fix: auto-inject webhookId on webhook nodes during create/update (#643) (#657)

n8n 2.10+ requires webhookId (UUID) on webhook-type nodes for proper
webhook URL registration. Without it, webhooks silently fail with 404.
The n8n UI always generates webhookId but programmatic creation via
n8n-mcp did not.

Add ensureWebhookIds() helper that injects crypto.randomUUID() on
webhook, webhookTrigger, formTrigger, and chatTrigger nodes when
webhookId is missing. Called from both cleanWorkflowForCreate() and
cleanWorkflowForUpdate(). Existing webhookId values are preserved.

Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -7,6 +7,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [2.40.5] - 2026-03-22
+
+### Fixed
+
+- **Webhook workflows created via MCP get 404 errors** (Issue #643): Auto-inject `webhookId` (UUID) on webhook-type nodes (`webhook`, `webhookTrigger`, `formTrigger`, `chatTrigger`) during `cleanWorkflowForCreate()` and `cleanWorkflowForUpdate()`. n8n 2.10+ requires this field for proper webhook URL registration; without it, webhooks silently fail with 404. Existing `webhookId` values are preserved.
+
+Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en
+
 ## [2.40.4] - 2026-03-22
 
 ### Fixed

dist/services/n8n-validation.d.ts.map

@@ -1 +1 @@
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+{"version":3,"file":"n8n-validation.d.ts","sourceRoot":"","sources":["../../src/services/n8n-validation.ts"],"names":[],"mappings":"AACA,OAAO,EAAE,CAAC,EAAE,MAAM,KAAK,CAAC;AACxB,OAAO,EAAE,YAAY,EAAE,kBAAkB,EAAE,QAAQ,EAAE,MAAM,kBAAkB,CAAC;AAM9E,eAAO,MAAM,kBAAkB;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;EAiB7B,CAAC;AAkBH,eAAO,MAAM,wBAAwB;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;gCAUpC,CAAC;AAEF,eAAO,MAAM,sBAAsB;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;EAWjC,CAAC;AAGH,eAAO,MAAM,uBAAuB;;;;;;CAMnC,CAAC;AAGF,wBAAgB,oBAAoB,CAAC,IAAI,EAAE,OAAO,GAAG,YAAY,CAEhE;AAED,wBAAgB,2BAA2B,CAAC,WAAW,EAAE,OAAO,GAAG,kBAAkB,CAEpF;AAED,wBAAgB,wBAAwB,CAAC,QAAQ,EAAE,OAAO,GAAG,CAAC,CAAC,KAAK,CAAC,OAAO,sBAAsB,CAAC,CAElG;AAmBD,wBAAgB,sBAAsB,CAAC,QAAQ,EAAE,OAAO,CAAC,QAAQ,CAAC,GAAG,OAAO,CAAC,QAAQ,CAAC,CAwBrF;AAiBD,wBAAgB,sBAAsB,CAAC,QAAQ,EAAE,QAAQ,GAAG,OAAO,CAAC,QAAQ,CAAC,CAsE5E;AAGD,wBAAgB,yBAAyB,CAAC,QAAQ,EAAE,OAAO,CAAC,QAAQ,CAAC,GAAG,MAAM,EAAE,CAkQ/E;AAGD,wBAAgB,iBAAiB,CAAC,QAAQ,EAAE,QAAQ,GAAG,OAAO,CAK7D;AAMD,wBAAgB,+BAA+B,CAAC,IAAI,EAAE,YAAY,GAAG,MAAM,EAAE,CA+F5E;AAMD,wBAAgB,yBAAyB,CAAC,QAAQ,EAAE,GAAG,EAAE,IAAI,EAAE,MAAM,GAAG,MAAM,EAAE,CA0D/E;AAGD,wBAAgB,aAAa,CAAC,QAAQ,EAAE,QAAQ,GAAG,MAAM,GAAG,IAAI,CAmB/D;AAGD,wBAAgB,2BAA2B,IAAI,MAAM,CA6CpD;AAGD,wBAAgB,yBAAyB,CAAC,MAAM,EAAE,MAAM,EAAE,GAAG,MAAM,EAAE,CAmBpE"}

