diff --git a/public/admin.css b/public/admin.css
index 8d86e9b..77a1670 100644
--- a/public/admin.css
+++ b/public/admin.css
@@ -225,6 +225,24 @@ label { display: grid; gap: 6px; color: var(--muted); font-size: 13px; }
   width: auto;
   margin: 0;
 }
+.effect-settings input[type="password"],
+.effect-settings select {
+  width: 100%;
+}
+.effect-settings small {
+  color: var(--muted);
+  font-size: 11px;
+}
+.model-row {
+  display: grid;
+  grid-template-columns: minmax(0, 1fr) auto;
+  gap: 8px;
+  align-items: center;
+}
+.model-row button {
+  height: 38px;
+  padding: 0 10px;
+}
 .list-tools {
   padding: 10px 14px;
   border-bottom: 1px solid var(--line);
diff --git a/public/admin.html b/public/admin.html
index 4f4ad30..69e7d1d 100644
--- a/public/admin.html
+++ b/public/admin.html
@@ -177,7 +177,16 @@
                     <option value="de">Nemcina</option>
                   </select>
                 </label>
-                <label>OpenAI model <input id="translationModel" placeholder="gpt-5.6-luna"></label>
+                <label>OpenAI API key
+                  <input id="openaiApiKey" type="password" autocomplete="off" placeholder="sk-...">
+                  <small id="openaiApiKeyStatus">Klic neni ulozeny.</small>
+                </label>
+                <label>OpenAI model
+                  <span class="model-row">
+                    <select id="translationModel"></select>
+                    <button id="refreshAiModels" type="button">Obnovit</button>
+                  </span>
+                </label>
               </fieldset>
             </div>
           </section>
diff --git a/public/admin.js b/public/admin.js
index de5e321..9e7d1e3 100644
--- a/public/admin.js
+++ b/public/admin.js
@@ -18,7 +18,8 @@ const state = {
   soundRepeatTimer: null,
   attentionOn: false,
   originalTitle: document.title,
-  originalFavicon: document.querySelector("link[rel='icon']")?.href || "/favicon.svg"
+  originalFavicon: document.querySelector("link[rel='icon']")?.href || "/favicon.svg",
+  aiModels: []
 };
 
 const $ = (selector) => document.querySelector(selector);
@@ -82,6 +83,8 @@ $("#adminSoundTest").addEventListener("click", () => {
 $("#translationEnabled").addEventListener("change", saveTranslationSettings);
 $("#operatorLanguage").addEventListener("change", saveTranslationSettings);
 $("#translationModel").addEventListener("change", saveTranslationSettings);
+$("#openaiApiKey").addEventListener("change", saveTranslationSettings);
+$("#refreshAiModels").addEventListener("click", loadAiModels);
 document.querySelectorAll("[data-settings-tab]").forEach((button) => {
   button.addEventListener("click", () => {
     const tab = button.dataset.settingsTab;
@@ -284,6 +287,7 @@ async function showApp() {
   $("#loginView").classList.add("hidden");
   $("#appView").classList.remove("hidden");
   await loadBootstrap();
+  await loadAiModels().catch(() => {});
   await Promise.all([loadConversations(), loadVisitors()]);
   connectEvents();
 }
@@ -390,7 +394,11 @@ function renderSite() {
   form.messageWiggle.checked = s.notifications?.wiggleOnAdminReply !== false;
   $("#translationEnabled").checked = Boolean(s.translations?.enabled);
   $("#operatorLanguage").value = s.translations?.operatorLanguage || "cs";
-  $("#translationModel").value = s.translations?.model || "gpt-5.6-luna";
+  $("#openaiApiKey").value = "";
+  $("#openaiApiKeyStatus").textContent = s.translations?.hasOpenaiApiKey
+    ? `Klic ulozeny (${s.translations.openaiApiKeyMasked || "sk-..."})`
+    : "Klic neni ulozeny.";
+  renderModelOptions(s.translations?.model || "gpt-5-mini");
 }
 
 async function saveTranslationSettings() {
@@ -400,9 +408,31 @@ async function saveTranslationSettings() {
     ...(settings.translations || {}),
     enabled: $("#translationEnabled").checked,
     operatorLanguage: $("#operatorLanguage").value,
-    model: $("#translationModel").value.trim() || "gpt-5.6-luna"
+    model: $("#translationModel").value.trim() || "gpt-5-mini"
   };
+  const apiKey = $("#openaiApiKey").value.trim();
+  if (apiKey) settings.translations.openaiApiKey = apiKey;
   await saveSite({ settings, isOnline: state.site.isOnline });
+  $("#openaiApiKey").value = "";
+  await loadAiModels().catch(() => {});
+}
+
+async function loadAiModels() {
+  const current = $("#translationModel").value || state.site?.settings?.translations?.model || "gpt-5-mini";
+  const data = await api("/api/admin/ai/models").catch((error) => error?.models ? error : null);
+  state.aiModels = data?.models || fallbackAiModels();
+  renderModelOptions(current);
+}
+
+function renderModelOptions(current) {
+  const select = $("#translationModel");
+  const models = [...new Set([current, ...state.aiModels, ...fallbackAiModels()].filter(Boolean))];
+  select.innerHTML = models.map((model) => `<option value="${escapeHtml(model)}">${escapeHtml(model)}</option>`).join("");
+  select.value = models.includes(current) ? current : models[0];
+}
+
+function fallbackAiModels() {
+  return ["gpt-5-mini", "gpt-5-nano", "gpt-5.1", "gpt-4.1-mini"];
 }
 
