Netcode 2.13.0 introduces race conditions and breaks flow after upgrading

[AliasgarBohra]

Description

After upgrading from the previous Netcode version to 2.13.0, my multiplayer project started experiencing multiple issues that were not present before the update.

The problems appear to be related to race conditions during the connection and spawning lifecycle. Since upgrading, I have observed:

• Player spawning no longer occurs consistently.
• Errors are thrown while hosting or joining sessions.
• Initialization order appears to have changed, causing systems that previously worked reliably to fail.
• Existing multiplayer flow is no longer functional without code changes.

No gameplay logic was intentionally modified besides updating the Netcode package.

Reproduction Steps

1. Open a project that works correctly on the previous Netcode version.
2. Upgrade the Netcode package to 2.13.0.
3. Host or join a multiplayer session.
4. Observe connection, spawning, and initialization behavior.

Actual Result

• Player spawning fails or becomes inconsistent.
• Multiple errors occur during host/client connection.
• Race condition-related issues appear during initialization.
• Multiplayer flow that previously worked correctly is broken.

Expected Result

Updating from the previous Netcode version should not introduce regressions. Existing multiplayer flow, including player spawning and session initialization, should continue to function as before.

Environment

• OS: Windows
• Unity Version: 6000.3.18f1
• Netcode Version: 2.13.0
• Netcode Commit: (if applicable)
• Topology: Client-Server

Additional Information

Downgrading to 2.12.0 makes everything work aggain.

[EmandM]

Hi, thank you for reporting this issue. Is there any chance you can share more details about your project setup and the errors that you're seeing? If possible, it would be helpful if you can report a bug in the editor and share the case number with us here.

[AliasgarBohra]

Just upgrading from 2.12 to 2.13 makes everything not work. So many race condition errors (When i create or join session). I even tried fixing all these but it coming with new and new always.

I have submitted in issues: CASE IN-147248

[EmandM]

Thank you! We'll make sure your case gets assigned to our team so we can take a look ASAP

[NoelStephensUnity]

@AliasgarBohra
These issues are very likely fixed in #4086 and/or #4073 which will be in the coming update.
If you want to verify one of these two PRs resolves the issue for your project, you can temporarily replace your manifest.json entry for com.unity.netcode.gameobjects with this:

"com.unity.netcode.gameobjects": "https://github.com/Unity-Technologies/com.unity.netcode.gameobjects.git?path=com.unity.netcode.gameobjects#develop-2.0.0",

If that does resolve your issue, then you can use that as a temporary resolution until the coming update.