Smart Light Switch to control half hot outlet (odd issue)

We just recently moved to a new home and have started integrating our SmartThings ecosystem into the house. Unfortunately all of the bedrooms do not have any dedicated lights. They all use half hot outlets which are triggered by light switches next to the doors, and in most cases the outlets don’t align to where we want lighting in the room. Up until today we have simply been using Wyze bulbs, and triggering them via Alexa, however my wife really wanted to get them working off of a switch.

Thankfully there is a neutral in the switch box, so I got to work throwing a smart switch in our bedroom. This is where things got odd with the installation. The original light switch was a single pole switch with a black cable connected to Line and another connect to the Switched Line.

The smart switch I am using was a 3 way switch. But I will be using it as a single pole switch. (I haven’t had an issue using a 3way switch in place of a single pole before)

I ran:
Black to Line
Traveler black to switched Line
Traveler red with capped off
White to neutral
Green to ground

I connected a small fan to the outlet so i would be able to test it when I restored power. The switch worked perfectly, and turned the fan on and off with out an issue. I even paired it up to the lights on the other side of the room. So when I hit the switch the lights would trigger using IFTT.

Everything was working great, until I switched the fan off (on the fan). And it turned the lights off. For some reason, if the switch doesn’t have a closed loop of power, it shuts the switch off. If nothing is plugged into the outlet, the switch doesn’t work.

I am trying to gauge if this is an issue with how I have wired the switch, or if this is standard to how a half hot outlet Is intended to function.

Any help would be greatly appreciated!

What kind of switch (exact model matters in HA)

Im assuming youre usita Jasco style switch since you mentioned travelers…

Travelers in Jadco swites arent meant to carru full current. Its just a signal between the main switch and a remote. So Im not sure what youre sending to the fan but its not what you expect im sure. So no travelers…

In your ‘half hot’ you should split the hot BEFORE the switch and send one of theze legs of the hot line to the outlet’s always hot load and the other hot leg to the switch’s hot. Then take the load off thd switch and send that to the switched hot on your half hot switch.