langchain-ai/langchain · error · ValueError

OpenAI Chat Completions does not support file URLs.

Error message

OpenAI Chat Completions does not support file URLs.

What it means

Raised when a file content block with a `url` key is formatted for the OpenAI Chat Completions API (`api="chat/completions"`). Chat Completions has no `file_url` input field — remote file URLs are only accepted by the newer Responses API, so the converter refuses rather than sending a request OpenAI would reject.

Source

Thrown at libs/core/langchain_core/messages/block_translators/openai.py:129

                    " in the content block, e.g.: {'type': 'file', 'mime_type': "
                    "'...', 'base64': '...', 'filename': 'my-file.pdf'}. "
                    "Using placeholder filename 'LC_AUTOGENERATED'.",
                    stacklevel=1,
                )
            formatted_block = {"type": "file", "file": file}
            if api == "responses":
                formatted_block = {"type": "input_file", **formatted_block["file"]}
        elif block.get("source_type") == "id" or "file_id" in block:
            # Handle v0 format (IDContentBlock): {"source_type": "id", "id": "...", ...}
            # Handle v1 format (IDCB): {"file_id": "...", ...}
            file_id = block["id"] if "source_type" in block else block["file_id"]
            formatted_block = {"type": "file", "file": {"file_id": file_id}}
            if api == "responses":
                formatted_block = {"type": "input_file", **formatted_block["file"]}
        elif "url" in block:  # Intentionally do not check for source_type="url"
            if api == "chat/completions":
                error_msg = "OpenAI Chat Completions does not support file URLs."
                raise ValueError(error_msg)
            # Only supported by Responses API; return in that format
            formatted_block = {"type": "input_file", "file_url": block["url"]}
        else:
            error_msg = "Keys base64, url, or file_id required for file blocks."
            raise ValueError(error_msg)

    elif block["type"] == "audio":
        if "base64" in block or block.get("source_type") == "base64":
            # Handle v0 format: {"source_type": "base64", "data": "...", ...}
            # Handle v1 format: {"base64": "...", ...}
            base64_data = block["data"] if "source_type" in block else block["base64"]
            audio_format = block["mime_type"].split("/")[-1]
            formatted_block = {
                "type": "input_audio",
                "input_audio": {"data": base64_data, "format": audio_format},
            }
        else:
            error_msg = "Key base64 is required for audio blocks."

View on GitHub (pinned to e32fa9a52e)

Solutions

1. Switch to a Responses-API model binding so the URL is emitted as `input_file.file_url`
2. Or download the file and send it as base64 with `mime_type` (e.g. `application/pdf`) on Chat Completions
3. Or upload the file to OpenAI and reference it by `file_id` instead of URL

Example fix

# before
block = {"type": "file", "url": "https://example.com/doc.pdf"}
resp = chat_model.invoke([HumanMessage(content=[block])])  # Chat Completions -> ValueError

# after
import base64
b64 = base64.b64encode(requests.get(url).content).decode()
block = {"type": "file", "base64": b64, "mime_type": "application/pdf"}

def file_url_allowed(block: dict, api: str) -> bool:
    if block.get("type") == "file" and "url" in block:
        return api == "responses"
    return True

try:
    out = convert_to_openai_data_block(block, api="chat/completions")
except ValueError as e:
    if "does not support file URLs" in str(e):
        out = convert_to_openai_data_block(download_to_b64(block), api="chat/completions")
    else:
        raise

When it happens

Trigger: Sending a file block like `{"type": "file", "url": "https://..."}` through a Chat Completions model or calling `convert_to_openai_data_block(block, api="chat/completions")` on it.

Common situations: Switching an app between Responses and Chat Completions model bindings while keeping file-URL blocks; assuming the two OpenAI APIs share the same multimodal input schema; PDFs hosted on a CDN passed to `gpt-4o`-style chat models.

Related errors

• Keys base64, url, or file_id required for file blocks.
• mime_type key is required for base64 data.
• Unsupported source type. Only 'url' and 'base64' are support
• Key base64 is required for audio blocks.
• Block of type {block['type']} is not supported.

AI-assisted analysis of langchain-ai/langchain@e32fa9a52e (2026-08-14). Data as JSON: /api/errors/0753382c58453b76. Report an issue: GitHub.