diff --git a/codeflash/code_utils/instrument_existing_tests.py b/codeflash/code_utils/instrument_existing_tests.py
index d025f6f35..3e45fbed5 100644
--- a/codeflash/code_utils/instrument_existing_tests.py
+++ b/codeflash/code_utils/instrument_existing_tests.py
@@ -97,14 +97,34 @@ def collect_instance_variables(self, func_node: ast.FunctionDef) -> None:
         if self.class_name is None or self.only_function_name != "forward":
             return
 
-        for node in ast.walk(func_node):
+        class_name = self.class_name
+        instance_vars = self.instance_variable_names
+        
+        # Manually traverse only assignment nodes instead of walking entire tree
+        nodes_to_check = list(func_node.body)
+        while nodes_to_check:
+            node = nodes_to_check.pop()
+            
             # Look for assignments like: model = ClassName(...)
             if isinstance(node, ast.Assign):
-                if isinstance(node.value, ast.Call) and isinstance(node.value.func, ast.Name):
-                    if node.value.func.id == self.class_name:
+                value = node.value
+                if isinstance(value, ast.Call):
+                    func = value.func
+                    if isinstance(func, ast.Name) and func.id == class_name:
                         for target in node.targets:
                             if isinstance(target, ast.Name):
-                                self.instance_variable_names.add(target.id)
+                                instance_vars.add(target.id)
+            
+            # Add nested statements to check
+            if hasattr(node, 'body'):
+                nodes_to_check.extend(node.body)
+            if hasattr(node, 'orelse'):
+                nodes_to_check.extend(node.orelse)
+            if hasattr(node, 'finalbody'):
+                nodes_to_check.extend(node.finalbody)
+            if hasattr(node, 'handlers'):
+                for handler in node.handlers:
+                    nodes_to_check.extend(handler.body)
 
     def find_and_update_line_node(
         self, test_node: ast.stmt, node_name: str, index: str, test_class_name: str | None = None