diff --git a/src/openai/_exceptions.py b/src/openai/_exceptions.py
index 7a30e4a336..5f5f911faf 100644
--- a/src/openai/_exceptions.py
+++ b/src/openai/_exceptions.py
@@ -69,7 +69,8 @@ def __init__(self, message: str, request: httpx2.Request, *, body: object | None
         self.body = body
 
         if is_dict(body):
-            self.code = cast(Any, construct_type(type_=Optional[str], value=body.get("code")))
+            raw_code = body.get("code")
+            self.code = str(raw_code) if raw_code is not None else None
             self.param = cast(Any, construct_type(type_=Optional[str], value=body.get("param")))
             self.type = cast(Any, construct_type(type_=str, value=body.get("type")))
         else:
diff --git a/tests/test_client.py b/tests/test_client.py
index d82c39e616..9edd41c808 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -3038,3 +3038,32 @@ def provider() -> str:
             assert len(calls) == 2
 
             assert provider_call_count == 1
+
+
+def test_api_error_code_coercion() -> None:
+    """Regression test: APIError.code must always be Optional[str], never int.
+
+    The API can return a numeric code (e.g. 400) in the error body. Before the
+    fix, construct_type returned the raw int when the target type didn't match,
+    and cast(Any, ...) hid that from the type checker — so .code was silently int
+    at runtime, breaking any caller using str methods like .strip() or ==.
+    """
+    from openai._exceptions import APIError
+
+    request = httpx2.Request("GET", "http://localhost")
+
+    # Integer code must be coerced to str.
+    err = APIError("msg", request, body={"code": 400, "param": None, "type": "t"})
+    assert err.code == "400"
+    assert isinstance(err.code, str)
+
+    # String code must pass through unchanged.
+    err = APIError("msg", request, body={"code": "invalid_api_key", "param": None, "type": "t"})
+    assert err.code == "invalid_api_key"
+
+    # Absent / null code must yield None.
+    err = APIError("msg", request, body={"code": None, "param": None, "type": "t"})
+    assert err.code is None
+
+    err = APIError("msg", request, body={"param": None, "type": "t"})
+    assert err.code is None