Update: Posted on X, the Halo Support account mentioned they're looking into it - "The #HaloMCC team is investigating reports that players on Steam Deck are experiencing Easy Anti-Cheat error messages after Tuesday's update. Stay tuned for updates on this bug investigation."
Original article below:
After a recent update Halo: The Master Chief Collection seems to have broken online play support for Steam Deck due to Easy Anti-Cheat.
If you remember, back in April they did announce Steam Deck support for online play and put up a support article for it. This came with a few minor issues, like needing to pick the Steam launch option that actually says it's off (the options were backwards). Since the update on September 19th, it just doesn't work with Easy Anti-Cheat errors.
When you go to launch multiplayer from the main menu with the option that has anti-cheat turned on you'll see an error like this when you try to go into multiplayer:
And when picking the Steam launch option with anti-cheat off, which going by their support article is still the option to actually use to have it enabled as it's backwards, you're met with this:
Going by the error messages, it seems like they may have put the Steam options actually the right way around now but broke it in the process. I've tested this myself across both Proton 8 and Proton Experimental and neither works. Restarting it doesn't change anything, rebooting the Steam Deck doesn't help either.
Lots of people on Reddit have noticed it and report the same issue (but a few note oddly it still works for them?), so hopefully Microsoft / 343 will fix whatever they did soon. I've reached out to their teams to see what's going on - will update if I get any reply.
Article taken from GamingOnLinux.com.
ElectricPrism Sep 20, 2023
I hope their goodwill is plain, and we see them fix it very soon.
I bet a lot of their customers have decks, we'll see if they are enough to wake the lion up to do something.
Linux_Rocks Sep 20, 2023
I've finally started a co-op play through with a friend 1.5 weeks ago, it was an awesome nostalgia trip until now. I guess it's on hold for the moment...
pleasereadthemanual 
Sep 21, 2023
Quoting: pleasereadthemanualI've never managed to get multiplayer to work on the desktop, despite many attempts.
I had to completely uninstall it last week to finally make it work. Also, I think I had an old Proton version selected, prior to that.
I bought MCC for my steam deck back in February when it was broken. Played through a couple of campaigns then uninstalled.
You mean to tell me THE EXACT SAME DAY I decide to check on the status of multiplayer and redownload after hearing that it was fixed in April, that it breaks again???
WTF
I submitted a report (see my post in the steam forums for details), unsure if additional reports would be considered helpful or spammy.
Edit: I guess it helps, this is what I've received in the automated answer:
QuoteHalo Support Agents will review your submitted media and, if it shows an in-game bug, link your Flag Report to the bug in our internal bug database. Reporting issues to Halo Support helps the development team understand how often an issue occurs, the issue's impact on players, and how they should prioritize addressing the issue.
Liam, the URL contained parenthesis that I had to manually transform to %{28,29}, I think the parser could be improved :)
Last edited by MayeulC on 21 September 2023 at 1:00 pm UTC
ElectricPrism Sep 21, 2023
Quoting: steamdeckguyBRUH
I bought MCC for my steam deck back in February when it was broken. Played through a couple of campaigns then uninstalled.
You mean to tell me THE EXACT SAME DAY I decide to check on the status of multiplayer and redownload after hearing that it was fixed in April, that it breaks again???
WTF
Exactly, reasons like this are why I don't play Halo daily anymore. Microsoft needs to step up their game and not be so nepotistic.
I could play MCC every day for a decade and have fun -- but when I don't know if I'm going to have the whole thing come crashing down and break, additional new obnoxious microsoft account logins, hard-anti-cheats, etc... I am sick of being poked and prodded. I just end up playing CounterStrike instead because it's easy and reliable, and with CS2 around the corner and in beta now it's not like I'm a choosing beggar.
Thanks everyone who puts a word in, I DO want to see them sort this out real soon. Here's to hope ^.
benstor214 Sep 21, 2023
Quoting: MayeulCLiam, the URL contained parenthesis that I had to manually transform to %{28,29}, I think the parser could be improved :)Hmm... looking at the URL you mention (especially the part where a string is passed)
[...]/signin?return_to= this might be done by the very website you linked to for reason of protection against injection methods... I don't think the GOL Forum is to blame here.edit:grammar
Last edited by benstor214 on 21 September 2023 at 7:26 pm UTC
Quoting: benstor214Protection against injection methods? You mean they're anti-vaxxers?Quoting: MayeulCLiam, the URL contained parenthesis that I had to manually transform to %{28,29}, I think the parser could be improved :)Hmm... looking at URL you mention (especially the part where a string is passed)[...]/signin?return_to=this might be done by the very website you linked to for reason of protection against injection methods... I don't think the GOL Forum is to blame here.
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