fix(metadata-overwrite): use sentinel default for clip_skip to accept wired 0

py/metadata_collector/constants.py

@@ -1,5 +1,11 @@
 """Constants used by the metadata collector"""
 
+# Sentinel value for clip_skip to distinguish "unconnected / widget default"
+# from "user wired value 0".  Both ComfyUI CLIPSetLastLayer (-24..-1) and
+# A1111 conventions treat 0 as meaningless for clip skipping, but users may
+# explicitly wire 0 to the overwrite node to express "no clip skip / default".
+CLIP_SKIP_SENTINEL = -25
+
 # Metadata categories
 MODELS = "models"
 PROMPTS = "prompts"

py/metadata_collector/metadata_processor.py

@@ -678,7 +678,12 @@ class MetadataProcessor:
         for overwrite_info in metadata.get(OVERWRITE, {}).values():
             overwrite_params = overwrite_info.get("parameters", {})
             for key, value in overwrite_params.items():
-                if value:  # truthy check — only overwrite when user provided a real value
+                if key == "clip_skip":
+                    # Accept any value from overwrite node (sentinel -25 already
+                    # filtered upstream).  Needed because falsy check treats 0
+                    # as "not set" even though 0 is a valid wired input here.
+                    params[key] = value
+                elif value:  # truthy check — only overwrite when user provided a real value
                     params[key] = value
 
         # Bridge: the overwrite node exposes the field as "model" (more accurate),

py/metadata_collector/node_extractors.py

@@ -2,7 +2,7 @@ import json
 import os
 import re
 
-from .constants import MODELS, PROMPTS, SAMPLING, LORAS, SIZE, IMAGES, IS_SAMPLER, OVERWRITE, METADATA_OVERWRITE_FIELDS
+from .constants import CLIP_SKIP_SENTINEL, MODELS, PROMPTS, SAMPLING, LORAS, SIZE, IMAGES, IS_SAMPLER, OVERWRITE, METADATA_OVERWRITE_FIELDS
 
 
 def _store_checkpoint_metadata(metadata, node_id, model_name):
@@ -1236,7 +1236,10 @@ class MetadataOverwriteExtractor(NodeMetadataExtractor):
         overwrite_params = {}
         for key in METADATA_OVERWRITE_FIELDS:
             value = inputs.get(key)
-            if value:  # truthy — only overwrite when user provided a real value
+            if key == "clip_skip":
+                if value != CLIP_SKIP_SENTINEL:
+                    overwrite_params[key] = value
+            elif value:  # truthy — only overwrite when user provided a real value
                 overwrite_params[key] = value
 
         if overwrite_params:

py/nodes/metadata_overwrite.py

@@ -1,13 +1,18 @@
 """Metadata Overwrite node — allows users to manually specify generation parameters
 that override the automatically collected/inferred metadata.
 
-All inputs have falsy defaults: only truthy (non-empty / non-zero) values
-will overwrite the corresponding field in the final metadata.
+Most inputs have falsy defaults (empty string / 0) which are skipped.
+clip_skip uses a sentinel default (-25) so that a wired value of 0 is
+preserved — both ComfyUI and A1111 conventions have no meaningful 0 value,
+but users may wire 0 to express "no clip skip / default".
 """
 
 from typing import Any
 
-from ..metadata_collector.constants import METADATA_OVERWRITE_FIELDS
+from ..metadata_collector.constants import (
+    CLIP_SKIP_SENTINEL as _CLIP_SKIP_SENTINEL,
+    METADATA_OVERWRITE_FIELDS,
+)
 
 
 class MetadataOverwriteLM:
@@ -116,10 +121,14 @@ class MetadataOverwriteLM:
                 "clip_skip": (
                     "INT",
                     {
-                        "default": 0,
-                        "min": -24,
+                        "default": _CLIP_SKIP_SENTINEL,
+                        "min": -25,
                         "max": 24,
-                        "tooltip": "Clip skip. Only overwrites when non-zero.",
+                        "tooltip": (
+                            "Clip skip (ComfyUI: -24..-1, A1111: 1+). "
+                            "Default -25 means not set — any other value "
+                            "overwrites."
+                        ),
                     },
                 ),
                 "additional_data": (
@@ -144,14 +153,18 @@ class MetadataOverwriteLM:
     OUTPUT_NODE = True
 
     def collect_metadata(self, **kwargs: Any) -> tuple[dict[str, Any]]:
-        """Collect non-falsy input values into a metadata dict.
+        """Collect non-default input values into a metadata dict.
 
