app/lib/session.ts

@@ -44,6 +44,10 @@ function readFromStorage(): Session | null {
       typeof parsed.token !== "string"
     )
       return null
+    // An expired JWT is not a session: without this the shell renders as
+    // "logged in" and every API call 401s silently. Treat it as null so the
+    // app bounces to /login. (Frontend audit 2026-06-20.)
+    if (isTokenExpired(parsed.token)) return null
     return {
       userId: parsed.userId,
       name:
@@ -76,6 +80,35 @@ export function loadSession(): Session | null {
   return readFromStorage()
 }
 
+// A token counts as expired only if it's a JWT carrying an `exp` in the past
+// (minus a small clock-skew grace). Non-JWT dev/mock tokens (no decodable
+// `exp`) are treated as non-expiring so offline/test flows keep working.
+const TOKEN_EXPIRY_SKEW_S = 30
+export function isTokenExpired(token: string | undefined | null): boolean {
+  if (!token) return true
+  const claims = decodeJwtPayload(token)
+  const exp =
+    claims && typeof claims.exp === "number" ? (claims.exp as number) : null
+  if (exp === null) return false
+  return Date.now() / 1000 >= exp - TOKEN_EXPIRY_SKEW_S
+}
+
+function decodeJwtPayload(token: string): Record<string, unknown> | null {
+  const parts = token.split(".")
+  if (parts.length !== 3) return null
+  try {
+    const b64 = parts[1].replace(/-/g, "+").replace(/_/g, "/")
+    const pad = b64.length % 4 === 0 ? "" : "=".repeat(4 - (b64.length % 4))
+    const json =
+      typeof atob === "function"
+        ? atob(b64 + pad)
+        : Buffer.from(b64 + pad, "base64").toString("utf-8")
+    return JSON.parse(json) as Record<string, unknown>
+  } catch {
+    return null
+  }
+}
+
 export function signOut() {
   if (typeof window === "undefined") return
   localStorage.removeItem(STORAGE_KEY)

app/root.tsx

@@ -15,6 +15,7 @@ import { CommandBusProvider } from "@crema/action-bus"
 import { ArcadiaProvider } from "@crema/arcadia-client"
 import { LlmConfigBootstrap } from "~/lib/llm-config-bootstrap"
 import { ProfileBootstrap } from "~/lib/profile-bootstrap"
+import { signOut } from "~/lib/session"
 // CREMA:PROVIDERS-IMPORTS
 
 const ARCADIA_URL = import.meta.env.VITE_ARCADIA_URL ?? "http://localhost:4000"
@@ -59,6 +60,10 @@ export default function App() {
           if (typeof window !== "undefined") {
             sessionStorage.removeItem("arcadia_access_token")
             sessionStorage.removeItem("arcadia_refresh_token")
+            // Also clear the localStorage Session (crema.session); otherwise
+            // useSession() still reports "logged in" after a 401 and the shell
+            // keeps mounting with a dead token. (Frontend audit 2026-06-20.)
+            signOut()
           }
         }}
       >