diff --git a/src/bun.js/bindings/InternalForTesting.cpp b/src/bun.js/bindings/InternalForTesting.cpp
index 9e1afc3c0630..6f36f8d97153 100644
--- a/src/bun.js/bindings/InternalForTesting.cpp
+++ b/src/bun.js/bindings/InternalForTesting.cpp
@@ -42,4 +42,35 @@ JSC_DEFINE_HOST_FUNCTION(jsFunction_lsanDoLeakCheck, (JSC::JSGlobalObject * glob
     return encodedJSUndefined();
 }
 
+extern "C" bool JSC__isBigIntInInt64Range(JSC::EncodedJSValue value, int64_t min, int64_t max);
+extern "C" bool JSC__isBigIntInUInt64Range(JSC::EncodedJSValue value, uint64_t min, uint64_t max);
+
+// For testing JSC__isBigIntInInt64Range / JSC__isBigIntInUInt64Range from JS.
+// args: (bigint, min: number|bigint, max: number|bigint, unsigned: boolean)
+JSC_DEFINE_HOST_FUNCTION(jsFunction_isBigIntInRange, (JSC::JSGlobalObject * globalObject, JSC::CallFrame* callFrame))
+{
+    auto& vm = globalObject->vm();
+    auto scope = DECLARE_THROW_SCOPE(vm);
+
+    JSValue value = callFrame->argument(0);
+    JSValue minArg = callFrame->argument(1);
+    JSValue maxArg = callFrame->argument(2);
+    bool isUnsigned = callFrame->argument(3).toBoolean(globalObject);
+    RETURN_IF_EXCEPTION(scope, {});
+
+    if (isUnsigned) {
+        uint64_t min = minArg.toBigUInt64(globalObject);
+        RETURN_IF_EXCEPTION(scope, {});
+        uint64_t max = maxArg.toBigUInt64(globalObject);
+        RETURN_IF_EXCEPTION(scope, {});
+        return JSValue::encode(jsBoolean(JSC__isBigIntInUInt64Range(JSValue::encode(value), min, max)));
+    }
+
+    int64_t min = minArg.toBigInt64(globalObject);
+    RETURN_IF_EXCEPTION(scope, {});
+    int64_t max = maxArg.toBigInt64(globalObject);
+    RETURN_IF_EXCEPTION(scope, {});
+    return JSValue::encode(jsBoolean(JSC__isBigIntInInt64Range(JSValue::encode(value), min, max)));
+}
+
 }
diff --git a/src/bun.js/bindings/InternalForTesting.h b/src/bun.js/bindings/InternalForTesting.h
index 52e1b4a76bf0..4311017a80f2 100644
--- a/src/bun.js/bindings/InternalForTesting.h
+++ b/src/bun.js/bindings/InternalForTesting.h
@@ -8,5 +8,6 @@ namespace Bun {
 JSC_DECLARE_HOST_FUNCTION(jsFunction_arrayBufferViewHasBuffer);
 JSC_DECLARE_HOST_FUNCTION(jsFunction_hasReifiedStatic);
 JSC_DECLARE_HOST_FUNCTION(jsFunction_lsanDoLeakCheck);
+JSC_DECLARE_HOST_FUNCTION(jsFunction_isBigIntInRange);
 
 }
diff --git a/src/bun.js/bindings/bindings.cpp b/src/bun.js/bindings/bindings.cpp
index 8af5f71b18e8..085100d7522f 100644
--- a/src/bun.js/bindings/bindings.cpp
+++ b/src/bun.js/bindings/bindings.cpp
@@ -5265,34 +5265,32 @@ extern "C" void JSC__JSValue__forEachPropertyNonIndexed(JSC::EncodedJSValue JSVa
     JSC__JSValue__forEachPropertyImpl<true>(JSValue0, globalObject, arg2, iter);
 }
 
-extern "C" [[ZIG_EXPORT(nothrow)]] bool JSC__isBigIntInUInt64Range(JSC::EncodedJSValue value, uint64_t max, uint64_t min)
+extern "C" [[ZIG_EXPORT(nothrow)]] bool JSC__isBigIntInUInt64Range(JSC::EncodedJSValue value, uint64_t min, uint64_t max)
 {
     JSValue jsValue = JSValue::decode(value);
     if (!jsValue.isHeapBigInt())
         return false;
 
