eyaltoledano/claude-task-master · error

Prompt cannot be empty unless metadata is provided. Please p

Error message

Prompt cannot be empty unless metadata is provided. Please provide context for the subtask update or metadata to merge.

What it means

The update prompt may be omitted only when a metadata object is supplied for a metadata-only merge. If both prompt and metadata are missing/empty, this error is thrown.

Source

Thrown at scripts/modules/task-manager/update-subtask-by-id.js:85

			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
		// So update-subtask and update-task work identically
		const remoteResult = await tryUpdateViaRemote({
			taskId: subtaskId,
			prompt,
			projectRoot,
			tag,
			appendMode: true, // Subtask updates are always append mode

View on GitHub (pinned to c0c98d367c)

Solutions

1. Provide a non-empty prompt describing the update
2. Pass a metadata object instead if you only want field merges
3. Ensure the prompt string is not just whitespace; trim and check length before calling

Example fix

// before
await updateSubtaskById('5.2', '   ', options); // blank prompt, no metadata
// after
const prompt = buildPrompt();
await updateSubtaskById('5.2', prompt.trim() ? prompt : null, { ...options, metadata: { notes: 'sync fields' } });

if ((!prompt || typeof prompt !== 'string' || prompt.trim() === '') && !metadata) {
  throw new Error('Provide a non-empty prompt or a metadata object');
}

function hasUpdateInput(prompt, metadata) {
  return (typeof prompt === 'string' && prompt.trim() !== '') || (metadata !== null && typeof metadata === 'object');
}

try {
  await updateSubtaskById(subtaskId, prompt, options);
} catch (err) {
  if (err.message.startsWith('Prompt cannot be empty')) {
    console.error('Supply a prompt or pass metadata for a metadata-only update');
  } else throw err;
}

When it happens

Trigger: Calling updateSubtaskById with an empty/whitespace prompt and no metadata; MCP clients sending only the subtaskId.

Common situations: Automations that send an empty prompt, users invoking the CLI update-subtask command without a prompt argument while expecting defaults.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• Test results required for GREEN phase transition
• MISSING_ARGUMENT
• INPUT_VALIDATION_ERROR
• MISSING_ARGUMENT
• INPUT_VALIDATION_ERROR

AI-assisted analysis of eyaltoledano/claude-task-master@c0c98d367c (2026-08-29). Data as JSON: /api/errors/6f63b333f3794256. Report an issue: GitHub.