fix: correct version extraction and typeVersion validation for langchain nodes

This commit fixes two critical bugs affecting AI Agent and other langchain nodes:

1. Version Extraction Bug (node-parser.ts)
   - AI Agent was returning version "3" instead of "2.2" (the defaultVersion)
   - Root cause: extractVersion() checked non-existent instance.baseDescription.defaultVersion
   - Fix: Updated priority to check currentVersion first, then description.defaultVersion
   - Impact: All VersionedNodeType nodes now return correct version

2. typeVersion Validation Bypass (workflow-validator.ts)
   - Langchain nodes with invalid typeVersion passed validation (even typeVersion: 99999)
   - Root cause: langchain skip happened before typeVersion validation
   - Fix: Moved typeVersion validation before langchain parameter skip
   - Impact: Invalid typeVersion values now properly caught for all nodes

Also includes:
- Database rebuilt with corrected version data (536 nodes)
- Version bump: 2.17.3 → 2.17.4
- Comprehensive CHANGELOG entry

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

CHANGELOG.md

@@ -5,6 +5,95 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [2.17.4] - 2025-10-07
+
+### 🔧 Validation
+
+**Fixed critical version extraction and typeVersion validation bugs.**
+
+This release fixes two critical bugs that caused incorrect version data and validation bypasses for langchain nodes.
+
+#### Fixed
+
+- **Version Extraction Bug (CRITICAL)**
+  - **Issue:** AI Agent node returned version "3" instead of "2.2" (the defaultVersion)
+  - **Impact:**
+    - MCP tools (`get_node_essentials`, `get_node_info`) returned incorrect version "3"
+    - Version "3" exists but n8n explicitly marks it as unstable ("Keep 2.2 until blocking bugs are fixed")
+    - AI agents created workflows with wrong typeVersion, causing runtime issues
+  - **Root Cause:** `extractVersion()` in node-parser.ts checked `instance.baseDescription.defaultVersion` which doesn't exist on VersionedNodeType instances
+  - **Fix:** Updated version extraction priority in `node-parser.ts:137-200`
+    1. Priority 1: Check `currentVersion` property (what VersionedNodeType actually uses)
+    2. Priority 2: Check `description.defaultVersion` (fixed property name from `baseDescription`)
+    3. Priority 3: Fallback to max(nodeVersions) as last resort
+  - **Verification:** AI Agent node now correctly returns version "2.2" across all MCP tools
+
+- **typeVersion Validation Bypass (CRITICAL)**
+  - **Issue:** Langchain nodes with invalid typeVersion passed validation (even `typeVersion: 99999`)
+  - **Impact:**
+    - Invalid typeVersion values were never caught during validation
+    - Workflows with non-existent typeVersions passed validation but failed at runtime in n8n
+    - Validation was completely bypassed for all langchain nodes (AI Agent, Chat Trigger, OpenAI Chat Model, etc.)
+  - **Root Cause:** `workflow-validator.ts:400-405` skipped ALL validation for langchain nodes before typeVersion check
+  - **Fix:** Moved typeVersion validation BEFORE langchain skip in `workflow-validator.ts:447-493`
+    - typeVersion now validated for ALL nodes including langchain
+    - Validation runs before parameter validation skip
+    - Checks for missing, invalid, outdated, and exceeding-maximum typeVersion values
+  - **Verification:** Workflows with invalid typeVersion now correctly fail validation
+
+#### Technical Details
+
+**Version Extraction Fix:**
+```typescript
+// BEFORE (BROKEN):
+if (instance?.baseDescription?.defaultVersion) {  // Property doesn't exist!
+  return instance.baseDescription.defaultVersion.toString();
+}
+
+// AFTER (FIXED):
+if (instance?.currentVersion !== undefined) {  // What VersionedNodeType actually uses
+  return instance.currentVersion.toString();
+}
+if (instance?.description?.defaultVersion) {  // Correct property name
+  return instance.description.defaultVersion.toString();
+}
+```
+
+**typeVersion Validation Fix:**
+```typescript
+// BEFORE (BROKEN):
+// Skip ALL node repository validation for langchain nodes
+if (normalizedType.startsWith('nodes-langchain.')) {
+  continue;  // typeVersion validation never runs!
+}
+
+// AFTER (FIXED):
+// Validate typeVersion for ALL versioned nodes (including langchain)
+if (nodeInfo.isVersioned) {
+  // ... typeVersion validation ...
+}
+
+// THEN skip parameter validation for langchain nodes
+if (normalizedType.startsWith('nodes-langchain.')) {
+  continue;
+}
+```
+
+#### Impact
+
+- **Version Accuracy:** AI Agent and all VersionedNodeType nodes now return correct version (2.2, not 3)
+- **Validation Reliability:** Invalid typeVersion values are now caught for langchain nodes
+- **Workflow Stability:** Prevents creation of workflows with non-existent typeVersions
+- **Database Rebuilt:** 536 nodes reloaded with corrected version data
+
+#### Testing
+
+- **Unit Tests:** All existing tests passing
+- **Integration Tests:** Verified with n8n-mcp-tester agent
+  - Version consistency between `get_node_essentials` and `get_node_info` ✅
+  - typeVersion validation catches invalid values (99, 100000) ✅
+  - AI Agent correctly reports version "2.2" ✅
+
 ## [2.17.3] - 2025-10-07
 
