Track custom node startup errors and expose via API endpoint

Store import and prestartup errors in NODE_STARTUP_ERRORS dict (nodes.py,
main.py) and add GET /custom_node_startup_errors endpoint (server.py) so
the frontend/Manager can distinguish failed imports from missing nodes.

Ref: ComfyUI-Launcher#303
Amp-Thread-ID: https://ampcode.com/threads/T-019d2346-6e6f-75e0-a97f-cdb6e26859f7
Co-authored-by: Amp <amp@ampcode.com>

comfy_extras/nodes_curve.py

@@ -1,7 +1,5 @@
 from __future__ import annotations
 
-import numpy as np
-
 from comfy_api.latest import ComfyExtension, io
 from comfy_api.input import CurveInput
 from typing_extensions import override
@@ -34,58 +32,10 @@ class CurveEditor(io.ComfyNode):
         return io.NodeOutput(result, ui=ui) if ui else io.NodeOutput(result)
 
 
-class ImageHistogram(io.ComfyNode):
-    @classmethod
-    def define_schema(cls):
-        return io.Schema(
-            node_id="ImageHistogram",
-            display_name="Image Histogram",
-            category="utils",
-            inputs=[
-                io.Image.Input("image"),
-            ],
-            outputs=[
-                io.Histogram.Output("rgb"),
-                io.Histogram.Output("luminance"),
-                io.Histogram.Output("red"),
-                io.Histogram.Output("green"),
-                io.Histogram.Output("blue"),
-            ],
-        )
-
-    @classmethod
-    def execute(cls, image) -> io.NodeOutput:
-        img = image[0].cpu().numpy()
-        img_uint8 = np.clip(img * 255, 0, 255).astype(np.uint8)
-
-        def bincount(data):
-            return np.bincount(data.ravel(), minlength=256)[:256]
-
-        hist_r = bincount(img_uint8[:, :, 0])
-        hist_g = bincount(img_uint8[:, :, 1])
-        hist_b = bincount(img_uint8[:, :, 2])
-
-        # Average of R, G, B histograms (same as Photoshop's RGB composite)
-        rgb = ((hist_r + hist_g + hist_b) // 3).tolist()
-
-        # ITU-R BT.709-6, Item 3.2 (p.6) — Derivation of luminance signal
-        # https://www.itu.int/rec/R-REC-BT.709-6-201506-I/en
-        lum = 0.2126 * img[:, :, 0] + 0.7152 * img[:, :, 1] + 0.0722 * img[:, :, 2]
-        luminance = bincount(np.clip(lum * 255, 0, 255).astype(np.uint8)).tolist()
-
-        return io.NodeOutput(
-            rgb,
-            luminance,
-            hist_r.tolist(),
-            hist_g.tolist(),
-            hist_b.tolist(),
-        )
-
-
 class CurveExtension(ComfyExtension):
     @override
     async def get_node_list(self):
-        return [CurveEditor, ImageHistogram]
+        return [CurveEditor]
 
 
 async def comfy_entrypoint():

main.py

@@ -139,7 +139,16 @@ def execute_prestartup_script():
             spec.loader.exec_module(module)
             return True
         except Exception as e:
+            import traceback
             logging.error(f"Failed to execute startup-script: {script_path} / {e}")
+            from nodes import NODE_STARTUP_ERRORS, get_module_name
+            node_module_name = get_module_name(os.path.dirname(script_path))
+            NODE_STARTUP_ERRORS[node_module_name] = {
+                "module_path": os.path.dirname(script_path),
+                "error": str(e),
+                "traceback": traceback.format_exc(),
+                "phase": "prestartup",
+            }
         return False
 
     node_paths = folder_paths.get_folder_paths("custom_nodes")

nodes.py

@@ -2181,6 +2181,9 @@ EXTENSION_WEB_DIRS = {}
 # Dictionary of successfully loaded module names and associated directories.
 LOADED_MODULE_DIRS = {}
 
+# Dictionary of custom node startup errors, keyed by module name.
+NODE_STARTUP_ERRORS: dict[str, dict] = {}
+
 
 def get_module_name(module_path: str) -> str:
     """
@@ -2298,6 +2301,13 @@ async def load_custom_node(module_path: str, ignore=set(), module_parent="custom
     except Exception as e:
         logging.warning(traceback.format_exc())
         logging.warning(f"Cannot import {module_path} module for custom nodes: {e}")
+        module_name = get_module_name(module_path)
+        NODE_STARTUP_ERRORS[module_name] = {
+            "module_path": module_path,
+            "error": str(e),
+            "traceback": traceback.format_exc(),
+            "phase": "import",
+        }
         return False
 
 async def init_external_custom_nodes():

server.py

@@ -753,6 +753,10 @@ class PromptServer():
                 out[node_class] = node_info(node_class)
             return web.json_response(out)
 
+        @routes.get("/custom_node_startup_errors")
+        async def get_custom_node_startup_errors(request):
+            return web.json_response(nodes.NODE_STARTUP_ERRORS)
+
         @routes.get("/api/jobs")
         async def get_jobs(request):
             """List all jobs with filtering, sorting, and pagination.