Me and my friends have been playing Bloodborne co-op on PC for hours at a time now, and I'm still kind of surprised how well it holds up. Nobody rings bells or waits on signs, and fog walls don't lock anyone out. The host can die, a boss can go down, whatever, nobody gets sent home. You just keep going. We've done Chalice Dungeons this way too.
It's called Nightwatch Co-op. It's free and open source, and it's still in beta.
I made a quick setup tutorial
It runs on the open-source Lantern Engine. The co-op itself is visy's work: they hooked into the game's own summoning, patched out everything that normally kills a session, and progress still saves to each person's own character. Go check out visy's repo, they did the hard part.
And yeah, parts of this were made with AI help. Most PC port stuff is right now. We do play it a lot though, and we fix things before we tell people they work.
You can play the whole game with up to 5 people including the host, and friendly fire is a toggle. Lamps take the whole party with you. Dying doesn't give you a loading screen anymore, you just get back up at your lamp. Enemies you kill stay dead for everyone, there's a ping key, and if your friends wander off the host can pull everyone back with one button (it asks them first, don't worry). Co-op uses its own saves, so your solo character is safe. You also get the usual PC stuff: DLSS, FSR, frame gen, high fps, and best mouse and keyboard available right now.
Connecting is peer to peer. One person hosts and everyone else pastes in a code. The host needs an open port, or you all join the same Radmin, Tailscale or Hamachi network. The tutorial covers all of it. There's no public online, so no messages, bloodstains or random summons.
Download and credits are on GitHub (https://github.com/vladtepes22/NightwatchCoop). If you need help or people to play with, there's a Discord (https://discord.gg/sBK9FKKeup).
You need your own dumped copy of Bloodborne on update 1.09. No game files are included. works with most versions
Please don't go bugging Lantern Engine, The Hunter's Dream, FromSoftware or Sony about this, none of them are involved. It's a beta, so back up your saves. If something breaks, drop your `logs\last_session.log` in the Discord and I'll take a look.