diff --git a/packages/sdk/src/ids.test.ts b/packages/sdk/src/ids.test.ts
index fa9a4ff..969988a 100644
--- a/packages/sdk/src/ids.test.ts
+++ b/packages/sdk/src/ids.test.ts
@@ -10,6 +10,10 @@ describe("normalizeRoundId", () => {
     assert.equal(normalizeRoundId("001"), 1n);
     assert.equal(normalizeRoundId(7), 7n);
     assert.equal(normalizeRoundId(7n), 7n);
+    assert.equal(normalizeRoundId(1), 1n);
+    assert.equal(normalizeRoundId(1n), 1n);
+    assert.equal(normalizeRoundId(Number.MAX_SAFE_INTEGER), BigInt(Number.MAX_SAFE_INTEGER));
+    assert.equal(normalizeRoundId(BigInt(Number.MAX_SAFE_INTEGER) + 100n), BigInt(Number.MAX_SAFE_INTEGER) + 100n);
   });
 
   it("rejects malformed values with explicit errors", () => {
@@ -17,8 +21,30 @@ describe("normalizeRoundId", () => {
     assert.throws(() => normalizeRoundId("   "), /roundId/);
     assert.throws(() => normalizeRoundId("0"), /positive integer/);
     assert.throws(() => normalizeRoundId("-1"), /positive integer/);
-    assert.throws(() => normalizeRoundId("1.5"), /roundId/);
-    assert.throws(() => normalizeRoundId("abc"), /roundId/);
+    assert.throws(() => normalizeRoundId("1.5"), /positive integer/);
+    assert.throws(() => normalizeRoundId("abc"), /positive integer/);
+    assert.throws(() => normalizeRoundId("0x10"), /positive integer/);
+    assert.throws(() => normalizeRoundId("+5"), /positive integer/);
+  });
+
+  it("rejects zero and negative number or bigint inputs", () => {
+    assert.throws(() => normalizeRoundId(0), /positive integer/);
+    assert.throws(() => normalizeRoundId(-1), /positive integer/);
+    assert.throws(() => normalizeRoundId(-42), /positive integer/);
+    assert.throws(() => normalizeRoundId(0n), /positive integer/);
+    assert.throws(() => normalizeRoundId(-1n), /positive integer/);
+    assert.throws(() => normalizeRoundId(-42n), /positive integer/);
+  });
+
+  it("rejects unsafe, fractional, and non-finite numbers", () => {
+    assert.throws(() => normalizeRoundId(1.5), /positive integer/);
+    assert.throws(() => normalizeRoundId(0.1), /positive integer/);
+    assert.throws(() => normalizeRoundId(NaN), /positive integer/);
+    assert.throws(() => normalizeRoundId(Infinity), /positive integer/);
+    assert.throws(() => normalizeRoundId(-Infinity), /positive integer/);
+    assert.throws(() => normalizeRoundId(Number.MAX_SAFE_INTEGER + 1), /positive integer/);
+    assert.throws(() => normalizeRoundId(Number.MAX_SAFE_INTEGER + 2), /positive integer/);
+    assert.throws(() => normalizeRoundId(Number.MIN_SAFE_INTEGER), /positive integer/);
   });
 });
 
diff --git a/packages/sdk/src/ids.ts b/packages/sdk/src/ids.ts
index 493868b..eb1ec5b 100644
--- a/packages/sdk/src/ids.ts
+++ b/packages/sdk/src/ids.ts
@@ -7,11 +7,16 @@ function toTrimmedString(value: string | undefined): string | undefined {
 }
 
 export function normalizeRoundId(value: string | number | bigint): bigint {
-  if (typeof value === "bigint") return value;
+  if (typeof value === "bigint") {
+    if (value <= 0n) {
+      throw new Error(`roundId must be a positive integer, got ${value}`);
+    }
+    return value;
+  }
 
   if (typeof value === "number") {
-    if (!Number.isInteger(value)) {
-      throw new Error(`roundId must be an integer, got ${JSON.stringify(value)}`);
+    if (!Number.isSafeInteger(value) || value <= 0) {
+      throw new Error(`roundId must be a positive integer, got ${value}`);
     }
     return BigInt(value);
   }
@@ -21,18 +26,15 @@ export function normalizeRoundId(value: string | number | bigint): bigint {
     throw new Error("roundId must be a non-empty decimal string");
   }
 
-  try {
-    const parsed = BigInt(trimmed);
-    if (parsed < 1n) {
-      throw new Error(`roundId must be a positive integer, got ${JSON.stringify(trimmed)}`);
-    }
-    return parsed;
-  } catch (error) {
-    if (error instanceof Error && error.message.includes("roundId")) {
-      throw error;
-    }
+  if (!/^\d+$/.test(trimmed)) {
+    throw new Error(`roundId must be a positive integer, got ${JSON.stringify(trimmed)}`);
+  }
+
+  const parsed = BigInt(trimmed);
+  if (parsed <= 0n) {
     throw new Error(`roundId must be a positive integer, got ${JSON.stringify(trimmed)}`);
   }
+  return parsed;
 }
 
 export function normalizeSorobanContractId(value: string): string {