diff --git a/.jules/palette.md b/.jules/palette.md
index a1633627..77b98dcd 100644
--- a/.jules/palette.md
+++ b/.jules/palette.md
@@ -1,3 +1,7 @@
 ## 2024-05-18 - Disabled and Loading States for Async Actions
 **Learning:** Adding explicit loading and disabled states to asynchronous action buttons (like "Refresh") provides immediate feedback, reducing user confusion and preventing double-submissions.
 **Action:** Always ensure that buttons triggering network requests visually indicate the loading state and are disabled until the request completes.
+
+## 2026-07-06 - Async Button Loading States
+**Learning:** Asynchronous action buttons (e.g., Refresh, Submit) in this app require explicit visual loading states (updating textContent and disabled=true) to prevent double-submissions and improve UX.
+**Action:** Always implement disabled and text state changes on buttons triggering network requests, restoring them in a finally block.
diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 00000000..3f327cd6
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,5 @@
+# 변경 사항 (CHANGELOG)
+
+## [Unreleased]
+### 추가된 기능 (Added)
+- `demo.js` 내의 비동기 버튼(제출, 재시도, 새로고침)에 명시적인 시각적 로딩 상태(버튼 비활성화 및 텍스트 변경)를 추가하여 중복 제출을 방지하고 사용자 경험(UX)을 향상시켰습니다.
diff --git a/src/main/resources/static/assets/viewer/demo.js b/src/main/resources/static/assets/viewer/demo.js
index 84eb8f3a..ddf5b2f0 100644
--- a/src/main/resources/static/assets/viewer/demo.js
+++ b/src/main/resources/static/assets/viewer/demo.js
@@ -271,6 +271,8 @@ async function retryActiveJob() {
   const jobId = activeJobDetail.jobId;
   setStatus("Requesting operator retry...");
   el.retryJobBtn.disabled = true;
+  const originalText = el.retryJobBtn.textContent;
+  el.retryJobBtn.textContent = "Retrying...";
   try {
     const res = await fetch(`/api/v1/convert/jobs/${encodeURIComponent(jobId)}/retry`, {
       method: "POST",
@@ -308,6 +310,7 @@ async function retryActiveJob() {
     setError("Network error while requesting retry. Retry when the service is reachable.");
   } finally {
     el.retryJobBtn.disabled = false;
+    el.retryJobBtn.textContent = originalText;
   }
 }
 
@@ -380,6 +383,9 @@ async function refreshKpis() {
 }
 
 async function refreshKpiEvidence() {
+  el.refreshEvidenceBtn.disabled = true;
+  const originalText = el.refreshEvidenceBtn.textContent;
+  el.refreshEvidenceBtn.textContent = "Refreshing...";
   try {
     const { res, data } = await fetchJson(KPI_EXPORTS_ENDPOINT);
     if (!res.ok) {
@@ -390,6 +396,9 @@ async function refreshKpiEvidence() {
     renderKpiEvidence(data);
   } catch (err) {
     el.kpiExportStatus.textContent = "Snapshot evidence is unavailable while the service is unreachable.";
+  } finally {
+    el.refreshEvidenceBtn.disabled = false;
+    el.refreshEvidenceBtn.textContent = originalText;
   }
 }
 
@@ -436,6 +445,8 @@ async function submitDocument(event) {
   }
 
   el.submitBtn.disabled = true;
+  const originalText = el.submitBtn.textContent;
+  el.submitBtn.textContent = "Submitting...";
   setStatus("Submitting document...");
 
   try {
@@ -479,6 +490,7 @@ async function submitDocument(event) {
     setError("Network error while submitting. Retry when the service is reachable.");
   } finally {
     el.submitBtn.disabled = false;
+    el.submitBtn.textContent = originalText;
   }
 }
 
diff --git a/src/test/java/com/clearfolio/viewer/controller/ViewerUiControllerTest.java b/src/test/java/com/clearfolio/viewer/controller/ViewerUiControllerTest.java
index dadb8949..4bb69a5a 100644
--- a/src/test/java/com/clearfolio/viewer/controller/ViewerUiControllerTest.java
+++ b/src/test/java/com/clearfolio/viewer/controller/ViewerUiControllerTest.java
@@ -121,6 +121,9 @@ void demoScriptUsesExistingApiAndSessionHistory() throws Exception {
             assertTrue(script.contains("X-Clearfolio-Tenant-Id"));
             assertTrue(script.contains("X-Clearfolio-Permissions"));
             assertTrue(script.contains("deadLettered"));
+            assertTrue(script.contains("Refreshing..."));
+            assertTrue(script.contains("Submitting..."));
+            assertTrue(script.contains("Retrying..."));
         }
     }