diff --git a/tests/test_utils.py b/tests/test_utils.py
index 2e6bc78..ea123b2 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -81,6 +81,19 @@ def test_safe_error_detail_timeout() -> None:
     assert safe_error_detail(exc, "fallback") == "timeout"
 
 
+def test_safe_error_detail_http_status_without_message() -> None:
+    request = httpx.Request("GET", "https://example.com")
+    response = httpx.Response(503, json={"detail": "hidden"}, request=request)
+    exc = httpx.HTTPStatusError("bad", request=request, response=response)
+
+    assert safe_error_detail(exc, "fallback") == "http 503"
+
+
+def test_safe_error_detail_fallbacks_for_empty_runtime_and_generic() -> None:
+    assert safe_error_detail(RuntimeError("   "), "fallback") == "fallback"
+    assert safe_error_detail(ValueError("internal"), "fallback") == "fallback"
+
+
 def test_extract_bearer_token() -> None:
     request = DummyRequest({"Authorization": "Bearer token123"})
     assert extract_bearer_token(request) == "token123"