diff --git a/sim_b.py b/sim_b.py
new file mode 100644
index 000000000..cbe29a609
--- /dev/null
+++ b/sim_b.py
@@ -0,0 +1,9 @@
+"""Scenario B — feature work that lands first, then merge master in."""
+
+
+def compute_total(items):
+    """Shadows builtin 'sum'."""
+    sum = 0
+    for item in items:
+        sum += item
+    return sum