diff --git a/app/Models/Tenant/InjectorProtocol.php b/app/Models/Tenant/InjectorProtocol.php
index 68c6c7e..65bdc8b 100644
--- a/app/Models/Tenant/InjectorProtocol.php
+++ b/app/Models/Tenant/InjectorProtocol.php
@@ -86,10 +86,18 @@ class InjectorProtocol extends Model
         });
     }
 
-    /** PS-{tenantId}-{YYYY}-{seq6} — per-tenant, per-year sequence. */
+    /**
+     * {PREFIX}-{YYYY}-{seq6} — per-tenant, per-year sequence.
+     *
+     * PREFIX is derived from the tenant (settings.protocol_prefix override,
+     * else uppercase of the first 2–3 letters of the tenant slug —
+     * 'psauto' → 'PS', 'autoplus' → 'AP', etc.). Falls back to 'PR' when
+     * no tenant is resolvable.
+     */
     public static function generateNumber(): string
     {
-        $companyId = app(TenantManager::class)->current()?->id
+        $tenant = app(TenantManager::class)->current();
+        $companyId = $tenant?->id
             ?? auth()->user()?->company_id
             ?? 0;
         $year = now()->year;
@@ -97,6 +105,26 @@ class InjectorProtocol extends Model
             ->where('company_id', $companyId)
             ->whereYear('created_at', $year)
             ->count() + 1;
-        return sprintf('PS-%d-%d-%06d', $companyId, $year, $seq);
+
+        $prefix = self::resolvePrefix($tenant);
+
+        return sprintf('%s-%d-%06d', $prefix, $year, $seq);
+    }
+
+    /** Explicit tenant setting → slug initials → 'PR' fallback. */
+    protected static function resolvePrefix($tenant): string
+    {
+        if ($tenant) {
+            $explicit = trim((string) data_get($tenant->settings ?? [], 'protocol_prefix'));
+            if ($explicit !== '') {
+                return mb_strtoupper($explicit);
+            }
+            $slug = (string) ($tenant->slug ?? '');
+            if ($slug !== '') {
+                // Take first 2 characters of the slug — 'psauto' → 'PS'
+                return mb_strtoupper(mb_substr($slug, 0, 2));
+            }
+        }
+        return 'PR';
     }
 }