langflow-ai/langflow · error · HTTPException

Content type not found for extension {extension}

Error message

Content type not found for extension {extension}

What it means

HTTP 500 from GET /files/download/{flow_id}/{file_name} when build_content_type_from_extension returns a falsy value — the extension is syntactically fine but not present in the server's known extension→MIME map. The server refuses to guess a content type rather than defaulting, so the download cannot proceed.

Source

Thrown at src/backend/base/langflow/api/v1/files.py:143

@router.get("/download/{flow_id}/{file_name}")
async def download_file(
    file_name: ValidatedFileName,
    flow: Annotated[Flow, Depends(get_flow)],
    storage_service: Annotated[StorageService, Depends(get_storage_service)],
):
    # Authorization handled by get_flow dependency
    flow_id_str = str(flow.id)
    extension = file_name.split(".")[-1]

    if not extension:
        raise HTTPException(status_code=500, detail=f"Extension not found for file {file_name}")
    try:
        content_type = build_content_type_from_extension(extension)
    except Exception as e:
        raise HTTPException(status_code=500, detail=str(e)) from e

    if not content_type:
        raise HTTPException(status_code=500, detail=f"Content type not found for extension {extension}")

    try:
        file_content = await storage_service.get_file(flow_id=flow_id_str, file_name=file_name)
        headers = {
            "Content-Disposition": build_content_disposition(file_name),
            "Content-Type": "application/octet-stream",
            "Content-Length": str(len(file_content)),
        }
        return StreamingResponse(BytesIO(file_content), media_type=content_type, headers=headers)
    except Exception as e:
        raise HTTPException(status_code=500, detail=str(e)) from e


@router.get("/images/{flow_id}/{file_name}")
async def download_image(
    file_name: ValidatedFileName,
    # Security: resolve flow through get_flow so image access requires authentication and owner match.
    flow: Annotated[Flow, Depends(get_flow)],

View on GitHub (pinned to 976ec789d2)

Solutions

1. Re-upload/store the file with a mapped extension (e.g. .bin or .txt) if the exact type doesn't matter
2. Upgrade langflow-base so the content-type table includes the extension
3. Patch build_content_type_from_extension's mapping to add the missing extension and restart

Example fix

# before
GET /files/download/{flow_id}/run_42.parquet  # 500: content type not found

# after
# re-upload same bytes as run_42.bin, then
GET /files/download/{flow_id}/2024-01-01_00-00-00_run_42.bin

KNOWN_EXTS = {"txt", "pdf", "csv", "png", "jpg", "jpeg", "json", "zip", "bin"}

def extension_supported(file_name: str) -> bool:
    return file_name.rsplit(".", 1)[-1].lower() in KNOWN_EXTS

try:
    client.get(f"/files/download/{flow_id}/{file_name}").raise_for_status()
except HTTPError as e:
    if "Content type not found" in e.response.text:
        client.get(f"/files/download/{flow_id}/{renamed(file_name, '.bin')}")

When it happens

Trigger: Downloading a file with an extension the server has no MIME mapping for (e.g. .foo, .custom, niche formats like .parquet on older builds); files created by components with nonstandard suffixes.

Common situations: Custom file artifacts produced by flow components; older Langflow builds with smaller MIME tables; users uploading then downloading proprietary-format files.

Related errors

• Extension not found for file {file_name}
• Content type {content_type} is not an image
• str(e)
• {str(e)}
• HTTP error! status: ${response.status}

AI-assisted analysis of langflow-ai/langflow@976ec789d2 (2026-08-14). Data as JSON: /api/errors/9a282c417274f021. Report an issue: GitHub.