BerriAI/litellm · error · NotImplementedError

GoogleAIStudioFilesHandler does not support file listing

Error message

GoogleAIStudioFilesHandler does not support file listing

What it means

GoogleAIStudioFilesHandler.transform_list_files_request deliberately raises NotImplementedError: the Gemini files handler implements upload/retrieve/delete but not listing, even though Google's Files API exposes GET /v1beta/files. Any list-files call routed to the gemini provider (e.g. litellm.files_list / litellm.list_files with custom_llm_provider='gemini') fails here before any HTTP request is made.

Solutions

Call the Gemini Files API directly for listing: httpx.get(f'{base}/v1beta/files', headers={'x-goog-api-key': KEY}) and page through nextPageToken
Or use the google-genai SDK: client.files.list()
Track file ids in your own database at create time instead of relying on server-side listing
Upstream: open a GitHub issue/PR on BerriAI/litellm to implement transform_list_files_request for the Gemini handler

Example fix

# before
files = litellm.files_list(custom_llm_provider='gemini', api_key=KEY)
# NotImplementedError: GoogleAIStudioFilesHandler does not support file listing

# after - list directly against the Gemini Files API
import httpx
resp = httpx.get(
    'https://generativelanguage.googleapis.com/v1beta/files',
    headers={'x-goog-api-key': KEY},
)
resp.raise_for_status()
files = resp.json().get('files', [])

Defensive patterns

Strategy: validation

Validate before calling

GEMINI_FILES_UNSUPPORTED = {'list', 'content'}

def files_op_allowed(op: str, provider: str) -> bool:
    return not (provider == 'gemini' and op in GEMINI_FILES_UNSUPPORTED)

assert files_op_allowed('list', 'gemini') is False

Try / catch

try:
    files = litellm.files_list(custom_llm_provider='gemini', api_key=KEY)
except NotImplementedError:
    files = httpx.get(
        'https://generativelanguage.googleapis.com/v1beta/files',
        headers={'x-goog-api-key': KEY},
    ).json().get('files', [])

Prevention

Maintain a per-provider capability map for file operations and branch before calling litellm
Persist file ids at upload time so listing is never required
Know the gemini handler's supported set: create, retrieve, delete only

When it happens

Trigger: litellm.files_list(custom_llm_provider='gemini', api_key=KEY); any code that iterates uploaded files through LiteLLM's OpenAI-style files interface against the Gemini provider.

Common situations: Porting OpenAI file-management code (client.files.list()) to Gemini through LiteLLM; housekeeping scripts that list files before deleting; assuming provider parity because upload/get/delete work.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of BerriAI/litellm@77b7c6c40c (2026-08-18). Data as JSON: /api/errors/de6a814c2bbbd14b. Report an issue: GitHub.

Appendix: source

Thrown at litellm/llms/gemini/files/transformation.py:372

                        file_id = url.split("/files/")[-1].split("?")[0]
                        # Add the files/ prefix if not present
                        if not file_id.startswith("files/"):
                            file_id = f"files/{file_id}"

                return FileDeleted(id=file_id, deleted=True, object="file")
            else:
                raise ValueError(f"Failed to delete file: {raw_response.text}")
        except Exception as e:
            verbose_logger.exception("Error parsing file delete response: %s", e)
            raise ValueError(f"Error parsing file delete response: {e}")

    def transform_list_files_request(
        self,
        purpose: str | None,
        optional_params: dict,
        litellm_params: dict,
    ) -> tuple[str, dict]:
        raise NotImplementedError("GoogleAIStudioFilesHandler does not support file listing")

    def transform_list_files_response(
        self,
        raw_response: httpx.Response,
        logging_obj: LiteLLMLoggingObj,
        litellm_params: dict,
    ) -> list[OpenAIFileObject]:
        raise NotImplementedError("GoogleAIStudioFilesHandler does not support file listing")

    def transform_file_content_request(
        self,
        file_content_request,
        optional_params: dict,
        litellm_params: dict,
    ) -> tuple[str, dict]:
        raise NotImplementedError("GoogleAIStudioFilesHandler does not support file content retrieval")

    def transform_file_content_response(

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