diff --git a/public/app/dom.js b/public/app/dom.js
index ec67011..9406765 100644
--- a/public/app/dom.js
+++ b/public/app/dom.js
@@ -21,6 +21,8 @@ const loginUsernameInput = $("loginUsername");
 const loginPasswordInput = $("loginPassword");
 const registerUsernameInput = $("registerUsername");
 const registerPasswordInput = $("registerPassword");
+const registerInviteField = $("registerInviteField");
+const registerInviteCodeInput = $("registerInviteCode");
 const loginSubmit = $("loginSubmit");
 const registerSubmit = $("registerSubmit");
 const chatList = $("chatList");
@@ -190,6 +192,8 @@ export {
     popupModal,
     popupTitle,
     registerForm,
+    registerInviteCodeInput,
+    registerInviteField,
     registerPasswordInput,
     registerSubmit,
     registerUsernameInput,
diff --git a/public/index.html b/public/index.html
index dd70f3d..a2b7469 100644
--- a/public/index.html
+++ b/public/index.html
@@ -52,6 +52,10 @@
                         <span>Create password</span>
                         <input id="registerPassword" type="password" placeholder="Create a password" autocomplete="new-password"/>
                     </label>
+                    <label id="registerInviteField" class="field hidden">
+                        <span>Invite code</span>
+                        <input id="registerInviteCode" placeholder="Enter invite code" autocomplete="off"/>
+                    </label>
                     <div class="consent-container">
                         <input type="checkbox" id="consentCheckbox" required/>
                         <label for="consentCheckbox">
diff --git a/public/script.js b/public/script.js
index 805aaed..3dea1e0 100644
--- a/public/script.js
+++ b/public/script.js
@@ -78,6 +78,8 @@ import {
     popupModal,
     popupTitle,
     registerForm,
+    registerInviteCodeInput,
+    registerInviteField,
     registerPasswordInput,
     registerSubmit,
     registerUsernameInput,
@@ -1643,6 +1645,7 @@ async function displayModels() {
 
 async function checkSession() {
     const res = await get("/session");
+    if (registerInviteField) registerInviteField.classList.toggle("hidden", !res.inviteOnlyRegistration);
     if (!res.user) return false;
     currentUsername = res.user; authDiv.style.display = "none"; chatDiv.style.display = "block";
     await Promise.all([displayModels(), loadSummary(), loadChatSessions(), loadPersonas()]);
@@ -1654,7 +1657,10 @@ async function handleAuth(endpoint, credentials) {
     const {username, password} = credentials, submitBtn = endpoint === "login" ? loginSubmit : registerSubmit;
     if (!username || !password) return setAuthMessage("Please enter both username and password.", "error");
     submitBtn.disabled = true; setAuthMessage("Processing...");
-    const res = await post(`/${endpoint}`, {username, password});
+    const payload = endpoint === "register"
+        ? {username, password, inviteCode: registerInviteCodeInput?.value.trim() || ""}
+        : {username, password};
+    const res = await post(`/${endpoint}`, payload);
     submitBtn.disabled = false;
     if (res.error) return setAuthMessage(res.error, "error");
     if (endpoint === "login") {
diff --git a/public/settings.html b/public/settings.html
index ccac9aa..2dce1a6 100644
--- a/public/settings.html
+++ b/public/settings.html
@@ -81,6 +81,33 @@
                         <button id="savePassword" type="submit">Save password</button>
                     </form>
                 </div>
+
+                <div class="settings-panel">
+                    <div class="settings-section-header">
+                        <div>
+                            <p class="eyebrow">Account data</p>
+                            <h2>Export and sessions</h2>
+                            <p class="subtitle">Download your account data or sign out every active browser session.</p>
+                        </div>
+                    </div>
+                    <div class="persona-actions">
+                        <button id="exportAccount" type="button" class="secondary-action">Export account</button>
+                        <button id="logoutAllSessions" type="button" class="secondary-action">Logout all sessions</button>
+                    </div>
+                </div>
+
+                <div class="settings-panel">
+                    <div class="settings-section-header">
+                        <div>
+                            <p class="eyebrow">Danger zone</p>
+                            <h2>Delete account</h2>
+                            <p class="subtitle">This permanently removes your account, chats, personas, templates, and market activity.</p>
+                        </div>
+                    </div>
+                    <div class="persona-actions">
+                        <button id="deleteAccount" type="button" class="secondary-action danger">Delete account</button>
+                    </div>
+                </div>
             </section>
 
