diff --git a/frontend/int/forward/RestrictedForward.vue b/frontend/int/forward/RestrictedForward.vue
index 4206aab..8e3f205 100644
--- a/frontend/int/forward/RestrictedForward.vue
+++ b/frontend/int/forward/RestrictedForward.vue
@@ -2,7 +2,6 @@
   <RestrictedAuth
     :mode="authMode"
     @authenticated="handleAuthenticated"
-    @logout="handleLogout"
     @back="goBack"
     @home="returnHome"
   />
@@ -16,20 +15,21 @@ import { goBack } from '@/utils/helpers'
 
 const basePath = computed(() => uiBasePath())
 
-// Detect mode from URL parameters
+// Detect mode from data attribute on html tag only
+// (RestrictedApi uses URL query, RestrictedForward uses data injected by server)
 const authMode = computed(() => {
-  const params = new URLSearchParams(window.location.search)
-  return params.get('mode') === 'reauth' ? 'reauth' : 'login'
+  const htmlElement = document.documentElement
+  const dataMode = htmlElement.getAttribute('data-mode')
+  if (dataMode === 'reauth') return 'reauth'
+  if (dataMode === 'forbidden') return 'forbidden'
+  return 'login'
 })
 
 function handleAuthenticated() {
+  // Reload page to re-trigger forward auth validation
   location.reload()
 }
 
-function handleLogout() {
-  window.location.reload()
-}
-
 function returnHome() {
   const target = basePath.value || '/auth/'
   if (window.location.pathname !== target) history.replaceState(null, '', target)
diff --git a/frontend/src/components/RestrictedAuth.vue b/frontend/src/components/RestrictedAuth.vue
index d3c355e..85bb200 100644
--- a/frontend/src/components/RestrictedAuth.vue
+++ b/frontend/src/components/RestrictedAuth.vue
@@ -29,8 +29,8 @@
                 <button v-if="canAuthenticate" class="btn-primary" :disabled="loading" @click="authenticateUser">
                   {{ loading ? (mode === 'reauth' ? 'Verifying…' : 'Signing in…') : (mode === 'reauth' ? 'Verify' : 'Login') }}
                 </button>
-                <button v-if="isAuthenticated && mode !== 'reauth'" class="btn-danger" :disabled="loading" @click="logoutUser">Logout</button>
-                <button v-if="isAuthenticated && mode !== 'reauth'" class="btn-primary" :disabled="loading" @click="openProfile">Profile</button>
+                <button v-if="isAuthenticated && mode !== 'reauth' && mode !== 'forbidden'" class="btn-danger" :disabled="loading" @click="logoutUser">Logout</button>
+                <button v-if="isAuthenticated && mode !== 'reauth' && mode !== 'forbidden'" class="btn-primary" :disabled="loading" @click="openProfile">Profile</button>
               </slot>
             </div>
           </div>
@@ -49,7 +49,7 @@ const props = defineProps({
   mode: {
     type: String,
     default: 'login',
-    validator: (value) => ['login', 'reauth'].includes(value)
+    validator: (value) => ['login', 'reauth', 'forbidden'].includes(value)
   }
 })
 
@@ -69,15 +69,17 @@ const canAuthenticate = computed(() => {
   if (initializing.value) return false
   // In reauth mode, allow authentication even if already authenticated
   if (props.mode === 'reauth') return true
-  // In login view or initial state, allow if not authenticated
-  return currentView.value !== 'forbidden'
+  // In forbidden mode or forbidden view, don't allow authentication
+  if (props.mode === 'forbidden' || currentView.value === 'forbidden') return false
+  // In login view or initial state, allow authentication
+  return true
 })
 
 const headingTitle = computed(() => {
   if (props.mode === 'reauth') {
     return `🔐 Additional Verification Required`
   }
-  if (currentView.value === 'forbidden') return '🚫 Forbidden'
+  if (props.mode === 'forbidden' || currentView.value === 'forbidden') return '🚫 Forbidden'
   return `🔐 ${settings.value?.rp_name || location.origin}`
 })
 
