n8n-io/n8n · error · NodeOperationError

No rules defined

Error message

No rules defined

What it means

Thrown by ModelSelector.supplyData() when the 'rules.rule' parameter is empty or missing. Rules are how the node decides which connected model to use; without at least one rule the selection logic has nothing to evaluate and cannot return a model.

Source

Thrown at packages/@n8n/nodes-langchain/nodes/ModelSelector/ModelSelector.node.ts:172

	async supplyData(this: ISupplyDataFunctions, itemIndex: number): Promise<SupplyData> {
		const models = (await this.getInputConnectionData(
			NodeConnectionTypes.AiLanguageModel,
			itemIndex,
		)) as unknown[];

		if (!models || models.length === 0) {
			throw new NodeOperationError(this.getNode(), 'No models connected', {
				itemIndex,
				description: 'No models found in input connections',
			});
		}
		models.reverse();

		const rules = this.getNodeParameter('rules.rule', itemIndex, []) as ModeleSelectionRule[];

		if (!rules || rules.length === 0) {
			throw new NodeOperationError(this.getNode(), 'No rules defined', {
				itemIndex,
				description: 'At least one rule must be defined to select a model',
			});
		}

		for (let i = 0; i < rules.length; i++) {
			const rule = rules[i];
			const modelIndex = rule.modelIndex;

			if (modelIndex <= 0 || modelIndex > models.length) {
				throw new NodeOperationError(this.getNode(), `Invalid model index ${modelIndex}`, {
					itemIndex,
					description: `Model index must be between 1 and ${models.length}`,
				});
			}

			const conditionsMet = this.getNodeParameter(`rules.rule[${i}].conditions`, itemIndex, false, {
				extractValue: true,

View on GitHub (pinned to 5ac6606e81)

Solutions

1. Open the ModelSelector node and add at least one rule mapping a condition to a model index.
2. If loading the workflow from JSON, ensure the rules.rule array is populated before execution.
3. Pair each rule's modelIndex with a connected model (1-based).

Example fix

// before: parameters.rules.rule = []
// after: parameters.rules.rule = [{ modelIndex: 1, conditions: { ... } }]

const rules = this.getNodeParameter('rules.rule', itemIndex, []);
if (!Array.isArray(rules) || rules.length === 0) throw new Error('Define at least one rule');

function hasRules(r): r is ModeleSelectionRule[] { return Array.isArray(r) && r.length > 0; }

When it happens

Trigger: this.getNodeParameter('rules.rule', itemIndex, []) resolves to an empty array (or null/undefined), and the guard `if (!rules || rules.length === 0)` throws. Fires when the user has not added any selection rules in the node UI.

Common situations: New ModelSelector node left with default (empty) rules; rules parameter accidentally cleared by a workflow import/migration; user expects a default model but none is defined.

Related errors

• Invalid model index ${modelIndex}
• No matching rule found
• MCP server "${cfg.name}": exactly one of "url" or "command"
• MCP server "${cfg.name}": provide either "url" or "command",
• Unknown agents module: "${moduleName}". ${validTokens ? `Val

AI-assisted analysis of n8n-io/n8n@5ac6606e81 (2026-08-12). Data as JSON: /api/errors/b6d64ccd3f6d5b99. Report an issue: GitHub.