 function renderConversations() {
@@ -1019,8 +1049,13 @@ async function api(url, options = {}) {
     headers: { "Content-Type": "application/json" },
     body: options.body ? JSON.stringify(options.body) : undefined
   });
-  if (!response.ok) throw new Error(`HTTP ${response.status}`);
-  return response.json();
+  const data = await response.json().catch(() => ({}));
+  if (!response.ok) {
+    const error = new Error(`HTTP ${response.status}`);
+    Object.assign(error, data);
+    throw error;
+  }
+  return data;
 }
 
 function debounce(fn, delay) {
diff --git a/server.js b/server.js
index bce0de6..1ede4e2 100644
--- a/server.js
+++ b/server.js
@@ -17,7 +17,7 @@ const PUBLIC_BASE_URL = (process.env.PUBLIC_BASE_URL || `http://localhost:${PORT
 const AUTH_SECRET = process.env.AUTH_SECRET || "dev-secret-change-me";
 const COOKIE_NAME = "mf_session";
 const OPENAI_API_KEY = process.env.OPENAI_API_KEY || "";
-const OPENAI_TRANSLATION_MODEL = process.env.OPENAI_TRANSLATION_MODEL || "gpt-5.6-luna";
+const OPENAI_TRANSLATION_MODEL = process.env.OPENAI_TRANSLATION_MODEL || "gpt-5-mini";
 const ALLOWED_IMAGE_TYPES = new Set(["image/jpeg", "image/png", "image/webp", "image/gif", "image/avif"]);
 const ALLOWED_IMAGE_EXTENSIONS = new Set([".jpg", ".jpeg", ".png", ".webp", ".gif", ".avif"]);
 const MAX_ATTACHMENT_BYTES = 3_000_000;
@@ -85,6 +85,7 @@ async function adminApi(req, res, url) {
   if (url.pathname === "/api/admin/bootstrap" && req.method === "GET") return adminBootstrap(res);
   if (url.pathname === "/api/admin/events" && req.method === "GET") return eventStream(req, res, url, "admin");
   if (url.pathname === "/api/admin/site" && req.method === "PATCH") return updateSite(req, res);
+  if (url.pathname === "/api/admin/ai/models" && req.method === "GET") return adminAiModels(res);
   if (url.pathname === "/api/admin/conversations" && req.method === "GET") return adminConversations(res);
   if (url.pathname === "/api/admin/visitors" && req.method === "GET") return adminVisitors(res);
   if (url.pathname.match(/^\/api\/admin\/visitors\/[^/]+$/) && req.method === "PATCH") return updateVisitorProfile(req, res, url);
@@ -296,7 +297,8 @@ function defaultSettings() {
     translations: {
       enabled: false,
       operatorLanguage: "cs",
-      model: OPENAI_TRANSLATION_MODEL
+      model: OPENAI_TRANSLATION_MODEL,
+      openaiApiKey: ""
     }
   };
 }
@@ -435,7 +437,9 @@ function adminConversation(res, url) {
 async function updateSite(req, res) {
   const body = await readJson(req);
   const site = getDefaultSite();
-  const settings = { ...JSON.parse(site.settings_json), ...(body.settings || {}) };
+  const currentSettings = parseJson(site.settings_json, defaultSettings());
+  const incomingSettings = body.settings || {};
+  const settings = mergeSiteSettings(currentSettings, incomingSettings);
   db.prepare(`
     UPDATE sites
     SET is_online = ?, settings_json = ?, updated_at = CURRENT_TIMESTAMP
@@ -446,6 +450,27 @@ async function updateSite(req, res) {
   return json(res, 200, { site: formatSite(updated), snippet: snippetFor(updated) });
 }
 
+async function adminAiModels(res) {
+  const settings = getTranslationSettings();
+  const apiKey = settings.openaiApiKey;
+  if (!apiKey) return json(res, 400, { error: "missing_openai_api_key", models: fallbackTranslationModels() });
+  try {
+    const response = await fetch("https://api.openai.com/v1/models", {
+      headers: { "Authorization": `Bearer ${apiKey}` }
+    });
+    if (!response.ok) throw new Error(`OpenAI HTTP ${response.status}`);
+    const data = await response.json();
+    const models = (data.data || [])
+      .map((item) => item.id)
+      .filter(isUsableTextModel)
+      .sort((a, b) => a.localeCompare(b));
+    return json(res, 200, { models: models.length ? models : fallbackTranslationModels() });
+  } catch (error) {
+    console.error("openai_models_failed", error.message);
+    return json(res, 502, { error: "openai_models_failed", models: fallbackTranslationModels() });
+  }
+}
+
 async function updateConversationStatus(req, res, url) {
   const body = await readJson(req);
   const status = ["new", "open", "resolved", "spam"].includes(body.status) ? body.status : null;
@@ -742,7 +767,7 @@ async function translateStoredMessage(conversationId, messageId, senderType, bod
   if (!targetLanguage) return markMessageTranslation(messageId, null, null, null, "skipped");
 
