diff --git a/frontend/src/App.coverage.test.tsx b/frontend/src/App.coverage.test.tsx
index 0b9a20aa8..d5332b4b2 100644
--- a/frontend/src/App.coverage.test.tsx
+++ b/frontend/src/App.coverage.test.tsx
@@ -610,6 +610,7 @@ describe('App orchestration coverage', () => {
   it('logs auto-layout failures and preserves nodes added after the undo snapshot', async () => {
     await renderReadyApp()
     fireEvent.click(screen.getByRole('button', { name: '다이어그램' }))
+    await waitFor(() => expect(screen.getAllByRole('button', { name: '열기' }).length).toBeGreaterThan(0))
     vi.useFakeTimers()
     fireEvent.click(screen.getAllByRole('button', { name: '열기' })[0]!)
     await act(async () => {
@@ -641,6 +642,7 @@ describe('App orchestration coverage', () => {
       .mockRejectedValueOnce(new Error('terminal refresh down'))
     await renderReadyApp()
     fireEvent.click(screen.getByRole('button', { name: '다이어그램' }))
+    await waitFor(() => expect(screen.getAllByRole('button', { name: '열기' }).length).toBeGreaterThan(0))
     vi.useFakeTimers()
     fireEvent.click(screen.getAllByRole('button', { name: '열기' })[0]!)
     await act(async () => {
@@ -744,6 +746,7 @@ describe('App orchestration coverage', () => {
     }))
     await renderReadyApp()
     fireEvent.click(screen.getByRole('button', { name: '다이어그램' }))
+    await waitFor(() => expect(screen.getAllByRole('button', { name: '열기' }).length).toBeGreaterThan(0))
     vi.useFakeTimers()
     fireEvent.click(screen.getAllByRole('button', { name: '열기' })[0]!)
     await act(async () => {
@@ -784,6 +787,7 @@ describe('App orchestration coverage', () => {
     })
     await renderReadyApp()
     fireEvent.click(screen.getByRole('button', { name: '다이어그램' }))
+    await waitFor(() => expect(screen.getAllByRole('button', { name: '열기' }).length).toBeGreaterThan(0))
     vi.useFakeTimers()
     fireEvent.click(screen.getAllByRole('button', { name: '열기' })[0]!)
     await act(async () => {
diff --git a/frontend/src/erd/handleUtils.ts b/frontend/src/erd/handleUtils.ts
index 054d5ab2a..4dd087aac 100644
--- a/frontend/src/erd/handleUtils.ts
+++ b/frontend/src/erd/handleUtils.ts
@@ -1,16 +1,28 @@
+/**
+ * Encode a persisted column name into the canonical React Flow handle payload.
+ * The code-point format is a compatibility contract shared by graph rendering
+ * and exporters, so equivalent refactors must preserve the exact bytes.
+ */
 export function sanitizeHandleId(columnName: string): string {
-  const encoded = Array.from(columnName, (char) => {
-    // Array.from only yields non-empty Unicode scalars, so codePointAt(0) is defined.
-    return char.codePointAt(0)!.toString(16).padStart(4, '0')
-  }).join('-')
+  if (!columnName) return 'c-empty';
 
-  return `c-${encoded || 'empty'}`
+  let encoded = '';
+  for (const char of columnName) {
+    if (encoded.length > 0) {
+      encoded += '-';
+    }
+    encoded += char.codePointAt(0)!.toString(16).padStart(4, '0');
+  }
+
+  return `c-${encoded}`;
 }
 
+/** Return the canonical source-endpoint handle for a persisted column name. */
 export function sourceColumnHandleId(columnName: string): string {
   return `src-${sanitizeHandleId(columnName)}`
 }
 
+/** Return the canonical target-endpoint handle for a persisted column name. */
 export function targetColumnHandleId(columnName: string): string {
   return `tgt-${sanitizeHandleId(columnName)}`
 }