     JSC::JSBigInt* bigInt = jsValue.asHeapBigInt();
-    auto result = bigInt->compare(bigInt, min);
-    if (result == JSBigInt::ComparisonResult::GreaterThan || result == JSBigInt::ComparisonResult::Equal) {
-        return true;
-    }
-    result = bigInt->compare(bigInt, max);
-    return result == JSBigInt::ComparisonResult::LessThan || result == JSBigInt::ComparisonResult::Equal;
+    auto result = JSBigInt::compare(bigInt, min);
+    if (result == JSBigInt::ComparisonResult::LessThan)
+        return false;
+    result = JSBigInt::compare(bigInt, max);
+    return result != JSBigInt::ComparisonResult::GreaterThan;
 }
 
-extern "C" [[ZIG_EXPORT(nothrow)]] bool JSC__isBigIntInInt64Range(JSC::EncodedJSValue value, int64_t max, int64_t min)
+extern "C" [[ZIG_EXPORT(nothrow)]] bool JSC__isBigIntInInt64Range(JSC::EncodedJSValue value, int64_t min, int64_t max)
 {
     JSValue jsValue = JSValue::decode(value);
     if (!jsValue.isHeapBigInt())
         return false;
 
     JSC::JSBigInt* bigInt = jsValue.asHeapBigInt();
-    auto result = bigInt->compare(bigInt, min);
-    if (result == JSBigInt::ComparisonResult::GreaterThan || result == JSBigInt::ComparisonResult::Equal) {
-        return true;
-    }
-    result = bigInt->compare(bigInt, max);
-    return result == JSBigInt::ComparisonResult::LessThan || result == JSBigInt::ComparisonResult::Equal;
+    auto result = JSBigInt::compare(bigInt, min);
+    if (result == JSBigInt::ComparisonResult::LessThan)
+        return false;
+    result = JSBigInt::compare(bigInt, max);
+    return result != JSBigInt::ComparisonResult::GreaterThan;
 }
 
 [[ZIG_EXPORT(check_slow)]] void JSC__JSValue__forEachPropertyOrdered(JSC::EncodedJSValue JSValue0, JSC::JSGlobalObject* globalObject, void* arg2, void (*iter)([[ZIG_NONNULL]] JSC::JSGlobalObject* arg0, void* ctx, [[ZIG_NONNULL]] ZigString* arg2, JSC::EncodedJSValue JSValue3, bool isSymbol, bool isPrivateSymbol))
diff --git a/src/js/internal-for-testing.ts b/src/js/internal-for-testing.ts
index 35b7cd091664..17ad753d8cd4 100644
--- a/src/js/internal-for-testing.ts
+++ b/src/js/internal-for-testing.ts
@@ -194,6 +194,12 @@ export const getDevServerDeinitCount = $bindgenFn("DevServer.bind.ts", "getDeini
 export const getCounters = $newZigFunction("Counters.zig", "createCountersObject", 0);
 export const hasNonReifiedStatic = $newCppFunction("InternalForTesting.cpp", "jsFunction_hasReifiedStatic", 1);
 
