diff --git a/src/mir/builder/builder_calls.rs b/src/mir/builder/builder_calls.rs
index 5e5203b7..2d8a4441 100644
--- a/src/mir/builder/builder_calls.rs
+++ b/src/mir/builder/builder_calls.rs
@@ -160,6 +160,9 @@ impl super::MirBuilder {
                         .filter(|(_, &vid)| vid == r)
                         .map(|(k, _)| k.clone())
                         .collect();
+                    // CRITICAL DEBUG: Show type information sources
+                    let origin = self.value_origin_newbox.get(&r).cloned();
+                    let vtype = self.value_types.get(&r).cloned();
                     eprintln!(
                         "[builder/recv-trace] fn={} bb={:?} method={}.{} recv=%{} aliases={:?}",
                         current_fn,
@@ -169,6 +172,10 @@ impl super::MirBuilder {
                         r.0,
                         names
                     );
+                    eprintln!(
+                        "[builder/recv-trace]   value_origin_newbox: {:?}, value_types: {:?}",
+                        origin, vtype
+                    );
                 }
                 // Prefer pinning to a slot so start_new_block can propagate it across entries.
                 let r_pinned = self.pin_to_slot(r, "@recv").unwrap_or(r);
diff --git a/src/mir/builder/decls.rs b/src/mir/builder/decls.rs
index 19b61672..73912190 100644
--- a/src/mir/builder/decls.rs
+++ b/src/mir/builder/decls.rs
@@ -33,12 +33,18 @@ impl super::MirBuilder {
                     let func_name = format!("{}.{}", box_name, "main");
                     eprintln!("[DEBUG] build_static_main_box: Before lower_static_method_as_function");
                     eprintln!("[DEBUG]   variable_map = {:?}", self.variable_map);
+                    // ✅ CRITICAL FIX: Clear metadata maps BEFORE Phase 1 compilation
+                    // This prevents pollution from using statement resolution during Phase 1
+                    // from leaking into Phase 2 (inline main execution).
+                    // Root cause: Using statements create boxes (ParserBox, etc.) and their metadata
+                    // (variable_map, value_origin_newbox, value_types) gets saved/restored incorrectly.
+                    // This caused parameters like "args" to be incorrectly typed as "ParserBox".
+                    self.variable_map.clear();
+                    self.value_origin_newbox.clear();
+                    self.value_types.clear();
                     let _ = self.lower_static_method_as_function(func_name, params.clone(), body.clone());
                     eprintln!("[DEBUG] build_static_main_box: After lower_static_method_as_function");
                     eprintln!("[DEBUG]   variable_map = {:?}", self.variable_map);
-                    // ✅ PHI UseBeforeDef修正: 関数生成後、変数マップをクリア
-                    // 理由: cf_block()で同じbodyを再処理する際、前の関数の変数（PHI ID等）が混入するのを防ぐ
-                    self.variable_map.clear();
                     // Convert the method body to a Program AST node and lower it
                     let program_ast = ASTNode::Program {
                     statements: body.clone(),
diff --git a/src/mir/builder/exprs.rs b/src/mir/builder/exprs.rs
index feebec2d..c9c4469b 100644
--- a/src/mir/builder/exprs.rs
+++ b/src/mir/builder/exprs.rs
@@ -162,6 +162,19 @@ impl super::MirBuilder {
                 } else if is_static {
                     // Generic static box: lower all static methods into standalone MIR functions (BoxName.method/N)
                     self.user_defined_boxes.insert(name.clone());
+                    // ✅ CRITICAL FIX: Clear metadata maps BEFORE compiling each static box
+                    // This prevents pollution from using statement resolution from leaking between boxes.
+                    // Root cause: Using statements create boxes (ParserBox, etc.) and their metadata
+                    // (variable_map, value_origin_newbox, value_types) leaks into subsequent box compilations.
+                    // This caused parameters like "args" to be incorrectly typed as "ParserBox".
+                    eprintln!("[DEBUG/static-box] Processing static box: {}", name);
+                    eprintln!("[DEBUG/static-box]   BEFORE clear: value_origin_newbox size={}, value_types size={}",
+                              self.value_origin_newbox.len(), self.value_types.len());
+                    self.variable_map.clear();
+                    self.value_origin_newbox.clear();
+                    self.value_types.clear();
+                    eprintln!("[DEBUG/static-box]   AFTER clear: value_origin_newbox size={}, value_types size={}",
+                              self.value_origin_newbox.len(), self.value_types.len());
                     for (method_name, method_ast) in methods.clone() {
                         if let ASTNode::FunctionDeclaration { params, body, .. } = method_ast {
                             let func_name = format!(
diff --git a/src/mir/builder/lifecycle.rs b/src/mir/builder/lifecycle.rs
index 9e172c28..b36a1375 100644
--- a/src/mir/builder/lifecycle.rs
+++ b/src/mir/builder/lifecycle.rs
@@ -87,6 +87,14 @@ impl super::MirBuilder {
                             if name == "Main" {
                                 main_static = Some((name.clone(), methods.clone()));
                             } else {
+                                // ✅ CRITICAL FIX: Clear metadata maps BEFORE compiling each static box
+                                // This prevents pollution from using statement resolution and previous boxes
+                                // from leaking into this box's method compilations.
+                                // Root cause: Using statements and previous box compilations create metadata
+                                // (variable_map, value_origin_newbox, value_types) that leaks into subsequent compilations.
+                                self.variable_map.clear();
+                                self.value_origin_newbox.clear();
+                                self.value_types.clear();
                                 // Lower all static methods into standalone functions: BoxName.method/Arity
                                 for (mname, mast) in methods.iter() {
                                     if let N::FunctionDeclaration { params, body, .. } = mast {