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Download the latest released preview package of Fusion SDK 2.1.0.

What's New

Open the changelog section the latest released preview package of Fusion SDK 2.1.0.

To ensure quick support and iterations new SDK packages will be published as nightly builds.

Projects should be upgraded to the latest 2.0.x SDK before being upgraded to 2.1.

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Release Notes

2.1.0

Preview

Build 1543 (Dec 04, 2025)

What's New

• NetworkTransform.TriggerLocalOverridesExtrapolated() On a proxy, collisions cause the local physics to be favoured over the remote extrapolation. This triggers that effect manually, which can be useful for sudden actions e.g. proxy prediction of e.g. jumps

Changes

• Move Forecast sleeping with non-zero velocity warnings to the Forecast trace channel

Bug Fixes

• Fixed: Correct key indexing in input type lookup, fixes issue where GetInputs would not return false when no INetworkInput was set

Build 1521 (Dec 02, 2025)

Changes

• Improve compatibility with older (V1) baked prefabs
• Never deliver RPCs on resim ticks, only on forward ticks. This enables sending a reply RPC within the context of the the received RPC

Build 1513 (Nov 27, 2025)

What's New

• PhysicsBody access on NetworkTransform
• Assembly Tags to mark builds as Preview or Stable
• Warning log when running Preview builds
• NetworkRunner.BuildStage, which returns the Build Stage (Preview/Stable)

Changes

• NetworkObjectFlags.GetVersion extension method returns NetworkObjectFlags now (was: int)
• Prefabs baked with V1 flags version are still valid and do not cause a runtime error
• If a prefab can't be baked due to being in a read-only location but it still has valid flags, no error is raised
• Allow time synchronization settings to be overriden in Shared Mode, achievable via NetworkProjectConfig.TimeSynchronizationOverride
• Improve NetworkObjectFlags documentation
• Priority is now SendPriority, for clarity
• Make the underlying RigidBody(2D) accessible from AbstractPhysicsBody. Add AngularDrag access
• Update to Photon Realtime SDK to 5.1.9

Bug Fixes

• Fixed: In Shared Mode stop marking snapshots with the received servers tick, instead use the latest changed tick for the given object. This stops a tick mismatch between the render Timeline and the snapshots returned from NetworkBehaviour.TryGetSnapshotsBuffers
• Fixed: When having send rate set to 4 times a second ensure the timeline idle detection code does not execute
• Fixed: Stop interpolation jumping object momentarily to wrong location when using Forecast and switching Kinematic on and off
• Fixed: CanInterpolate now always interpolates when Forecasting is disabled as well as for State Authorities when kinematic is enabled
• Fixed: NetworkObjectBaker incorrectly detecting the main NetworkTransform if there was a NetworkTransform in a child GameObject without a NetworkObject
• Fixed: StateAuthority changes to rigidbody interpolation were not being correctly mirrored on other clients
• Fixed: NetworkTRSP is now abstract, as documented
• Fixed: Connection fallback to Relay timing out after the first handshake

Build 1460 (Nov 12, 2025)

What's New

• Physics, FSM and Interest Management addon to hub
• NetworkedAttribute.AllowPrediction - if set to false, only state authority can write to the property; writes from input authority and proxies are ignored (value will not be changed)
• NetworkObjectTypeId.FromPrefabNestedObject and NesteorkObjectTypeId.IsPrefabNestedObject

Changes

• NetworkBehaviourBufferInterpolator provides explicit functions for NetworkBool and obsoleted explicit .bool functions with a warning to discourage use of bool in Networked Properties
• [SharedMode] Plugin can invoke and send any Rpc and is not limited by Sources
• NetworkObjectReleaseContext.IsNestedObject made obsolete
• Nested objects no longer have their type set to invalid

Bug Fixes

• Fixed: Connection fallback to Relay timing out after the first handshake
• Fixed: Fusion Intro link in the Hub advanced documentation
• Fixed: The State Authority having state overwritten if it changed state immediately upon gaining State Authority, particularly with high ping
• Fixed: Lag compensation internal AABB constructor fix assignment order
• Fixed: NetworkRunner.GetAvailableRegions always throws a OperationStartException: Must be inside a room
• Fixed: MissingMethodException raised in Unity 6000.3 beta
• Fixed: Unity 6000.3 beta obsolete warnings in NetworkProjectConfigImporter
• Fixed: [Plugin] [Rpc, PreserveInPlugin] combination resulting in errors being logged
• Fixed: FusionPluginNetworkTypesExporter not exporting INetworkInput types
• Fixed: State auth request handling did not update auth lists; fixed that
• Fixed: NetworkTransform area of interest override was being overwritten internally
• Fixed: Warnings due to usage of Fusion.Native in the weaver