+export const isBigIntInRange: (value: bigint, min: bigint, max: bigint, unsigned: boolean) => boolean = $newCppFunction(
+  "InternalForTesting.cpp",
+  "jsFunction_isBigIntInRange",
+  4,
+);
+
 interface setSocketOptionsFn {
   (socket: Bun.Socket, sendBuffer: 1, size: number): void;
   (socket: Bun.Socket, recvBuffer: 2, size: number): void;
diff --git a/test/js/bun/jsc/bigint-range-check.test.ts b/test/js/bun/jsc/bigint-range-check.test.ts
new file mode 100644
index 000000000000..2ef36d138ebd
--- /dev/null
+++ b/test/js/bun/jsc/bigint-range-check.test.ts
@@ -0,0 +1,85 @@
+import { isBigIntInRange } from "bun:internal-for-testing";
+import { describe, expect, test } from "bun:test";
+
+// Regression test for JSC__isBigIntInInt64Range / JSC__isBigIntInUInt64Range.
+// Previously the C++ implementation had swapped (min, max) parameter names AND
+// used OR-short-circuit logic, causing the function to return true when the
+// value was OUTSIDE the range and false when it was INSIDE.
+// This affected MySQL BigInt parameter binding (all in-range values were
+// rejected with ERR_OUT_OF_RANGE).
+
+const I64_MIN = -9223372036854775808n;
+const I64_MAX = 9223372036854775807n;
+const U64_MAX = 18446744073709551615n;
+
+describe("isBigIntInInt64Range (signed)", () => {
+  test("100n is in [i64_min, i64_max]", () => {
+    expect(isBigIntInRange(100n, I64_MIN, I64_MAX, false)).toBe(true);
+  });
+
+  test("0n is in [i64_min, i64_max]", () => {
+    expect(isBigIntInRange(0n, I64_MIN, I64_MAX, false)).toBe(true);
+  });
+
+  test("-100n is in [i64_min, i64_max]", () => {
+    expect(isBigIntInRange(-100n, I64_MIN, I64_MAX, false)).toBe(true);
+  });
+
+  test("i64_max boundary is in range", () => {
+    expect(isBigIntInRange(I64_MAX, I64_MIN, I64_MAX, false)).toBe(true);
+  });
+
+  test("i64_min boundary is in range", () => {
+    expect(isBigIntInRange(I64_MIN, I64_MIN, I64_MAX, false)).toBe(true);
+  });
+
+  test("i64_max + 1 is out of range", () => {
+    expect(isBigIntInRange(I64_MAX + 1n, I64_MIN, I64_MAX, false)).toBe(false);
+  });
+
+  test("i64_min - 1 is out of range", () => {
+    expect(isBigIntInRange(I64_MIN - 1n, I64_MIN, I64_MAX, false)).toBe(false);
+  });
+
+  test("very large positive bigint is out of range", () => {
+    expect(isBigIntInRange(2n ** 128n, I64_MIN, I64_MAX, false)).toBe(false);
+  });
+
+  test("very large negative bigint is out of range", () => {
+    expect(isBigIntInRange(-(2n ** 128n), I64_MIN, I64_MAX, false)).toBe(false);
+  });
+
+  test("narrow range [0, 100]", () => {
+    expect(isBigIntInRange(50n, 0n, 100n, false)).toBe(true);
+    expect(isBigIntInRange(0n, 0n, 100n, false)).toBe(true);
+    expect(isBigIntInRange(100n, 0n, 100n, false)).toBe(true);
+    expect(isBigIntInRange(-1n, 0n, 100n, false)).toBe(false);
+    expect(isBigIntInRange(101n, 0n, 100n, false)).toBe(false);
+  });
+});
+
+describe("isBigIntInUInt64Range (unsigned)", () => {
+  test("100n is in [0, u64_max]", () => {
+    expect(isBigIntInRange(100n, 0n, U64_MAX, true)).toBe(true);
+  });
+
+  test("0n is in [0, u64_max]", () => {
+    expect(isBigIntInRange(0n, 0n, U64_MAX, true)).toBe(true);
+  });
+
+  test("u64_max boundary is in range", () => {
+    expect(isBigIntInRange(U64_MAX, 0n, U64_MAX, true)).toBe(true);
+  });
+
+  test("u64_max + 1 is out of range", () => {
+    expect(isBigIntInRange(U64_MAX + 1n, 0n, U64_MAX, true)).toBe(false);
+  });
+
+  test("-1n is out of [0, u64_max]", () => {
+    expect(isBigIntInRange(-1n, 0n, U64_MAX, true)).toBe(false);
+  });
+
+  test("very large bigint is out of range", () => {
+    expect(isBigIntInRange(2n ** 128n, 0n, U64_MAX, true)).toBe(false);
+  });
+});
diff --git a/test/js/sql/sql-mysql.test.ts b/test/js/sql/sql-mysql.test.ts
index 0228dcf82d4d..42841e475b55 100644
--- a/test/js/sql/sql-mysql.test.ts
+++ b/test/js/sql/sql-mysql.test.ts
@@ -483,9 +483,7 @@ if (isDockerEnabled()) {
         test("Binary", async () => {
           const random_name = ("t_" + Bun.randomUUIDv7("hex").replaceAll("-", "")).toLowerCase();
           await sql`CREATE TEMPORARY TABLE ${sql(random_name)} (a binary(1), b varbinary(1), c blob)`;
-          const values = [
-            { a: Buffer.from([1]), b: Buffer.from([2]), c: Buffer.from([3]) },
-          ];
+          const values = [{ a: Buffer.from([1]), b: Buffer.from([2]), c: Buffer.from([3]) }];
           await sql`INSERT INTO ${sql(random_name)} ${sql(values)}`;
           const results = await sql`select * from ${sql(random_name)}`;
           // return buffers
@@ -497,7 +495,7 @@ if (isDockerEnabled()) {
           expect(results2[0].a).toEqual(Buffer.from([1]));
           expect(results2[0].b).toEqual(Buffer.from([2]));
           expect(results2[0].c).toEqual(Buffer.from([3]));
-        })
+        });
 
