KSA Multiplayer

Fly together in Kitten Space Agency. See each other's craft in orbit and on the surface, dock across the network, share craft files, and talk while you do it.

Windows and Linux. Requires KSA v2026.8.19.5261.

v0.4.0 is not compatible with 0.2.1 or earlier. The network format changed. Everyone on a server — and the server itself — must be on v0.4.0. A mismatched client is refused at join and told which version to get.

Features

• Shared universe — starts empty and keeps every vessel launched during the session, replaying them to anyone who joins later. Your existing craft are hidden for the session and restored untouched when you disconnect.
• Cross-player docking — dock to another player's craft from the stock port menu. The player who initiates takes control of the combined stack; the other keeps ownership of their craft and their camera, and gets control back on undock. A docked passenger can ask to be let off, and the owner is prompted.
• Craft sharing — upload a saved craft to the server, browse what others have shared, and download one straight into your vehicle folder, where KSA's own VEHICLE SAVES window lists it. Stock craft included. "Share what I'm flying" snapshots your current vessel, so you don't need to save first. Downloads never overwrite a craft of the same name.
• Dedicated server — nobody has to host from inside the game. Runs headless on Windows or Linux.
• Independent time warp — warp on your own schedule. The player list shows how far apart everyone's clocks are, and a Sync control jumps you forward to match someone who is ahead.
• In-game chat, player nametags, and EVA astronaut sync.
• Mismatch protection — the server refuses clients running a different mod version, a different Game Type, or a different solar system, and says exactly what to change.

Requirements

• Kitten Space Agency v2026.8.19.5261
• .NET 10 runtime — needed to run a dedicated server. Get it from https://dotnet.microsoft.com/download/dotnet/10.0 (The Windows installer sets up a private runtime for the client, so you only need this yourself if you are hosting a server.)

Installation

Windows — installer (easiest)

1. Run KSA-Multiplayer-Setup-v0.4.0.exe
2. Point it at your Kitten Space Agency folder
3. Launch with the KSA with Mods shortcut

The installer also handles the StarMap loader and a private .NET runtime.

Windows — manual

From KSA-Multiplayer-v0.4.0-windows.zip, copy Content\Multiplayer into your KSA installation:

...\Kitten Space Agency\Content\Multiplayer\Multiplayer.dll
...\Kitten Space Agency\Content\Multiplayer\mod.toml

Linux

From KSA-Multiplayer-v0.4.0-linux.tar.gz, copy the Multiplayer folder into:

~/Documents/My Games/Kitten Space Agency/mods/

so you end up with mods/Multiplayer/Multiplayer.dll and mod.toml. Nothing else is needed — 0Harmony ships with the game.

Running a server

Both archives include the dedicated server. It holds no KSA files of its own — it finds your game installation at startup and loads the game's assemblies from there, so it has to be told where the game is:

Windows

RunServer.cmd -gamepath "C:\Program Files\Kitten Space Agency"

Linux

./run-server.sh -gamepath /path/to/KSA

You can also set KSA_PATH, or put "gamePath" in server_config.json.

Edit server_config.json for the port, player limit, password, message of the day, and craft sharing. Type help at the server prompt for the console commands. Forward UDP 7777 if you are opening it to the internet.

Playing

Open the multiplayer panel beside the HUD, enter the server address and your player name, and connect. Pick a name that isn't the default placeholder — the server refuses those, along with duplicates.

Console commands (press ~):

There is no mp_host. Play goes through a dedicated server.

Troubleshooting

"Version mismatch" at join — the client and the server must both be on v0.4.0. The message names the version the server is running.

"System mismatch" — everyone must pick the same solar system at startup.

"Game Type mismatch" — the server tells you which one to select on KSA's configuration screen.

Mod doesn't load on Windows — launch through the KSA with Mods shortcut, not the plain KSA executable.

Server won't start — it needs the .NET 10 runtime and a valid game path. Make sure KSA.dll is in the folder you pointed it at.

Something looks wrong in flight — logs are written to a logs folder beside the mod, and beside the server. Debug logging is on by default and there is a checkbox for it in the panel. When reporting a problem, please include the mod version from both machines, both clients' logs, and the server console output — and say who was flying what and whether anyone was time warping. Most of the interesting bugs come from two players being at different points in time.

Known limitations

• Surface operations are less tested than orbital flight.
• The passenger undock request is new and lightly tested.

Links

• Source and releases: https://github.com/racerx2/KSA-Multiplayer-Mod
• Discord: https://discord.gg/qZ6qjNZ8hz
• Bug reports: https://github.com/racerx2/KSA-Multiplayer-Mod/issues
• Questions and ideas: https://github.com/racerx2/KSA-Multiplayer-Mod/discussions

Licensed under PolyForm Noncommercial 1.0.0 — free for any noncommercial use, including personal, hobby, education, research and nonprofit. Commercial use requires a separate licence.