diff --git a/src/ast/compiler/lambda_collector.rs b/src/ast/compiler/lambda_collector.rs
index 41ad384..2a40d1e 100644
--- a/src/ast/compiler/lambda_collector.rs
+++ b/src/ast/compiler/lambda_collector.rs
@@ -33,7 +33,7 @@ impl<'a, T: Clone> LambdaCollector<'a, T> {
 
                     if let BoundKind::Lambda { .. } = &current.kind {
                         self.registry
-                            .insert(*global_index, Rc::new((**current).clone()));
+                            .insert(*global_index, (*current).clone());
                     }
                 }
                 self.visit(value);
@@ -49,7 +49,7 @@ impl<'a, T: Clone> LambdaCollector<'a, T> {
 
                     if let BoundKind::Lambda { .. } = &current.kind {
                         self.registry
-                            .insert(*global_index, Rc::new((**current).clone()));
+                            .insert(*global_index, (*current).clone());
                     }
                 }
                 self.visit(value);
diff --git a/src/ast/types.rs b/src/ast/types.rs
index 234785d..fa51f46 100644
--- a/src/ast/types.rs
+++ b/src/ast/types.rs
@@ -67,6 +67,9 @@ impl NodeIdentity {
 pub struct Keyword(pub u32);
 
 static KEYWORD_REGISTRY: OnceLock<Mutex<HashMap<String, u32>>> = OnceLock::new();
+// We use String here instead of Arc<str> because benchmarks (e.g. record_optimizations.myc)
+// showed a 4% performance regression with Arc due to atomic overhead during formatting.
+// Since name() is mostly used for diagnostics and UI, the deep clone is acceptable.
 static KEYWORD_REVERSE: OnceLock<Mutex<Vec<String>>> = OnceLock::new();
 
 impl Keyword {