diff --git a/cortex/llm_client.py b/cortex/llm_client.py
index 6f0cc4d..dfd39a6 100644
--- a/cortex/llm_client.py
+++ b/cortex/llm_client.py
@@ -4,6 +4,7 @@ import os
 import signal
 import subprocess
 from config import settings
+import event_bus
 
 logger = logging.getLogger(__name__)
 
@@ -48,7 +49,10 @@ async def complete(
         response = await _dispatch(primary, system_prompt, messages, model)
         return response, primary
     except Exception as e:
+        err_str = str(e)
         logger.warning("%s failed (%s) — falling back to %s", primary, e, fallback)
+        if primary == "claude" and any(k in err_str for k in ("401", "authenticate", "expired", "OAuth")):
+            await event_bus.publish({"type": "claude_auth_expired"})
         response = await _dispatch(fallback, system_prompt, messages, None)
         return response, fallback
 
diff --git a/cortex/routers/auth.py b/cortex/routers/auth.py
index b234453..b8f2e11 100644
--- a/cortex/routers/auth.py
+++ b/cortex/routers/auth.py
@@ -20,7 +20,8 @@ router = APIRouter(prefix="/auth")
 CLAUDE_CREDS  = Path.home() / ".claude" / ".credentials.json"
 GEMINI_CREDS  = Path.home() / ".gemini" / "oauth_creds.json"
 GEMINI_ACCTS  = Path.home() / ".gemini" / "google_accounts.json"
-WARN_HOURS = 24
+WARN_HOURS = 24          # no refresh token — warn a day ahead
+WARN_HOURS_REFRESH = 1  # refresh token present — only warn if CLI hasn't rotated in time
 
 
 def _claude_status() -> dict:
@@ -31,11 +32,13 @@ def _claude_status() -> dict:
         expires_dt = datetime.fromtimestamp(oauth["expiresAt"] / 1000, tz=timezone.utc)
         now = datetime.now(tz=timezone.utc)
         hours_remaining = (expires_dt - now).total_seconds() / 3600
-        # If a refresh token is present the session is long-lived (~1 year).
-        # expiresAt only reflects the current access token window (~8 h) and
-        # rotates automatically — do not warn based on it when a refresh token exists.
-        warning = not has_refresh and hours_remaining < WARN_HOURS
-        expired = hours_remaining <= 0 and not has_refresh
+        # When a refresh token is present the CLI *should* auto-rotate the access
+        # token, but sometimes it doesn't.  Use a tight 1-hour window so a fresh
+        # 8-hour token doesn't immediately trigger a warning, but a stale token
+        # that the CLI missed will still surface before it expires.
+        expired = hours_remaining <= 0
+        threshold = WARN_HOURS_REFRESH if has_refresh else WARN_HOURS
+        warning = expired or hours_remaining < threshold
         return {
             "ok": True,
             "has_refresh_token": has_refresh,
diff --git a/cortex/static/app.js b/cortex/static/app.js
index 2fadc7f..08b67d1 100644
--- a/cortex/static/app.js
+++ b/cortex/static/app.js
@@ -975,6 +975,20 @@
             let data;
             try { data = JSON.parse(e.data); } catch { return; }
             if (data.type === 'keepalive') return;
+
+            if (data.type === 'claude_auth_expired') {
+                let banner = document.getElementById('claude-auth-banner');
+                if (!banner) {
+                    banner = document.createElement('div');
+                    banner.id = 'claude-auth-banner';
+                    banner.style.cssText = 'position:fixed;top:0;left:0;right:0;z-index:9999;background:#7c2d12;color:#fef2f2;padding:0.6rem 1rem;font-size:0.85rem;display:flex;align-items:center;justify-content:space-between;gap:1rem;';
+                    banner.innerHTML = '<span>⚠️ Claude authentication expired — run <code style="background:#991b1b;padding:0.1rem 0.3rem;border-radius:3px;">claude</code> in your terminal to re-authenticate, then reload.</span>'
+                        + '<button onclick="this.parentElement.remove()" style="background:none;border:none;color:#fef2f2;font-size:1.1rem;cursor:pointer;padding:0 0.3rem;">✕</button>';
+                    document.body.prepend(banner);
+                }
+                return;
+            }
+
             if (data.type !== 'nct_message' && data.type !== 'nct_response') return;
 
             if (sessionId === data.session_id) {
@@ -1188,7 +1202,7 @@
                         warnings.push('✕ Claude CLI token has expired');
                         anyExpired = true;
                     } else {
-                        warnings.push(`⚠ Claude CLI token expires in ${d.claude.hours_remaining}h`);
+                        warnings.push(`⚠ Claude CLI token expires in ${d.claude.access_token_hours_remaining}h`);
                     }
                     fixes.push('<code>claude</code>');
                 }