fix(proxy): move pricing strip below the litellm_metadata JSON-string parse

The strip ran before the proxy parses ``litellm_metadata`` from a JSON
string into a dict (a path used by multipart/form-data and ``extra_body``
callers), so ``isinstance(metadata, dict)`` was False and ``model_info``
survived the strip. Move the call to the same post-parse position the
``user_api_key_*`` strip already uses for the same reason. Adds a
regression test exercising the JSON-string ``litellm_metadata`` path.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

litellm/proxy/litellm_pre_call_utils.py

@@ -1164,8 +1164,6 @@ async def add_litellm_data_to_request(  # noqa: PLR0915
         if _allow_client_mock_response and _internal_key in _CLIENT_MOCK_CONTROL_FIELDS:
             continue
         data.pop(_internal_key, None)
-    if not _key_or_team_allows_client_pricing_override(user_api_key_dict):
-        _strip_client_pricing_overrides(data)
     # Strip spoofable auth metadata from user-supplied metadata dict
     _user_metadata = data.get("metadata")
     if isinstance(_user_metadata, dict):
@@ -1367,6 +1365,14 @@ async def add_litellm_data_to_request(  # noqa: PLR0915
             ]:
                 _user_meta.pop(_k, None)
 
+    # Strip pricing overrides AFTER the litellm_metadata string-to-dict parse
+    # above, for the same reason as the user_api_key_* strip — JSON-string
+    # metadata (sent via multipart/form-data or extra_body) wouldn't be a
+    # dict yet at the earlier strip point and the isinstance(dict) guard
+    # would silently skip the field.
+    if not _key_or_team_allows_client_pricing_override(user_api_key_dict):
+        _strip_client_pricing_overrides(data)
+
     # Strip caller-supplied routing/budget tags unless the admin has opted
     # this key or team in via metadata.allow_client_tags=True. Tags drive
     # tag-based routing and tag budget attribution — accepting them from

tests/test_litellm/proxy/test_pricing_field_strip.py

@@ -231,6 +231,35 @@ async def test_add_litellm_data_to_request_skips_strip_with_key_opt_in():
     assert updated["metadata"]["model_info"] == {"output_cost_per_token": 0.0002}
 
 
+@pytest.mark.asyncio
+async def test_add_litellm_data_to_request_strips_json_string_litellm_metadata():
+    """``litellm_metadata`` may arrive as a JSON-encoded string (multipart/
+    form-data or ``extra_body``). The strip has to run after the proxy parses
+    it into a dict; otherwise the ``isinstance(dict)`` guard skips the field
+    and ``model_info`` survives the strip via the string path.
+    """
+    import json
+
+    data = {
+        "model": "gpt-4",
+        "messages": [{"role": "user", "content": "hi"}],
+        "litellm_metadata": json.dumps({"model_info": {"input_cost_per_token": 0.0}}),
+    }
+
+    updated = await add_litellm_data_to_request(
+        data=data,
+        request=_make_request_mock(),
+        user_api_key_dict=_user_api_key_auth(),
+        proxy_config=MagicMock(),
+        general_settings={},
+        version="test-version",
+    )
+
+    parsed_metadata = updated.get("litellm_metadata")
+    assert isinstance(parsed_metadata, dict)
+    assert "model_info" not in parsed_metadata
+
+
 @pytest.mark.asyncio
 async def test_add_litellm_data_to_request_skips_strip_with_team_opt_in():
     data = {