What causes "File too large" in langflow-ai/langflow?

Read the file in slices if the API offers range/offset parameters; otherwise use a different transfer path (e.g. the storage service) for large files.

langflow-ai/langflow · warning · HTTPException

File too large

Error message

File too large

What it means

The agentic file router enforces MAX_FILE_SIZE_BYTES (imported from lfx's FileSystemToolComponent). If stat reports a size above the cap, it raises HTTP 413 'File too large' before reading any content, protecting the API from oversized payloads.

Source

Thrown at src/backend/base/langflow/agentic/api/files_router.py:167

        raise HTTPException(status_code=404, detail="Not found") from None

    if not resolved.exists() or resolved.is_dir():
        logger.warning(
            "agentic.files.read.missing user_id=%s path=%s resolved=%s exists=%s is_dir=%s",
            current_user.id,
            path,
            resolved,
            resolved.exists(),
            resolved.is_dir(),
        )
        raise HTTPException(status_code=404, detail="Not found")

    try:
        size = resolved.stat().st_size
    except OSError:
        raise HTTPException(status_code=404, detail="Not found") from None
    if size > MAX_FILE_SIZE_BYTES:
        raise HTTPException(status_code=413, detail="File too large")

    # Binary sniff before the full read — same heuristic the FS tool uses.
    try:
        head = _read_head_no_follow(resolved, BINARY_SNIFF_BYTES)
    except (OSError, PermissionError):
        raise HTTPException(status_code=404, detail="Not found") from None
    if _looks_binary(head):
        raise HTTPException(status_code=415, detail="Binary content not supported")

    try:
        body_bytes = _read_bytes_no_follow(resolved)
    except (OSError, PermissionError):
        raise HTTPException(status_code=404, detail="Not found") from None

    # Audit log — relative path only, never the absolute sandbox-resolved path.
    logger.info(
        "agentic.files.read user_id=%s path=%s size=%d download=%s",
        current_user.id,

View on GitHub (pinned to 976ec789d2)

Solutions

Read the file in slices if the API offers range/offset parameters; otherwise use a different transfer path (e.g. the storage service) for large files.
Trim or split the file in the sandbox before reading (via the agent's FS tools).
If you operate the deployment and genuinely need bigger reads, raise the FileSystemToolComponent size limit — do not bypass the check.

Defensive patterns

Strategy: validation

Validate before calling

MAX = 10 * 1024 * 1024  # mirror the deployed MAX_FILE_SIZE_BYTES
import os
if os.path.getsize(sandbox_path) > MAX:
    use_bulk_transfer_instead(sandbox_path)

Try / catch

if resp.status_code == 413:
    split_or_stream_via_storage_service(path)  # never blind-retry

Prevention

Keep sandbox artifacts small; route large files through the storage service.
Have agents write summaries/trims rather than full datasets.
Know the deployed MAX_FILE_SIZE_BYTES before serving files from sandboxes.

When it happens

Trigger: GET /api/v1/agentic/files on a sandbox file larger than MAX_FILE_SIZE_BYTES (e.g. a dataset, log, or binary the agent saved).

Common situations: Agent writes large tool output into the sandbox; user drops a big CSV/log and tries to preview it through the endpoint.

Related errors

AI-assisted analysis of langflow-ai/langflow@976ec789d2 (2026-08-14). Data as JSON: /api/errors/bd14fac2a4b638b8. Report an issue: GitHub.