langflow-ai/langflow · warning · Error

File type ${fileExtension} not allowed. Allowed types: ${typ

Error message

File type ${fileExtension} not allowed. Allowed types: ${types?.join(", ")}

What it means

400 returned when the config path resolved for the requested client exists in the schema but its parent directory does not — i.e. that editor has never been installed/started on this machine. The message names the client and asks to install it first.

Source

Thrown at src/frontend/src/hooks/files/use-upload-file.ts:66

        validFiles = filesToUpload.filter((file) => {
          const fileExtension = file.name.split(".").pop()?.toLowerCase();
          return fileExtension && types.includes(fileExtension);
        });

        if (validFiles.length === 0) {
          throw new Error(
            `No supported files found in folder. Allowed types: ${types?.join(", ")}`,
          );
        }
      }

      for (const file of validFiles) {
        validateFileSize(file);
        // Check if file extension is allowed (for non-folder selection)
        if (!webkitdirectory) {
          const fileExtension = file.name.split(".").pop()?.toLowerCase();
          if (!fileExtension || (types && !types.includes(fileExtension))) {
            throw new Error(
              `File type ${fileExtension} not allowed. Allowed types: ${types?.join(", ")}`,
            );
          }
          if (!multiple && filesToUpload.length !== 1) {
            throw new Error("Multiple files are not allowed");
          }
        }

        const res = await uploadFileMutation({
          file,
        });

        if (!webkitdirectory && res?.path) {
          const existing = getRelativePathForServerPath(res.path);
          if (existing && existing.includes("/")) {
            const flatName = String(res.path).split("/").filter(Boolean).pop();
            setRelativePathForServerPath(
              res.path,

View on GitHub (pinned to 976ec789d2)

Solutions

Launch the target editor at least once so it creates its config directory, then retry install.
Verify the expected path exists (e.g. ~/.cursor/mcp.json parent, %APPDATA%/Claude).
If running Langflow in docker, remember /install writes files inside the container — run the install from a Langflow on the same host/user as the editor.

Defensive patterns

Strategy: validation

Validate before calling

from pathlib import Path
config_parents = {"cursor": Path.home() / ".cursor", "claude": Path.home() / "Library/Application Support/Claude"}
if not config_parents.get(client, Path(".")).exists():
    print("Launch the editor once so it creates its config dir, then retry")

Try / catch

except httpx.HTTPStatusError as e:
    if e.response.status_code == 400 and "not installed" in e.response.json().get("detail", ""):
        prompt_user_to_launch_editor()

Prevention

Open the target editor once before using one-click install.
Run Langflow under the same OS user as the editor so home-dir checks match.

When it happens

Trigger: POST /{project_id}/install with client='claude' on Windows where %APPDATA%\Claude is absent, or client='cursor' with ~/.cursor never created because Cursor was never run.

Common situations: User has Cursor installed but has never opened it (it creates ~/.cursor on first run); installing Claude config on a machine that only has Claude in the browser; wrong user account/home dir in a container.

Related errors

AI-assisted analysis of langflow-ai/langflow@976ec789d2 (2026-08-14). Data as JSON: /api/errors/3800fea8c938d869. Report an issue: GitHub.