n8n-io/n8n · error · Error

Delegated child checkpoint does not match the selected sub-a

Error message

Delegated child checkpoint does not match the selected sub-agent

What it means

Thrown by restoreDelegateRequest when the checkpoint's subAgentId does not match the subAgentId in the current resume input. This guard prevents resuming a delegated child under a different sub-agent than the one that originally started — which would execute the wrong agent's logic with stale context.

Source

Thrown at packages/@n8n/agents/src/runtime/tools/delegate-sub-agent-tool.ts:774

	);
}

function restoreDelegateRequest(
	input: DelegateSubAgentInput,
	ctx: ToolContext,
	continuation: JSONValue,
	policy: DelegateSubAgentPolicy | undefined,
	childPathIndexes: Map<string, number>,
): {
	checkpoint: DelegateSubAgentContinuation & { taskPath: SubAgentTaskPath };
	request: DelegateSubAgentRequest;
} {
	const checkpoint = parseDelegateSubAgentContinuation(continuation);
	if (!checkpoint) {
		throw new Error('Delegated child checkpoint metadata is missing or invalid');
	}
	if (checkpoint.subAgentId !== input.subAgentId) {
		throw new Error('Delegated child checkpoint does not match the selected sub-agent');
	}
	const { taskPath } = checkpoint;
	assertSubAgentTaskPath(taskPath);
	const key = getChildPathIndexKey(ctx);
	childPathIndexes.set(key, Math.max(childPathIndexes.get(key) ?? 0, checkpoint.childCount + 1));
	const request = createDelegateSubAgentRequest(
		input,
		ctx,
		taskPath,
		checkpoint.childCount,
		policy,
	);
	return { checkpoint: { ...checkpoint, taskPath }, request };
}

function getChildCheckpointTarget(checkpoint: DelegateSubAgentContinuation) {
	return {
		childRunId: checkpoint.runId,

View on GitHub (pinned to 5ac6606e81)

Solutions

1. Ensure the sub-agent configuration is stable between suspend and resume (same availableSubAgents list and identifiers).
2. If the sub-agent set legitimately changed, start a new delegation rather than resuming the stale one.
3. Verify that sub-agent IDs are deterministic and not regenerated on each build.

function continuationMatchesInput(continuation: DelegateSubAgentContinuation, input: DelegateSubAgentInput): boolean {
  return continuation.subAgentId === input.subAgentId;
}
if (!continuationMatchesInput(storedContinuation, resumeInput)) {
  // sub-agent set changed; do not resume
}

try {
  await agent.resume(resumeData);
} catch (e) {
  if (e instanceof Error && e.message.includes('does not match')) {
    // re-select the correct sub-agent or start fresh
  } else throw e;
}

When it happens

Trigger: The availableSubAgents list or selection logic changed between suspend and resume, causing the resume input to reference a different subAgentId than the one recorded in the continuation checkpoint. Also triggered by manual tampering with the resume payload or a bug in sub-agent selection logic.

Common situations: Editing the agent configuration (adding/removing/reordering sub-agents) between when a delegation suspended and when the user resumes. Dynamic sub-agent registration that is non-deterministic across restarts. Passing a hand-crafted resume payload with the wrong subAgentId.

Related errors

• Delegated child checkpoint metadata is missing or invalid
• No pending tool call found for toolCallId: ${resumedId}
• Run ${runId} is not suspended. Cannot resume.
• Invalid delegate sub-agent tool name "${name}": must start w
• ${toolName} requires resumeSubAgent and cancelSubAgent to be

AI-assisted analysis of n8n-io/n8n@5ac6606e81 (2026-08-12). Data as JSON: /api/errors/688b0e97366cc3a2. Report an issue: GitHub.