eyaltoledano/claude-task-master · error · Error

New tag name can only contain letters, numbers, hyphens, and

Error message

New tag name can only contain letters, numbers, hyphens, and underscores

What it means

New tag names must match /^[a-zA-Z0-9_-]+$/ — only letters, digits, hyphens, and underscores. This error is thrown when the supplied newName contains other characters such as spaces, slashes, dots, or unicode, because tags are used as object keys in tasks.json and must stay filesystem/JSON safe.

Source

Thrown at scripts/modules/task-manager/tag-management.js:967

		info: (...args) => log('info', ...args),
		warn: (...args) => log('warn', ...args),
		error: (...args) => log('error', ...args),
		debug: (...args) => log('debug', ...args),
		success: (...args) => log('success', ...args)
	};

	try {
		// Validate parameters
		if (!oldName || typeof oldName !== 'string') {
			throw new Error('Old tag name is required and must be a string');
		}
		if (!newName || typeof newName !== 'string') {
			throw new Error('New tag name is required and must be a string');
		}

		// Validate new tag name format
		if (!/^[a-zA-Z0-9_-]+$/.test(newName)) {
			throw new Error(
				'New tag name can only contain letters, numbers, hyphens, and underscores'
			);
		}

		// Prevent renaming master tag
		if (oldName === 'master') {
			throw new Error('Cannot rename the "master" tag');
		}

		// Reserved tag names
		const reservedNames = ['master', 'main', 'default'];
		if (reservedNames.includes(newName.toLowerCase())) {
			throw new Error(`"${newName}" is a reserved tag name`);
		}

		logFn.info(`Renaming tag from "${oldName}" to "${newName}"`);

		// Read current tasks data

View on GitHub (pinned to c0c98d367c)

Solutions

1. Rewrite the tag name using only letters, numbers, hyphens, and underscores (e.g. 'feature-auth' instead of 'feature/auth')
2. Sanitize/replace invalid characters before calling: newName.replace(/[^a-zA-Z0-9_-]/g, '-')
3. Trim whitespace from user input and re-prompt if the result is empty

Example fix

// before
await renameTag(tasksPath, 'dev', 'release 1.0');
// after
await renameTag(tasksPath, 'dev', 'release-1-0');

const TAG_NAME_RE = /^[a-zA-Z0-9_-]+$/;
if (!TAG_NAME_RE.test(newName)) {
  throw new Error(`Invalid tag name "${newName}": use only letters, numbers, hyphens, underscores`);
}

function isValidTagName(name) {
  return typeof name === 'string' && /^[a-zA-Z0-9_-]+$/.test(name);
}

try {
  await renameTag(tasksPath, oldName, newName);
} catch (err) {
  if (err.message.includes('can only contain letters, numbers, hyphens')) {
    const sanitized = newName.trim().replace(/[^a-zA-Z0-9_-]/g, '-');
    return renameTag(tasksPath, oldName, sanitized);
  }
  throw err;
}

When it happens

Trigger: Calling renameTag with newName containing spaces ('my tag'), slashes ('feat/x'), dots ('v1.0'), special characters ('tag!'), or empty-after-trim values like whitespace-only strings.

Common situations: Users typing tag names with spaces or path-like separators in the CLI; deriving tag names from branch names like 'feature/auth-refactor' (slash) or versions like '1.2.0' (dots); copy-pasting names with trailing whitespace.

Related errors

• "${newName}" is a reserved tag name
• MFA_VERIFICATION_FAILED
• Failed to initialize services: ${(error as Error).message}
• Invalid format: ${options.format}. Valid formats are: text,
• Failed to fetch tasks from any tag. First error: ${failedTag

AI-assisted analysis of eyaltoledano/claude-task-master@c0c98d367c (2026-08-29). Data as JSON: /api/errors/ab42874838ba4217. Report an issue: GitHub.