diff --git a/src/mir/control_tree/step_tree.rs b/src/mir/control_tree/step_tree.rs
index 996665db..ead355d4 100644
--- a/src/mir/control_tree/step_tree.rs
+++ b/src/mir/control_tree/step_tree.rs
@@ -55,7 +55,11 @@ pub struct AstNodeHandle(pub Box<ASTNode>);
 #[derive(Debug, Clone, PartialEq)]
 pub enum StepStmtKind {
     LocalDecl { vars: Vec<String> },
-    Assign { target: Option<String> },
+    Assign {
+        target: Option<String>,
+        /// Phase 128: assignment value AST (for Normalized lowering)
+        value_ast: Option<AstNodeHandle>,
+    },
     Print,
     Return {
         /// Phase 123: return value AST (for Normalized lowering)
@@ -188,7 +192,7 @@ impl StepStmtKind {
     fn to_compact_string(&self) -> String {
         match self {
             StepStmtKind::LocalDecl { vars } => format!("local({})", vars.join(",")),
-            StepStmtKind::Assign { target } => match target {
+            StepStmtKind::Assign { target, .. } => match target {
                 Some(name) => format!("assign({name})"),
                 None => "assign(?)".to_string(),
             },
@@ -374,7 +378,7 @@ impl StepTreeBuilderBox {
                 },
                 StepTreeFeatures::default(),
             ),
-            ASTNode::Assignment { span, .. } => (
+            ASTNode::Assignment { span, value, .. } => (
                 StepNode::Stmt {
                     kind: StepStmtKind::Assign {
                         target: match ast {
@@ -384,6 +388,8 @@ impl StepTreeBuilderBox {
                             },
                             _ => None,
                         },
+                        /// Phase 128: Store value AST for Normalized lowering
+                        value_ast: Some(AstNodeHandle(value.clone())),
                     },
                     span: span.clone(),
                 },
@@ -507,12 +513,14 @@ fn walk_for_facts(node: &StepNode, facts: &mut StepTreeFacts) {
                         facts.add_write(v.clone());
                     }
                 }
-                StepStmtKind::Assign { target } => {
+                StepStmtKind::Assign { target, value_ast } => {
                     if let Some(name) = target.as_ref() {
                         facts.add_write(name.clone());
                     }
-                    // Note: Assign RHS is not in StepStmtKind
-                    // We rely on If/Loop condition AST for reads extraction
+                    // Phase 128: Extract reads from assignment value AST
+                    if let Some(ast) = value_ast {
+                        extract_variables_from_ast(&ast.0, facts);
+                    }
                 }
                 StepStmtKind::Print => {}
                 StepStmtKind::Return { value_ast } => {