diff --git a/README.md b/README.md
index 3853127..43a515b 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,7 @@ message meets a specified criterion.
 - **Advanced parameters** – tune generation settings like temperature, top‑p and more from the options page.
 - **Markdown conversion** – optionally convert HTML bodies to Markdown before sending them to the AI service.
 - **Debug logging** – optional colorized logs help troubleshoot interactions with the AI service.
+- **Debug tab** – view the last request payload sent to the AI service.
 - **Light/Dark themes** – automatically match Thunderbird's appearance with optional manual override.
 - **Automatic rules** – create rules that tag, move, copy, forward, reply, delete, archive, mark read/unread or flag/unflag messages based on AI classification. Rules can optionally apply only to unread messages and can ignore messages outside a chosen age range.
 - **Rule ordering** – drag rules to prioritize them and optionally stop processing after a match.
diff --git a/modules/AiClassifier.js b/modules/AiClassifier.js
index b35cb2c..8313654 100644
--- a/modules/AiClassifier.js
+++ b/modules/AiClassifier.js
@@ -308,6 +308,11 @@ async function classifyText(text, criterion, cacheKey = null) {
   }
 
   const payload = buildPayload(text, criterion);
+  try {
+    await storage.local.set({ lastPayload: JSON.parse(payload) });
+  } catch (e) {
+    aiLog('failed to save last payload', { level: 'warn' }, e);
+  }
 
   aiLog(`[AiClassifier] Sending classification request to ${gEndpoint}`, {debug: true});
   aiLog(`[AiClassifier] Classification request payload:`, { debug: true }, payload);
diff --git a/options/options.html b/options/options.html
index 69158b1..d14ce99 100644
--- a/options/options.html
+++ b/options/options.html
@@ -47,6 +47,7 @@
                             <li class="is-active" data-tab="settings"><a><span class="icon is-small"><img data-icon="settings" data-size="16" src="../resources/img/settings-light-16.png" alt=""></span><span>Settings</span></a></li>
                             <li data-tab="rules"><a><span class="icon is-small"><img data-icon="clipboarddata" data-size="16" src="../resources/img/clipboarddata-light-16.png" alt=""></span><span>Rules</span></a></li>
                             <li data-tab="maintenance"><a><span class="icon is-small"><img data-icon="gear" data-size="16" src="../resources/img/gear-light-16.png" alt=""></span><span>Maintenance</span></a></li>
+                            <li id="debug-tab-button" class="is-hidden" data-tab="debug"><a><span class="icon is-small"><img data-icon="average" data-size="16" src="../resources/img/average-light-16.png" alt=""></span><span>Debug</span></a></li>
                         </ul>
                     </div>
                 </div>
@@ -215,6 +216,11 @@
                             <input class="input" type="number" step="0.01" id="tfs">
                         </div>
                     </div>
+                    <div class="field">
+                        <label class="checkbox">
+                            <input type="checkbox" id="show-debug-tab"> Advanced Options
+                        </label>
+                    </div>
                 </div>
             </div>
 
@@ -273,6 +279,14 @@
                     </p>
                 </div>
             </div>
+
+            <div id="debug-tab" class="tab-content is-hidden">
+                <h2 class="title is-4">
+                    <span class="icon is-small"><img data-icon="average" data-size="16" src="../resources/img/average-light-16.png" alt=""></span>
+                    <span>Debug</span>
+                </h2>
+                <pre id="payload-display"></pre>
+            </div>
         </div>
     </section>
     <script src="options.js"></script>
diff --git a/options/options.js b/options/options.js
index ee2914a..ebd7497 100644
--- a/options/options.js
+++ b/options/options.js
@@ -19,7 +19,9 @@ document.addEventListener('DOMContentLoaded', async () => {
         'tokenReduction',
         'aiRules',
         'aiCache',
-        'theme'
+        'theme',
+        'showDebugTab',
+        'lastPayload'
     ]);
     const tabButtons = document.querySelectorAll('#main-tabs li');
     const tabs = document.querySelectorAll('.tab-content');
@@ -64,6 +66,10 @@ document.addEventListener('DOMContentLoaded', async () => {
     }
 
     await applyTheme(themeSelect.value);
+    const payloadDisplay = document.getElementById('payload-display');
+    if (defaults.lastPayload) {
+        payloadDisplay.textContent = JSON.stringify(defaults.lastPayload, null, 2);
+    }
     themeSelect.addEventListener('change', async () => {
         markDirty();
         await applyTheme(themeSelect.value);
@@ -119,6 +125,16 @@ document.addEventListener('DOMContentLoaded', async () => {
     const tokenReductionToggle = document.getElementById('token-reduction');
     tokenReductionToggle.checked = defaults.tokenReduction === true;
 
+    const debugTabToggle = document.getElementById('show-debug-tab');
+    const debugTabBtn = document.getElementById('debug-tab-button');
+    function updateDebugTab() {
+        const visible = debugTabToggle.checked;
+        debugTabBtn.classList.toggle('is-hidden', !visible);
+    }
+    debugTabToggle.checked = defaults.showDebugTab === true;
+    debugTabToggle.addEventListener('change', () => { updateDebugTab(); markDirty(); });
+    updateDebugTab();
+
 
     const aiParams = Object.assign({}, DEFAULT_AI_PARAMS, defaults.aiParams || {});
     for (const [key, val] of Object.entries(aiParams)) {
@@ -797,8 +813,9 @@ document.addEventListener('DOMContentLoaded', async () => {
         const altTextImages = altTextToggle.checked;
         const collapseWhitespace = collapseWhitespaceToggle.checked;
         const tokenReduction = tokenReductionToggle.checked;
+        const showDebugTab = debugTabToggle.checked;
         const theme = themeSelect.value;
-        await storage.local.set({ endpoint, templateName, customTemplate: customTemplateText, customSystemPrompt, aiParams: aiParamsSave, debugLogging, htmlToMarkdown, stripUrlParams, altTextImages, collapseWhitespace, tokenReduction, aiRules: rules, theme });
+        await storage.local.set({ endpoint, templateName, customTemplate: customTemplateText, customSystemPrompt, aiParams: aiParamsSave, debugLogging, htmlToMarkdown, stripUrlParams, altTextImages, collapseWhitespace, tokenReduction, aiRules: rules, theme, showDebugTab });
         await applyTheme(theme);
         try {
             await AiClassifier.setConfig({ endpoint, templateName, customTemplate: customTemplateText, customSystemPrompt, aiParams: aiParamsSave, debugLogging });