Nightly

Build 1390 (Oct 14, 2025)

What's New

• Tick and send rates for Shared Mode are now configurable and may be set up to 32. The default tick rate of 32 and send rate of 16 remains the same
• Equality Operators and GetHashCode() to ReliableKey
• Support request for a Host Migration data clean-up via NetworkRunner.ClearHostMigrationSnapshot
• New NetworkRunner.GetResumeSnapshotNetworkObjectPlayerObjects API to get access to associated Player Object NetworkIDs when running Host Migration
• Reset object client prediction with NetworkObject.ResetToLatestState()
• Expose the Photon Cloud Connection RTT via NetworkRunner.GetRealtimeRtt()

Changes

• The tick and send rates can now be configured more flexibly
• Improve the NetworkRunner generated documentation
• In Forecast Physics, when setting Rigidbody(2D).isKinematic to true, disable physics interpolation on the RigidBody. Otherwise, this prevents smooth movement. Physics interpolation is restored when isKinematic is set to false. This behaviour can be disabled on a NetworkTransform by setting PhysicsSettings.SetPhysicsInterpolationToDisabledWhenKinematic to false in code
• Forecast Physics Drag and Mass are no longer synced. Use [Networked] properties to sync Physics attributes manually, if required
• Swap internal asserts to warning logs to confirm velocities while Forecast Physics objects are sleeping
• Physics Forecast objects may now be toggled to and from kinematic. When kinematic they are handled as Forecast disabled. Toggling kinematic is the preferred way to handle this as it synced over the network
• Better docs for NetworkSceneManagerDefault.OnSceneInfoChanged()
• NetworkRunner Editor Inspector displays ping as milliseconds
• Shared mode clients can now draw their local area of interest cells with RunnerAOIGizmos
• Release/RequestStateAuthority returns a bool; false means the call has been unsuccessful

Bug Fixes

• Fixed: Invalid warning message suggesting to use [Networked] for float/vector properties on structs
• Fixed: Error during import reporting PhotonAppSettings not being loadable
• Fixed: AssetDatabase.RegisterCustomDependency errors on Import
• Fixed: Tick-aligned RPCs are no longer unnecessarily delayed by the plugin in shared mode
• Fixed: Global INetworkRunner AOI Callbacks are executed on clients in Host/Server mode and not just on the Server
• Fixed: NetworkLinkedList.IndexOf returns -1 if the value is not found
• Fixed: Kinematic flag, parenting and scale now correctly applied for Physics Forecast objects
• Fixed: Checking TRSP in ResolveAOIOverride
• Fixed: NetworkTransform SyncScale in shared mode
• Fixed: NMA error when animator has 8 bool parameters or a multiple of 8
• Fixed: Global INetworkRunner AOI Callbacks are executed on clients in Host/Server mode and not just on the Server
• Fixed: Enforce Fusion Defines to all supported Build Targets
• Fixed: Realtime Protocol Fallback Operation Timeout
• Fixed: A possible disconnect when receiving a very large packet
• Fixed: RPCs are not invoked when called on state authority when InvokeLocalMode = RpcInvokeLocalMode.ForwardToServer

Build 1240 (Aug 08, 2025)

Breaking Changes

• NetworkTransform.DisableSharedModeInterpolation option is now a flag enum value
• Prefabs and scenes need to be reimported due to baking changes
• SendReliableDataToPlayer(), SendReliableDataToServer(), OnReliableDataReceived() all now pass ReadOnlySpan<byte> to avoid allocations