             <section class="settings-view" role="tabpanel" aria-hidden="true" data-settings-panel="my-roleplay-companions">
diff --git a/public/settings.js b/public/settings.js
index 8b33fed..c5ba6d7 100644
--- a/public/settings.js
+++ b/public/settings.js
@@ -21,6 +21,9 @@ const usernamePasswordInput = $("usernamePassword");
 const currentPasswordInput = $("currentPassword");
 const newPasswordInput = $("newPassword");
 const repeatPasswordInput = $("repeatPassword");
+const exportAccountBtn = $("exportAccount");
+const logoutAllSessionsBtn = $("logoutAllSessions");
+const deleteAccountBtn = $("deleteAccount");
 const usernameForm = $("usernameForm");
 const passwordForm = $("passwordForm");
 const settingsNavItems = document.querySelectorAll("[data-settings-view]");
@@ -458,6 +461,56 @@ async function unpublishPersona(id) {
     setNotice("Persona unpublished.", "success");
 }
 
+function downloadJson(filename, payload) {
+    const blob = new Blob([JSON.stringify(payload, null, 2)], {type: "application/json;charset=utf-8"});
+    const url = URL.createObjectURL(blob);
+    const link = document.createElement("a");
+    link.href = url;
+    link.download = filename;
+    document.body.appendChild(link);
+    link.click();
+    link.remove();
+    URL.revokeObjectURL(url);
+}
+
+async function exportAccount() {
+    const res = await get("/settings/export");
+    if (res.error) return setNotice(res.error, "error");
+    const username = currentUsernameInput.value || "account";
+    downloadJson(`account-export-${username}-${new Date().toISOString().slice(0, 10)}.json`, res.account);
+    setNotice("Account export downloaded.", "success");
+}
+
+async function logoutAllSessions() {
+    const confirmed = await promptSettingsPopup({
+        eyebrow: "Security",
+        title: "Logout all sessions",
+        description: "Type logout to sign out this browser and every other active session.",
+        label: "Confirmation",
+        placeholder: "logout",
+        confirmLabel: "Logout all"
+    });
+    if (String(confirmed || "").trim().toLowerCase() !== "logout") return;
+    const res = await post("/settings/logout-all-sessions", {});
+    if (res.error) return setNotice(res.error, "error");
+    window.location.href = "/";
+}
+
+async function deleteAccount() {
+    const currentPassword = await promptSettingsPopup({
+        eyebrow: "Danger zone",
+        title: "Delete account",
+        description: "Enter your current password to permanently delete your account and all account data.",
+        label: "Current password",
+        placeholder: "Password",
+        confirmLabel: "Delete account"
+    });
+    if (currentPassword === null) return;
+    const res = await request("/settings/account", {currentPassword}, "DELETE");
+    if (res.error) return setNotice(res.error, "error");
+    window.location.href = "/";
+}
+
 usernameForm.addEventListener("submit", async (event) => {
     event.preventDefault();
     const username = newUsernameInput.value.trim();
@@ -514,6 +567,9 @@ workspaceModeSelect.addEventListener("change", (event) => {
     localStorage.setItem("krishd-workspace-mode", mode);
     setNotice(`Workspace mode set to ${mode}.`, "success");
 });
+exportAccountBtn.addEventListener("click", () => { void exportAccount(); });
+logoutAllSessionsBtn.addEventListener("click", () => { void logoutAllSessions(); });
+deleteAccountBtn.addEventListener("click", () => { void deleteAccount(); });
 refreshDiagnosticsBtn.addEventListener("click", () => { void loadDiagnostics(); });
 
 settingsNavItems.forEach((item) => item.addEventListener("click", () => setSettingsView(item.dataset.settingsView)));
diff --git a/src/app.js b/src/app.js
index 93790ee..e57d6f4 100644
--- a/src/app.js
+++ b/src/app.js
@@ -137,6 +137,23 @@ function sameOriginProtection(config) {
     };
 }
 
