diff --git a/web_app/static/index.html b/web_app/static/index.html
index 0d56371..a9e2343 100644
--- a/web_app/static/index.html
+++ b/web_app/static/index.html
@@ -116,7 +116,10 @@ <h2 id="contentHeading">Lyrics</h2>
                                 </div>
                             </div>
 
-                            <button id="generateBtn" class="primary-btn">Generate Poster</button>
+                            <button id="generateBtn" class="primary-btn">
+                                <span class="btn-text">Generate Poster</span>
+                                <div class="button-spinner" style="display: none;"></div>
+                            </button>
                         </div>
                     </div>
 
diff --git a/web_app/static/script.js b/web_app/static/script.js
index 441a4ed..1d27fcb 100644
--- a/web_app/static/script.js
+++ b/web_app/static/script.js
@@ -613,7 +613,16 @@ function handleLyricLineClick(lineNumber) {
 async function generatePoster() {
     if (!currentMetadata) return;
 
-    loadingOverlay.style.display = 'flex';
+    const btnText = generateBtn.querySelector('.btn-text');
+    const btnSpinner = generateBtn.querySelector('.button-spinner');
+
+    const resetButtonState = () => {
+        generateBtn.disabled = false;
+        generateBtn.classList.remove('loading');
+        if(btnText) btnText.textContent = 'Generate Poster';
+        if(btnSpinner) btnSpinner.style.display = 'none';
+        generateBtn.removeAttribute('aria-label');
+    };
 
     const indexingToggle = document.getElementById('indexingToggle');
     const accentToggle = document.getElementById('accentToggle');
@@ -628,14 +637,12 @@ async function generatePoster() {
     };
 
     if (payload.type === 'track') {
-        // Lyrics Logic (Same as before)
         const startVal = parseInt(startLineInput.value) || 1;
         const endVal = parseInt(endLineInput.value) || 1;
         const start = startVal - 1;
         const end = endVal;
 
         if (isNaN(start) || isNaN(end) || start >= end) {
-            loadingOverlay.style.display = 'none';
             showToast("Please enter a valid range (Start must be less than End).", "error");
             return;
         }
@@ -644,10 +651,16 @@ async function generatePoster() {
         payload.lyrics_end = end;
 
     } else {
-        // Album Logic
         payload.indexing = indexingToggle ? indexingToggle.checked : false;
     }
 
+    // Set loading state AFTER validation
+    generateBtn.disabled = true;
+    generateBtn.classList.add('loading');
+    if(btnText) btnText.textContent = 'Generating...';
+    if(btnSpinner) btnSpinner.style.display = 'block';
+    generateBtn.setAttribute('aria-label', 'Generating poster, please wait');
+
     try {
         const response = await fetch('/api/generate', {
             method: 'POST',
@@ -669,13 +682,17 @@ async function generatePoster() {
             posterContainer.innerHTML = '';
             posterContainer.appendChild(img);
             showDownloadButton(imageUrl, data.filename);
-            loadingOverlay.style.display = 'none';
+            resetButtonState();
+        };
+        img.onerror = () => {
+            showToast('Error: Failed to load the generated poster image.', 'error');
+            resetButtonState();
         };
 
     } catch (error) {
         console.error("Generation failed", error);
         showToast(`Error: ${error.message}`, "error");
-        loadingOverlay.style.display = 'none';
+        resetButtonState();
     }
 }
 
diff --git a/web_app/static/style.css b/web_app/static/style.css
index 468eb76..a63b9bb 100644
--- a/web_app/static/style.css
+++ b/web_app/static/style.css
@@ -166,6 +166,28 @@ header p {
     transform: translateY(-1px);
 }
 
+.primary-btn:disabled {
+    background: var(--surface-elevated);
+    color: var(--text-muted);
+    cursor: not-allowed;
+    transform: none;
+}
+
+.primary-btn.loading .btn-text {
+    visibility: hidden;
+    opacity: 0;
+}
+
+.button-spinner {
+    position: absolute;
+    width: 20px;
+    height: 20px;
+    border: 2px solid rgba(0, 0, 0, 0.2);
+    border-top-color: var(--surface-base);
+    border-radius: 50%;
+    animation: spin 0.8s linear infinite;
+}
+
 .secondary-btn {
     background: transparent;
     border-color: var(--border-color);