diff --git a/src/backend/mir_interpreter/handlers/calls/global.rs b/src/backend/mir_interpreter/handlers/calls/global.rs
index 35b132f6..64a76700 100644
--- a/src/backend/mir_interpreter/handlers/calls/global.rs
+++ b/src/backend/mir_interpreter/handlers/calls/global.rs
@@ -142,9 +142,11 @@ impl MirInterpreter {
                 }
                 Ok(VMValue::Void)
             }
-            _ => Err(
-                self.err_with_context("global function", &format!("Unknown: {}", func_name)),
-            ),
+            _ => {
+                // NamingBox SSOT: ここで canonical に失敗したら素直に Unknown とする。
+                // レガシーフォールバック（functions.get(func_name) 再探索）は Phase 25.x で廃止済み。
+                Err(self.err_with_context("global function", &format!("Unknown: {}", func_name)))
+            }
         }
     }
 }
diff --git a/src/mir/builder/decls.rs b/src/mir/builder/decls.rs
index 5e392769..45c6ed1b 100644
--- a/src/mir/builder/decls.rs
+++ b/src/mir/builder/decls.rs
@@ -42,7 +42,8 @@ impl super::MirBuilder {
                     .as_deref()
                     == Some("1")
                 {
-                    let func_name = format!("{}.{}", box_name, "main");
+                    // NamingBox SSOT: Use encode_static_method for main/arity entry
+                    let func_name = crate::mir::naming::encode_static_method(&box_name, "main", params.len());
                     eprintln!(
                         "[DEBUG] build_static_main_box: Before lower_static_method_as_function"
                     );