[NoelStephensUnity]

Purpose of this PR

Hybrid prefab instances now always spawn their GhostObject in their own NetworkManager's world, NGO parenting of hybrid instances no longer produces visual artifacts, and a rejected NGO parent change now restores the object's original position. This PR bundles four related hybrid changes, one NGO parenting fix and one test-compile fix.

Spawning a hybrid instance in its NetworkManager's world: N4E spawns a ghost into its active world. A hybrid player prefab, InstantiateAndSpawn, or Instantiate followed by Spawn could therefore spawn the ghost into a client world and fail with "Invalid world ... for spawn". Hybrid prefabs now delay their ghost spawn (GhostObject.DelaySpawning), and the spawn authority spawns the ghost in its own NetworkManager's world before OnNetworkSpawn. The integration test harness no longer sets N4E's active world itself.

Parent replication compatibility: when GhostObject.ParentReplication is enabled, N4E replicates the parent of a hybrid instance and the NGO parenting API and processing are disabled for those instances: TrySetParent / TryRemoveParent log a warning and return false, OnTransformParentChanged early-exits, and the spawn message no longer carries a parent (one less byte per parented hybrid spawn). When hybrid parent replication is enabled, the normal transform.SetParent and direct assignment of transform.parent are how user scripts activate parenting.

NGO parenting of hybrid instances requires worldPositionStays disabled: when NGO handles the parenting (ParentReplication disabled), a reparent with worldPositionStays enabled made clients apply the new parent before the ghost's rebased local transform arrived, so the object popped by the full reparent offset, and with full-tick smoothing it stayed displaced. Users attempting this will now see an error and the parent change does not happen:

• TrySetParent(parent, true) / TryRemoveParent(true) return false. Note: both default to true, so TrySetParent(parent) must become TrySetParent(parent, false) for hybrid instances.
• A direct transform.parent = parent (or SetParent(parent, true)) is reverted to the previous parent and local transform. A direct SetParent(parent, false) is accepted and synchronized as worldPositionStays disabled.
• Parenting in local space (worldPositionStays disabled) still works as expected. A hybrid instance parented under a non-hybrid one still logs the mixed-timelines warning.

A rejected parent change restores the original position (NGO): when NGO rejects a parent change (for example a client without parenting authority, an unspawned NetworkObject, or a parent without a NetworkObject), it reverted the parent by assigning transform.parent, which keeps the world position. A change made with worldPositionStays disabled had already moved the object, so the parent was restored but the object kept its moved position. The position, rotation and scale from before the change are now captured in OnBeforeTransformParentChanged and restored along with the parent.

Hybrid instances need a hybrid session: NGO only checked hybrid prefabs when they were registered, not when an instance was spawned. An unregistered hybrid prefab instance, for example one spawned through a prefab handler, spawned into a session that never entered hybrid mode. Spawning one now logs an error and the spawn does not happen.

NetworkRigidbody tests never compiled: the runtime test assembly was missing the com.unity.modules.physics2d version define, so NetworkRigidbodyTest compiled to nothing on every branch. It now compiles and runs.

PR Scope:

• NetworkSpawnManager: ghost spawn in the NetworkManager's world for hybrid instances, and hybrid instances are rejected when no hybrid prefab was registered before the session started.
• NetworkObjectBridge: hybrid prefabs set DelaySpawning.
• NetworkObject: parent replication disabling NGO parenting, worldPositionStays rejection, the direct parent change check, and restoring the original pose when a parent change is reverted (OnBeforeTransformParentChanged).
• Tests: HybridSpawnWorldSelectionTests, HybridParentingTests, NetworkObjectParentRevertTests, testproject NetworkObjectSpawning hybrid fixture re-enabled, the runtime test asmdef physics2d define (the two 3D-only physics fixtures now guard on COM_UNITY_MODULES_PHYSICS alone), and UnifiedHybridPrefabValidationTests.HybridSpawnWithoutHybridPrefabsIsRejected.

Issues found, but were not fixed for this pass and require one or more follow-up PRs

• A child surviving its parent's despawn with ParentReplication enabled is intermittent until N4E PR 129044 ships.

The affected test (ParentReplication_ParentDespawned_ChildSurvivesAtRoot, parent replication enabled) is ignored until trunk PR-129044 lands.

Jira ticket

MTT-15275 ---> NGO side.

Changelog

• Fixed: Issue where a rejected parent change, for example one made by a client without parenting authority, restored the NetworkObject's parent but left it at the moved position when the change was made with worldPositionStays disabled. The original position, rotation and scale are now restored.

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?

Up-port

Not applicable.

Backports

The parent revert fix will be ported to develop-2.0.0 in a separate PR. The hybrid changes exist on develop-3.x.x only.

[u-pr]

💡 Harness Review

The runtime changes have focused regression coverage, but the expanded test compilation needs a compatibility correction.

_{Reviewed commit 4e9e5f3}

_{🤖 Helpful? 👍/👎}