diff --git a/frontend/src/utils/ChartManager.ts b/frontend/src/utils/ChartManager.ts
index f070252..87ac240 100644
--- a/frontend/src/utils/ChartManager.ts
+++ b/frontend/src/utils/ChartManager.ts
@@ -1397,6 +1397,17 @@ export class ChartManager {
       .filter(p => p.value != null && !isNaN(p.value) && bMap.has(p.time))
       .map(p => ({ time: p.time as number, spanA: p.value, spanB: bMap.get(p.time)! }));
 
+    // 진단 로그: spanA/spanB 원본 값 비교
+    const aValid = (spanAPlot ?? []).filter(p => p.value != null && !isNaN(p.value));
+    const bValid = (spanBPlot ?? []).filter(p => p.value != null && !isNaN(p.value));
+    const aLast3 = aValid.slice(-3).map(p => p.value);
+    const bLast3 = bValid.slice(-3).map(p => p.value);
+    const histLast3 = historical.slice(-3).map(p => ({ a: p.spanA, b: p.spanB, eq: p.spanA === p.spanB }));
+    const maxHistDiff = historical.length > 0 ? Math.max(...historical.map(p => Math.abs(p.spanA - p.spanB))) : 0;
+    console.log('[IchimokuCloud] BUILD RAW: spanA last3=', aLast3, 'spanB last3=', bLast3,
+      '| hist last3=', JSON.stringify(histLast3), '| maxDiff=', maxHistDiff,
+      '| histLen=', historical.length, 'sameRef=', spanAPlot === spanBPlot);
+
     // 미래 구름
     const N = this.rawBars.length;
     if (N < 2) return historical;