diff --git a/web/filament-js/extensions.js b/web/filament-js/extensions.js
index 32d6938812..baaf47c7fc 100644
--- a/web/filament-js/extensions.js
+++ b/web/filament-js/extensions.js
@@ -73,16 +73,35 @@ Filament.loadClassExtensions = function() {
 
         // Create the WebGL 2.0 context.
         const ctx = canvas.getContext("webgl2", options);
-        Filament.glOptions = options;
-        Filament.glContext = ctx;
 
         // Enable all desired extensions by calling getExtension on each one.
         ctx.getExtension('WEBGL_compressed_texture_s3tc');
         ctx.getExtension('WEBGL_compressed_texture_astc');
         ctx.getExtension('WEBGL_compressed_texture_etc');
 
+        // These transient globals are used temporarily during Engine construction.
+        window.filament_glOptions = options;
+        window.filament_glContext = ctx;
+
         // Register the GL context with emscripten and create the Engine.
-        return Filament.Engine._create();
+        const engine = Filament.Engine._create();
+
+        // Annotate the engine with the GL context to support multiple canvases.
+        engine.context = window.filament_glContext;
+        engine.handle = window.filament_contextHandle;
+
+        // Ensure that we do not pollute the global namespace.
+        delete window.filament_glOptions;
+        delete window.filament_glContext;
+        delete window.filament_contextHandle;
+
+        return engine;
+    };
+
+    Filament.Engine.prototype.execute = function() {
+        window.filament_contextHandle = this.handle;
+        this._execute();
+        delete window.filament_contextHandle;
     };
 
     /// createMaterial ::method::
diff --git a/web/filament-js/jsbindings.cpp b/web/filament-js/jsbindings.cpp
index 33a7c27cc9..7ddcf6a781 100644
--- a/web/filament-js/jsbindings.cpp
+++ b/web/filament-js/jsbindings.cpp
@@ -472,16 +472,27 @@ register_vector<const MaterialInstance*>("MaterialInstanceVector");
 class_<Engine>("Engine")
     .class_function("_create", (Engine* (*)()) [] {
         EM_ASM_INT({
-            const handle = GL.registerContext(Filament.glContext, Filament.glOptions);
+            const options = window.filament_glOptions;
+            const context = window.filament_glContext;
+            const handle = GL.registerContext(context, options);
+            window.filament_contextHandle = handle;
             GL.makeContextCurrent(handle);
         });
         return Engine::create();
     }, allow_raw_pointers())
+
+    .function("_execute", EMBIND_LAMBDA(void, (Engine* engine), {
+        EM_ASM_INT({
+            const handle = window.filament_contextHandle;
+            GL.makeContextCurrent(handle);
+        });
+        engine->execute();
+    }), allow_raw_pointers())
+
     /// destroy ::static method:: Destroys an engine instance and cleans up resources.
     /// engine ::argument:: the instance to destroy
     .class_function("destroy", (void (*)(Engine*)) []
             (Engine* engine) { Engine::destroy(&engine); }, allow_raw_pointers())
-    .function("execute", &Engine::execute)
 
     /// getTransformManager ::method::
     /// ::retval:: an instance of [TransformManager]