxState.success) return;
     calculateInstanceAddress({
       user,
       validTo,
@@ -113,6 +116,8 @@ export const DebtSwapActionsViaCoW = ({
     state.orderType,
     state.chainId,
     APP_CODE_PER_SWAP_TYPE[state.swapType],
+    approvalTxState.loading,
+    approvalTxState.success,
   ]);
 
   const amountToApprove = useMemo(() => {
diff --git a/src/components/transactions/Swap/actions/RepayWithCollateral/RepayWithCollateralActionsViaCoW.tsx b/src/components/transactions/Swap/actions/RepayWithCollateral/RepayWithCollateralActionsViaCoW.tsx
index 336b16da98..ab3d0a9e4e 100644
--- a/src/components/transactions/Swap/actions/RepayWithCollateral/RepayWithCollateralActionsViaCoW.tsx
+++ b/src/components/transactions/Swap/actions/RepayWithCollateral/RepayWithCollateralActionsViaCoW.tsx
@@ -81,8 +81,11 @@ export const RepayWithCollateralActionsViaCoW = ({
     [state.expiry]
   );
 
-  // Pre-compute instance address
+  // Pre-compute instance address.
+  // Skip recalculation while approval is in progress or succeeded to prevent in-flight quote
+  // responses from changing the adapter address and invalidating the user's signature.
   useEffect(() => {
+    if (approvalTxState.loading || approvalTxState.success) return;
     calculateInstanceAddress({
       user,
       validTo,
@@ -113,6 +116,8 @@ export const RepayWithCollateralActionsViaCoW = ({
     state.orderType,
     state.chainId,
     APP_CODE_PER_SWAP_TYPE[state.swapType],
+    approvalTxState.loading,
+    approvalTxState.success,
   ]);
 
   // Approval is aToken ERC20 Approval
diff --git a/src/components/transactions/Swap/helpers/cow/adapters.helpers.ts b/src/components/transactions/Swap/helpers/cow/adapters.helpers.ts
index afe3c35e8a..15cbe42284 100644
--- a/src/components/transactions/Swap/helpers/cow/adapters.helpers.ts
+++ b/src/components/transactions/Swap/helpers/cow/adapters.helpers.ts
@@ -58,7 +58,6 @@ export const calculateInstanceAddress = async ({
   const {
     sellAmountWithMarginForDustProtection,
     buyAmountWithMarginForDustProtection,
-    buyAmount,
     sellToken,
     buyToken,
     quoteId,
@@ -77,7 +76,6 @@ export const calculateInstanceAddress = async ({
       state.orderType
     ),
     sellToken: state.sellAmountToken,
-    buyAmount: state.buyAmountBigInt,
     buyToken: state.buyAmountToken,
     quoteId: isCowProtocolRates(state.swapRate) ? state.swapRate?.quoteId : undefined,
     side: state.processedSide,
@@ -100,7 +98,7 @@ export const calculateInstanceAddress = async ({
     buyToken: buyToken.underlyingAddress,
     buyTokenDecimals: buyToken.decimals,
     sellAmount: sellAmountToSign.toString(),
-    buyAmount: buyAmount.toString(),
+    buyAmount: buyAmountWithMarginForDustProtection.toString(),
     kind: side === 'buy' ? OrderKind.BUY : OrderKind.SELL,
     quoteId,
     validTo,
diff --git a/src/components/transactions/Swap/hooks/useSwapQuote.ts b/src/components/transactions/Swap/hooks/useSwapQuote.ts
index 453f0a1671..962f59059b 100644
--- a/src/components/transactions/Swap/hooks/useSwapQuote.ts
+++ b/src/components/transactions/Swap/hooks/useSwapQuote.ts
@@ -227,8 +227,13 @@ export const useSwapQuote = ({
     }
   }, [ratesError]);
 
+  // Apply incoming quote to state. Discard in-flight responses that arrive after
+  // the user has started the approval flow (quoteRefreshPaused) to prevent
+  // amount changes that would invalidate the adapter instance address / signature.
   useEffect(() => {
     if (swapQuote) {
+      if (state.quoteRefreshPaused) return;
+
       const isAutoRefreshed = Boolean(state.quoteLastUpdatedAt);
       trackingHandlers?.trackSwapQuote(isAutoRefreshed, swapQuote);