The OST does prohibit nuking the Moon, but stationing conventional weapons like the Almaz cannons (or the USSR's IS anti-satellite weapons) in Earth orbit isn't actually a violation. The prohibition on stationing weapons in space is specifically on "weapons of mass destruction", so lasers and guns and conventional explosives are all fine. There was a Soviet program that arguably violated it though: the Fractional Orbital Bombardment System, which would put nuclear warheads onto a low Earth orbit trajectory (rather than the higher and slower trajectories used by ICBMs) and then deorbit them onto their targets. The Soviet position was that because the nuclear weapons would only complete a fraction of an orbit, it didn't violate their obligation "not to place in orbit" weapons of mass destruction.
The OST does prohibit nuking the Moon, but stationing conventional weapons like the Almaz cannons (or the USSR's IS anti-satellite weapons) in Earth orbit isn't actually a violation. The prohibition on stationing weapons in space is specifically on "weapons of mass destruction", so lasers and guns and conventional explosives are all fine. There was a Soviet program that arguably violated it though: the Fractional Orbital Bombardment System, which would put nuclear warheads onto a low Earth orbit trajectory (rather than the higher and slower trajectories used by ICBMs) and then deorbit them onto their targets. The Soviet position was that because the nuclear weapons would only complete a fraction of an orbit, it didn't violate their obligation "not to place in orbit" weapons of mass destruction.