diff --git a/deploy/nixos/hardware/batm3.nix b/deploy/nixos/hardware/batm3.nix
index bedbdc0..f037e2e 100644
--- a/deploy/nixos/hardware/batm3.nix
+++ b/deploy/nixos/hardware/batm3.nix
@@ -68,9 +68,13 @@
   };
 
   # Serial port access for bill validator/dispenser (USB-serial adapters)
+  # Stable symlinks by adapter serial number (prevents ttyUSB reordering on reboot)
   services.udev.extraRules = lib.mkAfter ''
     KERNEL=="ttyS[0-9]*", MODE="0666"
     KERNEL=="ttyUSB[0-9]*", MODE="0666"
     KERNEL=="ttyACM[0-9]*", MODE="0666"
+    SUBSYSTEM=="tty", ATTRS{serial}=="DDDLb103Y23", SYMLINK+="ttyF56", MODE="0666"
+    SUBSYSTEM=="tty", ATTRS{serial}=="A9YW78OC", SYMLINK+="ttyMEI", MODE="0666"
+    SUBSYSTEM=="tty", ATTRS{serial}=="A9ZF8ELY", SYMLINK+="ttyNFC", MODE="0666"
   '';
 }