Propagation
Propagation is the process in which the timeline becomes more consistent by past events influencing future events. It's driven by propagators, namely the natural timewaves and the player lines.
Constantly at each time where a propagator lies, the immediate consequence of the state of the world at that time is enforced into the immediately following state of the world. As propagators move forward these piecewise time-local consequences accumulate ensuring that each new time encountered comes into consistency with all previous times swept (as they were when swept).
The most visible and apparent facet of propagation are the big changes that happen when the past has been changed. These changes do not take place immediately to the whole timeline. Instead the process of propagation slowly over time makes parts of the timeline reflect the changed fact. This fact that the timewaves have a finite speed is a common conceptual hurdle to get acquainted on how Achron's time travel works .
Propagation isn't sensitive whether or not any events have changed. When nothing has changed the result of the propagation remains the same. Thus propagation is more of note when changes have happened.
Each propagator can only rectify the timeline upto the changes it has swept. It's possible that a player goes behind a timewave to change the past. These kind of "unseen" changes are not brought forward by that particular timewave. However because timewaves are constantly spawning the next wave is likely to catch the new change. If changes are made rapidly it's possible that every timewave contains different changes. This can make it frustrating to determine what "really" goes on as each wave only tells part of the story. A timewave sweep means more up to date information but doesn't guarantee a perfectly recent view.
Typically changes briefly disturb the state of the timeline until they are fully propagated and the timeline has changed into the new state. A timeline that has no new changes propagating is said to be stable.
Sometimes a change only makes the near future different leaving the far future the same. An example would be that instead of just sitting still, an unit would visit some location and come back. Both of these histories lead to the unit being exactly in the same place in exactly the same state. Thus the whether the unit did or did not visit the other place the history from the return point onwards is the same regardless. a timeline that has every time compatible with each other is said to be consistent. This way a timeline might become stable even when not every change has propagated fully.
It also makes sense to speak of parts of the timeline that are stable or consistent. Say that there are units A and B. Then a change is made into the past that kills A. Looking into the past we can see that A is dead and B is alive. If we look into the future it will seem that both A and B are alive until a propagator propagates unit As death. However because we know such propagation is going to happen, we are more confident that Bs life will not be changed ie that B is stable and A is not. Similarly if we have units C and D and go in time to give both order to move somewhere else. Say that C is ordered to visit a nearby location while D is commanded to visit a far away location. If we order both units to come back from their visit locations unit C will come back sooner. Thus unit C will have more future similar before the visiting orders and is thus more consistent.
Mostly the immediate consequences of the state of a time are completely located in the immediately following time. However this is not true if chronoporting is involved. The immediately following consequence will locate in some far of time. When a chronoport is swept by the timewave the far-off time is updated in that instance. However because the timewave moves next to the immediately following time, the chronoports propagation will not be immediately continued. It must wait for the next timewave to sweep it's time.
It's possible that due to backwards chronoports a change will never lead to a stable timeline. This will always be because the change will lead it to be changed. Due to chronoports breaking the linear structure of time it's possible that the change is in it's own future. Propagation involving chronoports can be and often do get stabilised. When they are not see Paradox. Even when there is no stable state to be archived propagation determines when and in what state a paradox appears.
