diff --git a/src/vk_parser_app/admin.py b/src/vk_parser_app/admin.py
index 666e2bd..d1bc33a 100644
--- a/src/vk_parser_app/admin.py
+++ b/src/vk_parser_app/admin.py
@@ -384,21 +384,30 @@ def pkce_challenge(verifier: str) -> str:
 
 
 async def bootstrap_admin() -> None:
+    """Create or sync the bootstrap admin user from env secrets on every startup."""
     if not settings.admin_bootstrap_login or not settings.admin_bootstrap_password:
         return
     pool = await get_pool()
-    exists = await pool.fetchval("SELECT 1 FROM admin_users WHERE login=$1", settings.admin_bootstrap_login)
+    login = settings.admin_bootstrap_login.strip().lower()
+    exists = await pool.fetchval("SELECT 1 FROM admin_users WHERE login=$1", login)
     if exists:
+        # Always sync password from env so rotating the secret takes effect immediately.
+        await pool.execute(
+            "UPDATE admin_users SET password_hash=$1, is_active=TRUE, updated_at=NOW() WHERE login=$2",
+            hash_password(settings.admin_bootstrap_password),
+            login,
+        )
+        logger.info("Bootstrap admin password synced from env: {}", login)
         return
     await pool.execute(
         """
         INSERT INTO admin_users(login, password_hash, role, is_active)
         VALUES($1, $2, 'admin', TRUE)
         """,
-        settings.admin_bootstrap_login.strip().lower(),
+        login,
         hash_password(settings.admin_bootstrap_password),
     )
-    logger.warning("Bootstrap admin user created: {}", settings.admin_bootstrap_login)
+    logger.warning("Bootstrap admin user created: {}", login)
 
 
 async def get_current_user(request: Request) -> dict | None:
@@ -1907,7 +1916,8 @@ async def login_post(request: Request, login: str = Form(...), password: str = F
         )
         or 0
     )
-    if ip_failures >= 10 or login_failures >= 5:
+    # Stricter limits: 5 bad attempts per IP or 3 per login in 15 minutes → block.
+    if ip_failures >= 5 or login_failures >= 3:
         await pool.execute(
             "INSERT INTO admin_login_attempts(ip, login, success) VALUES($1, $2, FALSE)",
             ip,
@@ -1930,6 +1940,8 @@ async def login_post(request: Request, login: str = Form(...), password: str = F
             login_value,
         )
         await audit(None, "auth.login_failed", "admin_login", None, {"login": login_value}, request)
+        # Constant-time delay to slow brute-force attempts.
+        await asyncio.sleep(1.0)
         return templates.TemplateResponse("login.html", base_context(request, None, error="Неверный логин или пароль"))
 
     await pool.execute("INSERT INTO admin_login_attempts(ip, login, success) VALUES($1, $2, TRUE)", ip, login_value)
@@ -3855,6 +3867,12 @@ async def user_toggle(request: Request, user_id: int, csrf_token: str = Form(...
     if user["role"] != "admin" or int(user["id"]) == user_id:
         return redirect("/users")
     pool = await get_pool()
+    # Prevent deactivating the bootstrap admin account (managed via env secrets).
+    bootstrap_login = settings.admin_bootstrap_login.strip().lower()
+    target_login = await pool.fetchval("SELECT login FROM admin_users WHERE id=$1", user_id)
+    if target_login and target_login == bootstrap_login:
+        logger.warning("Attempt to deactivate bootstrap admin '{}' was blocked", bootstrap_login)
+        return redirect("/users")
     await pool.execute("UPDATE admin_users SET is_active=NOT is_active, updated_at=NOW() WHERE id=$1", user_id)
     await audit(user["id"], "user.toggle", "user", user_id)
     return redirect("/users")