What causes "AI service did not return a valid task object." in eyaltoledano/claude-task-master?

Retry generation, optionally with a more schema-compliant model, since this is usually malformed model output.

AI service did not return a valid task object.

Error message

AI service did not return a valid task object.

What it means

Even when the AI service responds with a mainResult, addTask() requires the unwrapped object (mainResult itself, or mainResult.object) to contain title and description fields, since that object becomes taskData. If neither location yields a valid task object, it throws rather than persisting a broken task.

Source

Thrown at scripts/modules/task-manager/add-task.js:461

					throw new Error(
						'AI service did not return the expected object structure.'
					);
				}

				// Prefer mainResult if it looks like a valid task object, otherwise try mainResult.object
				if (
					aiServiceResponse.mainResult.title &&
					aiServiceResponse.mainResult.description
				) {
					taskData = aiServiceResponse.mainResult;
				} else if (
					aiServiceResponse.mainResult.object &&
					aiServiceResponse.mainResult.object.title &&
					aiServiceResponse.mainResult.object.description
				) {
					taskData = aiServiceResponse.mainResult.object;
				} else {
					throw new Error('AI service did not return a valid task object.');
				}

				report('Successfully generated task data from AI.', 'success');

				// Success! Show checkmark
				if (loadingIndicator) {
					succeedLoadingIndicator(
						loadingIndicator,
						'Task generated successfully'
					);
					loadingIndicator = null; // Clear it
				}
			} catch (error) {
				// Failure! Show X
				if (loadingIndicator) {
					failLoadingIndicator(loadingIndicator, 'AI generation failed');
					loadingIndicator = null;
				}

View on GitHub (pinned to c0c98d367c)

Solutions

Retry generation, optionally with a more schema-compliant model, since this is usually malformed model output.
Check the zod task schema in generateObjectService — ensure it requires title and description so invalid output is rejected/retried upstream.
Fall back to manual add-task with explicit title and description arguments.

Example fix

// before
const data = await generateObjectService(...); // schema allows optional title
// after
const data = await generateObjectService(...); // schema: z.object({ title: z.string().min(1), description: z.string().min(1) })

Defensive patterns

Strategy: type-guard

Type guard

function isValidTaskObject(res) {
  const o = res?.mainResult?.object ?? res?.mainResult;
  return !!o && typeof o === 'object' && typeof o.title === 'string' && o.title.length > 0 && typeof o.description === 'string' && o.description.length > 0;
}

Try / catch

try {
  await addTask(tasksPath, { prompt });
} catch (err) {
  if (err.message.includes('did not return a valid task object')) {
    // retry once, then fall back to manual entry
    await addTask(tasksPath, { taskData: { title: manualTitle, description: manualDescription } });
  } else throw err;
}

Prevention

Use models known to follow JSON schemas for task generation.
Enforce strict zod schemas (title/description required) in the generation service.
Retry generation automatically on schema mismatch before giving up.

When it happens

Trigger: generateObjectService returns { mainResult } but mainResult lacks title/description (e.g. it's an array, a validation-error stub, or the object is nested under a different key not named 'object').

Common situations: Model output that fails zod schema validation and is returned partially; provider returning a different schema after a model change; using a model that ignores the requested JSON schema and returns prose or a wrapped envelope.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

AI-assisted analysis of eyaltoledano/claude-task-master@c0c98d367c (2026-08-29). Data as JSON: /api/errors/15d90f6d174372d5. Report an issue: GitHub.