fix(responses): count input_file tokens instead of silently dropping the file

The Responses-to-chat transform dropped the filename OpenAI requires next to
file_data, so a request carrying an inline PDF counted 13 tokens instead of 36
and a real completion through the chat bridge got a 400.

litellm/llms/openai/responses/count_tokens/transformation.py

@@ -21,7 +21,13 @@ class ResponsesInputImagePart(TypedDict):
     detail: ReadOnly[str]
 
 
-ResponsesInputPart = ResponsesInputTextPart | ResponsesInputImagePart
+class ResponsesInputFilePart(TypedDict):
+    type: ReadOnly[Literal["input_file"]]
+    filename: ReadOnly[str]
+    file_data: ReadOnly[str]
+
+
+ResponsesInputPart = ResponsesInputTextPart | ResponsesInputImagePart | ResponsesInputFilePart
 
 ResponsesContentRole = Literal["user", "assistant"]
 
@@ -39,6 +45,22 @@ def _chat_image_block_to_responses_part(image_url: object) -> ResponsesInputImag
     return part
 
 
+def _chat_file_block_to_responses_part(file_value: object) -> ResponsesInputFilePart | None:
+    """Only an inline file round trips: OpenAI rejects `file_data` without the `filename` beside it."""
+    if not isinstance(file_value, Mapping):
+        return None
+    filename: Final = file_value.get("filename")
+    file_data: Final = file_value.get("file_data")
+    if not isinstance(filename, str) or not filename or not isinstance(file_data, str) or not file_data:
+        return None
+    part: Final[ResponsesInputFilePart] = {
+        "type": "input_file",
+        "filename": filename,
+        "file_data": file_data,
+    }
+    return part
+
+
 def _chat_block_to_responses_part(block: object, role: ResponsesContentRole) -> ResponsesInputPart | None:
     if isinstance(block, str):
         bare: Final[ResponsesInputTextPart] = {"type": "input_text", "text": block}
@@ -55,6 +77,8 @@ def _chat_block_to_responses_part(block: object, role: ResponsesContentRole) ->
             return text
         case "image_url" if role == "user":
             return _chat_image_block_to_responses_part(block.get("image_url"))
+        case "file" if role == "user":
+            return _chat_file_block_to_responses_part(block.get("file"))
         case _:
             return None
 
@@ -65,7 +89,7 @@ def chat_content_blocks_to_responses_content(
 ) -> str | tuple[ResponsesInputPart, ...]:
     """Text-only content collapses to a joined string, which every role accepts and counts identically.
 
-    Only a user turn may carry an image part: the Responses API rejects any part but
+    Only a user turn may carry an image or file part: the Responses API rejects any part but
     output_text and refusal inside an assistant turn.
     """
     parts: Final = tuple(

litellm/responses/litellm_completion_transformation/transformation.py

@@ -1629,6 +1629,8 @@ class LiteLLMCompletionResponsesConfig:
             file_dict["file_id"] = file_id
         if item.get("file_data"):
             file_dict["file_data"] = item["file_data"]
+        if item.get("filename"):
+            file_dict["filename"] = item["filename"]
 
         new_item: Final[dict[str, object]] = {"type": "file", "file": file_dict}
         if "cache_control" in item:

tests/test_litellm/llms/openai/responses/test_openai_count_tokens_transformation.py

@@ -323,6 +323,80 @@ def test_messages_to_responses_input_keeps_user_image_alongside_an_assistant_tur
     ]
 
 
+def test_messages_to_responses_input_preserves_inline_files():
+    """An inline file must survive the round trip, or the count silently drops the file.
+
+    A small PDF is worth 36 tokens to OpenAI's counting API; dropping it left the same
+    request counting 13, the text-only total.
+    """
+    messages = [
+        {
+            "role": "user",
+            "content": [
+                {"type": "text", "text": "Summarize this file."},
+                {
+                    "type": "file",
+                    "file": {"filename": "report.pdf", "file_data": "data:application/pdf;base64,JVBERi0="},
+                },
+            ],
+        }
+    ]
+
+    input_items, _ = OpenAICountTokensConfig.messages_to_responses_input(messages)
+
+    assert input_items == [
+        {
+            "role": "user",
+            "content": (
+                {"type": "input_text", "text": "Summarize this file."},
+                {
+                    "type": "input_file",
+                    "filename": "report.pdf",
+                    "file_data": "data:application/pdf;base64,JVBERi0=",
+                },
+            ),
+        }
+    ]
+
+
+def test_messages_to_responses_input_drops_a_file_with_no_inline_data():
+    """OpenAI rejects `file_data` without a `filename`, and a rejected request loses the whole count."""
+    messages = [
+        {
+            "role": "user",
+            "content": [
+                {"type": "text", "text": "Summarize this file."},
+                {"type": "file", "file": {"file_data": "data:application/pdf;base64,JVBERi0="}},
+                {"type": "file", "file": {"file_id": "file-abc123"}},
+            ],
+        }
+    ]
+
+    input_items, _ = OpenAICountTokensConfig.messages_to_responses_input(messages)
+
+    assert input_items == [{"role": "user", "content": "Summarize this file."}]
+
+
+def test_messages_to_responses_input_assistant_file_block_is_dropped():
+    """A file part is illegal inside an assistant turn, so it must not reach the provider."""
+    messages = [
+        {
+            "role": "assistant",
+            "content": [
+                {"type": "text", "text": "Here it is"},
+                {
+                    "type": "file",
+                    "file": {"filename": "report.pdf", "file_data": "data:application/pdf;base64,JVBERi0="},
+                },
+            ],
+        }
+    ]
+
+    input_items, _ = OpenAICountTokensConfig.messages_to_responses_input(messages)
+
+    assert input_items == [{"role": "assistant", "content": "Here it is"}]
+
+
 def test_validate_request_valid():
     """Test that valid requests pass validation."""
     config = OpenAICountTokensConfig()

tests/test_litellm/responses/litellm_completion_transformation/test_litellm_completion_responses.py

@@ -124,6 +124,25 @@ class TestLiteLLMCompletionResponsesConfig:
         assert "extra_field" not in result["file"]
         assert "another_field" not in result["file"]
 
+    def test_transform_input_file_item_to_file_item_keeps_filename(self):
+        """OpenAI rejects file_data with no filename beside it, so dropping it 400s the request"""
+        result = (
+            LiteLLMCompletionResponsesConfig._transform_input_file_item_to_file_item(
+                {
+                    "type": "input_file",
+                    "filename": "report.pdf",
+                    "file_data": "data:application/pdf;base64,JVBERi0=",
+                }
+            )
+        )
+        assert result == {
+            "type": "file",
+            "file": {
+                "file_data": "data:application/pdf;base64,JVBERi0=",
+                "filename": "report.pdf",
+            },
+        }
+
     def test_transform_input_file_item_to_file_item_with_file_url(self):
         """file_url should be mapped to file_id for downstream URL handling"""
         result = (