What causes "Failed to write scorer: ${errorMessage}" in mastra-ai/mastra?

Fix write permissions on the scorers directory or existing file

Failed to write scorer: ${errorMessage}

Error message

Failed to write scorer: ${errorMessage}

What it means

`writeScorer` wraps any failure from fs.writeFileSync when saving the generated scorer file. The underlying OS error (EACCES, ENOSPC, EISDIR, etc.) is embedded in the message. The directory was created successfully but the file write itself failed.

Source

Thrown at packages/cli/src/commands/scorers/file-utils.ts:34

    } catch (error) {
      const errorMessage = error instanceof Error ? error.message : String(error);
      throw new Error(`Failed to create directory: ${errorMessage}`);
    }
  }

  const filePath = path.join(fullPath, filename);

  if (fs.existsSync(filePath)) {
    throw new Error(`Skipped: Scorer ${filename} already exists at ${scorersPath}`);
  }

  try {
    fs.writeFileSync(filePath, content);

    return { ok: true, message: `Created scorer at ${path.relative(rootDir, filePath)}` };
  } catch (error) {
    const errorMessage = error instanceof Error ? error.message : String(error);
    throw new Error(`Failed to write scorer: ${errorMessage}`);
  }
}

View on GitHub (pinned to 75dd419e61)

Solutions

Fix write permissions on the scorers directory or existing file
Check that the destination path is not a directory
Free disk space if the message includes ENOSPC
Run the command as a user with access to the project directory

Defensive patterns

Strategy: try-catch

Validate before calling

import { accessSync, constants, existsSync, statSync } from 'node:fs';
if (existsSync(target)) {
  if (!statSync(target).isFile()) throw new Error(`${target} is not a regular file`);
}
accessSync(scorersPath, constants.W_OK);

Type guard

const writableTarget = (dir: string, name: string): boolean => {
  try { accessSync(dir, constants.W_OK); return true; } catch { return false; }
};

Try / catch

try {
  await writeScorer({ ... });
} catch (e) {
  const msg = (e as Error).message;
  if (msg.startsWith('Failed to write scorer')) {
    console.error('Write failed (permissions/disk/path):', msg);
  } else throw e;
}

Prevention

Verify directory write permissions before generation
Ensure the destination filename is not a directory
Monitor disk space/quota in CI
Fix ownership of files created by other users (e.g. root)

When it happens

Trigger: fs.writeFileSync fails after the directory check — target path is read-only, path is actually a directory, out of space, or permission denied on the existing file.

Common situations: An existing scorer file is owned by root/read-only; the target filename is a directory; quota or disk-full conditions.

Related errors

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/e4a3c6a27b414b37. Report an issue: GitHub.