What's New

• Fusion Version Scripting Define Symbols: FUSION_2, FUSION_2_1, FUSION_2_1_0, FUSION_2_OR_NEWER, FUSION_2_0_OR_NEWER, FUSION_2_1_OR_NEWER
• NetworkRunner.HasCustomPlugin - returns true if the game is run against a custom plugin
• NetworkRunner.FailedToResolveNetworkObject - an event that can be used to detect cases where [Networked] NetworkObject properties return null not due to underlying NetworkId being zero, but because the object was not found (due to AoI, being destroyed locally etc.)
• NetworkTransform supports the use of physics i.e. Rigidbody or Rigidbody2D in both Shared and Client-Server modes
• Object Priority gives control over the update rate of objects
• [Shared Mode] the size of the Area of Interest cells and the size of the grid can be adjusted in the NetworkProjectConfig
• Added RpcChannel.ReliableLargeData to send RPCs that exceed 512 bytes. Not tick accurate
• NetworkRunner.RequestMasterClientReassign to promote the local player as the master client
• Non-addressable scenes can now also be loaded with NetworkRunner.LoadScene(SceneRef.FromPath(...))
• [Multipeer] Ensure we execute physics for non-default scenes last in FixedUpdate, so this as close to Unity's normal position of running the physics as possible
• FusionUnityHostProfiler - Fusions integration with Unity profiler
• Added FusionMppmCommand.ExecuteAsync
• MatchmakingArgumentsExtensions Utility Methods. Helps to setup MatchmakingArguments for Fusion
• Updated to Realtime SDK 5.1.5
• New Fusion Intro Sample and switch Fusion Menu to standalone
• New Fusion Hub
• NetworkRunner.LocalAddress to access the address Fusion bound to for direct connections
• StartGameArgs.PlayerUniqueId enables reconnects to maintain the same PlayerRef
• Support for breakpoints: ClientServer Mode only. Working on both Multi-Peer and Unity MPPM
• RpcAttribute.InvokeLocalMode. If set to RpcInvokeLocalMode.ForwardToServer, locally invokable RPCs will always be forwarded to the server/plugin from clients

Changes

• RPCs targeted at state authority do not get sent if the local client is the state authority
• Failed to unwrap warning no longer logged for NetworkBehaviour references that fail to resolve, regardless of the reason
• Failed to find behaviour is now logged for an invalid NetworkBehaviour on a valid NetworkObject
• Update to Photon Realtime SDK to 5.1.7
• Clamp PlayerCount to a valid range (1-2048) in Shared Mode
• Clamp Heap PageCount to a valid range (16-4096) in Shared Mode
• Inline help icons added to config's Client/Server Tick/Send rates
• In/out packets statistics reflect packet fragmentation
• Update NanoSockets for Android to support 16 KB page sizes
• OnChangedRender now called at alpha = 0.5 to match interpolators (and reduce perceived latency)
• Unity-provided packages are ignored when looking for assets. To override, define FUSION_ENABLE_SEARCH_IN_UNITY_PACKAGES
• NetworkObjectBaker uses Fusion.Log instead of UnityEngine.Debug
• Check if in Session before leaving it
• Check if connected to Photon Cloud before running disconnect
• Clicking animator bake failure error messages now shows the relevant gameObject in the hierarchy
• Keep Session running only if Host/Server disconnected by Timeout
• Leave Session before disconnect from Photon Cloud
• Removed SendReliableDataToPlayer and SendReliableDataToServer with byte arrays; use overloads with with ReadOnlySpan<byte> instead. Avoids allocation
• Editor trace logs are more granular, with following defines controlling specific streams: FUSION_EDITOR_TRACE_IMPORT, FUSION_EDITOR_TRACE_INSPECTOR, FUSION_EDITOR_TRACE_TEST, FUSION_EDITOR_TRACE_MPPM
• INetPeerGroupCallbacks no longer deal with NetSendEnvelope; NotifyData packet type is assumed and data is passed
• INetworkRunnerCallbacks.OnUserSimulationMessage is now obsolete and no longer used
• SimulationMessage is now obsolete
• Simulation.IsStateAuthority handles PlayerRef.None correctly (i.e. when it represents the host)
• Simulation.IsInputAuthority handles PlayerRef.None and PlayerRef.MasterClient correctly
• Skip opening Fusion Hub in batchmode
• NetworkTRSP state authority change error correction delta default value set to 0
• Assemblies with FUSION_FORCE_WEAVING version define will be weaved even if they are not included in the config's AssembliesToWeave
• Fusion.Unity assembly no longer has to be added to the config's AssembliesToWeave
• NetworkObjectInterestModes made public
• NetworkObject.ObjectInterest internal field renamed to NetworkObject.LegacyObjectInterest; it is used only to migrate to storing interest settings in object flags (handled by the baker)
• Current flag versions set to NetworkObjectFlags.V2. All prefabs and scenes need a rebake
• NetworkObject editor: Prefab Source is now selectable
• NetworkRunner.FindObject/TryFindObject no longer throw if simulation is not started
• NetworkTransform on root NetworkObject is now always placed at index 0, regardless of component order
• Join Session Log to be more clear
• Made NetworkSceneManagerDefault.OnSceneInfoChanged method virtual
• NetworkObjects that remains after shared mode authority leaves now has state authority set to PlayerRef.None
• DestroyWhenStateAuthorityLeaves prefab flag is now independent from the AllowStateAuthorityOverride
• Shared mode master client can now despawn network objects with PlayerRef.None as state authority
• Apply NetworkTransform.DisableSharedModeInterpolation in Single Mode

