What causes "streamObjectService requires a schema parameter" in eyaltoledano/claude-task-master?

Pass a schema: streamObjectService({ ..., schema: myZodObject }).

streamObjectService requires a schema parameter

Error message

streamObjectService requires a schema parameter

What it means

A synchronous argument-validation error thrown at the top of streamObjectService. Streaming structured objects requires a Zod/JSON schema to validate and shape each streamed output, so calling without one is rejected before any client or API call is made.

Source

Thrown at scripts/modules/ai-services-unified.js:847

 * Uses Vercel AI SDK's streamObject for proper JSON streaming.
 *
 * @param {object} params - Parameters for the service call.
 * @param {string} params.role - The initial client role ('main', 'research', 'fallback').
 * @param {object} [params.session=null] - Optional MCP session object.
 * @param {string} [params.projectRoot=null] - Optional project root path for .env fallback.
 * @param {import('zod').ZodSchema} params.schema - The Zod schema for the expected object.
 * @param {string} params.prompt - The prompt for the AI.
 * @param {string} [params.systemPrompt] - Optional system prompt.
 * @param {string} params.commandName - Name of the command invoking the service.
 * @param {string} [params.outputType='cli'] - 'cli' or 'mcp'.
 * @returns {Promise<object>} Result object containing the stream and usage data.
 */
async function streamObjectService(params) {
	const defaults = { outputType: 'cli' };
	const combinedParams = { ...defaults, ...params };
	// Stream object requires a schema
	if (!combinedParams.schema) {
		throw new Error('streamObjectService requires a schema parameter');
	}
	return _unifiedServiceRunner('streamObject', combinedParams);
}

/**
 * Unified service function for generating structured objects.
 * Handles client retrieval, retries, and fallback sequence.
 *
 * @param {object} params - Parameters for the service call.
 * @param {string} params.role - The initial client role ('main', 'research', 'fallback').
 * @param {object} [params.session=null] - Optional MCP session object.
 * @param {string} [params.projectRoot=null] - Optional project root path for .env fallback.
 * @param {import('zod').ZodSchema} params.schema - The Zod schema for the expected object.
 * @param {string} params.prompt - The prompt for the AI.
 * @param {string} [params.systemPrompt] - Optional system prompt.
 * @param {string} [params.objectName='generated_object'] - Name for object/tool.
 * @param {number} [params.maxRetries=3] - Max retries for object generation.
 * @param {string} params.commandName - Name of the command invoking the service.

View on GitHub (pinned to c0c98d367c)

Solutions

Pass a schema: streamObjectService({ ..., schema: myZodObject }).
Ensure the schema import is defined (not undefined) before the call.
If you don't need structured output, use streamTextService instead.
Wrap schema construction so defaults exist for the streaming path.

Example fix

// before
await streamObjectService({ role: 'main', prompt });
// after
await streamObjectService({ role: 'main', prompt, schema: TaskSchema });

Defensive patterns

Strategy: validation

Validate before calling

function assertSchema(schema) {
  if (schema == null) throw new TypeError('streamObjectService: schema is required');
  const isZod = typeof schema === 'object' && typeof schema.parse === 'function' && typeof schema.safeParse === 'function';
  if (!isZod) throw new TypeError('streamObjectService: schema must be a Zod schema');
}
assertSchema(schema);

Type guard

function isZodSchema(s) {
  return s != null && typeof s === 'object' && typeof s.safeParse === 'function';
}

Try / catch

if (!isZodSchema(schema)) {
  throw new TypeError('A Zod schema is required before calling streamObjectService');
}
try {
  await streamObjectService({ role: 'main', prompt, schema });
} catch (e) {
  if (e.message.includes('requires a schema parameter')) return streamTextService({ role: 'main', prompt });
  throw e;
}

Prevention

Always co-locate the schema with the streaming call in a single object literal.
Type helpers so schema is a required parameter, catching omissions at compile time.
Don't conditionally build params objects that can omit schema.

When it happens

Trigger: Calling streamObjectService({ ... }) where params omits the schema property — e.g. copying a generateTextService call and only renaming the function, or building params dynamically where schema is conditionally undefined.

Common situations: Refactoring from generateTextService to streaming without migrating the schema, passing a schema variable that is undefined due to a failed import or typo, or building a generic AI helper that only sometimes supplies a schema.

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

AI-assisted analysis of eyaltoledano/claude-task-master@c0c98d367c (2026-08-29). Data as JSON: /api/errors/4497576fc2ec37a9. Report an issue: GitHub.