diff --git a/src/backend/src/routers/hosting/puterSiteMiddleware.js b/src/backend/src/routers/hosting/puterSiteMiddleware.js
index d207a757f..0da172f6b 100644
--- a/src/backend/src/routers/hosting/puterSiteMiddleware.js
+++ b/src/backend/src/routers/hosting/puterSiteMiddleware.js
@@ -28,6 +28,7 @@ import selectors from '../../filesystem/node/selectors.js';
 import { get_app, get_user } from '../../helpers.js';
 import api_error_handler from '../../modules/web/lib/api_error_handler.js';
 import { Actor, SiteActorType, UserActorType } from '../../services/auth/Actor.js';
+import { DB_READ } from '../../services/database/consts.js';
 import { PermissionUtil } from '../../services/auth/permissionUtils.mjs';
 import { Context } from '../../util/context.js';
 import { stream_to_buffer as streamToBuffer } from '../../util/streamutil.js';
@@ -97,18 +98,125 @@ function getSubdomainFromHostedRequest (req) {
 }
 
 function buildPrivateHostRedirectUrl (req, app) {
-    if ( !app?.index_url || typeof app.index_url !== 'string' ) {
+    if ( ! app ) {
         return null;
     }
 
     try {
-        const redirectUrl = new URL(req.originalUrl || '/', app.index_url);
+        const privateHostingDomain = `${privateAppHostingDomain ?? 'puter.dev'}`
+            .trim()
+            .toLowerCase()
+            .replace(/^\./, '');
+        if ( ! privateHostingDomain ) {
+            return null;
+        }
+
+        const subdomain = req.subdomains?.[0] || getSubdomainFromHostedRequest(req);
+        if ( ! subdomain ) {
+            return null;
+        }
+
+        const protocol = `${config.protocol ?? 'https'}`
+            .trim()
+            .replace(/:$/, '') || 'https';
+        const requestUrl = `${req.originalUrl || '/'}`.startsWith('/')
+            ? req.originalUrl || '/'
+            : `/${req.originalUrl}`;
+        const privateHostOrigin = `${protocol}://${subdomain}.${privateHostingDomain}`;
+        const redirectUrl = new URL(requestUrl, privateHostOrigin);
         return redirectUrl.toString();
     } catch {
         return null;
     }
 }
 
+function normalizeHostFromHeader (hostValue) {
+    if ( typeof hostValue !== 'string' ) return null;
+    const normalizedHost = hostValue.trim().toLowerCase();
+    if ( ! normalizedHost ) return null;
+    try {
+        return new URL(`http://${normalizedHost}`).host;
+    } catch {
+        return normalizedHost;
+    }
+}
+
+function normalizeConfiguredHost (hostValue) {
+    if ( typeof hostValue !== 'string' ) return null;
+    const normalizedHost = hostValue.trim().toLowerCase().replace(/^\./, '');
+    if ( ! normalizedHost ) return null;
+    return normalizedHost;
+}
+
+function buildPrivateAppIndexUrlCandidates (req) {
+    const protocol = `${config.protocol ?? 'https'}`.trim().replace(/:$/, '') || 'https';
+    const hostCandidates = new Set();
+
+    const hostnameCandidate = normalizeHostFromHeader(req.hostname);
+    if ( hostnameCandidate ) {
+        hostCandidates.add(hostnameCandidate);
+    }
+
+    const headerHostCandidate = normalizeHostFromHeader(req.headers?.host);
+    if ( headerHostCandidate ) {
+        hostCandidates.add(headerHostCandidate);
+    }
+
+    const hostedSubdomain = getSubdomainFromHostedRequest(req);
+    if ( hostedSubdomain ) {
+        const staticHostingDomainCandidate = normalizeConfiguredHost(staticHostingDomain);
+        const staticHostingDomainAltCandidate = normalizeConfiguredHost(staticHostingDomainAlt);
+        const privateHostingDomainCandidate = normalizeConfiguredHost(privateAppHostingDomain);
+
+        if ( staticHostingDomainCandidate ) {
+            hostCandidates.add(`${hostedSubdomain}.${staticHostingDomainCandidate}`);
+        }
+        if ( staticHostingDomainAltCandidate ) {
+            hostCandidates.add(`${hostedSubdomain}.${staticHostingDomainAltCandidate}`);
+        }
+        if ( privateHostingDomainCandidate ) {
+            hostCandidates.add(`${hostedSubdomain}.${privateHostingDomainCandidate}`);
+        }
+    }
+
+    const candidates = [];
+    for ( const host of hostCandidates ) {
+        const base = `${protocol}://${host}`;
+        candidates.push(base);
+        candidates.push(`${base}/`);
+        candidates.push(`${base}/index.html`);
+    }
+
+    return [...new Set(candidates)];
+}
+
+async function resolvePrivateAppForHostedSite ({ req, site, services, associatedApp }) {
+    if ( associatedApp ) return associatedApp;
+    if ( ! site?.user_id ) return null;
+
+    const indexUrlCandidates = buildPrivateAppIndexUrlCandidates(req);
+    if ( indexUrlCandidates.length === 0 ) return null;
+
+    const databaseService = services.get('database');
+    const dbService = databaseService.get(DB_READ, 'apps');
+    const placeholders = indexUrlCandidates.map(() => '?').join(', ');
+
+    const apps = await dbService.read(
+        `SELECT * FROM apps WHERE owner_user_id = ? AND is_private = 1 AND index_url IN (${placeholders}) LIMIT 2`,
+        [site.user_id, ...indexUrlCandidates],
+    );
+
+    if ( apps.length > 1 ) {
+        logPrivateAccessEvent('private_access.host_match_ambiguous', {
+            requestHost: req.hostname,
+            siteOwnerUserId: site.user_id,
+            matchCount: apps.length,
+        });
+    }
+
+    return apps[0] || null;
+}
+
 function getPrivateDeniedRedirectUrl (app, denyRedirectUrl) {
     if ( typeof denyRedirectUrl === 'string' && denyRedirectUrl.trim() ) {
         return denyRedirectUrl.trim();
@@ -159,9 +267,15 @@ function getBootstrapPrivateToken (req) {
     const authorizationToken = getTokenFromAuthorizationHeader(req);
     if ( authorizationToken ) return authorizationToken;
 
