diff --git a/static/js/app.js b/static/js/app.js
index 5ac24f8..39b8ae7 100644
--- a/static/js/app.js
+++ b/static/js/app.js
@@ -2769,8 +2769,28 @@ let currentImageMap = {};
 let readerScrollSaveTimer = null;
 let _resizeObserver = null;
 let _currentPositionAnchor = '';
+let _currentBookCharCount = 0;
 const bookMetaCache = {}; // id → {title, author, type}
 
+// Reading-position percentages (the progress readout, annotation "% im Buch"
+// coordinates): a whole percent is fine for a normal book, but on a long one
+// (~600-700 physical pages and up) it barely moves during a whole scrolling
+// session, which reads as broken. Past that length, show one decimal —
+// formatted with the browser locale's own decimal separator.
+const LONG_BOOK_CHAR_THRESHOLD = 1000000;
+
+function _formatBookPercent(fraction) {
+  const pct = Math.max(0, Math.min(100, fraction * 100));
+  const decimals = _currentBookCharCount > LONG_BOOK_CHAR_THRESHOLD ? 1 : 0;
+  return pct.toLocaleString(undefined, {minimumFractionDigits: decimals, maximumFractionDigits: decimals});
+}
+
+// Accepts both '45.3' and '45,3' (locale-typed input)
+function _parseLocalePercent(str) {
+  const v = parseFloat(String(str).trim().replace(',', '.'));
+  return isNaN(v) ? 0 : v;
+}
+
 // ---------------------------------------------------------------------------
 // Reader "scrolled too far" safety net — offers a toast to jump back after a
 // sudden, large scroll (accidental fling, fat-fingered keybind, etc.). Only
@@ -3722,6 +3742,9 @@ async function openBook(bookId) {
         contentEl.appendChild(frag);
         await new Promise(r => requestAnimationFrame(r));
       }
+      // Used to decide whole-percent vs one-decimal display further down —
+      // see _formatBookPercent().
+      _currentBookCharCount = contentEl.textContent.length;
     }
 
     currentBookToc = toc;
@@ -3752,14 +3775,10 @@ async function openBook(bookId) {
     if (progressInput) {
       progressInput.style.display = '';
       if (isPdf) {
-        progressInput.min = 1;
-        progressInput.max = numPages;
         progressInput.value = 1;
         if (progressSuffix) progressSuffix.textContent = `/ ${numPages}`;
       } else {
-        progressInput.min = 0;
-        progressInput.max = 100;
-        progressInput.value = 0;
+        progressInput.value = _formatBookPercent(0);
         if (progressSuffix) progressSuffix.textContent = '%';
       }
 
@@ -3774,8 +3793,8 @@ async function openBook(bookId) {
             contentEl.scrollBy({top: top - 8, behavior: 'smooth'});
           }
         } else {
-          const pct = Math.min(100, Math.max(0, parseInt(this.value, 10) || 0));
-          this.value = pct;
+          const pct = Math.min(100, Math.max(0, _parseLocalePercent(this.value)));
+          this.value = _formatBookPercent(pct / 100);
           contentEl.scrollTop = (pct / 100) * contentEl.scrollHeight;
         }
       });
@@ -3847,7 +3866,7 @@ async function openBook(bookId) {
         progressInput.value = currentPage;
       } else {
         const f = contentEl.scrollTop / (contentEl.scrollHeight - contentEl.clientHeight || 1);
-        progressInput.value = Math.round(f * 100);
+        progressInput.value = _formatBookPercent(f);
       }
     });
 
@@ -4061,6 +4080,7 @@ function closeReader() {
   // Reset all state
   currentBookId = null;
   currentBookToc = [];
+  _currentBookCharCount = 0;
   currentPdfDoc = null;
   currentPdfBuffer = null;
   currentBookmarks = [];
@@ -5599,7 +5619,7 @@ function exportAnnotations() {
       lastChapter = chapterTitle;
     }
     const pct = _percentFromRange(range);
-    const coord = pct !== null ? ` (≈${Math.round(pct)}% im Buch)` : '';
+    const coord = pct !== null ? ` (≈${_formatBookPercent(pct / 100)}% im Buch)` : '';
     if (h.type === 'note') {
       lines.push(`[Note]${coord} near: "${(h.anchor?.quote || '').trim()}"`);
       if (h.note) lines.push(`    ${h.note}`);
@@ -5635,7 +5655,7 @@ function openAnnotationsSidebar() {
   let html = '<ul style="list-style:none;padding:0;">';
   for (const {h, range} of resolved) {
     const pct = _percentFromRange(range);
-    const pctLabel = pct !== null ? `≈${Math.round(pct)}%` : '';
+    const pctLabel = pct !== null ? `≈${_formatBookPercent(pct / 100)}%` : '';
     const kind = h.type === 'note' ? 'Note' : `Highlight${h.color ? ' · ' + h.color : ''}`;
     const preview = h.note || h.anchor?.quote || '(no text)';
     html += `<li class="bookmark-entry">
diff --git a/static/js/sw.js b/static/js/sw.js
index 5022ab8..615ac52 100644
--- a/static/js/sw.js
+++ b/static/js/sw.js
@@ -2,7 +2,7 @@
  * diora service worker — caches the app shell for offline use.
  */
 
-const CACHE = 'diora-v26';
+const CACHE = 'diora-v27';
 const PODCAST_CACHE = 'diora-podcast-v1';
 const SHELL = [
   '/static/css/app.css',
diff --git a/templates/radio/player.html b/templates/radio/player.html
index c7a5c93..a675e93 100644
--- a/templates/radio/player.html
+++ b/templates/radio/player.html
@@ -335,7 +335,7 @@
     <span id="reader-title" class="reader-title"></span>
     <div class="reader-header-actions">
       <span class="reader-progress-wrap">
-        <input type="number" id="reader-progress-input" class="volume-num" min="0" max="100" value="0" style="display:none;">
+        <input type="text" inputmode="decimal" id="reader-progress-input" class="volume-num" value="0" style="display:none;">
         <span id="reader-progress-suffix" class="muted"></span>
       </span>
       <button class="btn-icon" id="reader-search-btn"   onclick="toggleReaderSearch()"        title="Search">⌕</button>