Troubleshooting

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API Manual is empty

1. Confirm that you started the full client, not client-without-yoko.
2. Keep ClassicUO.exe beside the complete Basic IDE/API payload.
3. Close the IDE and client, then restart the full client.
4. Do not copy IDE directories from an older package over the current files.
5. Inspect Output or logs for Runtime metadata or local Theia host loading errors.

An empty navigation usually means the frontend opened but did not receive the Runtime catalogue.

Run opens launch.json

Use the Basic commands in the embedded Run menu: Run Current Script, Start Script (SUB Main) / Run Without Debugging, or Start Debugging. A generic Theia/VS Code command with no matching configuration can open launch.json; the Basic commands must be provided by the bundled Basic extension.

Already running: Main

The selected Main instance is still active according to Runtime. Select that script in Explorer and press Stop (Shift+F5) before starting it again. If the UI is stale, reopen the IDE so it rereads the live Runtime state. Do not start another copy of the same entry point while the first one is active.

F10 or F11 is disabled

Stepping requires a stopped debug state:

1. start debugging with F4;
2. set a breakpoint with F9 or wait for the first stop;
3. use F10, F11 or Shift+F11.

“Selected script is not running” is expected after the instance has already stopped.

Script appears only after scrolling

This is obsolete behavior. The current IDE indexes the whole document when opened or changed. If it still occurs, the IDE or language extension was probably mixed with files from another package; install into a clean directory.

State marker is missing or wrong

• select the script in Explorer;
• confirm a successful start in Output;
• refresh/reload the IDE state;
• ensure the IDE is connected to the same ClassicUO process;
• avoid running two client directories that share one IDE payload.

Green means running, yellow means paused, and black/normal theme color marks a selected stopped script.

Client stalls during a Basic command

Add UO.Wait(...) to repeated loops, remove busy infinite loops, avoid a large synchronous search on every iteration, and split expensive work into small steps. Use Runtime and IDE files from the same package.

Font becomes black

Enable Use original game/source color, press Apply, and confirm the client was not overlaid with older text-rendering libraries. When the checkbox is disabled, choose the desired hue manually.

NPC/monster cast indicator is absent

Check the separate NPC/Monster switch, a non-zero length, visible hue, position and visibility range. Some servers do not transmit enough speech, action codes or animations for reliable remote cast detection.

Texture not found for sprite

The selected game data does not contain that sprite. The client caches the negative result and uses its fallback. If the object must be visible, verify that your Ultima Online data matches the server.

FPS returns to 60

Apply the value, verify write permission for the client settings directory, and ensure profiles or settings from different installations are not being mixed. FPS is a global installation setting rather than a character-only value.

Auto Open Doors does not act

Verify the checkbox, door serial, range and server rules. The client sends the concrete door action before movement and throttles repeat actions for the same door to roughly 500 ms.