From 32621c6a11f6ce1c0dd46aeb08e35dd64ec804f0 Mon Sep 17 00:00:00 2001
From: Christian Byrne <cbyrne@comfy.org>
Date: Sat, 31 Jan 2026 22:13:48 -0800
Subject: [PATCH] fix: improve error message when node type is missing (#12194)

- Change error type from 'invalid_prompt' to 'missing_node_type' for frontend detection
- Add extra_info with node_id, class_type, and node_title (from _meta.title)
- Improve user-facing message: 'Node X not found. The custom node may not be installed.'
---
 execution.py | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/execution.py b/execution.py
index 93fafc4a2..3dbab82e6 100644
--- a/execution.py
+++ b/execution.py
@@ -1014,22 +1014,34 @@ async def validate_prompt(prompt_id, prompt, partial_execution_list: Union[list[
     outputs = set()
     for x in prompt:
         if 'class_type' not in prompt[x]:
+            node_data = prompt[x]
+            node_title = node_data.get('_meta', {}).get('title')
             error = {
-                "type": "invalid_prompt",
-                "message": "Cannot execute because a node is missing the class_type property.",
+                "type": "missing_node_type",
+                "message": f"Node '{node_title or f'ID #{x}'}' has no class_type. The workflow may be corrupted or a custom node is missing.",
                 "details": f"Node ID '#{x}'",
-                "extra_info": {}
+                "extra_info": {
+                    "node_id": x,
+                    "class_type": None,
+                    "node_title": node_title
+                }
             }
             return (False, error, [], {})
 
         class_type = prompt[x]['class_type']
         class_ = nodes.NODE_CLASS_MAPPINGS.get(class_type, None)
         if class_ is None:
+            node_data = prompt[x]
+            node_title = node_data.get('_meta', {}).get('title', class_type)
             error = {
-                "type": "invalid_prompt",
-                "message": f"Cannot execute because node {class_type} does not exist.",
+                "type": "missing_node_type",
+                "message": f"Node '{node_title}' not found. The custom node may not be installed.",
                 "details": f"Node ID '#{x}'",
-                "extra_info": {}
+                "extra_info": {
+                    "node_id": x,
+                    "class_type": class_type,
+                    "node_title": node_title
+                }
             }
             return (False, error, [], {})