CoplayDev/unity-mcp · error · Exception

provider returned a disallowed file type '.{ext}'

Error message

provider returned a disallowed file type '.{ext}'

What it means

WriteFile checks the provider-returned file extension against a per-kind allowlist (image/model/marketplace), defaulting to NoAllowedExtensions (fail-closed) for any unknown kind. A disallowed extension throws a generic Exception. This is a security gate preventing unexpected or executable content from landing under Assets/.

Source

Thrown at MCPForUnity/Editor/Services/AssetGen/AssetGenJobManager.cs:484

        private static HashSet<string> AllowedExtensionsFor(string kind)
        {
            switch ((kind ?? string.Empty).ToLowerInvariant())
            {
                case "audio": return AudioAllowedExtensions;
                case "image": return ImageAllowedExtensions;
                case "model":
                case "marketplace": return ModelAllowedExtensions;
                default: return NoAllowedExtensions; // fail closed for unexpected kinds
            }
        }

        private static string WriteFile(Runner r, byte[] bytes)
        {
            string chosen = !string.IsNullOrEmpty(r.OverrideExt) ? r.OverrideExt : r.Ext;
            string ext = string.IsNullOrEmpty(chosen) ? "bin" : chosen.TrimStart('.').ToLowerInvariant();
            if (!IsAllowedResultExtension(r.Job.Kind, ext))
                throw new Exception($"provider returned a disallowed file type '.{ext}'");
            string requestedRoot = !string.IsNullOrEmpty(r.OutputFolder) ? r.OutputFolder
                                                                         : (AssetGenPrefs.OutputRoot + "/" + r.Subfolder);
            if (!AssetGenPaths.TryGetAssetsFolder(requestedRoot, out string root))
                root = AssetGenPrefs.DefaultOutputRoot + "/" + r.Subfolder;
            string absRoot = AssetGenPaths.ToAbsolute(root);
            Directory.CreateDirectory(absRoot);
            string baseName = SanitizeName(r.Name);
            string fileName = baseName + "." + ext;
            string abs = Path.Combine(absRoot, fileName);
            int n = 1;
            while (File.Exists(abs)) { fileName = baseName + "_" + n++ + "." + ext; abs = Path.Combine(absRoot, fileName); }
            File.WriteAllBytes(abs, bytes);
            return (root.TrimEnd('/') + "/" + fileName).Replace('\\', '/');
        }

        private static string NameFrom(string explicitName, string prompt, string jobId)
        {
            if (!string.IsNullOrWhiteSpace(explicitName)) return explicitName;

View on GitHub (pinned to c21bf496bc)

Solutions

1. Confirm the provider legitimately returns that type and, if safe, add it to the relevant AllowedExtensions list for the kind.
2. Verify OverrideExt/Ext on the Runner is set to an allowed extension for the job kind.
3. For any new job kind, register an explicit allowlist rather than relying on the fail-closed default in production.

// Before writing, confirm the resolved extension is allowlisted for the job kind.
string ext = (r.OverrideExt ?? r.Ext ?? "bin").TrimStart('.').ToLowerInvariant();
if (!AssetGenJob.IsAllowedResultExtension(r.Job.Kind, ext))
    throw new InvalidOperationException($"Provider ext '.{ext}' is not allowed for kind '{r.Job.Kind}'.");

try { AssetGenJob.WriteFile(runner, bytes); }
catch (Exception ex) when (ex.Message.Contains("disallowed file type"))
{
    // Either the provider misbehaved or the allowlist needs updating for a safe new format.
    Log.Warn(ex.Message);
    throw;
}

When it happens

Trigger: A provider returns a file type not in the kind's allowlist (e.g. a model job returning .exe or .zip when only model formats are allowed); an unknown job kind with no allowlist entry; OverrideExt or Ext on the Runner mis-set to a disallowed value.

Common situations: A provider API change returning a new format not yet allowlisted; a misconfigured ext override in tests; a new job kind registered without an allowlist entry, hitting the fail-closed default.

Related errors

• uid required
• zipPath required
• Unsafe zip entry rejected: {name}
• Unsafe zip entry escapes destination: {name}
• Unknown model provider '{id}'.

AI-assisted analysis of CoplayDev/unity-mcp@c21bf496bc (2026-08-13). Data as JSON: /api/errors/f70532455d652760. Report an issue: GitHub.