[EmandM]

Purpose of this PR

Currently, when a client starts the session as a DA session owner their NetworkSceneManger initializes all the existing loaded scenes so they can correctly synchronize incoming clients.

This PR ensures that clients promoted to session owner mid-session also initialize their existing loading scenes.

This fixes an error where an active scene that was loaded before the game started would break synchronization on late-joining clients after a new session owner was promoted.

Jira ticket

UUM-154485

Changelog

• Fixed: Issue where a client promoted to session owner could throw an exception when synchronizing a newly joining client.

Documentation

• No documentation changes or additions were necessary.

Testing & QA (How your changes can be verified during release Playtest)

Functional Testing

Manual testing :

• Manual testing done

Automated tests:

• Covered by existing automated tests
• Covered by new automated tests

Does the change require QA team to:

• Review automated tests?
• Execute manual tests?
• Provide feedback about the PR?

If any boxes above are checked the QA team will be automatically added as a PR reviewer.

Up-port

n/a

Backports

Was reported on 2.0.0 so probably needs a backport.

[u-pr]

💡 Harness Review

The change extends scene initialization to session-owner promotion, but late-join correctness still needs stronger handling and verification.

_{Reviewed commit 00c2276}

_{🤖 Helpful? 👍/👎}

[u-pr]

After promotion, CMB late joining still throws with server-to-client mapping 7 -> 3 and an unregistered, non-active local scene 7. Scene handles are only locally unique. ClientSceneHandleToServerSceneHandle lacks 7, so this check passes. UpdateServerClientSceneHandle(7, 7, ...) returns false because ServerSceneHandleToClientSceneHandle already contains 7. Initialization ignores that result. If validation accepts the scene, AddSceneToClientSynchronization indexes the missing reverse-map entry and throws. Preserve existing mappings. Assign the new scene a collision-free canonical handle. Check that registration succeeds.

_{🤖 Helpful? 👍/👎}

[EmandM]

I tested this, it's working fine. I think this is a theoretical case rather than a real thing

[u-pr]

This test can pass if a future change removes promotion-time scene registration and the late joiner never synchronizes EmptyScene. AddActiveSceneToClientSynchronization now warns and returns when the active scene has no mapping. EmptyScene contains no NetworkObject, and CreateAndStartNewClient checks connection and player clones rather than scene synchronization. Assert that the promoted owner registers the scene after promotion. Assert that the late joiner has a synchronized EmptyScene mapped to the promoted owner's canonical handle.

_{🤖 Helpful? 👍/👎}

[EmandM]

This is a regression test for a bug where subsequent joins fail. I don't really care if the scene fails to synchronize, only that subsequent joiners can successfully join.

[codecov-github-com]

Codecov Report

Attention: Patch coverage is 88.46154% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...cts/Runtime/SceneManagement/NetworkSceneManager.cs	86.36%	3 Missing ⚠️

@@              Coverage Diff               @@
##           develop-3.x.x    #4214   +/-   ##
==============================================
  Coverage          76.05%   76.05%           
==============================================
  Files                159      159           
  Lines              27344    27341    -3     
==============================================
- Hits               20797    20795    -2     
+ Misses              6547     6546    -1     

Flag	Coverage Δ
NGOv2_project_testproject_ubuntu	75.10% <88.46%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...cts/Runtime/Connection/NetworkConnectionManager.cs	82.19% <ø> (-0.02%)	⬇️
...netcode.gameobjects/Runtime/Core/NetworkManager.cs	72.48% <100.00%> (+0.11%)	⬆️
...me/Messaging/Messages/ConnectionApprovedMessage.cs	67.35% <ø> (+1.09%)	⬆️
...cts/Runtime/SceneManagement/NetworkSceneManager.cs	80.01% <86.36%> (+0.16%)	⬆️

... and 1 file with indirect coverage changes

Components	Coverage Δ
com.unity.netcode.gameobjects	76.05% <88.46%> (+<0.01%)	⬆️

ℹ️ Need help interpreting these results?

[NoelStephensUnity]

🐱

[u-pr]

💡 Harness Review

The change centralizes loaded-scene registration on session owner promotion and adjusts active-scene synchronization for CMB. I examined startup and promotion ordering, scene tracking, service synchronization, and the regression test; no additional actionable issues emerged beyond those previously reported.

_{Reviewed commit 84d252d}

_{⚠️ Earlier blocking findings with unresolved threads: 1. The rating above does not cover them; resolve each thread after addressing it.}

_{🤖 Helpful? 👍/👎}