fix(clarity-values): strip 0x prefix from buffer args in parseArgToClarityValue

src/transactions/clarity-values.ts

@@ -73,8 +73,12 @@ export function parseArgToClarityValue(arg: unknown): ClarityValue {
           return boolCV(typedArg.value as boolean);
         case "principal":
           return principalCV(typedArg.value as string);
-        case "buffer":
-          return bufferCV(Buffer.from(typedArg.value as string, "hex"));
+        case "buffer": {
+          // Strip optional 0x/0X prefix — without this, Buffer.from("0x...", "hex")
+          // silently produces an empty buffer (aibtcdev/landing-page#1012 Finding 2)
+          const hexStr = (typedArg.value as string).replace(/^0x/i, "");
+          return bufferCV(Buffer.from(hexStr, "hex"));
+        }
         case "none":
           return noneCV();
         case "some":

tests/transactions/clarity-values.test.ts

@@ -210,6 +210,20 @@ describe("parseArgToClarityValue", () => {
       expect(cv.type).toBe(ClarityType.Buffer);
     });
 
+    it("should accept 0x-prefixed hex and produce the same bytes as raw hex", () => {
+      const raw = parseArgToClarityValue({ type: "buffer", value: "deadbeef" });
+      const prefixed = parseArgToClarityValue({ type: "buffer", value: "0xdeadbeef" });
+      expect(prefixed.type).toBe(ClarityType.Buffer);
+      expect(cvToString(prefixed)).toBe(cvToString(raw));
+    });
+
+    it("should accept 0X-prefixed hex (uppercase prefix)", () => {
+      const raw = parseArgToClarityValue({ type: "buffer", value: "deadbeef" });
+      const prefixed = parseArgToClarityValue({ type: "buffer", value: "0Xdeadbeef" });
+      expect(prefixed.type).toBe(ClarityType.Buffer);
+      expect(cvToString(prefixed)).toBe(cvToString(raw));
+    });
+
     it("should convert Buffer instance", () => {
       const buffer = Buffer.from([0xde, 0xad, 0xbe, 0xef]);
       const cv = parseArgToClarityValue(buffer);