eyaltoledano/claude-task-master · error

Prompt cannot be empty or only whitespace

Error message

Prompt cannot be empty or only whitespace

What it means

validatePrompt() rejects prompts that are strings but contain only whitespace (or nothing after trim), because sending an all-whitespace prompt to an LLM is always a caller bug. It fires after the non-string/null check in the same method.

Source

Thrown at packages/tm-core/src/modules/ai/interfaces/ai-provider.interface.ts:420

			timeout: 30000,
			retries: 3,
			...this.config.defaultOptions,
			...userOptions
		};
	}

	/**
	 * Validate prompt input
	 * @param prompt - Prompt to validate
	 * @throws Error if prompt is invalid
	 */
	protected validatePrompt(prompt: string): void {
		if (!prompt || typeof prompt !== 'string') {
			throw new Error('Prompt must be a non-empty string');
		}

		if (prompt.trim().length === 0) {
			throw new Error('Prompt cannot be empty or only whitespace');
		}
	}
}

View on GitHub (pinned to c0c98d367c)

Solutions

1. Check prompt.trim().length > 0 before calling the provider
2. Fix the template/interpolation that produced a whitespace-only prompt
3. Provide a fallback or reject the request upstream when the assembled prompt is empty

Example fix

// before
const prompt = `Summarize: ${context}`; // context was ''
await provider.generateCompletion(prompt);
// after
const prompt = `Summarize: ${context}`;
if (!prompt.trim()) throw new Error('Cannot generate: empty prompt');
await provider.generateCompletion(prompt);

const trimmed = typeof prompt === 'string' ? prompt.trim() : '';
if (!trimmed) throw new Error('Prompt is empty after trimming — check template variables');

function hasContent(p: unknown): p is string {
  return typeof p === 'string' && p.trim().length > 0;
}

try {
  return await provider.generateCompletion(prompt);
} catch (err) {
  if (err.message.includes('empty or only whitespace')) {
    console.error('Prompt was:', JSON.stringify(prompt));
    throw new Error('Refusing to send empty prompt');
  }
  throw err;
}

When it happens

Trigger: generateCompletion(' '); generateCompletion('\n\t') from template strings whose interpolated variables were empty; prompts built by joining empty fragments.

Common situations: Prompt templates where every ${var} expanded to empty (missing context, failed retrieval); copy-paste artifacts that are just spaces; trimming logic upstream that emptied the prompt before the call.

Related errors

• Prompt must be a non-empty string
• Model "${model}" is not available for provider "${this.getNa
• AUTHENTICATION_ERROR
• VALIDATION_ERROR
• ${this.getName()} provider error: ${errorMessage}

AI-assisted analysis of eyaltoledano/claude-task-master@c0c98d367c (2026-08-29). Data as JSON: /api/errors/b53dbb3baa2e0bb9. Report an issue: GitHub.