Lan Multiplayer Fixed (v0.111.0)

LAN Multiplayer — updated for v0.111.0

Play Slay the Spire 2 multiplayer over your local network or a direct IP address, without Steam lobbies or friend invites. Host a run from one machine, join it from another.

This is a rebuild of the existing LAN Multiplayer mod against game version v0.111.0. The v0.108.0 → v0.111.0 updates reworked the game's lobby code, and every earlier release of this mod fails to initialize on 0.111.0 with:

Assembly DLL for mod SlayTheSpire2.LAN.Multiplayer failed to initialize!
Eight separate breaks had to be fixed to get it loading again — the visible error was only the first one, because Harmony stops patching at the first failure.

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Features

• LAN lobby browser — automatically finds games hosted on your network, no IP typing needed.
• Direct connect — join by IP or IP:port for anything discovery can't reach (VPNs, Radmin/Hamachi, different subnets).
• Host any run type — Standard, Daily and Custom runs.
• Configurable — host port, max players, display name and NetID, all in the in-game Settings screen.
• More than 4 players when every player is running this mod.
• Compatibility mode — if you join a host that isn't running this mod (for example an Android/emulated build with LAN support already integrated), the mod detects it during the handshake and falls back to the game's stock lobby format automatically, so the join still works. To host for such a player, switch on Vanilla Protocol in Settings.

Tested end to end on v0.111.0: hosting and joining both work, including a complete run played start to finish, and cross-play against a build with LAN support integrated rather than modded in.

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Requirements

• Slay the Spire 2 v0.111.0
• No other dependencies

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Installation

1. Extract the archive into your game's mods folder, so you end up with: <game install>\mods\SlayTheSpire2.LAN.Multiplayer\
2. That folder should contain: SlayTheSpire2.LAN.Multiplayer.dll mod_manifest.json mod_image.png localization\
3. Launch the game. The title screen should read "Running Modded. Loaded 1 mod." with no error badge.

To uninstall, delete the folder.

Upgrading from an older LAN Multiplayer build: delete the old folder entirely before extracting this one. Don't just overwrite the DLL — the localization files changed too.

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How to use

To host: Main menu → Multiplayer → LAN Host → pick your run type.
To join: Main menu → Multiplayer → LAN Join → pick a lobby from the list, or type the host's address into Direct Connect and press Join.

Settings (host port, max players, your display name, NetID and Vanilla Protocol) live in Settings → General, below the Modding row.

Ports: the host listens on UDP 33771 for the game and UDP 33772 for lobby discovery. If the lobby list stays empty but a direct IP connect works, discovery broadcasts are being blocked — allow the game through your firewall, or check that both machines are on the same subnet.

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Compatibility

• Game version: built and tested against v0.111.0. It will very likely break on the next game update — that has happened with every previous release of this mod.
• Between players: everyone should be on the same game version and the same mod build. Mixed builds are the single most common cause of failed joins.
• Joining a host without this mod: supported via the automatic compatibility mode described above, and confirmed working against an integrated-LAN Android build. While in that mode the lobby is limited to the vanilla 4-player cap and custom LAN player names are unavailable.

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Notes and known issues

• This mod declares itself as not gameplay-affecting. That is deliberate — the game refuses any join where the two sides' gameplay-affecting mod lists differ, which would block connecting to a host that doesn't have this exact mod at this exact version. The side effect is that the game will no longer stop you from joining a genuinely incompatible peer, so make sure you're on matching game versions.
• Playing with someone who doesn't run this mod: if you join them, the fallback is automatic — nothing to configure. If they join you, switch on Vanilla Protocol in Settings first; a host has no way to tell what a connecting player is running, so it has to be told. Leave that setting off when playing with people who do run this mod, or you'll break their join instead.
• It will very likely break on the next game update. If it does, please post the log rather than assuming it's unfixable — it's usually a handful of renamed methods.
• If a join fails, the log is at: %APPDATA%\SlayTheSpire2\logs\godot.logPlease include it in any bug report — the useful part is the first block.

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Credits

• kmyuhkyuk — original SlayTheSpire2.LAN.Multiplayer mod, which everything here is built on.
• afamdafam — the LAN lobby browser and separate LAN menu UI.
• ipX3k — earlier compatibility fixes and the widely used "fixed" build.

This release is an update of their work, not a new mod from scratch.

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Permissions and license

This mod is licensed under the GNU General Public License v3.0, inherited from the original.

• You may freely use, modify and redistribute it, including reuploading fixed builds.
• Any redistribution must stay under GPL-3.0 and must credit the original authors.
• Complete source code is included as a separate download on the Files tab of this page.

If this mod stops working after a game update and I haven't updated it, you are explicitly welcome to fix and reupload it yourself under the same license.