dist/services/n8n-validation.js

@@ -1,4 +1,7 @@
 "use strict";
+var __importDefault = (this && this.__importDefault) || function (mod) {
+    return (mod && mod.__esModule) ? mod : { "default": mod };
+};
 Object.defineProperty(exports, "__esModule", { value: true });
 exports.defaultWorkflowSettings = exports.workflowSettingsSchema = exports.workflowConnectionSchema = exports.workflowNodeSchema = void 0;
 exports.validateWorkflowNode = validateWorkflowNode;
@@ -13,6 +16,7 @@ exports.validateOperatorStructure = validateOperatorStructure;
 exports.getWebhookUrl = getWebhookUrl;
 exports.getWorkflowStructureExample = getWorkflowStructureExample;
 exports.getWorkflowFixSuggestions = getWorkflowFixSuggestions;
+const crypto_1 = __importDefault(require("crypto"));
 const zod_1 = require("zod");
 const node_type_utils_1 = require("../utils/node-type-utils");
 const node_classification_1 = require("../utils/node-classification");
@@ -76,11 +80,27 @@ function validateWorkflowConnections(connections) {
 function validateWorkflowSettings(settings) {
     return exports.workflowSettingsSchema.parse(settings);
 }
+const WEBHOOK_NODE_TYPES = new Set([
+    'n8n-nodes-base.webhook',
+    'n8n-nodes-base.webhookTrigger',
+    'n8n-nodes-base.formTrigger',
+    '@n8n/n8n-nodes-langchain.chatTrigger',
+]);
+function ensureWebhookIds(nodes) {
+    if (!nodes)
+        return;
+    for (const node of nodes) {
+        if (WEBHOOK_NODE_TYPES.has(node.type) && !node.webhookId) {
+            node.webhookId = crypto_1.default.randomUUID();
+        }
+    }
+}
 function cleanWorkflowForCreate(workflow) {
     const { id, createdAt, updatedAt, versionId, meta, active, tags, ...cleanedWorkflow } = workflow;
     if (!cleanedWorkflow.settings || Object.keys(cleanedWorkflow.settings).length === 0) {
         cleanedWorkflow.settings = exports.defaultWorkflowSettings;
     }
+    ensureWebhookIds(cleanedWorkflow.nodes);
     return cleanedWorkflow;
 }
 function cleanWorkflowForUpdate(workflow) {
@@ -116,6 +136,7 @@ function cleanWorkflowForUpdate(workflow) {
     else {
         cleanedWorkflow.settings = { executionOrder: 'v1' };
     }
+    ensureWebhookIds(cleanedWorkflow.nodes);
     return cleanedWorkflow;
 }
 function validateWorkflowStructure(workflow) {

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "n8n-mcp",
-  "version": "2.37.3",
+  "version": "2.40.5",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "n8n-mcp",
-      "version": "2.37.3",
+      "version": "2.40.5",
       "license": "MIT",
       "dependencies": {
         "@modelcontextprotocol/sdk": "^1.27.1",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "n8n-mcp",
-  "version": "2.40.4",
+  "version": "2.40.5",
   "description": "Integration between n8n workflow automation and Model Context Protocol (MCP)",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",

src/services/n8n-validation.ts

@@ -1,3 +1,4 @@
+import crypto from 'crypto';
 import { z } from 'zod';
 import { WorkflowNode, WorkflowConnection, Workflow } from '../types/n8n-api';
 import { isTriggerNode, isActivatableTrigger } from '../utils/node-type-utils';
@@ -87,6 +88,22 @@ export function validateWorkflowSettings(settings: unknown): z.infer<typeof work
   return workflowSettingsSchema.parse(settings);
 }
 
+const WEBHOOK_NODE_TYPES = new Set([
+  'n8n-nodes-base.webhook',
+  'n8n-nodes-base.webhookTrigger',
+  'n8n-nodes-base.formTrigger',
+  '@n8n/n8n-nodes-langchain.chatTrigger',
+]);
+
+function ensureWebhookIds(nodes?: WorkflowNode[]): void {
+  if (!nodes) return;
+  for (const node of nodes) {
+    if (WEBHOOK_NODE_TYPES.has(node.type) && !node.webhookId) {
+      node.webhookId = crypto.randomUUID();
+    }
+  }
+}
+
 // Clean workflow data for API operations
 export function cleanWorkflowForCreate(workflow: Partial<Workflow>): Partial<Workflow> {
   const {
@@ -109,6 +126,8 @@ export function cleanWorkflowForCreate(workflow: Partial<Workflow>): Partial<Wor
     cleanedWorkflow.settings = defaultWorkflowSettings;
   }
 
+  ensureWebhookIds(cleanedWorkflow.nodes);
+
   return cleanedWorkflow;
 }
 
@@ -194,6 +213,8 @@ export function cleanWorkflowForUpdate(workflow: Workflow): Partial<Workflow> {
     cleanedWorkflow.settings = { executionOrder: 'v1' as const };
   }
 
+  ensureWebhookIds(cleanedWorkflow.nodes);
+
   return cleanedWorkflow;
 }
 

tests/unit/services/n8n-validation.test.ts

@@ -19,6 +19,14 @@ import { WorkflowBuilder } from '../../utils/builders/workflow.builder';
 import { z } from 'zod';
 import { WorkflowNode, WorkflowConnection, Workflow } from '../../../src/types/n8n-api';
 
