Fix loop skip row indexing

README.md

@@ -92,17 +92,18 @@ pattern, but add a dedicated collector output for building a result sequence.
 Basic loop wiring:
 
 1. Connect `For Loop Start.flow` to `For Loop End.flow`.
-2. Use `For Loop Start.index` inside the loop for seed/index changes.
+2. Use `For Loop Start.index` inside the loop for row/seed/index changes.
 3. Connect the per-iteration output you want to keep, such as an image, latent,
    prompt, or metadata string, to `For Loop End.collect_value`.
 4. Optionally connect `For Loop Start.collected` to `For Loop End.collected`.
    If omitted, the end node uses the start collector internally.
 5. After the loop finishes, use `For Loop End.collected` as the combined output.
 
-`For Loop Start.skip` skips the first N iterations while keeping the index
+`For Loop Start.index` is 1-based so it can be wired directly into prompt-builder
-stable. For example, `total=10` and `skip=1` runs indexes `1..9`; `skip=5` runs
+`row_number` inputs. `For Loop Start.skip` skips the first N iterations while
-indexes `5..9`. This is useful when you want to resume a loop without changing
+keeping the remaining row numbers stable. For example, `total=10` and `skip=1`
-index-derived seeds or row numbers.
+runs indexes `2..10`; `skip=5` runs indexes `6..10`. This is useful when you
+want to resume a loop without changing index-derived seeds or row numbers.
 
 `collection_mode` controls how values are stored:
 

loop_nodes.py

@@ -279,8 +279,10 @@ class SxCPForLoopStart:
 
     def start(self, total, skip=0, initial_index=None, initial_collected=None, **kwargs):
         _require_graph_builder()
+        total = max(1, int(total))
         skip = max(0, int(skip))
-        index = skip if initial_index is None else max(int(initial_index), skip)
+        first_index = skip + 1
+        index = first_index if initial_index is None else max(int(initial_index), first_index)
         collected = initial_collected
         initial_values = {
             "initial_value0": index,
@@ -289,7 +291,7 @@ class SxCPForLoopStart:
         for carry_index in range(1, MAX_CARRY_VALUES + 1):
             initial_values[f"initial_value{carry_index + 1}"] = kwargs.get(f"initial_value{carry_index}")
         graph = GraphBuilder()
-        graph.node("SxCPWhileLoopStart", condition=index < int(total), **initial_values)
+        graph.node("SxCPWhileLoopStart", condition=index <= total, **initial_values)
         return {
             "result": tuple(["stub", index, collected] + [kwargs.get(f"initial_value{index}") for index in range(1, MAX_CARRY_VALUES + 1)]),
             "expand": graph.finalize(),
@@ -357,7 +359,7 @@ class SxCPForLoopEnd:
             raise ValueError("SxCP For Loop End must receive flow from SxCP For Loop Start.")
         total = start_node["inputs"]["total"]
         next_index = graph.node("SxCPLoopIntAdd", a=[loop_start, 1], b=1)
-        condition = graph.node("SxCPLoopLessThan", a=next_index.out(0), b=total)
+        condition = graph.node("SxCPLoopLessThanOrEqual", a=next_index.out(0), b=total)
         collection = kwargs.get("collected") or [loop_start, 2]
         collect_value = kwargs.get("collect_value")
         next_collection = graph.node(
@@ -418,6 +420,24 @@ class SxCPLoopLessThan:
         return (int(a) < int(b),)
 
 
+class SxCPLoopLessThanOrEqual:
+    @classmethod
+    def INPUT_TYPES(cls):
+        return {
+            "required": {
+                "a": ("INT", {"default": 0}),
+                "b": ("INT", {"default": 0}),
+            }
+        }
+
+    RETURN_TYPES = ("BOOLEAN",)
+    FUNCTION = "compare"
+    CATEGORY = "prompt_builder/loop/internal"
+
+    def compare(self, a, b):
+        return (int(a) <= int(b),)
+
+
 LOOP_NODE_CLASS_MAPPINGS = {
     "SxCPWhileLoopStart": SxCPWhileLoopStart,
     "SxCPWhileLoopEnd": SxCPWhileLoopEnd,
@@ -426,6 +446,7 @@ LOOP_NODE_CLASS_MAPPINGS = {
     "SxCPLoopAppend": SxCPLoopAppend,
     "SxCPLoopIntAdd": SxCPLoopIntAdd,
     "SxCPLoopLessThan": SxCPLoopLessThan,
+    "SxCPLoopLessThanOrEqual": SxCPLoopLessThanOrEqual,
 }
 
 LOOP_NODE_DISPLAY_NAME_MAPPINGS = {
@@ -436,4 +457,5 @@ LOOP_NODE_DISPLAY_NAME_MAPPINGS = {
     "SxCPLoopAppend": "SxCP Loop Append",
     "SxCPLoopIntAdd": "SxCP Loop Int Add",
     "SxCPLoopLessThan": "SxCP Loop Less Than",
+    "SxCPLoopLessThanOrEqual": "SxCP Loop Less Than Or Equal",
 }