diff --git a/userspace/root/usr/comma/init_mss.py b/userspace/root/usr/comma/init_mss.py
new file mode 100644
index 0000000..34c0d42
--- /dev/null
+++ b/userspace/root/usr/comma/init_mss.py
@@ -0,0 +1,10 @@
+#!/usr/bin/python3
+import signal
+
+# The on-chip Wi-Fi firmware runs in the SDM845 modem subsystem.
+# Opening this device boots it and holds a reference; the kernel shuts it
+# down when the last reference is released. Keep it open for this service's
+# lifetime so Wi-Fi stays available.
+# https://github.com/commaai/agnos-kernel-sdm845/blob/8b0e4d289b246a5cc1b0484b25a3f9f8d4772544/drivers/soc/qcom/subsystem_restart.c#L1215-L1251
+with open("/dev/subsys_modem", "rb"):
+  signal.pause()
diff --git a/userspace/root/usr/lib/systemd/system/init_sys_mss.service b/userspace/root/usr/lib/systemd/system/init_sys_mss.service
index 65ccb4e..bb20084 100644
--- a/userspace/root/usr/lib/systemd/system/init_sys_mss.service
+++ b/userspace/root/usr/lib/systemd/system/init_sys_mss.service
@@ -2,7 +2,7 @@
 Description=Boot the modem subsystem, which runs the Wi-Fi firmware
 
 [Service]
-ExecStart=/usr/sbin/init_mss
+ExecStart=/usr/bin/python3 /usr/comma/init_mss.py
 Restart=on-failure
 
 [Install]
diff --git a/userspace/root/usr/sbin/init_mss b/userspace/root/usr/sbin/init_mss
deleted file mode 100755
index 6ca18c0..0000000
Binary files a/userspace/root/usr/sbin/init_mss and /dev/null differ