-    const queryToken = req.query?.['puter.auth.token'];
-    if ( typeof queryToken === 'string' && queryToken.trim() ) {
-        return queryToken.trim();
+    const queryTokenCandidates = [
+        req.query?.['puter.auth.token'],
+        req.query?.puter?.auth?.token,
+        req.query?.auth_token,
+    ];
+    for ( const queryTokenCandidate of queryTokenCandidates ) {
+        if ( typeof queryTokenCandidate === 'string' && queryTokenCandidate.trim() ) {
+            return queryTokenCandidate.trim();
+        }
     }
 
     const headerToken = req.headers?.['x-puter-auth-token'];
@@ -249,6 +363,7 @@ async function resolvePrivateIdentity ({ req, services, appUid }) {
 
     const bootstrapToken = getBootstrapPrivateToken(req);
     if ( typeof bootstrapToken === 'string' && bootstrapToken ) {
+        let strictAuthError;
         try {
             const actor = await authService.authenticate_from_token(bootstrapToken);
             const identity = actorToPrivateIdentity(actor);
@@ -261,8 +376,37 @@ async function resolvePrivateIdentity ({ req, services, appUid }) {
                     hasInvalidPrivateCookie,
                 };
             }
-        } catch {
-            // no valid identity from bootstrap token
+        } catch (e) {
+            strictAuthError = e;
+        }
+
+        if ( typeof authService.resolvePrivateBootstrapIdentityFromToken === 'function' ) {
+            try {
+                const identity = await authService.resolvePrivateBootstrapIdentityFromToken(bootstrapToken);
+                if ( identity ) {
+                    logPrivateAccessEvent('private_access.bootstrap_fallback_allowed', {
+                        appUid,
+                        userUid: identity.userUid ?? null,
+                        requestHost: req.hostname,
+                        source: 'bootstrap-token',
+                    });
+                    return {
+                        source: 'bootstrap-token',
+                        ...identity,
+                        hasValidPrivateCookie: false,
+                        hasPrivateCookie,
+                        hasInvalidPrivateCookie,
+                    };
+                }
+            } catch (e) {
+                logPrivateAccessEvent('private_access.bootstrap_fallback_rejected', {
+                    appUid,
+                    requestHost: req.hostname,
+                    source: 'bootstrap-token',
+                    reason: e?.code || e?.message || 'unknown',
+                    strictReason: strictAuthError?.code || strictAuthError?.message || null,
+                });
+            }
         }
     }
 
@@ -377,34 +521,57 @@ function respondPrivateLoginBootstrap ({ res, app }) {
                     const statusNode = document.getElementById('status');
                     const loginButton = document.getElementById('loginButton');
                     const retryButton = document.getElementById('retryButton');
+                    const attemptedTokenStorageKey = 'puter.privateAppBootstrap.lastAttemptedToken';
 
                     const setStatus = (message) => {
                         statusNode.textContent = message;
                     };
 
