KH2 Co-op — Steam private preview

The Steam transport passed its two-account, two-PC rev11 check. The package passed launch/title/exit (UX07) and technical GUI host/join (JOIN05). Effective movement with a clearly responding puppet on both package screens and a physical-controller friend session still need qualification. Use the specific matching package supplied by your host; current source is protocol 34, AvatarBridge 4 and WorldBridge 12, not the old acceptance products. The checked-in package validator/pins still target protocol 18; they cannot produce a current protocol-34 ZIP unchanged. See packaging.

You need Steam running, signed in to your account owning KINGDOM HEARTS HD 1.5+2.5 ReMIX, Windows, and the exact supported Steam Global KH2 build. No Tailscale, VPN, port forwarding or firewall changes are needed. Connections must use Valve relays; there is no direct-IP fallback. Up to three players can play.

1. Unzip into a new folder beside the game folder, not inside it. Keep the files together. Open Start KH2 Co-op.cmd from your normal Windows desktop.
2. Browse to the folder containing KINGDOM HEARTS II FINAL MIX.exe. Leave Steam (beta) selected. If steam_appid.txt is missing, check the permission box to create it beside KH2 with app ID 2552430. Existing correct files are preserved; a different app ID is refused. No administrator access is needed.
3. If your supplied package offers Character, choose it before starting the game (current source offers Roxas or Sora; see limits below). Click Start game. Wait for save protection and your actual SteamID. Check that it is your account, then tick the account confirmation. You can enter an expected SteamID to catch the wrong account. This must be a 17-digit SteamID64, not a profile name, URL or friend code.
4. Load your existing save manually. Do not save during this preview. If KH2 shows a corrupt-save or deletion prompt, stop and contact the host. Do not dismiss it or copy someone else's save into your account.
5. Host: choose host, paste one or two friends' actual SteamIDs separated by commas, and confirm that only those accounts may join. When your room is ready, check the ready box and click Start hosting. Wait for Hosting — roster verified, then Copy invitation and share that text with your friends.
6. Friend: choose join, select the slot the host assigned, and paste the host SteamID or invitation (kh2coop:steam: followed by the host ID). Confirm your account and readiness, then click Join. The host must separately allowlist your actual SteamID. The invitation alone grants no admission.
7. Wait for Connected — roster verified. The HUD can show connection latency. To finish, click Disconnect, then Exit & close game. Disconnect leaves the game open. Closing stops only the game and helpers started here.

The allowlist is fixed for a hosting session. To change it, Disconnect, edit and confirm it, then Start hosting again. Disconnecting as host ends the friends' session. Steam overlay invites, a friends picker and Steam's Join game button are not supported; use the copied invitation text.

If Steam is unavailable, start it and sign in to the account owning KH2, using the same normal desktop session as this launcher. Close this game and start again. Broker startup can take up to 60 seconds. If authentication or Valve relay is unavailable, check Steam online status and retry a fresh launch. These failures cannot always be distinguished; preserve the logs when reporting a problem.

If the account is wrong, close this game, switch accounts in Steam, then start again. If joining fails, verify the host ID and the host's explicit allowlist. A generic timeout does not prove which side failed. Privacy/ICE failures are refused; do not change network settings to bypass them.

Short transport interruptions use bounded reconnection. Host left is terminal: there is no automatic rejoin; ask the host before joining a new session. Session errors remain visible in the launcher. Logs stay in this package. Sessions have a 30-minute limit.

SaveGuard redirects save writes into a sandbox; never copy those files over your saves. The launcher removes only an unchanged app-ID file it created, after confirmed owned game closure. Changed or pre-existing app-ID files are preserved. After an uncertain launch, leave the file in place until the game is closed and check the launch receipt. Never delete your saves as a troubleshooting step.

Current-source launcher defaults enable host enemy mirroring/population, all-player targeting, normal co-op difficulty, friendly fire, event hold, downed handling and revive prompts. Experimental population spawning remains disabled. These settings do not imply full-story qualification. The launcher currently connects after a loaded save; the New Game/title-time route remains a separate development and acceptance path, not a completed package workflow.

Roxas+Roxas and a Roxas host with a Sora friend have local two-instance prologue field/reload evidence and separate runs at the checked Day 1-6 prologue sites. The Twilight Thorn boss, opening-scene friend representation, two-PC profile qualification and the full New Game-to-Shan-Yu route remain open. The current gameplay limits apply; older supplied packages keep their original defaults. Stop on antivirus warnings and contact the host rather than adding exclusions. To uninstall, close the game and launcher, then delete the extracted package and ZIP.