   try {
-    const result = await translateText(message.body, targetLanguage, settings.model);
+    const result = await translateText(message.body, targetLanguage, settings.model, settings.openaiApiKey);
     const sourceLanguage = normalizeLanguage(result.sourceLanguage);
     const translatedText = String(result.translatedText || "").trim();
     const translatedLanguage = normalizeLanguage(result.translatedLanguage || targetLanguage);
@@ -773,11 +798,11 @@ function markMessageTranslation(messageId, sourceLanguage, translatedBody, trans
   `).run(sourceLanguage, translatedBody, translatedLanguage, status, messageId);
 }
 
-async function translateText(text, targetLanguage, model) {
+async function translateText(text, targetLanguage, model, apiKey) {
   const response = await fetch("https://api.openai.com/v1/responses", {
     method: "POST",
     headers: {
-      "Authorization": `Bearer ${OPENAI_API_KEY}`,
+      "Authorization": `Bearer ${apiKey}`,
       "Content-Type": "application/json"
     },
     body: JSON.stringify({
@@ -828,6 +853,26 @@ function outputTextFromResponse(data) {
   return chunks.join("");
 }
 
+function mergeSiteSettings(currentSettings, incomingSettings) {
+  const settings = { ...currentSettings, ...incomingSettings };
+  const currentTranslations = currentSettings.translations || {};
+  const incomingTranslations = incomingSettings.translations || {};
+  settings.translations = {
+    ...currentTranslations,
+    ...incomingTranslations
+  };
+  if (!incomingTranslations.openaiApiKey) {
+    settings.translations.openaiApiKey = currentTranslations.openaiApiKey || "";
+  }
+  if (isMaskedApiKey(incomingTranslations.openaiApiKey)) {
+    settings.translations.openaiApiKey = currentTranslations.openaiApiKey || "";
+  }
+  settings.translations.openaiApiKey = normalizeOpenAiApiKey(settings.translations.openaiApiKey);
+  delete settings.translations.hasOpenaiApiKey;
+  delete settings.translations.openaiApiKeyMasked;
+  return settings;
+}
+
 function getTranslationSettings() {
   const site = getDefaultSite();
   const settings = parseJson(site.settings_json, defaultSettings());
@@ -835,10 +880,43 @@ function getTranslationSettings() {
   return {
     enabled: Boolean(translations.enabled),
     operatorLanguage: normalizeLanguage(translations.operatorLanguage) || "cs",
-    model: String(translations.model || OPENAI_TRANSLATION_MODEL).trim() || OPENAI_TRANSLATION_MODEL
+    model: String(translations.model || OPENAI_TRANSLATION_MODEL).trim() || OPENAI_TRANSLATION_MODEL,
+    openaiApiKey: normalizeOpenAiApiKey(translations.openaiApiKey) || OPENAI_API_KEY
   };
 }
 
+function normalizeOpenAiApiKey(value) {
+  const text = String(value || "").trim();
+  if (!text || isMaskedApiKey(text)) return "";
+  return text;
+}
+
+function isMaskedApiKey(value) {
+  return String(value || "").includes("...");
+}
+
+function maskApiKey(value) {
+  const text = normalizeOpenAiApiKey(value);
+  if (!text) return "";
+  return `${text.slice(0, 7)}...${text.slice(-4)}`;
+}
+
+function fallbackTranslationModels() {
+  return [
+    OPENAI_TRANSLATION_MODEL,
+    "gpt-5.1",
+    "gpt-5-mini",
+    "gpt-5-nano",
+    "gpt-4.1-mini",
+    "gpt-4.1-nano"
+  ].filter(Boolean);
+}
+
+function isUsableTextModel(id) {
+  return /^(gpt-|o[134])/.test(id)
+    && !/audio|realtime|transcribe|tts|image|search|embedding|moderation|codex/i.test(id);
+}
+
 function normalizeLanguage(value) {
   const text = String(value || "").trim().toLowerCase().replace("_", "-");
   if (!text) return "";
@@ -1036,6 +1114,10 @@ function formatSite(site) {
   settings.notifications = { ...defaultSettings().notifications, ...(settings.notifications || {}) };
   settings.launcherEffects = { ...defaultSettings().launcherEffects, ...(settings.launcherEffects || {}) };
   settings.translations = { ...defaultSettings().translations, ...(settings.translations || {}) };
+  const storedOpenAiKey = settings.translations.openaiApiKey || OPENAI_API_KEY;
+  settings.translations.hasOpenaiApiKey = Boolean(storedOpenAiKey);
+  settings.translations.openaiApiKeyMasked = maskApiKey(storedOpenAiKey);
+  settings.translations.openaiApiKey = "";
   return {
     id: site.id,
     siteKey: site.site_key,