@@ -85,7 +87,10 @@ const headerMessage = computed(() => {
   if (props.mode === 'reauth') {
     return 'Please verify your identity to continue with this action.'
   }
-  return currentView.value === 'forbidden' ? 'You lack the required permissions.' : 'Please sign in with your passkey.'
+  if (props.mode === 'forbidden' || currentView.value === 'forbidden') {
+    return 'You lack the required permissions.'
+  }
+  return 'Please sign in with your passkey.'
 })
 
 const userDisplayName = computed(() => userInfo.value?.user?.user_name || 'User')
diff --git a/passkey/fastapi/api.py b/passkey/fastapi/api.py
index 6e502ec..d2d9a5b 100644
--- a/passkey/fastapi/api.py
+++ b/passkey/fastapi/api.py
@@ -24,7 +24,7 @@ from ..authsession import (
 )
 from ..globals import db
 from ..globals import passkey as global_passkey
-from ..util import hostutil, passphrase, userinfo
+from ..util import hostutil, htmlutil, passphrase, userinfo
 from ..util.tokens import session_key
 from . import authz, session, user
 from .session import AUTH_COOKIE
@@ -109,18 +109,24 @@ async def forward_authentication(
     request: Request,
     response: Response,
     perm: list[str] = Query([]),
+    max_age: str | None = Query(None),
     auth=AUTH_COOKIE,
 ):
     """Forward auth validation for Caddy/Nginx.
 
     Query Params:
     - perm: repeated permission IDs the authenticated user must possess (ALL required).
+    - max_age: maximum age of authentication (e.g., "5m", "1h", "30s"). If the session
+               is older than this, user must re-authenticate.
 
     Success: 204 No Content with Remote-* headers describing the authenticated user.
-    Failure (unauthenticated / unauthorized): 4xx JSON body with detail.
+    Failure (unauthenticated / unauthorized): 4xx with HTML page for authentication.
+             The HTML includes data attributes for mode and other metadata.
     """
     try:
-        ctx = await authz.verify(auth, perm, host=request.headers.get("host"))
+        ctx = await authz.verify(
+            auth, perm, host=request.headers.get("host"), max_age=max_age
+        )
         role_permissions = set(ctx.role.permissions or [])
         if ctx.permissions:
             role_permissions.update(permission.id for permission in ctx.permissions)
@@ -147,14 +153,18 @@ async def forward_authentication(
             "Remote-Credential": str(ctx.session.credential_uuid),
         }
         return Response(status_code=204, headers=remote_headers)
-    except HTTPException as e:
-        # Let global handler clear cookie; still return HTML surface instead of JSON
-        html = frontend.file("int", "restricted", "index.html").read_bytes()
-        status = e.status_code
-        # If 401 we still want cookie cleared; rely on handler by raising again not feasible (we need HTML)
-        if status == 401:
+    except authz.AuthException as e:
+        # Authentication/authorization failed - return HTML with metadata
+        html = frontend.file("int", "forward", "index.html").read_bytes()
+        # Inject mode and any additional metadata
+        data_attrs = {"mode": e.mode, **e.metadata}
+        html = htmlutil.patch_html_data_attrs(html, **data_attrs)
+        # Clear cookie only if session is invalid (not for reauth)
+        if e.clear_session:
             session.clear_session_cookie(response)
-        return Response(html, status_code=status, media_type="text/html")
+        return Response(
+            html, status_code=e.status_code, media_type="text/html; charset=UTF-8"
+        )
 
 
 @app.get("/settings")
diff --git a/passkey/fastapi/authz.py b/passkey/fastapi/authz.py
index 90920f4..3114af2 100644
--- a/passkey/fastapi/authz.py
+++ b/passkey/fastapi/authz.py
@@ -2,31 +2,76 @@ import logging
 
 from fastapi import HTTPException
 
-from ..util import permutil
+from ..util import permutil, sessionutil
 
 logger = logging.getLogger(__name__)
 
