In a multiplayer game with bots running, only the host client runs bot logic. This logic must not alter the world state, or the host will desync from the other clients which do not run the bot logic.
The bot logic can interact with the pathfinder. This can eventually flow into HierarchicalPathFinder.BuildGrid which calls AbstractCellForLocalCells to determine the abstract cells within the grid.
This method chooses an abstract cell closest to the middle, but there can be multiple cells tied for this. The input comes from a local path search, whose ordering depends on current cell costs.
Previously, this ordering could would influence which of the equally close cells we would choose. In this case we'd choose the first in the ordering.
On non-host clients which don't run the bot logic, they may not build the grid until a later tick. If the cell costs have changed the the local path search would still explore the same set of cells, but the ordering may be different.
With the previous behaviour, they could choose a different abstract cell from the equally close cells. This results in a diverged state where their abstract graph differs subtly from the host abstract graph.
Eventually, a unit will path search in a manner where this state divergence causes it to take a different path, which will be detected as a desync.
To fix the issue, we ensure we pick the same abstract cell no matter the ordering of the list, by inserting an arbitrary tiebreaker rule.
This means the differing ordering of the explored cells from the local path search is still possible, but the ordering no longer influences the abstract cell we choose as a result.
This keeps the state of the abstract graph in sync across the clients, and thus prevents units from making different pathfinding decisions and desyncing.
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