-        Only values that are truthy (non-empty string, non-zero number)
-        are included — matching the overwrite logic in the metadata pipeline.
+        For most fields, a falsy value (empty string, 0) means "not set"
+        and is skipped.  clip_skip uses a dedicated sentinel (-25) so that
+        a wired value of 0 is preserved and reaches the metadata pipeline.
         """
         result: dict[str, Any] = {}
         for key in METADATA_OVERWRITE_FIELDS:
             value = kwargs.get(key)
-            if value:
+            if key == "clip_skip":
+                if value != _CLIP_SKIP_SENTINEL:
+                    result[key] = value
+            elif value:
                 result[key] = value
         return (result,)

py/nodes/save_image.py

@@ -476,11 +476,9 @@ class SaveImageLM:
             params.append(f"Seed: {seed}")
         if size:
             params.append(f"Size: {size}")
-        if clip_skip:
+        if clip_skip is not None:
             try:
-                cs = int(clip_skip)
-                if cs != 0:
-                    params.append(f"Clip skip: {abs(cs)}")
+                params.append(f"Clip skip: {abs(int(clip_skip))}")
             except (ValueError, TypeError):
                 pass
         additional_data = metadata_dict.get("additional_data", "")

tests/metadata_collector/test_metadata_collector.py

@@ -870,7 +870,8 @@ def test_metadata_overwrite_extractor_stores_truthy_values(metadata_registry):
     assert "steps" not in params
     assert "sampler" not in params
     assert "scheduler" not in params
-    assert "clip_skip" not in params
+    # clip_skip=0 is now stored (0 != sentinel -25) — wired 0 is valid
+    assert params["clip_skip"] == 0
 
     metadata_registry.clear_metadata()
 
@@ -880,8 +881,10 @@ def test_metadata_overwrite_extractor_empty_inputs(metadata_registry):
     metadata_registry.start_collection("prompt-ow2")
     metadata = metadata_registry.prompt_metadata["prompt-ow2"]
 
+    from py.metadata_collector.constants import CLIP_SKIP_SENTINEL
+
     inputs = {key: "" for key in METADATA_OVERWRITE_FIELDS}
-    inputs.update({"seed": 0, "steps": 0, "cfg_scale": 0.0, "clip_skip": 0})
+    inputs.update({"seed": 0, "steps": 0, "cfg_scale": 0.0, "clip_skip": CLIP_SKIP_SENTINEL})
 
     MetadataOverwriteExtractor.extract("ow-2", inputs, None, metadata)
 
@@ -950,7 +953,8 @@ def test_extract_generation_params_overwrite_falsy_skipped(metadata_registry, po
     registry_obj.set_current_prompt(populated_registry["prompt"])
     metadata2 = registry_obj.prompt_metadata["promptA"]
 
-    # Inject overwrite with falsy values
+    # Inject overwrite with falsy values (except clip_skip=0 which is now
+    # treated as a valid wired input thanks to the -25 sentinel)
     metadata2[OVERWRITE] = {
         "ow-1": {
             "parameters": {
@@ -974,6 +978,9 @@ def test_extract_generation_params_overwrite_falsy_skipped(metadata_registry, po
     assert params["prompt"] == "A castle on a hill"
     assert params["cfg_scale"] == 7.5
 
+    # clip_skip=0 is a valid wired value (not the -25 sentinel) — should be applied
+    assert params["clip_skip"] == 0
+
     registry_obj.clear_metadata()