eyaltoledano/claude-task-master · error

Subtask ID cannot be empty.

Error message

Subtask ID cannot be empty.

What it means

updateSubtaskById requires the subtaskId argument to be a non-empty string before doing any work. The error is the first validation gate in the function.

Source

Thrown at scripts/modules/task-manager/update-subtask-by-id.js:78

	// Report helper
	const report = (level, ...args) => {
		if (isMCP) {
			if (typeof logFn[level] === 'function') logFn[level](...args);
			else logFn.info(...args);
		} else if (!isSilentMode()) {
			logFn(level, ...args);
		}
	};

	let loadingIndicator = null;

	try {
		report('info', `Updating subtask ${subtaskId} with prompt: "${prompt}"`);

		// Basic validation - ID must be present
		if (!subtaskId || typeof subtaskId !== 'string') {
			throw new Error('Subtask ID cannot be empty.');
		}
		// Allow metadata-only updates (no prompt required if metadata is provided)
		if (
			(!prompt || typeof prompt !== 'string' || prompt.trim() === '') &&
			!metadata
		) {
			throw new Error(
				'Prompt cannot be empty unless metadata is provided. Please provide context for the subtask update or metadata to merge.'
			);
		}

		const projectRoot = providedProjectRoot || findProjectRoot();
		if (!projectRoot) {
			throw new Error('Could not determine project root directory');
		}

		// --- BRIDGE: Try remote update first (API storage) ---
		// In API storage, subtask IDs like "HAM-2611" are just regular task IDs

View on GitHub (pinned to c0c98d367c)

Solutions

1. Pass subtaskId as a non-empty string, e.g. '5.2' or 'HAM-2611'
2. Convert numeric IDs with String(id) before calling
3. Check the MCP tool call payload includes the subtaskId field

Example fix

// before
await updateSubtaskById(2, 'add tests', options); // number, not string
// after
await updateSubtaskById(String('5.2'), 'add tests', options);

if (!subtaskId || typeof subtaskId !== 'string' || subtaskId.trim() === '') {
  throw new Error('subtaskId must be a non-empty string');
}

function isValidSubtaskId(v) {
  return typeof v === 'string' && v.trim().length > 0;
}

try {
  await updateSubtaskById(subtaskId, prompt, options);
} catch (err) {
  if (err.message === 'Subtask ID cannot be empty.') {
    console.error('Pass subtaskId as a non-empty string like "5.2"');
  } else throw err;
}

When it happens

Trigger: Calling the MCP update-subtask tool or direct API with subtaskId undefined, null, an empty string, or a non-string value like a number.

Common situations: MCP clients omitting the subtaskId parameter, programmatic callers passing a numeric ID instead of a string, or prompt templating leaving a placeholder blank.

Related errors

• Manual task data must include at least a title and descripti
• Invalid message format. Each message must have role and cont
• INPUT_VALIDATION_ERROR
• INPUT_VALIDATION_ERROR
• INPUT_VALIDATION_ERROR

AI-assisted analysis of eyaltoledano/claude-task-master@c0c98d367c (2026-08-29). Data as JSON: /api/errors/c1f87ade196980cf. Report an issue: GitHub.