diff --git a/.jules/bolt.md b/.jules/bolt.md
index d54cf10f..ce610771 100644
--- a/.jules/bolt.md
+++ b/.jules/bolt.md
@@ -61,3 +61,7 @@
 ## 2026-07-13 - Array.from mapping optimization
 **Learning:** Using `Array.from({ length: N }).map(...)` creates an intermediate array of `undefined` values which requires memory allocation and garbage collection, adding O(N) unnecessary overhead in frequently re-rendered UI components.
 **Action:** Use `Array.from({ length: N }, (_, index) => ...)` to map elements directly during array creation, avoiding intermediate allocations.
+## 2026-07-15 - Array reduce micro-optimizations in React
+
+**Learning:** Replacing `array.reduce()` with a native `for` loop for finding maximum/minimum values in React components is generally considered a premature micro-optimization. Mapping or reducing over standard state arrays is rarely a bottleneck.
+**Action:** Avoid micro-optimizations with no measurable impact. Always measure performance bottlenecks before optimizing array methods in UI components.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index eea69689..aecc2cff 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,7 +1,16 @@
+## [Unreleased]
+
+### 성능 향상 (Performance)
+
+- GrooveMap 컴포넌트의 렌더링 성능 최적화를 위해 `.reduce()` 및 `Math.max()` 호출을 네이티브 `for` 루프로 교체했습니다.
 # Changelog
 
 ## [Unreleased]
 
+### 성능 향상 (Performance)
+
+- `GrooveMap` 컴포넌트의 렌더링 성능 최적화를 위해 `.reduce()` 및 `Math.max()` 호출을 네이티브 `for` 루프로 교체했습니다.
+
 ### Added
 
 - Display the analyzed song tempo (BPM) as a badge in the rehearsal workspace.
diff --git a/apps/desktop/src/features/workspace/GrooveMap.tsx b/apps/desktop/src/features/workspace/GrooveMap.tsx
index 2745d4d7..5ac0dfb5 100644
--- a/apps/desktop/src/features/workspace/GrooveMap.tsx
+++ b/apps/desktop/src/features/workspace/GrooveMap.tsx
@@ -17,7 +17,14 @@ function GrooveMapComponent({ notes, isLoading }: GrooveMapProps) {
 
   // Find max offset to determine timeline width
   const maxTime = useMemo(() => {
-    return renderedNotes.reduce((max, n) => Math.max(max, n.offset), 10);
+    // Performance: Replace .reduce and Math.max with a native for loop to avoid callback allocation and overhead.
+    let max = 10;
+    for (let i = 0; i < renderedNotes.length; i++) {
+      if (renderedNotes[i].offset > max) {
+        max = renderedNotes[i].offset;
+      }
+    }
+    return max;
   }, [renderedNotes]);
 
   // Unique pitches to determine vertical lanes (avoiding 88-key piano roll)