+                    const getStoredAuthToken = () => {
+                        return globalThis.puter?.authToken
+                            || localStorage.getItem('auth_token')
+                            || localStorage.getItem('puter.auth.token');
+                    };
+
                     const redirectWithToken = (token) => {
                         if ( typeof token !== 'string' || !token ) {
                             throw new Error('missing_auth_token');
                         }
+                        sessionStorage.setItem(attemptedTokenStorageKey, token);
                         const url = new URL(window.location.href);
                         url.searchParams.set('puter.auth.token', token);
                         window.location.replace(url.toString());
                     };
 
+                    const tryStoredTokenBootstrap = () => {
+                        const currentUrl = new URL(window.location.href);
+                        const currentUrlToken = currentUrl.searchParams.get('puter.auth.token');
+                        const storedToken = getStoredAuthToken();
+                        if ( typeof storedToken !== 'string' || !storedToken ) return false;
+
+                        // Avoid looping on the exact same token if backend already rejected it.
+                        if ( currentUrlToken && currentUrlToken === storedToken ) return false;
+
+                        const lastAttemptedToken = sessionStorage.getItem(attemptedTokenStorageKey);
+                        if ( lastAttemptedToken && lastAttemptedToken === storedToken ) return false;
+
+                        setStatus('Using saved Puter session...');
+                        redirectWithToken(storedToken);
+                        return true;
+                    };
+
                     const authenticate = async () => {
                         loginButton.disabled = true;
                         setStatus('Authenticating with Puter...');
                         try {
-                            if ( globalThis.puter?.authToken ) {
-                                redirectWithToken(globalThis.puter.authToken);
+                            if ( tryStoredTokenBootstrap() ) {
                                 return;
                             }
 
                             const result = await globalThis.puter.auth.signIn();
                             const authToken =
                                 result?.token
-                                || globalThis.puter?.authToken
-                                || localStorage.getItem('puter.auth.token');
+                                || getStoredAuthToken();
                             redirectWithToken(authToken);
                         } catch (error) {
                             console.error('private app sign in failed', error);
@@ -420,6 +587,10 @@ function respondPrivateLoginBootstrap ({ res, app }) {
                     retryButton.addEventListener('click', () => {
                         window.location.reload();
                     });
+
+                    if ( tryStoredTokenBootstrap() ) {
+                        return;
+                    }
                 })();
             </script>
         </body>
@@ -591,7 +762,13 @@ async function runInternal (req, res, next) {
     const associatedApp = site.associated_app_id
         ? await get_app({ id: site.associated_app_id })
         : null;
-    const privateAppEnabled = isPrivateApp(associatedApp);
+    const privateApp = await resolvePrivateAppForHostedSite({
+        req,
+        site,
+        services,
+        associatedApp,
+    });
+    const privateAppEnabled = isPrivateApp(privateApp);
     const privateAccessGateEnabled = isPrivateAccessGateEnabled();
 
     if (
@@ -599,10 +776,10 @@ async function runInternal (req, res, next) {
         && privateAppEnabled
         && !hostMatchesPrivateDomain(req.hostname)
     ) {
-        const privateHostRedirect = buildPrivateHostRedirectUrl(req, associatedApp);
+        const privateHostRedirect = buildPrivateHostRedirectUrl(req, privateApp);
         if ( privateHostRedirect ) {
             logPrivateAccessEvent('private_access.host_redirect', {
-                appUid: associatedApp?.uid ?? null,
+                appUid: privateApp?.uid ?? null,
                 requestHost: req.hostname,
                 requestPath: req.path,
                 redirectUrl: privateHostRedirect,
@@ -614,6 +791,7 @@ async function runInternal (req, res, next) {
 
     if (
         site.associated_app_id &&
+        !privateAppEnabled &&
         !req.query['puter.app_instance_id'] &&
         ( path === '' || path.endsWith('/') )
     ) {
@@ -669,7 +847,7 @@ async function runInternal (req, res, next) {
             req,
             res,
             services,
-            app: associatedApp,
+            app: privateApp,
             requestPath: req.path,
         });
         if ( ! accessAllowed ) return;
diff --git a/src/backend/src/routers/hosting/puterSiteMiddleware.test.js b/src/backend/src/routers/hosting/puterSiteMiddleware.test.js
index 69be52f23..c7db2f45e 100644
--- a/src/backend/src/routers/hosting/puterSiteMiddleware.test.js
+++ b/src/backend/src/routers/hosting/puterSiteMiddleware.test.js
@@ -261,7 +261,7 @@ describe('PuterSiteMiddleware', () => {
             capturedMiddleware = puterSiteMiddleware;
         });
 
