Upload alpha_factory/deterministic/expression_mutator.py

alpha_factory/deterministic/expression_mutator.py

@@ -90,7 +90,8 @@ def mutate_vol_scale(expression: str) -> list[dict]:
     """Add volatility scaling to the signal."""
     # If expression has a raw field, wrap it in vol-normalization
     # Pattern: find the innermost field reference and divide by ts_std
-    match = re.search(r"(ts_(?:rank|mean)\()([a-z][a-z0-9_]+)(,\s*\d+\))", expression)
+    # BRAIN field IDs can contain uppercase (e.g., mdl77_2GlobalDev...)
+    match = re.search(r"(ts_(?:rank|mean)\()([a-zA-Z][a-zA-Z0-9_]+)(,\s*\d+\))", expression)
     if not match:
         return []