diff --git a/src/Models/PortalSession.php b/src/Models/PortalSession.php
index 7daafc0..7f6c477 100644
--- a/src/Models/PortalSession.php
+++ b/src/Models/PortalSession.php
@@ -23,6 +23,23 @@ class PortalSession extends Model
         return $this->belongsTo(\App\Models\User::class);
     }
 
+    /**
+     * The rows that consume a device slot.
+     *
+     * Presence on the network is deliberately NOT part of this. UniFi holds an
+     * authorization for its full window whether or not the device is in the
+     * building, so a phone that went home still owns its slot — freeing it here
+     * is what let one person hold two authorizations against a one-device quota.
+     *
+     * A NULL expires_at is not live: it predates this being enforced.
+     */
+    public function scopeLive($query)
+    {
+        return $query->where('is_active', true)
+            ->whereNotNull('expires_at')
+            ->where('expires_at', '>', now());
+    }
+
     public function setMacAddressAttribute($value)
     {
         $this->attributes['mac_address'] = strtolower($value);