diff --git a/src/core/assets.mjs b/src/core/assets.mjs
index a959f80..f4d4627 100644
--- a/src/core/assets.mjs
+++ b/src/core/assets.mjs
@@ -40,7 +40,31 @@ export function numberToUnits(value, decimals, { mode = 'round' } = {}) {
 }
 
 export function bigintAmount(amount) {
-  return BigInt(String(amount || '0'));
+  if (typeof amount === 'bigint') return amount;
+  const str = String(amount ?? '0').trim();
+  if (!str) return 0n;
+  // BigInt() cannot parse scientific notation (e.g. "6.03e+25").
+  // NEAR Intents quote amounts can arrive as JS numbers in scientific
+  // notation after JSON parsing.  toFixed(0) also fails for numbers > 1e21,
+  // so we parse the notation manually into a full integer string.
+  if (str.includes('e') || str.includes('E')) {
+    const [mantissa, expStr] = str.toLowerCase().split('e');
+    const exp = parseInt(expStr, 10);
+    const negative = mantissa.startsWith('-');
+    const positive = negative ? mantissa.slice(1) : mantissa;
+    const [intPart, decPart] = positive.split('.');
+    const digits = intPart + (decPart || '');
+    const decLen = (decPart || '').length;
+    const targetLen = digits.length - decLen + exp;
+    if (targetLen <= 0) return 0n;
+    const padded = digits.padEnd(targetLen, '0');
+    const result = BigInt(padded.slice(0, targetLen) || '0');
+    return negative ? -result : result;
+  }
+  if (str.includes('.')) {
+    return BigInt(str.split('.')[0]);
+  }
+  return BigInt(str);
 }
 
 export function formatNumber(value, digits = 8) {