Each soldier's training tree is mostly randomly generated. Does not apply to MEC Troopers.
After a soldier reaches Squaddie rank (receiving a class and their first ability), future ranks will primarily grant randomized abilities from a pool of all the class abilities minus any skills that are dependent on a specific weapon (which remain class locked).
Class Ability Trees
- All random abilities are generated upon a soldier reaching Squaddie rank but are only unlocked as the soldier ranks up; this is to prevent save scumming.
- Alien Abductions that rewards higher ranked soldiers will come with skills unlocked. It is possible to save before the mission ends, and re-load to get a different soldier with different skills.
Random Ability Pool 
- Snipers cannot get Bullet Swarm
- Heavies cannot get Gunslinger
- Bullet Swarm + Rapid Fire + Holo-Targeting
- Assault exclusive allows for three shots, + 10 Aim and can reposition with Run & Gun after the first shot due to first basic shot not ending the turn and second action as movement not ending the turn when activated.
- Bullet Swarm + Rapid Fire + Close and Personal
- An Assault with this combination can fire up to four times in a turn at up to three different targets, provided an enemy finished the turn within Close and Personal's effect radius.
- Covering Fire + Opportunist + Sentinel/ Rapid Reaction
- Reaction shots on enemy fire + No Overwatch penalties + 2 shots.
- Deep Pockets + Grenadier + Sprinter
- Up to 6 grenades between 1-2 types (with Tactical Rigging), +1 basic grenade damage and bonus movement for better grenade placement.
- Sprinter + Low Profile
- Exceptional scout and Meld collector.
- Rifle Suppression is entirely absent; even Supports can't get this ability.