What causes "Parsed AI response for updated tasks was not an array." in eyaltoledano/claude-task-master?

Retry the operation; AI output variance is often transient

Parsed AI response for updated tasks was not an array.

Error message

Parsed AI response for updated tasks was not an array.

What it means

The AI is asked to return an array of updated tasks. After parsing the response (which usually enforces array-ness), updateTasks re-checks Array.isArray(parsedUpdatedTasks) as a defense-in-depth guard and throws if it is not an array. It signals the AI output did not match the expected batch-update schema.

Source

Thrown at scripts/modules/task-manager/update-tasks.js:252

					dependencies: task.dependencies ?? [],
					priority: task.priority ?? null,
					details: task.details ?? null,
					testStrategy: task.testStrategy ?? null,
					subtasks: task.subtasks
						? task.subtasks.map((subtask) => ({
								...subtask,
								dependencies: subtask.dependencies ?? [],
								status: subtask.status ?? 'pending',
								testStrategy: subtask.testStrategy ?? null
							}))
						: null
				})
			);

			// --- Update Tasks Data (Updated writeJSON call) ---
			if (!Array.isArray(parsedUpdatedTasks)) {
				// Should be caught by parser, but extra check
				throw new Error(
					'Parsed AI response for updated tasks was not an array.'
				);
			}
			if (isMCP)
				logFn.info(
					`Received ${parsedUpdatedTasks.length} updated tasks from AI.`
				);
			else
				logFn(
					'info',
					`Received ${parsedUpdatedTasks.length} updated tasks from AI.`
				);
			// Create a map for efficient lookup
			const updatedTasksMap = new Map(
				parsedUpdatedTasks.map((task) => [task.id, task])
			);

			let actualUpdateCount = 0;

View on GitHub (pinned to c0c98d367c)

Solutions

Retry the operation; AI output variance is often transient
Use --research or a stronger model for the batch update
Reduce the number of tasks updated in one call (lower fromId scope or update fewer tasks)
Check provider connectivity/model config if malformed responses recur

Defensive patterns

Strategy: validation

Validate before calling

if (!Array.isArray(parsedUpdatedTasks)) {
  // retry the AI call or fall back to per-task updates
}

Type guard

const isUpdatedTasksArray = (v) => Array.isArray(v) && v.every((t) => t && typeof t === 'object' && typeof t.id !== 'undefined');

Try / catch

try {
  await updateTasks(...);
} catch (e) {
  if (e.message.includes('was not an array')) {
    // retry with stronger model or smaller batch
  } else throw e;
}

Prevention

Batch fewer tasks per update call
Use research-tier models for multi-task operations
Verify parsed JSON shape before writing
Retry once on schema failures before surfacing to users

When it happens

Trigger: AI response parsed (e.g. from a JSON blob in text) into a non-array value — an object, null, or string — during the update-tasks batch operation.

Common situations: Model returning a single object instead of an array when only one task changes, malformed JSON wrapped in prose, or context overflow truncating the response.

Related errors

AI-assisted analysis of eyaltoledano/claude-task-master@c0c98d367c (2026-08-29). Data as JSON: /api/errors/0036271d028c279f. Report an issue: GitHub.