+function enforceSessionVersion(repositories) {
+    return (req, res, next) => {
+        if (!req.session.user) return next();
+        const user = repositories.getUser(req.session.user);
+        const currentVersion = Number(user?.session_version || 0);
+        const sessionVersion = Number(req.session.sessionVersion || 0);
+        if (user && currentVersion === sessionVersion) return next();
+
+        req.session.destroy(() => {
+            if (req.path === "/session") {
+                return res.json({user: null});
+            }
+            return res.status(403).json({error: "Session expired. Please log in again."});
+        });
+    };
+}
+
 export function createApp(options = {}) {
     const config = createConfig(options.config);
     const app = express();
@@ -181,6 +198,7 @@ export function createApp(options = {}) {
         }
     }));
     app.use(sameOriginProtection(config));
+    app.use(enforceSessionVersion(repositories));
 
     app.locals.config = config;
     app.locals.db = db;
@@ -188,7 +206,7 @@ export function createApp(options = {}) {
     app.locals.modelService = modelService;
     app.locals.close = createCloseHandler(closeHandlers);
 
-    app.use(createAuthRouter({repositories, authRateLimiters}));
+    app.use(createAuthRouter({repositories, authRateLimiters, config}));
     app.use(createSettingsRouter({repositories}));
     app.use(createChatsRouter({repositories, chatService, modelService, config, chatRateLimiters}));
     app.use(createPersonasRouter({repositories, chatService, modelService, config}));
diff --git a/src/config.js b/src/config.js
index 627bc6f..6019691 100644
--- a/src/config.js
+++ b/src/config.js
@@ -37,6 +37,7 @@ export function createConfig(overrides = {}) {
         allowInsecureCookies: bool(process.env.ALLOW_INSECURE_COOKIES, false),
         trustProxy: trustProxy(process.env.TRUST_PROXY, false),
         sessionMaxAgeMs: int(process.env.SESSION_MAX_AGE_MS, 7 * 24 * 60 * 60 * 1000),
+        registrationInviteCode: process.env.REGISTRATION_INVITE_CODE || "",
         sameOriginProtectionEnabled: bool(process.env.SAME_ORIGIN_PROTECTION_ENABLED, true),
         staticMaxAge: process.env.STATIC_MAX_AGE || (process.env.NODE_ENV === "production" ? "1h" : 0),
         staticEtag: bool(process.env.STATIC_ETAG, true),
diff --git a/src/db/repositories.js b/src/db/repositories.js
index ab1fafe..ed0e2b3 100644
--- a/src/db/repositories.js
+++ b/src/db/repositories.js
@@ -41,9 +41,10 @@ function normalizeMarketPersonaType(personaType) {
 export function createRepositories(db, config) {
     const statements = {
         insertUser: db.prepare("INSERT INTO users (username, password) VALUES (?, ?)"),
-        getUser: db.prepare("SELECT username, password FROM users WHERE username = ?"),
+        getUser: db.prepare("SELECT username, password, session_version FROM users WHERE username = ?"),
         updateUsername: db.prepare("UPDATE users SET username = ? WHERE username = ?"),
         updatePassword: db.prepare("UPDATE users SET password = ? WHERE username = ?"),
+        incrementSessionVersion: db.prepare("UPDATE users SET session_version = COALESCE(session_version, 0) + 1 WHERE username = ?"),
         insertChatSession: db.prepare(
             "INSERT INTO chat_sessions (username, title, assistant_persona_id, user_persona_id, folder_name, is_pinned, archived_at, scenario_prompt, scenario_summary) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)"
         ),
@@ -547,6 +548,17 @@ export function createRepositories(db, config) {
         updateMarketFavoritesUsername: db.prepare("UPDATE persona_market_favorites SET username = ? WHERE username = ?"),
         updateMarketRatingsUsername: db.prepare("UPDATE persona_market_ratings SET username = ? WHERE username = ?"),
         updateMarketReportsUsername: db.prepare("UPDATE persona_market_reports SET reporter_username = ? WHERE reporter_username = ?"),
+        deleteChatMemoriesByUser: db.prepare("DELETE FROM chat_memories WHERE username = ?"),
+        deleteChatSessionsByUser: db.prepare("DELETE FROM chat_sessions WHERE username = ?"),
+        deletePersonasByUser: db.prepare("DELETE FROM personas WHERE username = ?"),
+        deleteUserSettingsByUser: db.prepare("DELETE FROM user_settings WHERE username = ?"),
+        deletePersonaVersionsByUser: db.prepare("DELETE FROM persona_versions WHERE username = ?"),
+        deletePromptTemplatesByUser: db.prepare("DELETE FROM prompt_templates WHERE username = ?"),
+        deleteMarketPersonasByCreator: db.prepare("DELETE FROM persona_market WHERE creator_username = ?"),
+        deleteMarketFavoritesByUser: db.prepare("DELETE FROM persona_market_favorites WHERE username = ?"),
+        deleteMarketRatingsByUser: db.prepare("DELETE FROM persona_market_ratings WHERE username = ?"),
+        deleteMarketReportsByUser: db.prepare("DELETE FROM persona_market_reports WHERE reporter_username = ?"),
+        deleteUser: db.prepare("DELETE FROM users WHERE username = ?"),
         deleteMarketPersonaByPersonaId: db.prepare("DELETE FROM persona_market WHERE persona_id = ? AND creator_username = ?"),
         incrementMarketUsageCount: db.prepare("UPDATE persona_market SET usage_count = usage_count + 1 WHERE id = ?")
     };
@@ -566,6 +578,20 @@ export function createRepositories(db, config) {
         statements.updateMarketReportsUsername.run(nextUsername, currentUsername);
     });
 