-        it('redirects private app assets to puter.dev host', async () => {
+        it('redirects private app assets to puter.dev host even before index_url migration', async () => {
             const mockServices = {
                 get: vi.fn().mockImplementation((serviceName) => {
                     if ( serviceName === 'puter-site' ) {
@@ -285,7 +285,7 @@ describe('PuterSiteMiddleware', () => {
                 uid: 'app-11111111-1111-1111-1111-111111111111',
                 name: 'paid-app',
                 is_private: 1,
-                index_url: 'https://paid.puter.dev/',
+                index_url: 'https://paid.site.puter.localhost/',
             });
 
             const mockReq = {
@@ -315,6 +315,130 @@ describe('PuterSiteMiddleware', () => {
         });
 
         it('serves login bootstrap html when private app identity is missing', async () => {
+            const eventEmit = vi.fn().mockImplementation(async (_eventName, event) => {
+                event.result.allowed = false;
+                event.result.redirectUrl = 'https://puter.com/app/app-center/?item=app-11111111-1111-1111-1111-111111111111';
+            });
+            const dbRead = vi.fn().mockResolvedValue([
+                {
+                    uid: 'app-11111111-1111-1111-1111-111111111111',
+                    name: 'paid-app',
+                    is_private: 1,
+                    index_url: 'https://paid.puter.dev/',
+                    owner_user_id: 101,
+                },
+            ]);
+            const authService = {
+                getPrivateAssetCookieName: vi.fn().mockReturnValue('puter.private.asset.token'),
+                verifyPrivateAssetToken: vi.fn().mockImplementation(() => {
+                    throw new Error('invalid');
+                }),
+                authenticate_from_token: vi.fn().mockImplementation(() => {
+                    throw new Error('invalid');
+                }),
+                createPrivateAssetToken: vi.fn().mockReturnValue('private-token'),
+                getPrivateAssetCookieOptions: vi.fn().mockReturnValue({}),
+            };
+            const mockServices = {
+                get: vi.fn().mockImplementation((serviceName) => {
+                    if ( serviceName === 'puter-site' ) {
+                        return {
+                            get_subdomain: vi.fn().mockResolvedValue({
+                                user_id: 101,
+                                associated_app_id: null,
+                                root_dir_id: 303,
+                            }),
+                        };
+                    }
+                    if ( serviceName === 'filesystem' ) {
+                        return {
+                            node: vi.fn().mockResolvedValue({
+                                exists: vi.fn().mockResolvedValue(true),
+                                get: vi.fn().mockImplementation(async (fieldName) => {
+                                    if ( fieldName === 'type' ) return 'directory';
+                                    if ( fieldName === 'path' ) return '/alice/Public';
+                                    return null;
+                                }),
+                            }),
+                        };
+                    }
+                    if ( serviceName === 'acl' ) {
+                        return {
+                            check: vi.fn().mockResolvedValue(true),
+                        };
+                    }
+                    if ( serviceName === 'database' ) {
+                        return {
+                            get: vi.fn().mockReturnValue({
+                                read: dbRead,
+                            }),
+                        };
+                    }
+                    if ( serviceName === 'event' ) return { emit: eventEmit };
+                    if ( serviceName === 'auth' ) return authService;
+                    return {};
+                }),
+            };
+            mockContextInstance.get.mockImplementation((key) => {
+                if ( key === 'services' ) return mockServices;
+                return null;
+            });
+            getUserMockImpl = async () => ({ id: 101, suspended: false });
+            getAppMockImpl = async () => ({
+                uid: 'app-11111111-1111-1111-1111-111111111111',
+                name: 'paid-app',
+                is_private: 1,
+                index_url: 'https://paid.puter.dev/',
+            });
+
+            const mockReq = {
+                hostname: 'paid.puter.dev',
+                subdomains: [],
+                is_custom_domain: false,
+                baseUrl: '',
+                path: '/index.html',
+                originalUrl: '/index.html',
+                cookies: {},
+                headers: {},
+                query: {},
+                ctx: mockContextInstance,
+            };
+            const mockRes = {
+                redirect: vi.fn(),
+                cookie: vi.fn(),
+                set: vi.fn().mockReturnThis(),
+                setHeader: vi.fn(),
+                status: vi.fn().mockReturnThis(),
+                send: vi.fn(),
+            };
+            const mockNext = vi.fn();
+
+            await capturedMiddleware(mockReq, mockRes, mockNext);
+
+            expect(eventEmit).not.toHaveBeenCalled();
+            expect(dbRead).toHaveBeenCalledWith(
+                expect.stringContaining('index_url IN'),
+                expect.arrayContaining([
+                    101,
+                    'https://paid.puter.dev',
+                    'https://paid.puter.dev/',
+                    'https://paid.puter.dev/index.html',
+                    'https://paid.site.puter.localhost',
+                    'https://paid.site.puter.localhost/',
+                    'https://paid.site.puter.localhost/index.html',
+                ]),
+            );
+            expect(mockRes.status).toHaveBeenCalledWith(200);
+            expect(mockRes.send).toHaveBeenCalledWith(expect.stringContaining('https://js.puter.com/v2/'));
+            expect(mockRes.send).toHaveBeenCalledWith(expect.stringContaining('puter.auth.signIn()'));
+            expect(mockRes.send).toHaveBeenCalledWith(expect.stringContaining('localStorage.getItem(\'auth_token\')'));
+            expect(mockRes.send).toHaveBeenCalledWith(expect.stringContaining('tryStoredTokenBootstrap'));
+            expect(mockRes.redirect).not.toHaveBeenCalled();
+            expect(mockRes.cookie).not.toHaveBeenCalled();
+            expect(mockNext).not.toHaveBeenCalled();
+        });
+
+        it('does not redirect private root requests to puter.com app route before access bootstrap', async () => {
             const eventEmit = vi.fn().mockImplementation(async (_eventName, event) => {
                 event.result.allowed = false;
                 event.result.redirectUrl = 'https://puter.com/app/app-center/?item=app-11111111-1111-1111-1111-111111111111';
@@ -372,7 +496,7 @@ describe('PuterSiteMiddleware', () => {
                 uid: 'app-11111111-1111-1111-1111-111111111111',
                 name: 'paid-app',
                 is_private: 1,
-                index_url: 'https://paid.puter.dev/',
+                index_url: 'https://paid.site.puter.localhost/',
             });
 