 
+class AuthException(HTTPException):
+    """Exception raised during authentication/authorization with metadata for the UI.
+
+    Attributes:
+        status_code: HTTP status code (401 for auth, 403 for authz)
+        detail: Error message
+        mode: UI mode ('login' or 'reauth')
+        clear_session: Whether to clear the session cookie (True for invalid sessions)
+        metadata: Additional data to pass to the frontend
+    """
+
+    def __init__(
+        self,
+        status_code: int,
+        detail: str,
+        mode: str,
+        clear_session: bool = False,
+        **metadata,
+    ):
+        super().__init__(status_code=status_code, detail=detail)
+        self.mode = mode
+        self.clear_session = clear_session
+        self.metadata = metadata
+
+
 async def verify(
     auth: str | None,
     perm: list[str],
     match=permutil.has_all,
     host: str | None = None,
+    max_age: str | None = None,
 ):
     """Validate session token and optional list of required permissions.
 
     Returns the session context.
 
-    Raises HTTPException on failure:
-      401: unauthenticated / invalid session
-      403: required permissions missing
+    Raises AuthException on failure with metadata for UI rendering.
     """
     if not auth:
-        raise HTTPException(status_code=401, detail="Authentication required")
+        raise AuthException(
+            status_code=401,
+            detail="Authentication required",
+            mode="login",
+        )
 
     ctx = await permutil.session_context(auth, host)
     if not ctx:
-        raise HTTPException(status_code=401, detail="Session not found")
+        raise AuthException(
+            status_code=401,
+            detail="Your session has expired. Please sign in again.",
+            mode="login",
+            clear_session=True,
+        )
+    # Check max_age requirement if specified
+    if max_age:
+        try:
+            if not sessionutil.check_session_age(ctx.session, max_age):
+                raise AuthException(
+                    status_code=401,
+                    detail="Additional authentication required",
+                    mode="reauth",
+                )
+        except ValueError as e:
+            # Invalid max_age format - log but don't fail the request
+            logger.warning(f"Invalid max_age format '{max_age}': {e}")
 
     if not match(ctx, perm):
         # Determine which permissions are missing for clearer diagnostics
@@ -39,6 +84,8 @@ async def verify(
             perm,
             ctx.role.permissions,
         )
-        raise HTTPException(status_code=403, detail="Permission required")
+        raise AuthException(
+            status_code=403, mode="forbidden", detail="Permission required"
+        )
 
     return ctx
diff --git a/passkey/fastapi/mainapp.py b/passkey/fastapi/mainapp.py
index 2b24128..daa8469 100644
--- a/passkey/fastapi/mainapp.py
+++ b/passkey/fastapi/mainapp.py
@@ -59,6 +59,11 @@ app.mount(
     StaticFiles(directory=frontend.file("auth", "assets")),
     name="assets",
 )
+app.mount(
+    "/int/",
+    StaticFiles(directory=frontend.file("int"), html=True),
+    name="int",
+)
 
