eyaltoledano/claude-task-master · error

Prompt cannot be empty unless metadata is provided for updat

Error message

Prompt cannot be empty unless metadata is provided for update.

What it means

updateTaskById() requires a non-empty prompt string unless a metadata object is supplied. This allows metadata-only updates while rejecting calls that would give the AI nothing to act on. The error fires when both prompt is empty/not a string and metadata is absent.

Source

Thrown at scripts/modules/task-manager/update-task-by-id.js:84

		metadata
	} = context;
	const { report, isMCP } = createBridgeLogger(mcpLog, session);

	try {
		report('info', `Updating single task ${taskId} with prompt: "${prompt}"`);

		// --- Input Validations ---
		// Note: taskId can be a number (1), string with dot (1.2), or display ID (HAM-123)
		// So we don't validate it as strictly anymore
		if (taskId === null || taskId === undefined || String(taskId).trim() === '')
			throw new Error('Task ID cannot be empty.');

		// Allow metadata-only updates (prompt can be empty if metadata is provided)
		if (
			(!prompt || typeof prompt !== 'string' || prompt.trim() === '') &&
			!metadata
		) {
			throw new Error(
				'Prompt cannot be empty unless metadata is provided for update.'
			);
		}

		// Determine project root first (needed for API key checks)
		const projectRoot = providedProjectRoot || findProjectRoot();
		if (!projectRoot) {
			throw new Error('Could not determine project root directory');
		}

		if (useResearch && !isApiKeySet('perplexity', session)) {
			report(
				'warn',
				'Perplexity research requested but API key not set. Falling back.'
			);
			if (outputFormat === 'text')
				console.log(
					chalk.yellow('Perplexity AI not available. Falling back to main AI.')

View on GitHub (pinned to c0c98d367c)

Solutions

1. Provide a non-empty prompt string describing the update
2. If you only want to change metadata, pass a metadata object instead of a prompt
3. Validate/trim user-supplied prompt text before calling

Example fix

// before
await updateTaskById(5, ''); // throws
// after
await updateTaskById(5, '', { priority: 'high' }); // metadata-only update
// or
await updateTaskById(5, 'Add error handling to the parser');

function assertUpdateInput(prompt, metadata) {
  const hasPrompt = typeof prompt === 'string' && prompt.trim() !== '';
  const hasMetadata = metadata !== null && metadata !== undefined;
  if (!hasPrompt && !hasMetadata) {
    throw new Error('Provide a prompt or metadata for the update');
  }
}

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

try {
  await updateTaskById(5, prompt, metadata);
} catch (err) {
  if (err.message.includes('Prompt cannot be empty')) {
    console.error('Pass a non-empty prompt, or a metadata object for metadata-only updates');
  } else throw err;
}

When it happens

Trigger: Calling updateTaskById(5, '') or updateTaskById(5, ' ') with no metadata argument; calling updateTaskById(5) relying on defaults; passing a non-string (e.g., an object) as prompt without metadata.

Common situations: Forgetting to pass the update instructions when scripting; whitespace-only prompt from trimmed user input; intending a metadata-only update but forgetting to pass the metadata object.

Understand the failure class

Background: Missing required parameter errors: what 'X is required' and 'the required X param is missing' mean, and how to fix them — this error's family across 27 libraries.

Related errors

• Task ID cannot be empty.
• Task description is required
• Task status is required
• No valid task IDs provided
• Invalid task ID format: ${invalidIds.join(', ')}. Expected n

AI-assisted analysis of eyaltoledano/claude-task-master@c0c98d367c (2026-08-29). Data as JSON: /api/errors/8fce60938da0be89. Report an issue: GitHub.