             const mockReq = {
@@ -380,11 +504,13 @@ describe('PuterSiteMiddleware', () => {
                 subdomains: [],
                 is_custom_domain: false,
                 baseUrl: '',
-                path: '/index.html',
-                originalUrl: '/index.html',
+                path: '/',
+                originalUrl: '/?puter.auth.token=abc',
                 cookies: {},
                 headers: {},
-                query: {},
+                query: {
+                    'puter.auth.token': 'abc',
+                },
                 ctx: mockContextInstance,
             };
             const mockRes = {
@@ -399,12 +525,10 @@ describe('PuterSiteMiddleware', () => {
 
             await capturedMiddleware(mockReq, mockRes, mockNext);
 
-            expect(eventEmit).not.toHaveBeenCalled();
+            expect(mockRes.redirect).not.toHaveBeenCalledWith('https://puter.com/app/paid-app/');
             expect(mockRes.status).toHaveBeenCalledWith(200);
             expect(mockRes.send).toHaveBeenCalledWith(expect.stringContaining('https://js.puter.com/v2/'));
             expect(mockRes.send).toHaveBeenCalledWith(expect.stringContaining('puter.auth.signIn()'));
-            expect(mockRes.redirect).not.toHaveBeenCalled();
-            expect(mockRes.cookie).not.toHaveBeenCalled();
             expect(mockNext).not.toHaveBeenCalled();
         });
 
@@ -512,6 +636,215 @@ describe('PuterSiteMiddleware', () => {
             expect(mockNext).not.toHaveBeenCalled();
         });
 
