CoplayDev/unity-mcp · error · ArgumentException

'output_folder' must resolve under the project's Assets fold

Error message

'output_folder' must resolve under the project's Assets folder.

What it means

StageUnderAssets validates the user-supplied output_folder via AssetGenPaths.TryGetAssetsFolder, which requires the path to resolve under the project's Assets folder. When an explicit output_folder is given and fails this check, the import is rejected rather than writing outside Assets.

Source

Thrown at MCPForUnity/Editor/Tools/AssetGen/ImportModelFile.cs:84

            }
        }

        private static string ResolveSource(string source)
        {
            string s = source.Replace('\\', '/');
            if (s == "Assets" || s.StartsWith("Assets/")) return AssetGenPaths.ToAbsolute(s);
            return s; // absolute path on disk
        }

        private static string StageUnderAssets(string srcAbs, string baseName, string ext, string outputFolder)
        {
            string root = !string.IsNullOrWhiteSpace(outputFolder)
                ? outputFolder
                : AssetGenPrefs.OutputRoot + "/Imported";
            if (!AssetGenPaths.TryGetAssetsFolder(root, out root))
            {
                if (!string.IsNullOrWhiteSpace(outputFolder))
                    throw new ArgumentException("'output_folder' must resolve under the project's Assets folder.");
                root = AssetGenPrefs.DefaultOutputRoot + "/Imported";
            }

            string absRoot = AssetGenPaths.ToAbsolute(root);
            Directory.CreateDirectory(absRoot);

            string safe = SanitizeName(baseName);
            string fileName = safe + ext;
            string abs = Path.Combine(absRoot, fileName);
            int n = 1;
            while (File.Exists(abs)) { fileName = safe + "_" + n++ + ext; abs = Path.Combine(absRoot, fileName); }

            File.Copy(srcAbs, abs);
            return (root.TrimEnd('/') + "/" + fileName).Replace('\\', '/');
        }

        private static string SanitizeName(string raw)
        {

View on GitHub (pinned to c21bf496bc)

Solutions

1. Use a path relative to Assets, e.g. 'Assets/Models/Imported' or 'Models/Imported'.
2. Omit output_folder to fall back to the default Assets-rooted output location.
3. Ensure the path does not use '..' to escape the Assets folder.

Example fix

// before
{ "output_folder": "/tmp/exports" }
// after
{ "output_folder": "Assets/Models/Imported" }

if (!string.IsNullOrWhiteSpace(outputFolder) && !AssetGenPaths.TryGetAssetsFolder(outputFolder, out _))
{
    throw new ArgumentException("'output_folder' must resolve under the project's Assets folder.");
}

When it happens

Trigger: output_folder is an absolute OS path outside the project; a relative path that escapes Assets via '..'; a path pointing at Packages/ or Library/ instead of Assets.

Common situations: User passes a full disk path expecting a general export; user wants to write outside the project; relative path crafted to traverse out of Assets.

Related errors

• uid required
• provider returned a disallowed file type '.{ext}'
• zipPath required
• Unknown model provider '{id}'.
• Unknown image provider '{id}'.

AI-assisted analysis of CoplayDev/unity-mcp@c21bf496bc (2026-08-13). Data as JSON: /api/errors/6fec0aaca349f1e6. Report an issue: GitHub.