Removed

• EngineProfiler, the old DLL-side profiler integration
• FusionProfiler, the old Unity-side profiler integration

Bug Fixes

• Fixed: Empty IntrusiveLinkedListNode is now different than the one in a single-element list. This is done by the list always being cyclical
• Fixed: Fusion plugin crashing during stress tests due to the number of RPC to be tracked in an envelope
• Fixed: VisionOS NanoSockets Static Library
• Fixed: Prefabs not being replicated until a resimulation tick occur
• Fixed: MenuItem attribute preventing builds
• Fixed: Reset re-join attempts when peer is able to join Session
• Fixed: First item in SimulationConfig (ReplicationFeatures) does not draw it's help correctly in Unity inspector
• Fixed: Object destroys not being resent in case of a packet loss
• Fixed: OnNotifyDataLost ignoring objects/destroys if there haven't been any RPCs in the packet as well
• Fixed: Stop repeated Unity warning logging if simulating multi peer physics scenes by not simulating the default scene
• Fixed: RPCs targeting state authority were not being received when outside the area of interest
• Fixed: Alloc in NetSocketHybrid.Receive
• Fixed: Alloc in TimeSeries.Median
• Fixed: NetworkArray<T>.GetRef throwing NullReferenceException
• Fixed: NetworkBool drawer throwing ArgumentOutOfRangeException
• Fixed: Editor error when interacting with invalid network objects. Header can be uninitialized and causes null ref, checking Ptr to avoid it
• Fixed: Crash in some Unity versions when opening the project in batch mode due to forced recompilation
• Fixed: [Shared Mode] data not being sent to a client if the previous packet has just been acknowledged
• Fixed: Invalid authority checks when destroying hierarchies of NetworkObjects with mixed authorities
• Fixed: Error logged when input authority invokes RPC with state authority target mask
• Fixed: In Shared Mode, if a state authority makes a state change which races against the server removing state authority from it, then flag the original state needing to be re-sent
• Fixed: [Shared Mode] Pending local deletes being ignored when receiving object updates
• Fixed: Shutdown normally if Disconnected By PluginLogic
• Fixed: Use StartGameArgs.Config for PlayerCount, if supplied
• Fixed: Runtime spawned objects in scene are spawned/despawned multiple times in scene unload with a large amount of objects
• Fixed: WriteUsingAreOfInterest not terminating data block properly
• Fixed: Structs state authority not checked before writing
• Fixed: Received objects state authority not checked before applying
• Fixed: Plugin not deserializing private serializable fields of base types
• Fixed: Plugin exporter adding preserved protected fields to sub types
• Fixed: Prefab table not updating if running in batchmode
• Fixed: Client not rolling objects back to latest snapshot state in certain conditions
• Fixed: Data RPCs are no longer limited to be 1MB in size
• Fixed: SendReliableData always sending 1MB of data
• Fixed: SimulationPacketEnvelope not freed on packet delivered
• Fixed: BitScanReverse64 always returning one too high
• Fixed: Client sometimes not updating LatestServerTick after receiving a new snapshot
• Fixed: Unable to update Session properties after Host Migration
• Fixed: RPCs failing to send arrays
• Fixed: NullReferenceException when trying to spawn a prefab with NetworkObject reference without object provider being set
• Fixed: Simulation.Add/RemoveAlwaysInterested not working in Shared Mode
• Fixed: Incorrect reset/jump of time on proxy objects after a frame of exceptionally long duration
• Fixed: Lag Compensation box overlap problem with hitbox Y rotation
• Fixed: A sequence of lost packets resulting in a partial object data being sent
• Fixed: Lag Compensation box overlap having problems with hitboxes offset
• Fixed: Unable to spawn during StateAuthorityChanged callback on MasterClientObjects
• Fixed: Intro Sample Menu Dependency
• Fixed: Lag compensation layer masks being ignored with subtick accuracy
• Fixed: Odin drawers not finding underlying fields
• Fixed: NetworkObject.IsSpawnable setter not working
• Fixed: RPCs not being forwarded to stateauth (exclusive)
• Fixed: RpcSerializer offset error
• Fixed: Plugin can override state auth data again
• Fixed: Invalid copy of state-auth data for transforms
• Fixed: Not being able to send changes to plugin-spawned objects
• Fixed: RpcInfo.Source in single player mode now correctly points to the source player
• Fixed: NetworkRunner.SessionInfo Support for Single Player