+    const deleteUserTransaction = db.transaction((username) => {
+        statements.deleteMarketFavoritesByUser.run(username);
+        statements.deleteMarketRatingsByUser.run(username);
+        statements.deleteMarketReportsByUser.run(username);
+        statements.deleteMarketPersonasByCreator.run(username);
+        statements.deletePromptTemplatesByUser.run(username);
+        statements.deletePersonaVersionsByUser.run(username);
+        statements.deleteChatMemoriesByUser.run(username);
+        statements.deleteChatSessionsByUser.run(username);
+        statements.deleteUserSettingsByUser.run(username);
+        statements.deletePersonasByUser.run(username);
+        return statements.deleteUser.run(username);
+    });
+
     const savePersonaVersion = db.transaction((personaId, username) => {
         const persona = statements.getPersona.get(personaId, username);
         if (!persona) return null;
@@ -670,7 +696,12 @@ export function createRepositories(db, config) {
         getUser: (username) => statements.getUser.get(username),
         insertUser: (username, passwordHash) => statements.insertUser.run(username, passwordHash),
         updatePassword: (passwordHash, username) => statements.updatePassword.run(passwordHash, username),
+        incrementSessionVersion(username) {
+            statements.incrementSessionVersion.run(username);
+            return statements.getUser.get(username);
+        },
         renameUser: (currentUsername, nextUsername) => renameUserTransaction(currentUsername, nextUsername),
+        deleteUser: (username) => deleteUserTransaction(username),
         listChats: (username) => statements.listChatSessions.all(username),
         searchChats(username, query) {
             const like = `%${String(query || "").trim().toLowerCase()}%`;
diff --git a/src/db/schema.js b/src/db/schema.js
index 7ee0910..e834c89 100644
--- a/src/db/schema.js
+++ b/src/db/schema.js
@@ -6,7 +6,8 @@ export function initializeSchema(db) {
         CREATE TABLE IF NOT EXISTS users
         (
             username TEXT PRIMARY KEY,
-            password TEXT NOT NULL
+            password TEXT NOT NULL,
+            session_version INTEGER DEFAULT 0
         )
     `).run();
 
@@ -204,6 +205,10 @@ export function runMigrations(db, {dropLegacyChats = true} = {}) {
         }
     };
 
