The TTW team has created a post just for known and verified Fallout 4 facts, we will try to keep this updated. Anything found on this page can be considered to be as close to 100% confirmed as is possible at this point. If you know a fact not on this page, create a thread in the Fallout 4 - Facts forum and we will verify and add it to the main post.
- Will be optional [Source, Thread]
- Codsworth can be a companion [Source, Thread]
- Dogmeat cannot die [Source, Thread]
- Dogmeat CAN become incapacitated and require a stimpack to revive [Source, Thread]
- Todd Howard says "[companions] can't be killed in that state" which could be implying that they can be killed if they are not your current follower. [Source, Thread]