diff --git a/public/js/main.js b/public/js/main.js
index 7da5271..fafe3d3 100644
--- a/public/js/main.js
+++ b/public/js/main.js
@@ -94,6 +94,7 @@ document.addEventListener('DOMContentLoaded', () => {
     let managedSubtitleTracks = [];
     let selectedSubtitleTrackId = 'off';
     let pendingAutoPlayAfterDownload = false;
+    let lastPolledProgressSignature = '';
 
     if (videoPlayer) {
         videoPlayer.controls = false;
@@ -1377,10 +1378,22 @@ document.addEventListener('DOMContentLoaded', () => {
     const pollProgress = async () => {
         if (!currentVideoKey) return;
         try {
-            const res = await fetch(`/api/progress?key=${encodeURIComponent(currentVideoKey)}`);
+            const res = await fetch(`/api/progress?key=${encodeURIComponent(currentVideoKey)}&_=${Date.now()}`, {
+                cache: 'no-store'
+            });
             if (!res.ok) return;
             const data = await res.json();
             if (data?.progress) {
+                const nextSignature = `${data.progress.status}:${typeof data.progress.percent === 'number' ? data.progress.percent : 'na'}`;
+                if (lastPolledProgressSignature !== nextSignature) {
+                    lastPolledProgressSignature = nextSignature;
+                    console.log('[progress-poll]', {
+                        status: data.progress.status,
+                        percent: data.progress.percent,
+                        downloadedBytes: data.progress.downloadedBytes,
+                        totalBytes: data.progress.totalBytes
+                    });
+                }
                 handleProgress(data.progress);
                 if (typeof data.progress.duration === 'number' && data.progress.duration > 0) {
                     videoDuration = data.progress.duration;
diff --git a/server.js b/server.js
index d979d6f..2894228 100644
--- a/server.js
+++ b/server.js
@@ -91,6 +91,7 @@ const createS3Client = (credentials) => {
 const progressMap = {};
 const transcodeProcesses = new Map();
 const wsSubscriptions = new Map();
+const progressApiLogMap = new Map();
 
 const AVAILABLE_VIDEO_ENCODERS = [
     { value: 'h264_rkmpp', label: 'h264_rkmpp (RKMPP H.264)' },
@@ -822,6 +823,16 @@ app.get('/api/progress', (req, res) => {
 
         const progressKey = getProgressKey(key);
         const progress = progressMap[progressKey] || null;
+        const observedState = progress
+            ? `${progress.status}:${typeof progress.percent === 'number' ? progress.percent : 'na'}`
+            : 'null';
+        if (progressApiLogMap.get(progressKey) !== observedState) {
+            progressApiLogMap.set(progressKey, observedState);
+            console.log(`[progress-api] key=${key} status=${progress?.status || 'null'} percent=${typeof progress?.percent === 'number' ? progress.percent : 'na'}`);
+        }
+        res.setHeader('Cache-Control', 'no-store, no-cache, must-revalidate, proxy-revalidate');
+        res.setHeader('Pragma', 'no-cache');
+        res.setHeader('Expires', '0');
         res.json({ progress });
     } catch (error) {
         console.error('Error fetching progress:', error);