Bug: `tmux` session conflict prevents Minecraft server from launching

[Aotumuri]

@icwhite
When running evaluation_script.py with multi-agent task setup, the script fails due to a tmux session conflict. Specifically, it attempts to create a new tmux session with the same name (server_0) even though a session with that name already exists or was not properly cleaned up. This causes subprocess.run(...) to raise a CalledProcessError.

Steps to Reproduce:

1. Run the following command:

   python tasks/evaluation_script.py --task_path tasks/crafting_tasks/test_tasks/2_agent.json --model gemini-2.0-flash --template_profile profiles/tasks/crafting_profile.json

2. If a tmux session named server_0 already exists or is in an inconsistent state, the following error occurs:

   duplicate session: server_0
   subprocess.CalledProcessError: Command '['tmux', 'new-session', '-d', '-s', 'server_0']' returned non-zero exit status 1.
   

Expected Behavior:

If a tmux session named server_0 already exists, the script should either:

• Kill the existing session safely before launching a new one, or
• Generate a unique session name to avoid conflict.

Observed Behavior:

The script retries launching the world but fails due to tmux session name collision. It leads to no tasks completing successfully.

Possible Fix Suggestions:

• Add a check and safe cleanup before attempting to create the session:

  subprocess.run(['tmux', 'kill-session', '-t', session_name], check=False)

• Or generate unique session names using timestamps or UUIDs.

Environment:

• OS: macOS
• Python: 3.13 (via Anaconda)
• Command used: see above
• Script: evaluation_script.py