+        it('uses bootstrap fallback identity when strict bootstrap auth fails', async () => {
+            const eventEmit = vi.fn().mockImplementation(async (_eventName, event) => {
+                event.result.allowed = false;
+                event.result.redirectUrl = 'https://apps.puter.com/app/paid-app';
+            });
+            const authService = {
+                getPrivateAssetCookieName: vi.fn().mockReturnValue('puter.private.asset.token'),
+                verifyPrivateAssetToken: vi.fn().mockImplementation(() => {
+                    throw new Error('invalid');
+                }),
+                authenticate_from_token: vi.fn().mockImplementation(() => {
+                    throw new Error('token_auth_failed');
+                }),
+                resolvePrivateBootstrapIdentityFromToken: vi.fn().mockResolvedValue({
+                    userUid: 'user-111',
+                    sessionUuid: 'session-111',
+                }),
+                createPrivateAssetToken: vi.fn().mockReturnValue('private-token'),
+                getPrivateAssetCookieOptions: vi.fn().mockReturnValue({}),
+            };
+            const mockServices = {
+                get: vi.fn().mockImplementation((serviceName) => {
+                    if ( serviceName === 'puter-site' ) {
+                        return {
+                            get_subdomain: vi.fn().mockResolvedValue({
+                                user_id: 101,
+                                associated_app_id: 202,
+                                root_dir_id: 303,
+                            }),
+                        };
+                    }
+                    if ( serviceName === 'filesystem' ) {
+                        return {
+                            node: vi.fn().mockResolvedValue({
+                                exists: vi.fn().mockResolvedValue(true),
+                                get: vi.fn().mockImplementation(async (fieldName) => {
+                                    if ( fieldName === 'type' ) return 'directory';
+                                    if ( fieldName === 'path' ) return '/alice/Public';
+                                    return null;
+                                }),
+                            }),
+                        };
+                    }
+                    if ( serviceName === 'acl' ) {
+                        return {
+                            check: vi.fn().mockResolvedValue(true),
+                        };
+                    }
+                    if ( serviceName === 'event' ) return { emit: eventEmit };
+                    if ( serviceName === 'auth' ) return authService;
+                    return {};
+                }),
+            };
+            mockContextInstance.get.mockImplementation((key) => {
+                if ( key === 'services' ) return mockServices;
+                return null;
+            });
+            getUserMockImpl = async () => ({ id: 101, suspended: false });
+            getAppMockImpl = async () => ({
+                uid: 'app-11111111-1111-1111-1111-111111111111',
+                name: 'paid-app',
+                is_private: 1,
+                index_url: 'https://paid.puter.dev/',
+            });
+
+            const mockReq = {
+                hostname: 'paid.puter.dev',
+                subdomains: [],
+                is_custom_domain: false,
+                baseUrl: '',
+                path: '/index.html',
+                originalUrl: '/index.html?puter.auth.token=bootstrap-token',
+                cookies: {},
+                headers: {},
+                query: {
+                    'puter.auth.token': 'bootstrap-token',
+                },
+                ctx: mockContextInstance,
+            };
+            const mockRes = {
+                redirect: vi.fn(),
+                cookie: vi.fn(),
+                setHeader: vi.fn(),
+                status: vi.fn().mockReturnThis(),
+                send: vi.fn(),
+            };
+            const mockNext = vi.fn();
+
+            await capturedMiddleware(mockReq, mockRes, mockNext);
+
+            expect(authService.authenticate_from_token).toHaveBeenCalledWith('bootstrap-token');
+            expect(authService.resolvePrivateBootstrapIdentityFromToken)
+                .toHaveBeenCalledWith('bootstrap-token');
+            expect(eventEmit).toHaveBeenCalledWith(
+                'app.privateAccess.check',
+                expect.objectContaining({
+                    appUid: 'app-11111111-1111-1111-1111-111111111111',
+                    userUid: 'user-111',
+                }),
+            );
+            expect(mockRes.redirect).toHaveBeenCalledWith('https://apps.puter.com/app/paid-app');
+            expect(mockRes.send).not.toHaveBeenCalled();
+            expect(mockRes.cookie).not.toHaveBeenCalled();
+            expect(mockNext).not.toHaveBeenCalled();
