The open beta for Marvel Tōkon: Fighting Souls launched today with a glaring omission: it’s completely inaccessible on Steam Deck and other Linux-based systems. Instead of throwing punches, players are met with an Easy Anti-Cheat error that halts the game before it even loads.
A Promising Beta Stumbles Out of the Gate
Arc System Works’ new 4v4 tag fighter is one of the most anticipated fighting games of 2026. The open beta, running from July 24 through July 26, was supposed to give PC and PlayStation 5 players a broad taste of the game’s core systems. It includes online and local matches, ranked and casual play, training modes, and a sizable roster. But for anyone trying to play on Steam Deck, SteamOS, Bazzite, or desktop Linux via Proton, the experience ends before it begins.
The error message is blunt: “No anti-cheat module has been found for this game and platform.” That points directly at Easy Anti-Cheat, the same technology that protects countless online titles. The beta build appears to lack the Linux-compatible module needed to pass the security check, so the game refuses to launch.
What Actually Went Wrong: The Anti-Cheat Wall
This isn’t a case of poor performance or rendering bugs. Marvel Tōkon: Fighting Souls uses Easy Anti-Cheat (EAC) to safeguard its competitive online modes. When a player tries to start the game through Proton—the Windows compatibility layer that powers Steam Deck—EAC looks for a specific module that should be bundled with the game’s Linux configuration. In this beta, that module simply isn’t there.
Proton itself isn’t the problem. Valve, Epic, and game developers have collaborated for years to make EAC work on Linux. The tools exist. Games like Apex Legends, Elden Ring, and Fall Guys all run with EAC enabled on Steam Deck. But the burden is on each developer to flip the switch, package the right files, and test the build. For reasons yet unknown, Arc System Works didn’t do that for the beta.
The timing is awful. The full release is scheduled for August 6—less than two weeks away. An open beta is meant to stress-test servers and gather feedback; losing an entire hardware segment undermines that goal.
Who This Affects (And Who It Doesn’t)
If you’re a Windows PC player, breathe easy. The beta runs normally on Windows 10 and 11. You can install it, hop online, and start labbing combos with no extra steps. The anti-cheat works as intended, and you won’t see the Linux error. Your only real concern is whether the launch-day version will support cross-play with Steam Deck friends—but since the Deck version currently doesn’t work, that’s a moot point.
If you own a Steam Deck, Legion Go running SteamOS, or any Linux gaming handheld, you’re locked out. The beta is a non-starter. You can’t even reach the main menu to test controller latency or offline training. The same goes for desktop Linux users on distributions like Bazzite, Fedora, or Arch who rely on Proton. The game’s store page on Steam doesn’t yet carry a Deck Verified status, but that doesn’t excuse a total launch failure during a public test.
If you’re a developer or publisher watching this unfold, the lesson is blunt. Steam Deck has sold millions of units. Linux gaming, while still a minority, isn’t a rounding error anymore—especially for fighting games, where handheld training mode is a killer feature. Releasing a beta without proton-tested anti-cheat is like throwing a launch party and forgetting to unlock the door.
How We Got Here: Proton, Anti-Cheat, and the Steam Deck
For most of PC gaming history, anti-cheat and Linux mixed about as well as oil and water. Kernel-level drivers and Windows-specific hooks made porting these security suites a technical nightmare. That changed in 2021 when Valve and Epic announced official support for Easy Anti-Cheat and BattlEye on Proton. Developers could now enable compatibility by ticking a box in their backend settings and shipping a small runtime package.
It wasn’t magic. Games still required testing. Some titles, like Destiny 2 and Fortnite, opted out entirely. Others, like Apex Legends and Dead by Daylight, flipped the switch and have been running smoothly on Deck ever since. Fighting games have been a mixed bag. Street Fighter 6 and Tekken 8 work nearly flawlessly. Guilty Gear Strive—another Arc System Works title—runs on Deck but doesn’t support online play through Proton, forcing competitive players onto Windows. Marvel Tōkon lands precisely on that fault line.
The Steam Deck’s popularity has upped the stakes. Valve markets the device as a hassle-free console experience. When a high-profile beta fails to launch, the backlash is immediate and visible. Owners check ProtonDB, scan Reddit, and refund pre-orders. The “PC” label no longer means just a desktop tower; it encompasses a fragmented hardware landscape where anti-cheat decisions can gatekeep entire communities.
What You Can Do Right Now
- Windows users: Go play the beta. Report bugs through official channels so the devs have the data they need. If you plan to switch between desktop and Deck at launch, keep an eye on compatibility news.
- Steam Deck / Linux users: Don’t hunt for unofficial workarounds. Modifying anti-cheat files or swapping Proton builds can lead to account bans in competitive titles. Instead, make your voice heard: post on the Steam discussion hub, tag the official Twitter account, and file a support ticket. Developer awareness is the fastest path to a fix.
- Pre-order caution: If you reserved the game on Steam expecting to play on Deck, you might want to wait. Refunds are straightforward if you meet the playtime and purchase window, but it’s easier to hold off until Arc System Works issues a clear statement. Check the store page daily, and watch for a “Deck Verified” badge or an official FAQ update.
- General future-proofing: Before buying any competitive multiplayer game for Steam Deck, consult ProtonDB (protondb.com) and check for developer statements about anti-cheat. A green badge on the store is nice, but community reports on beta branches often tell a more accurate story.
The Run-Up to Launch: Fix or Fiasco?
Arc System Works hasn’t yet commented on the beta’s Linux failure. The studio’s silence is concerning given the August 6 deadline. If the issue is simply a matter of enabling the EAC module and pushing a build, it could be resolved quickly. But the beta’s short duration suggests testing was deprioritized, and the full game might ship with the same problem.
A broken Steam Deck launch would be a self-inflicted wound. The fighting game community loves portable practice. Marvel’s brand appeal could introduce a wave of casual players who only game on Deck. If those buyers see a “Playable” or “Unsupported” label on day one, many will walk away. Worse, negative reviews will pile up, and the game’s Steam score will suffer—not because the gameplay is bad, but because the anti-cheat gate is closed.
The optimistic view: developers often treat betas as separate branches with incomplete features. Anti-cheat configuration might simply be a final-release ticket. The fact that EAC already supports Proton means the heavy lifting is done; it’s just a matter of packaging and testing. If Arc System Works communicates a plan within the next week, trust can be salvaged.
For now, Windows players remain in the driver’s seat. The rest of the PC ecosystem is watching, waiting for a door that should have been open from the start.