 
 @app.get("/auth/restricted/")
diff --git a/passkey/util/htmlutil.py b/passkey/util/htmlutil.py
new file mode 100644
index 0000000..ed42e9f
--- /dev/null
+++ b/passkey/util/htmlutil.py
@@ -0,0 +1,47 @@
+"""Utility functions for HTML manipulation."""
+
+import re
+
+
+def patch_html_data_attrs(html: bytes, **data_attrs: str) -> bytes:
+    """Patch HTML by adding data attributes to the <html> tag.
+
+    If an <html> tag exists, adds data attributes to it.
+    If no <html> tag exists, prepends one with the data attributes.
+
+    Args:
+        html: The HTML content as bytes
+        **data_attrs: Key-value pairs for data attributes (e.g., mode='reauth')
+
+    Returns:
+        Modified HTML as bytes
+
+    Examples:
+        >>> patch_html_data_attrs(b'<html><body>test</body></html>', mode='reauth')
+        b'<html data-mode="reauth"><body>test</body></html>'
+
+        >>> patch_html_data_attrs(b'<body>test</body>', mode='reauth')
+        b'<html data-mode="reauth"><body>test</body>'
+    """
+    if not data_attrs:
+        return html
+
+    html_str = html.decode("utf-8")
+
+    # Build the data attributes string
+    attrs_str = " ".join(f'data-{key}="{value}"' for key, value in data_attrs.items())
+
+    # Check if there's an <html> tag (case-insensitive, may have existing attributes)
+    html_tag_pattern = re.compile(r"<html([^>]*)>", re.IGNORECASE)
+    match = html_tag_pattern.search(html_str)
+
+    if match:
+        # Insert data attributes into existing <html> tag
+        existing_attrs = match.group(1)
+        new_tag = f"<html{existing_attrs} {attrs_str}>"
+        html_str = html_tag_pattern.sub(new_tag, html_str, count=1)
+    else:
+        # Prepend <html> tag with data attributes
+        html_str = f"<html {attrs_str}>" + html_str
+
+    return html_str.encode("utf-8")
diff --git a/passkey/util/sessionutil.py b/passkey/util/sessionutil.py
new file mode 100644
index 0000000..83de3cd
--- /dev/null
+++ b/passkey/util/sessionutil.py
@@ -0,0 +1,27 @@
+"""Utility functions for session validation and checking."""
+
+from datetime import datetime, timezone
+
+from ..db import Session
+from .timeutil import parse_duration
+
+
+def check_session_age(session: Session, max_age: str | None) -> bool:
+    """Check if a session satisfies the max_age requirement.
+
+    Args:
+        session: The session record to check
+        max_age: Maximum age string (e.g., "5m", "1h", "30s") or None
+
+    Returns:
+        True if session is recent enough or max_age is None, False if too old
+
+    Raises:
+        ValueError: If max_age format is invalid
+    """
+    if not max_age:
+        return True
+
+    max_age_delta = parse_duration(max_age)
+    time_since_auth = datetime.now(timezone.utc) - session.renewed
+    return time_since_auth <= max_age_delta
diff --git a/passkey/util/timeutil.py b/passkey/util/timeutil.py
new file mode 100644
index 0000000..455e2e1
--- /dev/null
+++ b/passkey/util/timeutil.py
@@ -0,0 +1,47 @@
+"""Utility functions for parsing time durations."""
+
+import re
+from datetime import timedelta
+
+
+def parse_duration(duration_str: str) -> timedelta:
+    """Parse a duration string into a timedelta.
+
+    Supports units: s, m, min, h, d
+    Examples: "30s", "5m", "5min", "2h", "1d"
+
+    Args:
+        duration_str: A string like "30s", "5m", "2h"
+
+    Returns:
+        A timedelta object
+
+    Raises:
+        ValueError: If the format is invalid
+    """
+    duration_str = duration_str.strip().lower()
+
+    # Pattern matches: number + unit
+    # Units: s (seconds), m/min (minutes), h (hours), d (days)
+    pattern = r"^(\d+(?:\.\d+)?)(s|m|min|h|d)$"
+    match = re.match(pattern, duration_str)
+
+    if not match:
+        raise ValueError(
+            f"Invalid duration format: '{duration_str}'. "
+            "Expected format like '30s', '5m', '5min', '2h', or '1d'"
+        )
+
+    value = float(match.group(1))
+    unit = match.group(2)
+
+    if unit == "s":
+        return timedelta(seconds=value)
+    elif unit in ("m", "min"):
+        return timedelta(minutes=value)
+    elif unit == "h":
+        return timedelta(hours=value)
+    elif unit == "d":
+        return timedelta(days=value)
+    else:
+        raise ValueError(f"Unsupported time unit: {unit}")