A build check warning in the area "server.ts rules". A warning: the game still publishes, but fix it when you can.
The build check runs on every game LobbyLab builds, and each problem it finds has a stable code, the exact message, the file and line when it names one, and a link to this page.
What the check looks at
server.ts exports rulebook (init, advance, project, and tick for realtime games). It must be deterministic, so the check scans the code and its strings for APIs that are not allowed.
How to fix it
Remove tick, or set executionProfile to realtime if the game needs a tick.
Use context.random for randomness and context.logicalTimeMs for time, import only named imports from the sim kit, and keep display text with words like "Date" or "global" in the client.
See also: every error code, the API reference and the docs.