+        });
+
+        it('accepts nested query token key for bootstrap auth', async () => {
+            const eventEmit = vi.fn().mockImplementation(async (_eventName, event) => {
+                event.result.allowed = false;
+                event.result.redirectUrl = 'https://apps.puter.com/app/paid-app';
+            });
+            const authService = {
+                getPrivateAssetCookieName: vi.fn().mockReturnValue('puter.private.asset.token'),
+                verifyPrivateAssetToken: vi.fn().mockImplementation(() => {
+                    throw new Error('invalid');
+                }),
+                authenticate_from_token: vi.fn().mockImplementation(() => {
+                    throw new Error('token_auth_failed');
+                }),
+                resolvePrivateBootstrapIdentityFromToken: vi.fn().mockResolvedValue({
+                    userUid: 'user-111',
+                    sessionUuid: 'session-111',
+                }),
+                createPrivateAssetToken: vi.fn().mockReturnValue('private-token'),
+                getPrivateAssetCookieOptions: vi.fn().mockReturnValue({}),
+            };
+            const mockServices = {
+                get: vi.fn().mockImplementation((serviceName) => {
+                    if ( serviceName === 'puter-site' ) {
+                        return {
+                            get_subdomain: vi.fn().mockResolvedValue({
+                                user_id: 101,
+                                associated_app_id: 202,
+                                root_dir_id: 303,
+                            }),
+                        };
+                    }
+                    if ( serviceName === 'filesystem' ) {
+                        return {
+                            node: vi.fn().mockResolvedValue({
+                                exists: vi.fn().mockResolvedValue(true),
+                                get: vi.fn().mockImplementation(async (fieldName) => {
+                                    if ( fieldName === 'type' ) return 'directory';
+                                    if ( fieldName === 'path' ) return '/alice/Public';
+                                    return null;
+                                }),
+                            }),
+                        };
+                    }
+                    if ( serviceName === 'acl' ) {
+                        return {
+                            check: vi.fn().mockResolvedValue(true),
+                        };
+                    }
+                    if ( serviceName === 'event' ) return { emit: eventEmit };
+                    if ( serviceName === 'auth' ) return authService;
+                    return {};
+                }),
+            };
+            mockContextInstance.get.mockImplementation((key) => {
+                if ( key === 'services' ) return mockServices;
+                return null;
+            });
+            getUserMockImpl = async () => ({ id: 101, suspended: false });
+            getAppMockImpl = async () => ({
+                uid: 'app-11111111-1111-1111-1111-111111111111',
+                name: 'paid-app',
+                is_private: 1,
+                index_url: 'https://paid.puter.dev/',
+            });
+
+            const mockReq = {
+                hostname: 'paid.puter.dev',
+                subdomains: [],
+                is_custom_domain: false,
+                baseUrl: '',
+                path: '/index.html',
+                originalUrl: '/index.html?puter.auth.token=bootstrap-token',
+                cookies: {},
+                headers: {},
+                query: {
+                    puter: {
+                        auth: {
+                            token: 'bootstrap-token',
+                        },
+                    },
+                },
+                ctx: mockContextInstance,
+            };
+            const mockRes = {
+                redirect: vi.fn(),
+                cookie: vi.fn(),
+                setHeader: vi.fn(),
+                status: vi.fn().mockReturnThis(),
+                send: vi.fn(),
+            };
+            const mockNext = vi.fn();
+
+            await capturedMiddleware(mockReq, mockRes, mockNext);
+
+            expect(authService.authenticate_from_token).toHaveBeenCalledWith('bootstrap-token');
+            expect(authService.resolvePrivateBootstrapIdentityFromToken)
+                .toHaveBeenCalledWith('bootstrap-token');
+            expect(mockRes.redirect).toHaveBeenCalledWith('https://apps.puter.com/app/paid-app');
+            expect(mockRes.send).not.toHaveBeenCalled();
+            expect(mockRes.cookie).not.toHaveBeenCalled();
+            expect(mockNext).not.toHaveBeenCalled();
+        });
+
         it('skips private app gate when feature flag is disabled', async () => {
             config.enable_private_app_access_gate = false;
 
