diff --git a/apps/pwa/src/components/AuthSplash.tsx b/apps/pwa/src/components/AuthSplash.tsx
new file mode 100644
index 0000000..a4d3992
--- /dev/null
+++ b/apps/pwa/src/components/AuthSplash.tsx
@@ -0,0 +1,129 @@
+/**
+ * AuthSplash — full-screen auth interstitial (D-10 + D-11, Plan 06-05).
+ *
+ * Replaces the optimistic calendar/skeleton/alert renders while auth state is
+ * unknown (loading) or failing (redirecting), and surfaces the session-expired
+ * interstitial for mid-use 401s.
+ *
+ * States:
+ *   loading     — initial cold load; meQuery is still pending. Spin + "Signing you in".
+ *   redirecting — meQuery failed (cold load OR session-expiry); maybeRedirectToLogin()
+ *                 already fired (or the session-expiry handler fired it). Spin +
+ *                 heading/body driven by `copy` prop (defaults to cold-load copy).
+ *   dead-end    — one-shot guard has already fired; redirect failed or guard is exhausted.
+ *                 No spinner; "Sign-in required. Tap here to try again."
+ *
+ * Copy contract (UI-SPEC §Copywriting Contract §Surface 1 + §Surface 2):
+ *   loading:     heading="Signing you in"          body="Taking you to the sign-in page…"
+ *   redirecting: same defaults (or "Session expired" / "Signing you back in…" via props)
+ *   dead-end:    "Sign-in required. Tap here to try again." (tap calls clearLoginRedirect + maybeRedirectToLogin)
+ *
+ * Layout analog: SkeletonCalendar.tsx — full-screen centered column, inline styles only.
+ */
+
+import { Loader2 } from 'lucide-react'
+import { clearLoginRedirect, maybeRedirectToLogin } from '../lib/loginRedirect.js'
+
+export type AuthSplashState = 'loading' | 'redirecting' | 'dead-end'
+
+export interface AuthSplashProps {
+  state: AuthSplashState
+  /**
+   * Override the heading for the loading/redirecting states.
+   * Defaults to "Signing you in" (cold-load copy per UI-SPEC §Surface 1).
+   */
+  heading?: string
+  /**
+   * Override the body text for the loading/redirecting states.
+   * Defaults to "Taking you to the sign-in page…" (cold-load copy per UI-SPEC §Surface 1).
+   */
+  body?: string
+}
+
+export function AuthSplash({
+  state,
+  heading = 'Signing you in',
+  body = 'Taking you to the sign-in page…',
+}: AuthSplashProps) {
+  const isDeadEnd = state === 'dead-end'
+  const showSpinner = !isDeadEnd
+
+  return (
+    <div
+      role="status"
+      aria-label="Signing you in"
+      style={{
+        height: '100dvh',
+        display: 'flex',
+        flexDirection: 'column',
+        alignItems: 'center',
+        justifyContent: 'center',
+        gap: 'var(--space-4)',
+        background: 'var(--color-surface)',
+        fontFamily: 'var(--font-family-base)',
+        padding: 'var(--space-6)',
+        textAlign: 'center',
+      }}
+    >
+      {showSpinner && (
+        <Loader2
+          size={24}
+          aria-hidden="true"
+          style={{
+            color: 'var(--color-member-0)',
+            animation: 'spin 1s linear infinite',
+          }}
+        />
+      )}
+
+      {isDeadEnd ? (
+        // Dead-end: one-shot guard has already fired — show tap-to-retry
+        <button
+          onClick={() => {
+            clearLoginRedirect()
+            maybeRedirectToLogin()
+          }}
+          style={{
+            background: 'none',
+            border: 'none',
+            cursor: 'pointer',
+            padding: 0,
+            fontFamily: 'var(--font-family-base)',
+            fontSize: '15px',
+            fontWeight: 400,
+            lineHeight: 1.5,
+            color: 'var(--color-text-secondary)',
+            textDecoration: 'underline',
+          }}
+        >
+          Sign-in required. Tap here to try again.
+        </button>
+      ) : (
+        <>
+          <h1
+            style={{
+              margin: 0,
+              fontSize: '18px',
+              fontWeight: 600,
+              lineHeight: 1.25,
+              color: 'var(--color-text-primary)',
+            }}
+          >
+            {heading}
+          </h1>
+          <p
+            style={{
+              margin: 0,
+              fontSize: '15px',
+              fontWeight: 400,
+              lineHeight: 1.5,
+              color: 'var(--color-text-secondary)',
+            }}
+          >
+            {body}
+          </p>
+        </>
+      )}
+    </div>
+  )
+}
diff --git a/apps/pwa/src/components/CalendarShell.tsx b/apps/pwa/src/components/CalendarShell.tsx
index 542d417..fea479b 100644
--- a/apps/pwa/src/components/CalendarShell.tsx
+++ b/apps/pwa/src/components/CalendarShell.tsx
@@ -46,6 +46,7 @@ import { hydrateEvents } from '../lib/hydrateEvents.js'
 import { maybeRedirectToLogin, clearLoginRedirect } from '../lib/loginRedirect.js'
 import { buildCalendarConfig, SX_FIRST_DAY_OF_WEEK } from '../lib/calendarConfig.js'
 import { useCalendarStore } from '../store/calendarStore.js'
+import { AuthSplash } from './AuthSplash.js'
 import { EventDetailPopover } from './EventDetailPopover.js'
 import { EventForm } from './EventForm.js'
 import { DeleteConfirmationDialog } from './DeleteConfirmationDialog.js'
@@ -209,29 +210,32 @@ export function CalendarShell({ onOpenSettings }: { onOpenSettings?: () => void
 
