diff --git a/frontend/js/app.js b/frontend/js/app.js
index 36a0fdef..8a97b3f2 100644
--- a/frontend/js/app.js
+++ b/frontend/js/app.js
@@ -152,7 +152,7 @@ const CollectionAPI = {
             method: 'POST',
             headers: this.getHeaders(),
             credentials: 'include',
-            body: JSON.stringify({ user_id: parseInt(userId), name, description, is_public: isPublic })
+            body: JSON.stringify({ user_id: parseInt(userId, 10), name, description, is_public: isPublic })
         });
         if (!res.ok) {
             const errData = await res.json().catch(() => ({}));
@@ -222,7 +222,7 @@ const CollectionAPI = {
             headers: this.getHeaders(),
             credentials: 'include',
             body: JSON.stringify({
-                user_id: parseInt(userId),
+                user_id: parseInt(userId, 10),
                 google_books_id: bookId,
                 title: title,
                 authors: Array.isArray(authors) ? authors.join(', ') : authors,
@@ -939,7 +939,7 @@ class BookRenderer {
         const slider = scene.querySelector('.progress-slider');
         if (slider) {
             slider.addEventListener('change', (e) => {
-                const newProgress = parseInt(e.target.value);
+                const newProgress = parseInt(e.target.value, 10);
                 if (this.libraryManager) {
                     this.libraryManager.updateBook(id, { progress: newProgress });
                 }
@@ -3483,7 +3483,7 @@ document.addEventListener('DOMContentLoaded', async () => {
 
         if (saveGoalBtn) {
             saveGoalBtn.addEventListener('click', async () => {
-                const target = parseInt(goalInput.value);
+                const target = parseInt(goalInput.value, 10);
                 if (isNaN(target) || target < 1) return;
 
                 const token = SafeStorage.get('bibliodrift_token');
@@ -3782,13 +3782,13 @@ document.addEventListener('DOMContentLoaded', async () => {
                     const saveBtn = card.querySelector('.progress-card-save-btn');
 
                     slider.addEventListener('input', () => {
-                        const val = parseInt(slider.value);
+                        const val = parseInt(slider.value, 10);
                         barFill.style.width = `${val}%`;
                         pctLabel.textContent = `${val}%`;
                     });
 
                     saveBtn.addEventListener('click', async () => {
-                        const newProgress = parseInt(slider.value);
+                        const newProgress = parseInt(slider.value, 10);
                         saveBtn.disabled = true;
                         saveBtn.innerHTML = '<i class="fa-solid fa-spinner fa-spin"></i>';
                         try {
diff --git a/frontend/js/library-3d.js b/frontend/js/library-3d.js
index ba5cc1c6..de4ab340 100644
--- a/frontend/js/library-3d.js
+++ b/frontend/js/library-3d.js
@@ -2407,7 +2407,7 @@ class BookshelfRenderer3D {
                     if (progressBadge) progressBadge.textContent = `${clamped}% `;
                     // Sync pages input
                     if (pagesReadInput && pagesTotalInput) {
-                        const pages = Math.round((clamped / 100) * parseInt(pagesTotalInput.value || totalPages));
+                        const pages = Math.round((clamped / 100) * parseInt(pagesTotalInput.value || totalPages, 10));
                         pagesReadInput.value = pages;
                     }
                     if (pagesBar) pagesBar.style.width = `${clamped}% `;
@@ -2450,12 +2450,12 @@ class BookshelfRenderer3D {
                     progressSlider.parentNode.replaceChild(newSlider, progressSlider);
                     newSlider.value = currentProgress;
                     newSlider.addEventListener('input', () => {
-                        const pct = parseInt(newSlider.value);
+                        const pct = parseInt(newSlider.value, 10);
                         if (progressBar) progressBar.style.width = `${pct}% `;
                         if (progressValue) progressValue.textContent = `${pct}% `;
                         if (progressBadge) progressBadge.textContent = `${pct}% `;
                         // Sync pages
-                        const total = parseInt(document.getElementById('modal-pages-total')?.value || totalPages);
+                        const total = parseInt(document.getElementById('modal-pages-total', 10)?.value || totalPages);
                         const pages = Math.round((pct / 100) * total);
                         const pagesReadEl = document.getElementById('modal-pages-read');
                         if (pagesReadEl) pagesReadEl.value = pages;
@@ -2469,8 +2469,8 @@ class BookshelfRenderer3D {
                     const pagesTotalEl = document.getElementById('modal-pages-total');
                     const sliderEl = document.getElementById('modal-progress-slider');
                     if (!pagesReadEl || !pagesTotalEl) return;
-                    const read = Math.max(0, parseInt(pagesReadEl.value) || 0);
-                    const total = Math.max(1, parseInt(pagesTotalEl.value) || 1);
+                    const read = Math.max(0, parseInt(pagesReadEl.value, 10) || 0);
+                    const total = Math.max(1, parseInt(pagesTotalEl.value, 10) || 1);
                     const pct = Math.min(100, Math.round((read / total) * 100));
                     if (sliderEl) sliderEl.value = pct;
                     if (progressBar) progressBar.style.width = `${pct}% `;
@@ -2497,7 +2497,7 @@ class BookshelfRenderer3D {
                     progressSaveBtn.parentNode.replaceChild(newSaveBtn, progressSaveBtn);
                     newSaveBtn.addEventListener('click', async () => {
                         const sliderEl = document.getElementById('modal-progress-slider');
-                        const newProgress = sliderEl ? parseInt(sliderEl.value) : currentProgress;
+                        const newProgress = sliderEl ? parseInt(sliderEl.value, 10) : currentProgress;
 
                         newSaveBtn.disabled = true;
                         newSaveBtn.innerHTML = '<i class="fa-solid fa-spinner fa-spin"></i> Saving...';