diff --git a/litellm/main.py b/litellm/main.py
index 38591441e01..c756287542f 100644
--- a/litellm/main.py
+++ b/litellm/main.py
@@ -2678,7 +2678,10 @@ def _complete_custom_openai(
     if extra_headers is not None and not use_base_llm_http_handler:
         optional_params["extra_headers"] = extra_headers
 
-    if litellm.enable_preview_features and metadata is not None:  # [PREVIEW] allow metadata to be passed to OPENAI
+    # OpenAI accepts request metadata independently of preview features. Other
+    # providers keep the existing preview gate because compatible providers may
+    # reject the field.
+    if metadata is not None and (custom_llm_provider == "openai" or litellm.enable_preview_features):
         openai_metadata: Final = get_requester_metadata(metadata)
         if openai_metadata is not None:
             optional_params["metadata"] = openai_metadata
diff --git a/litellm/utils.py b/litellm/utils.py
index ff2c9012ec8..da98fb8be0f 100644
--- a/litellm/utils.py
+++ b/litellm/utils.py
@@ -10751,10 +10751,12 @@ def get_requester_metadata(metadata: Mapping[str, object]):
         return None
 
     requester_metadata: Final = metadata.get("requester_metadata")
-    if isinstance(requester_metadata, dict):
-        cleaned_metadata = add_openai_metadata(requester_metadata)
-        if cleaned_metadata:
-            return cleaned_metadata
+    if "requester_metadata" in metadata:
+        # The proxy-populated requester snapshot is authoritative. Falling back
+        # to the outer dictionary would expose auth fields such as
+        # user_api_key_hash when the snapshot has no forwardable strings.
+        cleaned_metadata = add_openai_metadata(requester_metadata) if isinstance(requester_metadata, dict) else None
+        return cleaned_metadata if cleaned_metadata else None
 
     cleaned_metadata = add_openai_metadata(metadata)
     if cleaned_metadata:
diff --git a/tests/unit/test_main.py b/tests/unit/test_main.py
index 63f440d4aba..1195d53ec9e 100644
--- a/tests/unit/test_main.py
+++ b/tests/unit/test_main.py
@@ -7680,34 +7680,30 @@ def test_completion_novita_ai_dynamic_params(api_key):
     "enable_preview_features",
     [True, False],
 )
-def test_completion_openai_metadata(monkeypatch, enable_preview_features):
+def test_completion_openai_metadata(
+    monkeypatch, enable_preview_features, respx_mock: respx.MockRouter
+):
     from openai import OpenAI
 
     client = OpenAI()
-
-    litellm.set_verbose = True
-
     monkeypatch.setattr(litellm, "enable_preview_features", enable_preview_features)
-    with patch.object(
-        client, "post", return_value=MagicMock()
-    ) as mock_completion:
-        try:
-            resp = litellm.completion(
-                model="openai/gpt-3.5-turbo",
-                messages=[{"role": "user", "content": "Hello world"}],
-                metadata={"my-test-key": "my-test-value"},
-                client=client,
-            )
-        except Exception as e:
-            print(f"Error: {e}")
+    respx_mock.post("https://api.openai.com/v1/chat/completions").mock(
+        return_value=_mocked_openai_chat_response("gpt-3.5-turbo")
+    )
 
-        mock_completion.assert_called_once()
-        if enable_preview_features:
-            assert mock_completion.call_args.kwargs["body"]["metadata"] == {
-                "my-test-key": "my-test-value"
-            }
-        else:
-            assert "metadata" not in mock_completion.call_args.kwargs["body"]
+    litellm.completion(
+        model="openai/gpt-3.5-turbo",
+        messages=[{"role": "user", "content": "Hello world"}],
+        metadata={
+            "session_id": "abc-123",
+            "hidden_params": {"api_key": "should-not-leak"},
+            "non_string": 123,
+        },
+        client=client,
+    )
+
+    request_body = json.loads(respx_mock.calls[0].request.content)
+    assert request_body["metadata"] == {"session_id": "abc-123"}
 
 
 AZURE_TTS_BASE: Final = "https://tts.example.azure.com"
diff --git a/tests/unit/test_utils_get_optional_params.py b/tests/unit/test_utils_get_optional_params.py
index 13a64577efb..e18c90fc627 100644
--- a/tests/unit/test_utils_get_optional_params.py
+++ b/tests/unit/test_utils_get_optional_params.py
@@ -57,6 +57,27 @@ def test_get_requester_metadata_returns_none_for_empty():
     assert get_requester_metadata(metadata) is None
 
 
+def test_get_requester_metadata_does_not_fall_back_to_sensitive_auth_metadata():
+    metadata = {
+        "requester_metadata": {
+            "hidden_params": "secret",
+            "non_string": 123,
+        },
+        "user_api_key": "sk-proxy-secret",
+        "user_api_key_hash": "opaque-custom-auth-token",
+        "user_api_key_auth": {"api_key": "sk-proxy-secret"},
+        "session_id": "should-not-leak",
+    }
+
+    assert get_requester_metadata(metadata) is None
+
+
+def test_get_requester_metadata_uses_outer_metadata_without_requester_snapshot():
+    assert get_requester_metadata({"session_id": "abc-123", "non_string": 123}) == {
+        "session_id": "abc-123"
+    }
+
+
 @patch("litellm.main.openai_chat_completions.completion")
 def test_requester_metadata_forwarded_to_openai(mock_completion):
     mock_completion.return_value = MagicMock()
@@ -87,6 +108,27 @@ def test_requester_metadata_forwarded_to_openai(mock_completion):
     assert sent_metadata == {"custom_meta_key": "value"}
 
 
+@patch("litellm.main.openai_chat_completions.completion")
+def test_sensitive_auth_metadata_is_not_forwarded_with_empty_requester_snapshot(
+    mock_completion, monkeypatch
+):
+    mock_completion.return_value = MagicMock()
+    monkeypatch.setattr(litellm, "api_key", "sk-test")
+
+    litellm.completion(
+        model="gpt-4o",
+        messages=[{"role": "user", "content": "hi"}],
+        metadata={
+            "requester_metadata": {"non_string": 123},
+            "user_api_key": "sk-proxy-secret",
+            "user_api_key_hash": "opaque-custom-auth-token",
+            "session_id": "should-not-leak",
+        },
+    )
+
+    assert "metadata" not in mock_completion.call_args.kwargs["optional_params"]
+
+
 def test_get_optional_params_with_allowed_openai_params():
     """
     Test if use can dynamically pass in allowed_openai_params to override default behavior