+    const userColumns = db.prepare("PRAGMA table_info(users)").all();
+    ensureColumn("users", userColumns, "session_version", "ALTER TABLE users ADD COLUMN session_version INTEGER DEFAULT 0");
+    db.prepare("UPDATE users SET session_version = 0 WHERE session_version IS NULL").run();
+
     const personaColumns = db.prepare("PRAGMA table_info(personas)").all();
     ensureColumn("personas", personaColumns, "custom_fields", "ALTER TABLE personas ADD COLUMN custom_fields TEXT");
     ensureColumn("personas", personaColumns, "persona_type", "ALTER TABLE personas ADD COLUMN persona_type TEXT DEFAULT 'assistant'");
diff --git a/src/routes/auth.js b/src/routes/auth.js
index 840ba43..2f398e3 100644
--- a/src/routes/auth.js
+++ b/src/routes/auth.js
@@ -5,18 +5,22 @@ import {validateBody} from "../middleware/validate.js";
 const credentialsValidator = (body) => {
     const username = String(body?.username || "").trim();
     const password = String(body?.password || "");
+    const inviteCode = String(body?.inviteCode || "").trim();
     if (!username) return {error: "Username is required"};
     if (username.length < 3) return {error: "Username must be at least 3 characters"};
     if (!password) return {error: "Password is required"};
     if (password.length < 6) return {error: "Password must be at least 6 characters"};
-    return {value: {username, password}};
+    return {value: {username, password, inviteCode}};
 };
 
-export function createAuthRouter({repositories, authRateLimiters}) {
+export function createAuthRouter({repositories, authRateLimiters, config}) {
     const router = express.Router();
 
     router.post("/register", ...authRateLimiters, validateBody(credentialsValidator), async (req, res) => {
-        const {username, password} = req.validatedBody;
+        const {username, password, inviteCode} = req.validatedBody;
+        if (config.registrationInviteCode && inviteCode !== config.registrationInviteCode) {
+            return res.status(403).json({error: "Valid invite code is required"});
+        }
         if (repositories.getUser(username)) {
             return res.status(400).json({error: "User already exists"});
         }
@@ -33,6 +37,7 @@ export function createAuthRouter({repositories, authRateLimiters}) {
         const valid = await bcrypt.compare(password, user.password);
         if (!valid) return res.status(403).json({error: "Invalid password"});
         req.session.user = username;
+        req.session.sessionVersion = Number(user.session_version || 0);
         return res.json({message: "Login successful"});
     });
 
@@ -41,7 +46,10 @@ export function createAuthRouter({repositories, authRateLimiters}) {
     });
 
     router.get("/session", (req, res) => {
-        return res.json({user: req.session.user || null});
+        return res.json({
+            user: req.session.user || null,
+            inviteOnlyRegistration: Boolean(config.registrationInviteCode)
+        });
     });
 
     return router;
diff --git a/src/routes/settings.js b/src/routes/settings.js
index d654adb..3174ce1 100644
--- a/src/routes/settings.js
+++ b/src/routes/settings.js
@@ -20,6 +20,14 @@ const passwordValidator = (body) => {
     return {value: {currentPassword, newPassword}};
 };
 
+const currentPasswordValidator = (body) => {
+    const currentPassword = String(body?.currentPassword || "");
+    if (!currentPassword) return {error: "Current password is required"};
+    return {value: {currentPassword}};
+};
+
+const destroySession = (req) => new Promise((resolve) => req.session.destroy(() => resolve()));
+
 export function createSettingsRouter({repositories}) {
     const router = express.Router();
     router.use(requireLogin);
@@ -59,8 +67,38 @@ export function createSettingsRouter({repositories}) {
         if (!valid) return res.status(403).json({error: "Current password is incorrect"});
         const hashed = await bcrypt.hash(newPassword, 10);
         repositories.updatePassword(hashed, username);
+        const updatedUser = repositories.incrementSessionVersion(username);
+        req.session.sessionVersion = Number(updatedUser.session_version || 0);
         return res.json({message: "Password updated"});
     });
 
