From 44d1835797173efc8e089a9fbd34c14bc21eef8d Mon Sep 17 00:00:00 2001
From: Danny Martini <danny@n8n.io>
Date: Thu, 16 Oct 2025 16:21:55 +0200
Subject: [PATCH] fix(Call n8n Sub-Workflow Tool Node): Return structured data
 from Workflow Tool when called by engine (#20869)

---
 .../ToolWorkflow/v2/ToolWorkflowV2.test.ts    | 29 +++++++++++++++++++
 .../v2/utils/WorkflowToolService.ts           | 12 ++++++--
 2 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/packages/@n8n/nodes-langchain/nodes/tools/ToolWorkflow/v2/ToolWorkflowV2.test.ts b/packages/@n8n/nodes-langchain/nodes/tools/ToolWorkflow/v2/ToolWorkflowV2.test.ts
index 445e867a44d..01cca5a6db5 100644
--- a/packages/@n8n/nodes-langchain/nodes/tools/ToolWorkflow/v2/ToolWorkflowV2.test.ts
+++ b/packages/@n8n/nodes-langchain/nodes/tools/ToolWorkflow/v2/ToolWorkflowV2.test.ts
@@ -137,6 +137,35 @@ describe('WorkflowTool::WorkflowToolService', () => {
 			});
 		});
 
+		it('returns un-stringified data if manualLogging is false (meaning it was called from the engine)', async () => {
+			const TEST_RESPONSE = { msg: 'test response' };
+
+			const mockExecuteWorkflowResponse: ExecuteWorkflowData = {
+				data: [[{ json: TEST_RESPONSE }]],
+				executionId: 'test-execution',
+			};
+
+			jest.spyOn(context, 'executeWorkflow').mockResolvedValueOnce(mockExecuteWorkflowResponse);
+			jest.spyOn(context, 'getNodeParameter').mockReturnValue('database');
+			jest.spyOn(context, 'getWorkflowDataProxy').mockReturnValue({
+				$execution: { id: 'exec-id' },
+				$workflow: { id: 'workflow-id' },
+			} as unknown as IWorkflowDataProxyData);
+
+			const tool = await service.createTool({
+				ctx: context,
+				name: 'Test Tool',
+				description: 'Test Description',
+				itemIndex: 0,
+				manualLogging: false,
+			});
+
+			// eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
+			const result = await tool.func('test query');
+
+			expect(result).toEqual([{ json: TEST_RESPONSE }]);
+		});
+
 		it('should handle errors during tool execution', async () => {
 			const toolParams = {
 				ctx: context,
diff --git a/packages/@n8n/nodes-langchain/nodes/tools/ToolWorkflow/v2/utils/WorkflowToolService.ts b/packages/@n8n/nodes-langchain/nodes/tools/ToolWorkflow/v2/utils/WorkflowToolService.ts
index e5c181599ae..43e7eb17fe0 100644
--- a/packages/@n8n/nodes-langchain/nodes/tools/ToolWorkflow/v2/utils/WorkflowToolService.ts
+++ b/packages/@n8n/nodes-langchain/nodes/tools/ToolWorkflow/v2/utils/WorkflowToolService.ts
@@ -160,6 +160,8 @@ export class WorkflowToolService {
 						};
 					}
 
+					// If manualLogging is enabled we've been called by the AgentExecutor
+					// and have to return a stringified response.
 					if (manualLogging) {
 						void context.addOutputData(
 							NodeConnectionTypes.AiTool,
@@ -167,9 +169,13 @@ export class WorkflowToolService {
 							[responseData],
 							metadata,
 						);
+
+						return processedResponse;
 					}
 
-					return processedResponse;
+					// If manualLogging is false we've been called by the engine and need
+					// the structured response.
+					return responseData;
 				} catch (error) {
 					// Check if error is due to cancellation
 					if (abortSignal?.aborted) {
@@ -240,7 +246,7 @@ export class WorkflowToolService {
 		items: INodeExecutionData[],
 		workflowProxy: IWorkflowDataProxyData,
 		runManager?: CallbackManagerForToolRun,
-	): Promise<{ response: string | IDataObject | INodeExecutionData[]; subExecutionId: string }> {
+	): Promise<{ response: IDataObject | INodeExecutionData[]; subExecutionId: string }> {
 		let receivedData: ExecuteWorkflowData;
 		try {
 			receivedData = await context.executeWorkflow(workflowInfo, items, runManager?.getChild(), {
@@ -280,7 +286,7 @@ export class WorkflowToolService {
 		query: string | IDataObject,
 		itemIndex: number,
 		runManager?: CallbackManagerForToolRun,
-	): Promise<string | IDataObject | INodeExecutionData[]> {
+	): Promise<IDataObject | INodeExecutionData[]> {
 		const source = context.getNodeParameter('source', itemIndex) as string;
 		const workflowProxy = context.getWorkflowDataProxy(0);