I'm just wondering if the BaseMission hooks have been exposed/integrated into uMod yet? I see they're not listed in the Rust API documentation, and when I try to do a simple test with any of them, they don't seem to work.

void OnMissionAssigned(BasePlayer assignee, IMissionProvider provider, BaseMission mission)
        {
            Puts("OnMissionAssigned works!");
        }

Or is there something else that I am missing?

Yes, they have been part of Oxide since 11/21. Add multiple hooks for missions · OxideMod/Oxide.Rust@b2f4d79 (github.com)

- bool CanAssignMission(BasePlayer assignee, BaseMission mission, IMissionProvider provider)
- void OnMissionAssigned(BaseMission mission, IMissionProvider missionProvider, BasePlayer assignee)
- void OnMissionFailed(BaseMission mission, BaseMission.MissionInstance missionInstance, BasePlayer assignee)
- object OnMissionStart(BaseMission mission, BaseMission.MissionInstance missionInstance, BasePlayer assignee)
- void OnMissionStarted(BaseMission mission, BaseMission.MissionInstance missionInstance, BasePlayer assignee)
- void OnMissionSucceeded(BaseMission mission, BaseMission.MissionInstance missionInstance, BasePlayer assignee)

Hmm very odd. I'll continue to play around. Not sure why they aren't working for me with just simple tests.

The signature you are using is not what I showed above per the commit.

Oh that would probably be it. I was just looking at the hook names and not the order of the variables.