Weapon Platforms + Supply

I was never concerned about that so it must be from the planet. However, that is only in the resupply phase of the turn. You can still run out of ammo in a combat turn.

WPs don't need supplies in space combat. They might in ground combat but in stock no WP weapons can fire in GC anyway so it doesn't matter much.

Well, in combat it uses up the weapon's ammo capacity (which is often good for only 5 to 10 shots). See your weapon's description for how much it uses per shot and how much it holds. I don't think you'd have a magazine with the entire planet's resources in it.

well, lets put it this way. an army can keep firing their guns as long as they want. eventually their supplies will run low and they need to get refilled by a supply train. so, they run out and need more. in space, pretend there are tiny little insignificant ships that run to the space-stations/ships and back to the planet again. thats how everyone stays resupplied and happy. until their supplies and ammo runs out and everyone starts panicing and screaming before they are reduced to a primal, savage state where everyone eats each other to survive so another ship can come and restore sanity. and the survivors swear it was a space monster from another universe that boarded their ship.

I've never bothered to put suplies on a WP, if in doubt though then use the combat sim

WP's don't need supplies. They use directly from the planet.

~Myrath

Like Myrath said, in space combat WP's do not need additional supply storage capacity, they will fire for as long as you need them to, as long as there is a resupply depot on that planet.
I have had WP's in ground combat run short of juice.

Can't you just put quantum reactors on them with 2-3 supply storage components? I understand that'll be hard on smaller WP, but the larger ones it should be possible for. Its what i usually do anyway, but then i've never had the chance to use them...

WP's are supplied from the planet they're on. But planets can and do run out of supplies.

After 1 or 2 size upgrades, I always put a supply component on my WP's.

Newly colonized worlds don't get supplied immediately either, so that's one more reason to make WP's somewhat self-sufficient. But there's no need to go overboard. 2 supply + 1 ammo is about the most I'd ever equip.

In the simulator at least a planet can have exactly zero supplies and ordnance and still the WPs on it fire no problems. I have no reason to believe an actual battle would behave any differently.