         test("bulk insert nested sql()", async () => {
           await using sql = new SQL({ ...getOptions(), max: 1 });
@@ -966,6 +964,51 @@ if (isDockerEnabled()) {
           expect((await sql`select 9223372036854777 as x`)[0].x).toBe(9223372036854777n);
         });
 
+        // Regression: previously any in-range BigInt parameter would throw
+        // ERR_OUT_OF_RANGE due to inverted logic in JSC__isBigIntInInt64Range.
+        describe("bigint parameter binding", () => {
+          test("binds BigInt values into BIGINT columns without ERR_OUT_OF_RANGE", async () => {
+            await using sql = new SQL({ ...getOptions(), bigint: true });
+            const table = "t_" + randomUUIDv7("hex").replaceAll("-", "");
+            await sql`CREATE TEMPORARY TABLE ${sql(table)} (s BIGINT, u BIGINT UNSIGNED)`;
+
+            // These should NOT throw ERR_OUT_OF_RANGE (the bug was that they all did)
+            await sql`INSERT INTO ${sql(table)} (s) VALUES (${100n})`;
+            await sql`INSERT INTO ${sql(table)} (s) VALUES (${0n})`;
+            await sql`INSERT INTO ${sql(table)} (s) VALUES (${-1n})`;
+            await sql`INSERT INTO ${sql(table)} (s) VALUES (${9223372036854775807n})`;
+            await sql`INSERT INTO ${sql(table)} (s) VALUES (${-9223372036854775808n})`;
+            await sql`INSERT INTO ${sql(table)} (u) VALUES (${0n})`;
+            await sql`INSERT INTO ${sql(table)} (u) VALUES (${9223372036854775808n})`;
+            await sql`INSERT INTO ${sql(table)} (u) VALUES (${18446744073709551615n})`;
+
+            // Verify i64 boundary values round-trip correctly as BigInt
+            const s = (await sql`SELECT s FROM ${sql(table)} WHERE s IS NOT NULL ORDER BY s`).map(r => r.s);
+            expect(s).toHaveLength(5);
+            expect(s[0]).toBe(-9223372036854775808n);
+            expect(s[s.length - 1]).toBe(9223372036854775807n);
+
+            // Verify u64 boundary values round-trip correctly
+            const u = (await sql`SELECT u FROM ${sql(table)} WHERE u IS NOT NULL ORDER BY u`).map(r => r.u);
+            expect(u).toHaveLength(3);
+            expect(u[u.length - 1]).toBe(18446744073709551615n);
+          });
+
+          test("throws ERR_OUT_OF_RANGE for BigInt exceeding u64", async () => {
+            await using sql = new SQL({ ...getOptions() });
+            await expect(sql`select ${18446744073709551616n} as x`).rejects.toMatchObject({
+              code: "ERR_OUT_OF_RANGE",
+            });
+          });
+
+          test("throws ERR_OUT_OF_RANGE for BigInt below i64 min", async () => {
+            await using sql = new SQL({ ...getOptions() });
+            await expect(sql`select ${-9223372036854775809n} as x`).rejects.toMatchObject({
+              code: "ERR_OUT_OF_RANGE",
+            });
+          });
+        });
+
         test("int is returned as Number", async () => {
           expect((await sql`select CAST(123 AS SIGNED) as x`)[0].x).toBe(123);
         });