wtf is tmhi-watchdog?

TMHI Gateway Watchdog is a self-hosted tool that watches your internet connection and automatically restarts your T-Mobile Home Internet gateway when it loses its cellular connection but is still reachable on your local network. This solves a specific and annoying problem: your phone or computer stays connected to Wi-Fi and can still reach the gateway's own settings page, yet no actual internet traffic is getting through. The tool runs as a Python program packaged in Docker, so you install it on something like a Linux server, a NAS device, or a small always on computer that sits on the same network as the gateway. Once running, it repeatedly checks several different internet addresses to confirm whether the connection is actually down, waits until the outage has lasted long enough to be sure it is not temporary, then logs into the gateway's own local web interface and asks it to reboot. It supports several specific gateway models used with T-Mobile Home Internet, though not all of them, and the README is careful to list exactly which ones work with the current version. Safety comes first in how the tool is designed. It starts in a dry run mode by default, meaning it will detect and log outages and even simulate what a reboot request would look like, without actually restarting anything, until you deliberately turn that mode off. It also includes built in limits like a grace period after startup, a cooldown between reboots, and a cap on how many reboots can happen per day, so it cannot get stuck in a restart loop. Once set up, you can watch what is happening through a small web dashboard and a REST API, both served from the same container, and every event is saved to a local database so you can look back at outage history. The project also publishes ready to use Docker images so you do not need to build the software yourself. This is built for people comfortable running Docker containers on their own hardware, rather than a plug and play consumer app.