After adding this mod to our multiplayer world anyone that isn't hosting the game is unable to join.
Tested it on a dedicated host and no one can join.

The observed issue:
When the world is downloaded and the player starts the catching up phase the server gets forced to save the map.
This then in turn causes the player trying to catch up to desync immediately which triggers an alignment desync map to server.
Then a local variant of the map is created and map is redownloaded but with a seriously bloated size (approx 4-5x as large as it should be).
When this process completes a desync failure is reported and player is rejected from connecting and can only exit.

The details of the crash from logdata:
103.193 Script @ai_combinator/src/events/event_handler.lua:235: ERROR in custom event handler '287': Gui element with name ai-combinator-ai-warning already present in the parent element.
stack traceback:
[C]: in function 'add'
...ombinator__/src/gui/dialogs/ai_bridge_warning_dialog.lua:15: in function 'show'
ai_combinator/control.lua:294: in function <ai_combinator/control.lua:289>
[C]: in function 'xpcall'
ai_combinator/src/events/event_handler.lua:232: in function 'raise_event'
ai_combinator/src/services/bridge.lua:195: in function <ai_combinator/src/services/bridge.lua:179>
[C]: in function 'xpcall'
ai_combinator/src/events/event_handler.lua:123: in function <ai_combinator/src/events/event_handler.lua:90>

Followed by 100's of lines of:
111.525 Error GameActionHandler.cpp:2808: Multiplayer desynchronisation: crc test (heuristic) failed for crcTick(26650076) serverCRC(1344839121) localCRC(1495887656)
111.529 Error GameActionHandler.cpp:2808: Multiplayer desynchronisation: crc test (heuristic) failed for crcTick(26650077) serverCRC(1821223517) localCRC(1973206014)
111.534 Error GameActionHandler.cpp:2808: Multiplayer desynchronisation: crc test (heuristic) failed for crcTick(26650078) serverCRC(150707130) localCRC(4192052029)
111.541 Error GameActionHandler.cpp:2808: Multiplayer desynchronisation: crc test (heuristic) failed for crcTick(26650079) serverCRC(3415050793) localCRC(3263985872)
111.545 Error GameActionHandler.cpp:2808: Multiplayer desynchronisation: crc test (heuristic) failed for crcTick(26650080) serverCRC(2691907011) localCRC(3110218848)

Hope this information will help you to resolve the issue and potentially make it multiplayer compatible.

You are right, at the moment this mod is not multiplayer compatible - I should have clarified this in the mod description!

Doing so comes with some logistical challenges when it comes to the communication with the mod launcher, because every player would try to communicate with each mod launcher. There is of course a solution to this, but it's a bit of a challenge to implement!

I'm definitely considering making it multiplayer-compatible in the future, so thank you for your detailed report, that will definitely help to make it happen :)

I'll keep you updated in this thread, when multiplayer support gets updated!