   // ── Render helpers ────────────────────────────────────────────────────────
 
-  // Determine which content to show in the calendar area
-  const isInitialLoading = meQuery.isLoading || (eventsQuery.isLoading && !eventsQuery.data)
+  // Determine which content to show in the calendar area.
+  // Note: meQuery.isLoading is handled above by an early AuthSplash return — it
+  // will always be false when we reach this line (meQuery.isSuccess is guaranteed).
+  const isInitialLoading = eventsQuery.isLoading && !eventsQuery.data
   const isEventsError = eventsQuery.isError
 
   const phone = isPhone()
 
-  // ── Sign-in required ───────────────────────────────────────────────────────
+  // ── Auth splash (D-10) ────────────────────────────────────────────────────
+  // Gate the calendar render on auth state so no calendar shell, skeleton, or
+  // "Sign-in required" alert paints before Authelia (D-10 success criterion 5).
+  //
+  // loading: meQuery is still pending — show the neutral "Signing you in" splash.
+  //          No skeleton, no CalendarContent — nothing app-specific until authed.
+  // isError: meQuery failed — the maybeRedirectToLogin() useEffect fires immediately
+  //          after this render. Show the "redirecting" splash while the browser navigates.
+  //          If the one-shot guard is exhausted (flag already set), maybeRedirectToLogin
+  //          returns false and this splash stays — the dead-end "Tap to try again" is
+  //          rendered by AuthSplash's dead-end state (wired in Task 3 via sessionExpired).
+  if (meQuery.isLoading) {
+    return <AuthSplash state="loading" />
+  }
 
   if (meQuery.isError) {
-    return (
-      <div
-        role="alert"
-        style={{
-          color: 'var(--color-destructive)',
-          padding: 'var(--space-4)',
-          background: 'var(--color-surface-dim)',
-          borderRadius: 'var(--space-2)',
-          fontFamily: 'var(--font-family-base)',
-        }}
-      >
-        Sign-in required
-      </div>
-    )
+    // useEffect at line 196 calls maybeRedirectToLogin() — splash shows while redirect fires
+    return <AuthSplash state="redirecting" />
   }
 
   // ── Calendar content ───────────────────────────────────────────────────────