Just launching into multiplayer, you get the notification
"Cannot join. the following mod event handlers are not identical between you and the server. This indicates that the following mods are not multiplayer (save/load) safe.
(See the log file for more details):

mod-came-prepared

Thank you for bringing this up, I'll work on this in the next few days.

I'm unable to reproduce the error.

Is it possible you could make that error happen again, quit the game then paste the contents of factorio-current.log in here?

Sorry, I did not get on at all yesterday, I will post this later today when I get my friend back on the game with me lol.

Here is the log;
https://gist.github.com/SensualBardNoise/e0361941c668a14a25323feaec27d4c6

Thanks for this! Wow, you have a lot of mods! I made a patch. Are you able to test if it works?

I will check later today again, sorry got distracted by last epoch release.

The mod no longer gives "not multiplayer safe" however we desync when the mod is enabled and we try to join, removing the mod no desync was caused. We put in the same per player settings, perhaps you would need it to be a startup setting instead of a per player setting?

I have a desync report from my friend, but I do not know if that would give you any valid information.

https://drive.google.com/file/d/1x6dBpxnMCywWanNTti7s26rdGPW0vBvB/view?usp=sharing

This was tested on a new save, I just pressed Multiplayer -> Host New Game -> Freeplay (Space Age).

Did some more testing, tried these variations, no success. Me (Host) Friend (Joiner)
Me + Friend; All default settings
Me; Default settings, Friend; No starting loadout
Me; Default settings, Friend; No Starting loadout + researches 0
Me + Friend; No Starting loadout, researches default
Me; No starting loadout, default research. Friend; No starting loadout, researches 0.

None of these worked.

I also realized i forgot to make the google drive file public, so now it is.

Hello! Thank you so much for this. I've found some time to look through the desync error and I think I fould the culprit.

FYI - The ship is cached on Tick 1 for the host. A peer joining won't have that cached (as ticks are happening as the host waits for people to join) making initialisation skip for that peer. I changed it to find the ship on the existing surface for each joining player instead of relying on what tick the game is in.

The update has been pushed.

Hopefully that works!

Again, I'm unable to test this - so thank you for helping me out!

We can connect now, both players having both same settings and differing settings connects fine.

The only weird thing is when an additional player joins, you get another set of starting equipment in the ship.
Regardless of secondary or other player settings, the starting loadout, armor, and research will take whatever the host has set.

Potentially allowing the armor to be different would make sense, but the research makes sense to grab host.

The interesting thing is the starting kit, giving additional items.

If you select none on the starting loadout, the ship is completely empty, doesn't even contain the factorio defaults - perhaps you may have to altar the coding here.

Additionally other mods that add items to the starting ship, like https://mods.factorio.com/mod/aai-vehicles-miner have their items missing. But they do not overwrite the default items found in a ship, not sure if you want to take a look through that code and see if you need to modify your implementation to not completely remove that.

Removing the ship does not give a secondary set of starting loadout, and the joining player has no modded armor, and gets the vanilla default items. This is just solved by not removing the ship, lol.

I apologize for all the edge case errors, but I am having fun bug hunting

I can also add you on discord if you want a more proper line of communication

Lol, I was just about to mention that! If you're a mean host - you can remove the ship before other players join which will negate their starting bonuses. I kinda saw that just now when going over what I changed.

Potentially allowing the armor to be different would make sense, but the research makes sense to grab host.

Both on point. Armour should happen, regardless. Research needs to be synced. I do have player loadouts which hand out items per player rather than what is in the ship. I mainly used the ships inventory because it's a static setting. Different armours have a different numbers of slots, so selecting a large loadout with no armor dumped excess on the ground for you to pick up.

The interesting thing is the starting kit, giving additional items.

That is interesting... I guess it would be better to only give the host's loadout. If you had 5+ players with Legendary loadouts - that'd create a pretty big mess. Yeah better to restrict it to just the host and say that joining player's research / loadouts are ignored in multiplayer.

If you select none on the starting loadout, the ship is completely empty, doesn't even contain the factorio defaults - perhaps you may have to altar the coding here.

This is kind of intentional. On tick one - everything is first removed from the starting player and the ship. I wanted to remove everything completely to make totally curated or completely naked starts. Eg. it doesn't make sense to have a burner mining drill when starting on Fulgora or some other modded planets.

I've been putting off removing the iron plates that come with the ship debris. You've just reminded me to get on to that.

Maybe better to have an option of Base game default. I might need to have a think about that though. If you select none and start on Vesta, you'll still receive absolute minimum necessary items to be able to make it into space. If you selected Base game default on Vesta, you'd be stuck on that planet and on Maraxsis, you'd have about 15 seconds of gameplay before you drown... but maybe some people might enjoy that kind difficulty setting. Maybe have it as an option with a warning.

I can also add you on discord if you want a more proper line of communication

Please do! My username is aronimaru. I just joined The Foundry server. You'll find me lurking around on there.