 ### 🔧 Validation

package.json

@@ -1,6 +1,6 @@
 {
   "name": "n8n-mcp",
-  "version": "2.17.3",
+  "version": "2.17.4",
   "description": "Integration between n8n workflow automation and Model Context Protocol (MCP)",
   "main": "dist/index.js",
   "bin": {

src/parsers/node-parser.ts

@@ -135,16 +135,23 @@ export class NodeParser {
   }
   
   private extractVersion(nodeClass: any): string {
-    // Check instance for baseDescription first
+    // Check instance properties first
     try {
       const instance = typeof nodeClass === 'function' ? new nodeClass() : nodeClass;
 
-      // Handle instance-level baseDescription
-      if (instance?.baseDescription?.defaultVersion) {
-        return instance.baseDescription.defaultVersion.toString();
+      // PRIORITY 1: Check currentVersion (what VersionedNodeType actually uses)
+      // For VersionedNodeType, currentVersion = defaultVersion ?? max(nodeVersions)
+      if (instance?.currentVersion !== undefined) {
+        return instance.currentVersion.toString();
       }
 
-      // Handle instance-level nodeVersions
+      // PRIORITY 2: Handle instance-level description.defaultVersion
+      // VersionedNodeType stores baseDescription as 'description', not 'baseDescription'
+      if (instance?.description?.defaultVersion) {
+        return instance.description.defaultVersion.toString();
+      }
+
+      // PRIORITY 3: Handle instance-level nodeVersions (fallback to max)
       if (instance?.nodeVersions) {
         const versions = Object.keys(instance.nodeVersions);
         return Math.max(...versions.map(Number)).toString();
@@ -154,7 +161,6 @@ export class NodeParser {
       if (instance?.description?.version) {
         const version = instance.description.version;
         if (Array.isArray(version)) {
-          // Find the maximum version from the array
           const maxVersion = Math.max(...version.map((v: any) => parseFloat(v.toString())));
           return maxVersion.toString();
         } else if (typeof version === 'number' || typeof version === 'string') {
@@ -167,8 +173,9 @@ export class NodeParser {
     }
 
     // Handle class-level VersionedNodeType with defaultVersion
-    if (nodeClass.baseDescription?.defaultVersion) {
-      return nodeClass.baseDescription.defaultVersion.toString();
+    // Note: Most VersionedNodeType classes don't have static properties
+    if (nodeClass.description?.defaultVersion) {
+      return nodeClass.description.defaultVersion.toString();
     }
 
     // Handle class-level VersionedNodeType with nodeVersions

src/services/workflow-validator.ts

@@ -397,14 +397,7 @@ export class WorkflowValidator {
           node.type = normalizedType;
         }
 
-        // Skip ALL node repository validation for langchain nodes
-        // They have dedicated AI-specific validators in validateAISpecificNodes()
-        // This prevents parameter validation conflicts and ensures proper AI validation
-        if (normalizedType.startsWith('nodes-langchain.')) {
-          continue;
-        }
-
-        // Get node definition using normalized type
+        // Get node definition using normalized type (needed for typeVersion validation)
         const nodeInfo = this.nodeRepository.getNode(normalizedType);
 
         if (!nodeInfo) {
@@ -451,7 +444,8 @@ export class WorkflowValidator {
           continue;
         }
 
-        // Validate typeVersion for versioned nodes
+        // Validate typeVersion for ALL versioned nodes (including langchain nodes)
+        // This validation runs BEFORE the langchain skip to ensure typeVersion is checked
         if (nodeInfo.isVersioned) {
           // Check if typeVersion is missing
           if (!node.typeVersion) {
@@ -491,6 +485,13 @@ export class WorkflowValidator {
           }
         }
 
+        // Skip parameter validation for langchain nodes
+        // They have dedicated AI-specific validators in validateAISpecificNodes()
+        // This prevents parameter validation conflicts and ensures proper AI validation
+        if (normalizedType.startsWith('nodes-langchain.')) {
+          continue;
+        }
+
         // Validate node configuration
         const nodeValidation = this.nodeValidator.validateWithMode(
           node.type,