Release Notes

Migrating to the Latest Fusion SDK

If you are upgrading an existing project from an earlier 3.x preview, walk through the five steps below.

1. FusionClient Singleton Renamed to Fusion

Project-wide find/replace FusionClient. → Fusion. covers almost everything.
The C++ class name is still FusionClient; only the GDScript singleton was renamed.

2. Remove initialize_from_settings()

Fusion now self-initializes from project settings.
Delete any initialize_from_settings() calls and the surrounding is_initialized() guard.
Use Fusion.set_app_id(...) only if you need to override the App ID at runtime (per-build flavor, remote config); otherwise put it in Project Settings and call connect_to_photon() directly.

3. Connection Symbols: server → photon

Before	After
connect_to_server()	connect_to_photon()
is_connected_to_server()	is_connected_to_photon()
disconnect_from_server()	disconnect_from_photon()
connected_to_server (signal)	connected_to_photon
STATUS_CONNECTING	STATUS_CONNECTING_TO_PHOTON
STATUS_CONNECTED	STATUS_CONNECTED_TO_PHOTON

Other STATUS_* values (STATUS_DISCONNECTED, STATUS_JOINING_ROOM, STATUS_IN_ROOM, STATUS_ERROR) are unchanged.
The rename disambiguates "connecting to the Photon Cloud" from the Client-Server topology's simulation-server role.

4. FusionReplicator → FusionSharedReplicator

FusionReplicator is now an abstract base.
For each replicator node in your scenes: right-click in the Scene tree → Change Type… → FusionSharedReplicator, then save.
Use FusionServerReplicator instead if your room uses Client-Server topology with input prediction.

Update script types to match:

GDScript

@onready var replicator: FusionSharedReplicator = $FusionReplicator

5. Re-check root_interpolation_mode

The InterpolationMode enum was simplified from four modes to two, so saved integers in .tscn files now resolve to different modes.

	Old enum	New enum
0	INTERPOLATION_SPRING_DAMPER (default)	INTERPOLATION_SNAPSHOT
1	INTERPOLATION_SNAPSHOT	INTERPOLATION_EXPONENTIAL (default)
2	INTERPOLATION_SIMPLE_LERP	(removed)
3	INTERPOLATION_EXPONENTIAL	(removed)

Open each replicator and confirm Root Interpolation Mode in the Inspector matches your intent; reset if not.
The exponential mode was previously called ASYMPTOTIC and its tuning property prefix changed from root_asym_* to root_smooth_*.

Exponential Decay is the new default for non-physics smoothing (replacing the removed Spring Damper).
Two error-detection thresholds gate its behaviour: root_max_smooth_dist (above this position error, a catch-up term blends in) and root_no_smooth_dist (above this error, the value snaps).
Both are world-space distances, so suitable values differ by an order of magnitude between 2D scenes (pixels) and 3D scenes (meters); the defaults (2.0 and 5.0) target 3D and likely need to be raised for 2D projects.

3.0.0

Preview

Build 424 (May 07, 2026)

What's New

• Warning for non replicable type
• Property path validator with warning icon for replicator

Bug Fixes

• Fixed: Issue with wrong data in stats and monitors
• Fixed: Added missing web paths to fusion.gdextension
• Fixed: Added missing web export templates
• Fixed: Issues with authority switch API
• Fixed: Ungarded spawn time log is now INFO
• Fixed: Issue where replicated property settings could be lost when rearranging scene trees

Build 407 (May 05, 2026)

Breaking Changes

• The singleton previously exposed as FusionClient is now Fusion. The connect-related methods, signal, and status enums were renamed to disambiguate "connecting to the Photon Cloud" from the Client-Server topology's simulation-server role (where a local peer can itself be the "server")

What's New

• Asymptotic decay interpolation mode
• Hability to overhaul shared/auth mode
• Player_joined signal (safe with handshake)
• Pre_spawn_function callable to Spawn()
• Support for RPCs in sub-nodes
• Added inspector tooltips for spawn_as_sub_object, spawn_map_mode, and bound_map_index on FusionSpawner
• Added Fusion.player_left(player_id: int, is_inactive: bool) signal - fires on every peer when a remote player leaves the room. is_inactive distinguishes a TTL-grace disconnect from a permanent leave. In Client-Server topology, the master client uses this to despawn the departed player's character (see the "Despawning on Player Leave" section in Spawning)
• Note: player_joined is intentionally not exposed in this release — Photon's underlying event fires before Fusion finishes starting locally. A reliable join notification will arrive later via an internal broadcast RPC

