How to reproduce:
1. Create a new Unity project and install the Multiplayer Services package
2. Link the project to a Unity Cloud project ID in Project Settings -> Services
3. Import the attached "Repro" script and attach it to any GameObject
4. Enter Play Mode
5. Observe the Console
Expected results: The errors refer to a session, matching the API the user called
Actual results: The errors refer to a lobby - "lobby not found" is thrown for both JoinSessionByIdAsync and ReconnectToSessionAsync, and "lobby code 'ZZZZZZ' contains an invalid character 'Z' (U+005A) at index 0" is thrown for JoinSessionByCodeAsync
Reproducible with: 2.3.1 (6000.5.9f1)
Reproducible on: Ubuntu 24.04.4 LTS, macOS Tahoe 26 (M1)
Not reproducible on: No other environment tested
Note: Joining a session the player already hosts also reports "player is already a member of the lobby". A developer who only uses the Sessions API never encounters the word "lobby" in that API, so these messages do not map to anything they wrote.
First lines of error:
SessionException: lobby not found