engine v5.1.6

Engine v5.1.6

June 26, 2026

A patch in the Connection line.

what's new

Large terrain worlds spend much less CPU maintaining stable physics colliders.
Weapons and other items attached to animated characters no longer jitter or warp while the character moves.
Objects you add or delete in GOD-MODE now stay added or deleted in multiplayer worlds.
Custom events triggered by interactions now work reliably in multiplayer, including while players join, leave, or host simulation changes hands.
A broken UI handler now leaves the last working UI in place and tells Savi which UI script needs repair.
Sprites now appear reliably during startup even when camera setup changes while their shaders compile.
Preloaded voice lines and sound effects now play immediately even when their optimized audio version is still being prepared in the background.

›technical notes

Made client terrain-collider tracking change-driven: collider installs, removals, despawns, runtime resets, and place cleanup now update readiness indexes directly. Physics ticks poll only unresolved installs, with a low-frequency full audit for recovery. In the captured large voxel world, tracking CPU fell by 93-98%.
Fixed bone-attached props receiving a second synthetic transform interpolation pass after their world transforms had already been derived from the displayed rig pose.
Fixed client-auth GOD-MODE structural edits so persistence trackers capture and save object spawns and deletes through the authoritative room sink, while the accepted batch immediately advances the room's live game spec.
Fixed client-auth custom event delivery by resolving ready clients through their durable session owner instead of the cleared join handoff field.
Preserved interaction-scoped authority for api.emit() calls when a place host changes while a forwarded onInteract hook is running.
Limit the iframe shell's generic window-error startup boundary to loading and evaluating index.js; after import, the engine's explicit startup producers and permanent client-error forwarding rail retain ownership.
Validate inline Tome UI event handlers before mounting rendered HTML, reject a render containing a malformed handler, and report a script-attributed ui.render fault instead of silently rewriting the authored UI.
Kept post-processing scene render targets alive until asynchronous WebGPU material compilation finishes reading their color and depth attachment descriptors. Camera or scene graph rebuilds can no longer invalidate depthStencil.format during pipeline creation.
Optional Ogg Opus audio companions no longer park the logical clip when their Magic CDN encode is still generating or unavailable before the CDN session is established. The loader starts companion generation, downgrades that clip registration, and immediately fetches and decodes the authored MP3, preserving preloadAsset() readiness while retaining Opus on later sessions.

what's new

Large terrain worlds spend much less CPU maintaining stable physics colliders.
Weapons and other items attached to animated characters no longer jitter or warp while the character moves.
Objects you add or delete in GOD-MODE now stay added or deleted in multiplayer worlds.
Custom events triggered by interactions now work reliably in multiplayer, including while players join, leave, or host simulation changes hands.
A broken UI handler now leaves the last working UI in place and tells Savi which UI script needs repair.
Sprites now appear reliably during startup even when camera setup changes while their shaders compile.
Preloaded voice lines and sound effects now play immediately even when their optimized audio version is still being prepared in the background.