+    router.post("/settings/logout-all-sessions", (req, res) => {
+        repositories.incrementSessionVersion(req.session.user);
+        req.session.destroy(() => res.json({message: "All sessions logged out"}));
+    });
+
+    router.get("/settings/export", (req, res) => {
+        const user = repositories.getUser(req.session.user);
+        if (!user) return res.status(404).json({error: "User not found"});
+        return res.json({
+            account: {
+                username: user.username,
+                exportedAt: new Date().toISOString(),
+                workspace: repositories.exportWorkspace(req.session.user)
+            }
+        });
+    });
+
+    router.delete("/settings/account", validateBody(currentPasswordValidator), async (req, res) => {
+        const username = req.session.user;
+        const user = repositories.getUser(username);
+        if (!user) return res.status(404).json({error: "User not found"});
+        const valid = await bcrypt.compare(req.validatedBody.currentPassword, user.password);
+        if (!valid) return res.status(403).json({error: "Current password is incorrect"});
+        repositories.deleteUser(username);
+        await destroySession(req);
+        return res.json({message: "Account deleted"});
+    });
+
     return router;
 }
diff --git a/test/app.test.js b/test/app.test.js
index b4a7e43..eceadb0 100644
--- a/test/app.test.js
+++ b/test/app.test.js
@@ -140,6 +140,25 @@ test("auth flow validates inputs and persists session", async () => {
     await server.close();
 });
 
+test("invite-only registration requires invite code", async () => {
+    const server = await startTestServer({config: {registrationInviteCode: "let-me-in"}});
+
+    await request(server.baseUrl, "/register", {
+        method: "POST",
+        body: {username: "invitee", password: "password123"}
+    }).then(({status, json}) => {
+        assert.equal(status, 403);
+        assert.match(json.error, /invite code/i);
+    });
+
+    await request(server.baseUrl, "/register", {
+        method: "POST",
+        body: {username: "invitee", password: "password123", inviteCode: "let-me-in"}
+    }).then(({status}) => assert.equal(status, 200));
+
+    await server.close();
+});
+
 test("createApp can use an injected session store", async () => {
     class CountingStore extends session.Store {
         constructor() {
@@ -183,6 +202,53 @@ test("createApp can use an injected session store", async () => {
     await server.close();
 });
 
+test("account export, logout-all, and deletion controls work", async () => {
+    const server = await startTestServer();
+    const firstJar = new CookieJar();
+    const secondJar = new CookieJar();
+
+    await request(server.baseUrl, "/register", {method: "POST", body: {username: "owner", password: "password123"}});
+    await request(server.baseUrl, "/login", {method: "POST", body: {username: "owner", password: "password123"}, jar: firstJar});
+    await request(server.baseUrl, "/login", {method: "POST", body: {username: "owner", password: "password123"}, jar: secondJar});
+
+    const exported = await request(server.baseUrl, "/settings/export", {jar: firstJar});
+    assert.equal(exported.status, 200);
+    assert.equal(exported.json.account.username, "owner");
+    assert.ok(exported.json.account.workspace);
+
+    const logoutAll = await request(server.baseUrl, "/settings/logout-all-sessions", {
+        method: "POST",
+        body: {},
+        jar: firstJar
+    });
+    assert.equal(logoutAll.status, 200);
+    const staleSession = await request(server.baseUrl, "/settings/profile", {jar: secondJar});
+    assert.equal(staleSession.status, 403);
+
+    await request(server.baseUrl, "/login", {method: "POST", body: {username: "owner", password: "password123"}, jar: firstJar});
+    const wrongDelete = await request(server.baseUrl, "/settings/account", {
+        method: "DELETE",
+        body: {currentPassword: "wrong-password"},
+        jar: firstJar
+    });
+    assert.equal(wrongDelete.status, 403);
+
+    const deleted = await request(server.baseUrl, "/settings/account", {
+        method: "DELETE",
+        body: {currentPassword: "password123"},
+        jar: firstJar
+    });
+    assert.equal(deleted.status, 200);
+
+    const loginAfterDelete = await request(server.baseUrl, "/login", {
+        method: "POST",
+        body: {username: "owner", password: "password123"}
+    });
+    assert.equal(loginAfterDelete.status, 400);
+
+    await server.close();
+});
+
 test("admin diagnostics require admin and return model status", async () => {
     const server = await startTestServer({
         config: {