fix(anthropic): ignore a non-string attachment format and keep count-route 400s as 400s

litellm/litellm_core_utils/prompt_templates/factory.py

@@ -909,7 +909,7 @@ def convert_to_anthropic_image_obj(openai_image_url: str, format: str | None) ->
         # Extract the media type and base64 data
         media_type, base64_data = openai_image_url.split("data:")[1].split(";base64,")
 
-        if format:
+        if isinstance(format, str) and format:
             media_type = format
         else:
             media_type = media_type.replace("\\/", "/")
@@ -954,7 +954,7 @@ def create_anthropic_image_param(
             return anthropic_content_element_factory(
                 convert_to_anthropic_image_obj(openai_image_url=base64_url, format=format)
             )
-        elif format is not None and format.partition(";")[0].strip().lower() == "application/pdf":
+        elif isinstance(format, str) and format.partition(";")[0].strip().lower() == "application/pdf":
             return AnthropicMessagesDocumentParam(
                 type="document",
                 source=AnthropicContentParamSourceUrl(type="url", url=image_url),
@@ -2365,8 +2365,10 @@ def anthropic_content_element_factory(
 
 
 def select_anthropic_content_block_type_for_file(
-    format: str,
+    format: object,
 ) -> Literal["document", "image", "container_upload"]:
+    if not isinstance(format, str):
+        return "container_upload"
     media_type: Final = format.strip().lower()
     if media_type == "application/pdf" or media_type == "text/plain":
         return "document"

litellm/llms/anthropic/count_tokens/handler.py

@@ -116,6 +116,8 @@ class AnthropicCountTokensHandler(AnthropicCountTokensConfig):
         except AnthropicError:
             # Re-raise Anthropic exceptions as-is
             raise
+        except litellm.BadRequestError as e:
+            raise AnthropicError(status_code=400, message=e.message) from e
         except httpx.HTTPStatusError as e:
             # HTTP errors - preserve the actual status code
             verbose_logger.error("HTTP error in CountTokens handler: %s", e)

litellm/llms/azure_ai/anthropic/count_tokens/handler.py

@@ -128,6 +128,8 @@ class AzureAIAnthropicCountTokensHandler(AzureAIAnthropicCountTokensConfig):
         except AnthropicError:
             # Re-raise Anthropic exceptions as-is
             raise
+        except litellm.BadRequestError as e:
+            raise AnthropicError(status_code=400, message=e.message) from e
         except httpx.HTTPStatusError as e:
             # HTTP errors - preserve the actual status code
             verbose_logger.error("HTTP error in CountTokens handler: %s", e)

tests/unit/litellm_core_utils/prompt_templates/test_litellm_core_utils_prompt_templates_factory.py

@@ -9488,3 +9488,31 @@ def test_create_anthropic_image_param_links_an_https_pdf_as_a_document_only_when
         "type": "image",
         "source": {"type": "url", "url": url},
     }
+
+
+@pytest.mark.parametrize("bad_format", (7, ["image/png"]), ids=("int", "list"))
+@pytest.mark.parametrize(
+    "block, expected",
+    (
+        (
+            {"type": "image_url", "image_url": {"url": "https://example.com/cat.png"}},
+            {"type": "image", "source": {"type": "url", "url": "https://example.com/cat.png"}},
+        ),
+        (
+            {"type": "image_url", "image_url": {"url": _PNG_DATA_URI}},
+            {"type": "image", "source": {"type": "base64", "media_type": "image/png", "data": _PNG_DATA_URI.split(",", 1)[1]}},
+        ),
+        (
+            {"type": "file", "file": {"file_id": "file_abc"}},
+            {"type": "container_upload", "file_id": "file_abc"},
+        ),
+    ),
+    ids=("https_link", "data_uri", "file_id"),
+)
+def test_anthropic_messages_pt_ignores_a_format_that_is_not_a_string(bad_format, block, expected):
+    payload_key = "image_url" if block["type"] == "image_url" else "file"
+    messages = [{"role": "user", "content": [{**block, payload_key: {**block[payload_key], "format": bad_format}}]}]
+
+    result = anthropic_messages_pt(messages=messages, model="claude-sonnet-5", llm_provider="anthropic")
+
+    assert result[0]["content"] == [expected]

tests/unit/llms/anthropic/test_anthropic_count_tokens_transformation.py

@@ -14,6 +14,7 @@ from pydantic import JsonValue, TypeAdapter
 
 import litellm
 from litellm.llms.anthropic.chat.transformation import AnthropicConfig
+from litellm.llms.anthropic.common_utils import AnthropicError
 from litellm.llms.anthropic.count_tokens.handler import AnthropicCountTokensHandler
 from litellm.llms.anthropic.count_tokens.token_counter import AnthropicTokenCounter
 from litellm.llms.anthropic.count_tokens.transformation import (
@@ -525,6 +526,35 @@ def test_count_drops_a_leading_system_message_without_text() -> None:
     assert result == {"model": "claude-opus-5-5", "messages": [{"role": "user", "content": "hi"}]}
 
 
+@pytest.mark.asyncio
+@pytest.mark.usefixtures("httpx_transport_clients")
+@pytest.mark.parametrize("handler_type", (AnthropicCountTokensHandler, AzureAIAnthropicCountTokensHandler))
+async def test_handler_answers_400_for_a_text_attachment_it_cannot_decode(
+    handler_type: type[AnthropicCountTokensHandler] | type[AzureAIAnthropicCountTokensHandler],
+) -> None:
+    text_attachment: Final = "data:text/plain;charset=bogus-cs;base64," + b64encode(b"hello").decode()
+    messages: Final[list[dict[str, JsonValue]]] = [
+        {"role": "user", "content": [{"type": "image_url", "image_url": {"url": text_attachment}}]}
+    ]
+    api_base: Final = "https://gateway.example"
+    handler: Final = handler_type()
+    with respx.mock:
+        route: Final = respx.post(f"{api_base}/v1/messages/count_tokens").mock(
+            return_value=httpx.Response(200, json={"input_tokens": 7})
+        )
+        with pytest.raises(AnthropicError) as exc_info:
+            await (
+                handler.handle_count_tokens_request(
+                    model="claude-opus-5-5", messages=messages, api_base=api_base, auth_header={"x-api-key": "test-key"}
+                ) if isinstance(handler, AnthropicCountTokensHandler) else handler.handle_count_tokens_request(
+                    model="claude-opus-5-5", messages=messages, api_base=api_base, api_key="test-key"
+                )
+            )
+
+    assert exc_info.value.status_code == 400
+    assert "bogus-cs" in exc_info.value.message
+    assert not route.called
+
 @pytest.mark.asyncio
 async def test_handler_sends_the_leading_system_run_as_system_not_as_a_message(httpx_transport_clients):
     """The wire body is what the provider judges: ``system`` carries the prompt and no message has