ComposioHQ/composio · error · ValidationError

Failed to fetch file from URL: {e.cause}

Error message

Failed to fetch file from URL: {e.cause}

What it means

Raised while uploading files by URL: _fetch_from_url tried to download the user-supplied URL and the underlying fetch failed with a network-level cause (DNS failure, TLS error, refused connection). The specific cause is embedded in the message and chained.

Source

Thrown at python/composio/core/models/tool_router_session_files.py:146

                response.close()
                raise _UrlFetchError(
                    size_detail="Response size exceeds maximum allowed size"
                )
            chunks.append(chunk)
    response.close()

    mimetype = response.headers.get("content-type", "application/octet-stream")
    mimetype = mimetype.split(";")[0].strip()
    return b"".join(chunks), mimetype


def _fetch_from_url(url: str) -> t.Tuple[bytes, str]:
    """Fetch file content from a user-supplied URL. Returns (content, mimetype)."""
    try:
        return _fetch_url_bytes(url)
    except _UrlFetchError as e:
        if e.cause is not None:
            raise ValidationError(f"Failed to fetch file from URL: {e.cause}") from e
        if e.redirected:
            raise ValidationError(
                "URL returned redirect. Please provide a direct URL to the file."
            ) from e
        if e.status_code is not None:
            raise ValidationError(
                f"Failed to fetch file from URL: {e.status_code} {e.status_text}"
            ) from e
        raise ValidationError(str(e)) from e


class RemoteFile:
    """Represents a file stored in a tool router session's file mount.

    Provides methods to fetch, save, and work with the file content.
    """

    def __init__(

View on GitHub (pinned to 64b1b85502)

Solutions

1. Verify the URL is publicly reachable (curl -I from an external host)
2. Use pre-signed public URLs (S3/GCS/Drive direct links)
3. If the file is local, upload bytes/path directly instead of by URL
4. Retry to rule out transient DNS/network issues

Example fix

# before
files.add(url='http://localhost:8000/report.pdf')

# after
with open('report.pdf','rb') as f:
    files.add(content=f.read(), filename='report.pdf')

from urllib.parse import urlparse
u = urlparse(url)
assert u.scheme in ('http','https') and u.netloc, 'bad URL'

try:
    files.add(url=url)
except ValidationError as e:
    # fall back to direct upload
    files.add(path=local_copy)

When it happens

Trigger: Passing a url=... input to the session file upload API where the host is unreachable, DNS doesn't resolve, or a proxy blocks the egress request from the Composio backend.

Common situations: Internal/localhost URLs not reachable from the internet, corporate proxies, transient DNS failures, typos in the hostname.

Related errors

• URL returned redirect. Please provide a direct URL to the fi
• Failed to fetch file from URL: {e.status_code} {e.status_tex
• Failed to download file: {message} (status_code, status_text
• File upload was aborted because before_file_upload returned
• File not found: {file}. Please provide a valid file path.

AI-assisted analysis of ComposioHQ/composio@64b1b85502 (2026-08-28). Data as JSON: /api/errors/410b08261f587f76. Report an issue: GitHub.