Before joining
- Create and save a single-player character first if you do not already have one.
- Choose the intended save before joining the friend's session.
- Keep a manual backup before testing recovery on an older co-op save.
What travels
- Appearance and equipment
- Regular items and gold
- Skills and perks
What stays host-side
- Quests
- Quest items
- The host's world state
Evidence boundary
Network, platform and old-save edge cases vary. Treat the official fix list as a starting point and record reproducible exceptions rather than assuming one universal cause.