update txn signer

Author: kevinfaveri

packages/backend/src/services/transaction-signer.ts

@@ -411,10 +411,31 @@ export class TransactionSigner {
       let usdcAmount = params.estimatedUsdcAmount;
       if (transferLog) {
         const actualUsdcAmount = BigInt(transferLog.data);
-        console.info('💰 [TX SIGNER] Actual USDC from previous claim receipt:', actualUsdcAmount.toString());
+        console.info('💰 [TX SIGNER] Actual USDC from claim receipt:', actualUsdcAmount.toString());
         usdcAmount = actualUsdcAmount;
       } else {
-        console.info('💰 [TX SIGNER] Using estimated amount for swap:', usdcAmount.toString());
+        console.info('💰 [TX SIGNER] Could not parse USDC from claim receipt, checking wallet balance...');
+      }
+
+      // SAFETY: Always verify we have enough USDC balance before swapping
+      // This prevents failures due to rounding differences or partial amounts
+      const walletUsdcBalance = await publicClient.readContract({
+        address: chainConfig.usdcAddress as Hex,
+        abi: ERC20_ABI,
+        functionName: 'balanceOf',
+        args: [this.account.address],
+      }) as bigint;
+
+      console.info('💰 [TX SIGNER] Wallet USDC balance:', walletUsdcBalance.toString());
+
+      // Use the minimum of estimated amount and actual balance (with small buffer for gas)
+      if (walletUsdcBalance < usdcAmount) {
+        console.warn(`⚠️  [TX SIGNER] Wallet balance (${walletUsdcBalance}) < estimated amount (${usdcAmount}), using actual balance`);
+        usdcAmount = walletUsdcBalance;
+      }
+
+      if (usdcAmount === 0n) {
+        throw new Error('No USDC balance available for swap');
       }
 
       // Swap USDC to native via Uniswap