diff --git a/src/backend/src/services/auth/AuthService.js b/src/backend/src/services/auth/AuthService.js
index 5efd39c76..13d609c9c 100644
--- a/src/backend/src/services/auth/AuthService.js
+++ b/src/backend/src/services/auth/AuthService.js
@@ -400,6 +400,75 @@ class AuthService extends BaseService {
         };
     }
 
+    resolvePrivateBootstrapSessionUuid (decoded) {
+        if ( !decoded || typeof decoded !== 'object' ) {
+            return null;
+        }
+
+        if ( decoded.type === 'session' || decoded.type === 'gui' ) {
+            if ( typeof decoded.uuid !== 'string' || !decoded.uuid ) {
+                return null;
+            }
+            return decoded.uuid;
+        }
+
+        if ( decoded.type === 'app-under-user' ) {
+            if ( typeof decoded.session !== 'string' || !decoded.session ) {
+                return null;
+            }
+            try {
+                return this.uuid_fpe.decrypt(decoded.session);
+            } catch (e) {
+                return null;
+            }
+        }
+
+        return null;
+    }
+
+    async resolvePrivateBootstrapIdentityFromToken (token) {
+        let decoded;
+        try {
+            decoded = this.modules.jwt.verify(token, this.global_config.jwt_secret);
+        } catch (e) {
+            throw APIError.create('token_auth_failed');
+        }
+
+        const userUid = typeof decoded?.user_uid === 'string'
+            ? decoded.user_uid
+            : null;
+        if ( ! userUid ) {
+            throw APIError.create('token_auth_failed');
+        }
+
+        const allowedTypes = new Set(['session', 'gui', 'app-under-user']);
+        if ( ! allowedTypes.has(decoded.type) ) {
+            throw APIError.create('token_auth_failed');
+        }
+
+        const sessionUuid = this.resolvePrivateBootstrapSessionUuid(decoded);
+        if ( ! sessionUuid ) {
+            throw APIError.create('token_auth_failed');
+        }
+
+        const session = await this.get_session_(sessionUuid);
+        if ( ! session ) {
+            throw APIError.create('token_auth_failed');
+        }
+
+        const sessionUserUid = typeof session.user_uid === 'string'
+            ? session.user_uid
+            : null;
+        if ( !sessionUserUid || sessionUserUid !== userUid ) {
+            throw APIError.create('token_auth_failed');
+        }
+
+        return {
+            userUid,
+            sessionUuid: session.uuid || sessionUuid,
+        };
+    }
+
     /**
      * Internal method for creating a session.
      *
diff --git a/src/backend/src/services/auth/AuthService.privateAssetToken.test.ts b/src/backend/src/services/auth/AuthService.privateAssetToken.test.ts
index bc59cf41d..95ac14ef0 100644
--- a/src/backend/src/services/auth/AuthService.privateAssetToken.test.ts
+++ b/src/backend/src/services/auth/AuthService.privateAssetToken.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it, vi } from 'vitest';
 import * as jwt from 'jsonwebtoken';
 import { AuthService } from './AuthService.js';
 
@@ -39,6 +39,8 @@ const createAuthService = (): AuthServiceForPrivateTokenTests => {
         encrypt: (value) => value,
         decrypt: (value) => value,
     };
+    // @ts-expect-error test-only lightweight stub
+    authService.get_session_ = vi.fn().mockResolvedValue(undefined);
     return authService;
 };
 
@@ -107,4 +109,53 @@ describe('AuthService private asset token helpers', () => {
         expect(options.maxAge).toBe(3_600_000);
         expect(options.domain).toBe('.app.puter.localhost');
     });
+
+    it('resolves bootstrap identity from app-under-user token without app lookup', async () => {
+        const authService = createAuthService();
+        const userUid = '4b0cecf8-dd6a-4eb5-bcc4-c76cc7e8d7f0';
+        const sessionUuid = 'f9000804-2fd3-4da5-819b-afc5296f90f7';
+        const token = jwt.sign({
+            type: 'app-under-user',
+            version: '0.0.0',
+            user_uid: userUid,
+            app_uid: 'app-7e2d3016-8d36-456a-9dc7-b75b0f4f7683',
+            session: sessionUuid,
+        }, authService.global_config.jwt_secret, { expiresIn: 60 });
+
+        // @ts-expect-error test-only lightweight stub
+        authService.get_session_ = vi.fn().mockResolvedValue({
+            uuid: sessionUuid,
+            user_uid: userUid,
+        });
+
+        const identity = await authService.resolvePrivateBootstrapIdentityFromToken(token);
+
+        expect(identity).toEqual({
+            userUid,
+            sessionUuid,
+        });
+        // @ts-expect-error test-only lightweight stub
+        expect(authService.get_session_).toHaveBeenCalledWith(sessionUuid);
+    });
+
+    it('rejects bootstrap identity when session owner does not match token user', async () => {
+        const authService = createAuthService();
+        const token = jwt.sign({
+            type: 'app-under-user',
+            version: '0.0.0',
+            user_uid: '4b0cecf8-dd6a-4eb5-bcc4-c76cc7e8d7f0',
+            app_uid: 'app-7e2d3016-8d36-456a-9dc7-b75b0f4f7683',
+            session: 'f9000804-2fd3-4da5-819b-afc5296f90f7',
+        }, authService.global_config.jwt_secret, { expiresIn: 60 });
+
+        // @ts-expect-error test-only lightweight stub
+        authService.get_session_ = vi.fn().mockResolvedValue({
+            uuid: 'f9000804-2fd3-4da5-819b-afc5296f90f7',
+            user_uid: '9885b80e-1a14-4c8d-9e3f-4fa5915b1136',
+        });
+
+        await expect(authService.resolvePrivateBootstrapIdentityFromToken(token))
+            .rejects
+            .toThrow();
+    });
 });