From a fresh clone to a running client, on Windows. Every step is a launcher under launchers\; each one calls launchers\_shared\common.bat first, which resolves the Configuration and locates the engine.

On Linux, every launcher here has a .sh twin; see Linux.

Other platforms start from the same clone: Windows Build (a standalone GUO.exe), Android Build (a debug APK) and Steam Deck (a Linux build pushed over ssh). To play without building anything, see Download a build.

git clone <repository url> GUO
cd GUO
launchers\pipeline\00_bootstrap.bat

The bootstrap fetches the pinned engine into tools\godot and clones ClassicUO at the reviewed commit into sources\ClassicUO (both gitignored). The upstream tree is a read-only reference: the client compiles against its cuoapi.dll, and the audit reads its sources. Never edit it.

launchers\_shared\config.bat holds every setting with its default and is committed. Your machine's values go in config.local.bat, which is gitignored:

copy launchers\_shared\config.local.bat.example launchers\_shared\config.local.bat
notepad launchers\_shared\config.local.bat

Set UO_CLIENT_DATA to the folder holding your .uop / .mul files. Keep the if not defined guard on every line you add so an environment variable still wins. Anything in config.bat can be overridden here; the resolution order everywhere is environment variable, then config.local.bat, then config.bat, then the optional shared config (UO_COMMON_CONFIG).

launchers\pipeline\01_verify_client_data.bat

Runs python tools\uodata\run.py verify: checks the install is complete against the known file registry and reports the version it found. Set UO_CLIENT_VERSION in config.local.bat if yours differs from the default.

dotnet build godot\GUO\GUO.csproj

This is the fast loop (about a second when nothing changed) and the one to use while working. launchers\dev\build.bat does the same through the launcher layer. The full health check is:

launchers\dev\smoke.bat

Five steps: the engine answers, the project imports, the C# builds, the client data verifies, and the client loads offline. It must pass before a commit (see Contributing).

launchers\game\play.bat

The client connects to UO_SHARD_HOST:UO_SHARD_PORT, 127.0.0.1:2593 by default. Nothing answers there until you run a server: see Dev Shard for the local ModernUO instance, or set the host and port in config.local.bat to play elsewhere.

Two variants of the launcher:

launchers\game\play.bat --offline       REM no shard; loads data and renders the login screen
launchers\game\play.bat --frames 400    REM run 400 frames and quit

Anything else on the command line is passed to the client; see Scripted Runs and Probes.

The release workflow (.github/workflows/release.yml) exports the client with the pinned Godot on GitHub's runners and uploads one artifact per platform:

Where to find them:

• Actions > release, pick a run, Artifacts at the bottom of its summary page (you need to be signed in to GitHub). The workflow runs on pushes to main that touch the client or the export tools, and on demand (Run workflow). Artifacts expire after GitHub's retention period.
• Releases: a v* tag makes a draft release with the Windows and Steam Deck builds zipped and attached; the owner publishes it.

Every build needs your own UO install. None of them contains any game data, and none ever will: point the client at your install. The exported executables read the same environment variables as the launchers (UO_CLIENT_DATA, UO_SHARD_HOST, UO_SHARD_PORT), or take them on the command line after --:

GUO.exe -- --play --client-data "<your UO folder>" --host <shard> --port 2593

./GUO.x86_64 -- --play --client-data "$HOME/UO" --host <shard> --port 2593

The APK is a debug build with the committed defaults baked in: it reads the data from /sdcard/Android/data/org.guo.client/files/uo and connects to 127.0.0.1:2593. Copy your install there and forward the shard port (adb reverse tcp:2593 tcp:2593), or export your own APK with UO_SHARD_HOST set: see Android Build. The Steam Deck steps, including getting the data onto the Deck, are in Steam Deck.

Add <your clone>\tools\godot to PATH and godot resolves everywhere. Use godot for the interactive editor and godot-console for scripts and CI: the console build blocks and writes to stdout; plain godot returns at once and prints nothing.

launchers\pipeline\02_warm_cache.bat

The client builds its runtime decode cache (UO_CACHE_DIR) lazily. Warming it removes the first-visit hitch. The cache can be deleted at any time.