Changes

• Updated fusion core to protocol v8
• Support to authority switch transaction
• Cleaned up logging for disambiguation
• Refactored input api
• Naming consistency: signal on_process_input(), and process_input(delta) as main entry point
• Changed (potentially breaking): FusionSpawner no longer auto-binds as a sub-spawner when placed under a FusionSharedReplicator. Sub-spawner mode is now opt-in via the inspector Spawn As Sub Object toggle or via bind_root_replicator(). Existing scenes using the explicit API are unaffected
• Changed (potentially breaking): FusionSpawner.spawn_map_mode default is now Bound (was Unbound). Spawners inside a registered scene now spawn into that scene's map by default. Set to Unbound to opt back into the global-map behavior
• Migration
• | Before | After |
• | --- | --- |
• | FusionClient.xxx | Fusion.xxx |
• | FusionClient.initialize(app_id, version) | Fusion.set_app_id(app_id) — drop the version. Set fusion/connection/app_version in Project Settings, or pass it via connect_to_photon(..., app_version) |
• | FusionClient.initialize_from_settings() | Delete the call — connect_to_photon() initializes from settings automatically |
• | FusionClient.connect_to_server(...) | Fusion.connect_to_photon(...) — same signature |
• | FusionClient.disconnect_from_server() | Fusion.disconnect_from_photon() |
• | FusionClient.is_connected_to_server() | Fusion.is_connected_to_photon() |
• | FusionClient.connected_to_server (signal) | Fusion.connected_to_photon |
• | STATUS_CONNECTING | STATUS_CONNECTING_TO_PHOTON |
• | STATUS_CONNECTED | STATUS_CONNECTED_TO_PHOTON |
• Other status values (STATUS_DISCONNECTED, STATUS_JOINING_ROOM, STATUS_IN_ROOM, STATUS_ERROR), signals, room APIs, RPC APIs, scene APIs, interest/AOI APIs and all other members are unchanged — only the connect-related surface was touched
• The initialize(app_id, app_version) and initialize_from_settings() methods are no longer part of the public API. Use set_app_id() for runtime App ID overrides (e.g., per-build flavor, remote config); otherwise put your App ID in Project Settings and call connect_to_photon() directly

Bug Fixes

• Fixed: Spawn guarded on client-server mode clients
• Fixed: Call-local ignored on target not matching
• Fixed: Call-local now has rpcinfo and sender
• Fixed: Usion monitors under wrong category

20/03/2026

• Fixed crash on disconnect when replicated string properties are active (use-after-free in string handle cleanup)
• Fixed crash when nodes are modified on despawn
• Fixed disconnect on app close not being detected
• Fixed join_room and join_or_create_room with empty name failing instead of using random matchmaking
• Changed improved snapshot interpolation with asymmetric delay adaptation (faster recovery, slower spike reaction)
• Changed exposed snapshot interpolation tuning parameters in inspector (max_snapshot_gap, adapt_speed_up, adapt_speed_down, max_delay)
• Changed decoupled position and rotation teleport detection (each evaluated independently)
• Changed RPC ID hash now includes script class path for uniqueness across scripts
• Added teleport snap mode setting (Source vs Projected) for forecast handler
• Fixed forecast teleports being applied for both rot/pos if only one triggered
• Fixed large-scene hash clash on nodes with same name
• Fixed broadcast RPCs not working due to a wrong early check for replicators (not needed)
• Fixed rotation teleport threshold 0 and 360 now both disable rotation teleport detection
• Fixed position teleport threshold 0 now disables position teleport detection

18/02/2026

• Added despawn_on_disconnect option to FusionSpawner - controls whether spawned objects are automatically cleaned up when the owning client leaves (enabled by default)
• Added scene_unloaded signal to Fusion - emitted during disconnect cleanup before the auto-loaded scene is freed
• Fixed disconnect callbacks not being processed correctly

17/02/2026

• Added auto-sync of velocity property for CharacterBody2D/3D roots (no manual .tres config needed)
• Fixed Replication Editor panel selector not updating when switching between nodes in the scene tree

12/02/2026

• Fixed editor plugin crash on startup by migrating from deprecated add_control_to_bottom_panel() to new Godot 4.6 EditorDock + add_dock() API
• Changed FusionReplicationEditor base class from VBoxContainer to EditorDock with DOCK_SLOT_BOTTOM default slot
• Fixed infinite NOTIFICATION_THEME_CHANGED loop caused by add_theme_stylebox_override() on EditorDock
• Removed timer-based deferred setup workaround in FusionEditorPlugin (no longer needed)

09/02/2026

• Added sub-objects (dynamic sub-object add)
• Added support for scene/map-objects (and setting for auto loader)
• Added update interval setting
• Fixed array tree editor support (capacity)
• Removed rate from Settings
• Updated Fusion to 3.0.0.728

06/02/2026

• Removed duplicated shadow-copy test from GDExtension plugin
• Fixed other minor concerns from code review

05/02/2026

• Added string serialization support (using string heap)
• Added support for arrays

04/02/2026

• Added different ownership modes to the settings
• Added physics and forecast replication (+ demo and docs)
• Refactored replication mode architecture: transform/physics data auto-synced without .tres config
• Added SmoothingMode enum (None, Interpolate, Forecast)
• Added sleeping state replication for physics objects
• Simplified demo scripts (removed manual interpolation code)

03/02/2026

• Updated to latest Fusion core (3.0.0.625)
• Added main settings asset for Fusion config
• Improved remote object updates using Client->HasBeenUpdatedByPlugin

Back to top