@@ -14,8 +14,10 @@
 knowable without running anything: `source` is an `asset:`/`output:`
 reference or a literal path the run may read (`dw/probe_paths.py`), probed
 header-only (`probe_metadata`, B9); `num_frames` and `overlap` are literal
-after substitution; and `videos` is a list - which is what `gather:<step>`
-becomes once `for_each` has expanded, one entry per member. The rule itself
+whole numbers after substitution - an int, an integral float or a numeric
+string, read by `whole_number` as the run reads them (#785); and `videos` is
+a list - which is what `gather:<step>` becomes once `for_each` has expanded,
+one entry per member. The rule itself
 is `window_count_problem` in `dw/task_domains.py`, the one the task calls at
 run time, so the two cannot drift.
 
@@ -28,24 +30,23 @@
 report, so it is skipped here rather than reported twice.
 """
 
-import numbers
-
 from .for_each import MEMBER_SEPARATOR, render_path
 from .media import probe_metadata
 from .probe_paths import resolve_probe_path
 from .references import author_index
-from .task_domains import window_count_problem
-
-
-def _literal_whole(value):
-    """`value` as an int when it is a literal whole number, else None."""
-    if isinstance(value, bool):
+from .task_domains import whole_number, window_count_problem
+
+
+def _literal_whole(value, name):
+    """`value` as an int when it is a literal whole number, read by
+    `whole_number`'s rules (`33`, `33.0`, `"33"`, `"33.0"` are all 33), else
+    None. A value that is not a whole number - a fraction, a bool, an
+    unresolved reference - is skipped here: `join_windows_errors` refuses it
+    with the "whole number" message, so it is not reported twice (#785)."""
+    try:
+        return whole_number(value, name, "join_windows")
+    except ValueError:
         return None
-    if isinstance(value, numbers.Integral):
-        return int(value)
-    if isinstance(value, float) and value.is_integer():
-        return int(value)
-    return None
 
 
 def _frame_count(path, probe):
@@ -87,8 +88,8 @@ def window_count_errors(
         videos = arguments.get("videos")
         if not isinstance(videos, list) or not videos:
             continue
-        num_frames = _literal_whole(arguments.get("num_frames"))
-        overlap = _literal_whole(arguments.get("overlap"))
+        num_frames = _literal_whole(arguments.get("num_frames"), "num_frames")
+        overlap = _literal_whole(arguments.get("overlap"), "overlap")
         if num_frames is None or overlap is None:
             continue
         if num_frames <= 0 or overlap < 0 or overlap >= num_frames:
 
@@ -6,6 +6,8 @@
 step) rather than a template.
 """
 
+import pytest
+
 from dw.media import probe_metadata
 from dw.window_count_errors import window_count_errors
 from dw.workflow import workflow_from_definition
@@ -55,12 +57,13 @@ def window_workflow(window_count, num_frames=NUM_FRAMES, overlap=OVERLAP):
     }
 
 
-def validate(monkeypatch, tmp_path, window_count, frames=50):
+def validate(monkeypatch, tmp_path, window_count, frames=50, **numbers):
     import os
 
     base_dir = workflow_dir_with_asset(monkeypatch, tmp_path, ("long.mp4", frames))
     workflow = workflow_from_definition(
-        window_workflow(window_count), os.path.join(base_dir, "workflow.json")
+        window_workflow(window_count, **numbers),
+        os.path.join(base_dir, "workflow.json"),
     )
     return [
         problem
@@ -110,6 +113,45 @@ def test_a_long_list_names_the_drop(self, monkeypatch, tmp_path):
         assert "got 5" in problems[0]["message"]
         assert "drop 1 entry (index 4)" in problems[0]["message"]
 
+    @pytest.mark.parametrize(
+        "num_frames, overlap",
+        [
+            (NUM_FRAMES, OVERLAP),
+            (str(NUM_FRAMES), str(OVERLAP)),
+            (float(NUM_FRAMES), float(OVERLAP)),
+            (f"{NUM_FRAMES}.0", float(OVERLAP)),
+            (f"{NUM_FRAMES}.0", f"{OVERLAP}.0"),
+        ],
+        ids=["int", "string", "float", "float-string+float", "float-strings"],
+    )
+    def test_every_whole_number_form_gets_the_int_refusal(
+        self, monkeypatch, tmp_path, num_frames, overlap
+    ):
+        """C-F354h (#785): "17", 17.0 and "17.0" are read by whole_number's
+        rules, as the run reads them, so validate refuses the short list the
+        same way it does for 17 instead of skipping the check."""
+        problems = validate(
+            monkeypatch, tmp_path, 3, num_frames=num_frames, overlap=overlap
+        )
+
+        assert problems == [
+            {
+                "path": "steps[1]",
+                "message": "join_windows needs 4 windows for a 50-frame source"
+                " with num_frames 17 and overlap 4 (stride 13), got 3"
+                " - add 1 entry (index 3)",
+            }
+        ]
+
+    def test_a_fractional_string_is_left_to_the_whole_number_refusal(
+        self, monkeypatch, tmp_path
+    ):
+        """A non-whole value names no count; the domain check refuses it."""
+        problems = validate(monkeypatch, tmp_path, 3, num_frames="17.5")
+
+        assert not [p for p in problems if "windows for a" in p["message"]]
+        assert any("whole number for 'num_frames'" in p["message"] for p in problems)
+
     def test_an_unreadable_literal_source_is_refused_at_its_path(
         self, monkeypatch, tmp_path
     ):