+function webhookNode(id: string, name: string, type: string, typeVersion = 2): WorkflowNode {
+  return { id, name, type, typeVersion, position: [250, 300] as [number, number], parameters: {} };
+}
+
+function workflowWithNodes(nodes: WorkflowNode[]): Partial<Workflow> {
+  return { name: 'Test', nodes, connections: {} };
+}
+
 describe('n8n-validation', () => {
   describe('Zod Schemas', () => {
     describe('workflowNodeSchema', () => {
@@ -301,6 +309,44 @@ describe('n8n-validation', () => {
         const cleaned = cleanWorkflowForCreate(workflow as Workflow);
         expect(cleaned.settings).toEqual(customSettings);
       });
+
+      it('should inject webhookId on webhook nodes missing it', () => {
+        const workflow = workflowWithNodes([
+          webhookNode('1', 'Webhook', 'n8n-nodes-base.webhook'),
+        ]);
+
+        const cleaned = cleanWorkflowForCreate(workflow as Workflow);
+        expect(cleaned.nodes![0].webhookId).toMatch(/^[0-9a-f]{8}-[0-9a-f]{4}-/);
+      });
+
+      it('should preserve existing webhookId on webhook nodes', () => {
+        const workflow = workflowWithNodes([
+          { ...webhookNode('1', 'Webhook', 'n8n-nodes-base.webhook'), webhookId: 'existing-id' },
+        ]);
+
+        const cleaned = cleanWorkflowForCreate(workflow as Workflow);
+        expect(cleaned.nodes![0].webhookId).toBe('existing-id');
+      });
+
+      it('should inject webhookId on formTrigger and chatTrigger nodes', () => {
+        const workflow = workflowWithNodes([
+          webhookNode('1', 'Form', 'n8n-nodes-base.formTrigger'),
+          webhookNode('2', 'Chat', '@n8n/n8n-nodes-langchain.chatTrigger'),
+        ]);
+
+        const cleaned = cleanWorkflowForCreate(workflow as Workflow);
+        expect(cleaned.nodes![0].webhookId).toMatch(/^[0-9a-f]{8}-[0-9a-f]{4}-/);
+        expect(cleaned.nodes![1].webhookId).toMatch(/^[0-9a-f]{8}-[0-9a-f]{4}-/);
+      });
+
+      it('should not inject webhookId on non-webhook nodes', () => {
+        const workflow = workflowWithNodes([
+          webhookNode('1', 'Set', 'n8n-nodes-base.set', 3.4),
+        ]);
+
+        const cleaned = cleanWorkflowForCreate(workflow as Workflow);
+        expect(cleaned.nodes![0].webhookId).toBeUndefined();
+      });
     });
 
     describe('cleanWorkflowForUpdate', () => {
@@ -533,6 +579,44 @@ describe('n8n-validation', () => {
         });
         expect(cleaned.settings).not.toHaveProperty('someOtherProperty');
       });
+
+      it('should inject webhookId on webhook nodes missing it', () => {
+        const workflow = workflowWithNodes([
+          webhookNode('1', 'Webhook', 'n8n-nodes-base.webhook'),
+        ]) as any;
+
+        const cleaned = cleanWorkflowForUpdate(workflow);
+        expect(cleaned.nodes![0].webhookId).toMatch(/^[0-9a-f]{8}-[0-9a-f]{4}-/);
+      });
+
+      it('should preserve existing webhookId on webhook nodes', () => {
+        const workflow = workflowWithNodes([
+          { ...webhookNode('1', 'Webhook', 'n8n-nodes-base.webhook'), webhookId: 'existing-id' },
+        ]) as any;
+
+        const cleaned = cleanWorkflowForUpdate(workflow);
+        expect(cleaned.nodes![0].webhookId).toBe('existing-id');
+      });
+
+      it('should inject webhookId on formTrigger and chatTrigger nodes', () => {
+        const workflow = workflowWithNodes([
+          webhookNode('1', 'Form', 'n8n-nodes-base.formTrigger'),
+          webhookNode('2', 'Chat', '@n8n/n8n-nodes-langchain.chatTrigger'),
+        ]) as any;
+
+        const cleaned = cleanWorkflowForUpdate(workflow);
+        expect(cleaned.nodes![0].webhookId).toMatch(/^[0-9a-f]{8}-[0-9a-f]{4}-/);
+        expect(cleaned.nodes![1].webhookId).toMatch(/^[0-9a-f]{8}-[0-9a-f]{4}-/);
+      });
+
+      it('should not inject webhookId on non-webhook nodes', () => {
+        const workflow = workflowWithNodes([
+          webhookNode('1', 'Set', 'n8n-nodes-base.set', 3.4),
+        ]) as any;
+
+        const cleaned = cleanWorkflowForUpdate(workflow);
+        expect(cleaned.nodes![0].webhookId).toBeUndefined();
+      });
     });
   });