diff --git a/frontend/apps/artcraft-website-next/src/components/landing/hero-wordmark.tsx b/frontend/apps/artcraft-website-next/src/components/landing/hero-wordmark.tsx
--- a/frontend/apps/artcraft-website-next/src/components/landing/hero-wordmark.tsx
+++ b/frontend/apps/artcraft-website-next/src/components/landing/hero-wordmark.tsx
@@ -166,7 +166,7 @@ export default function HeroMasthead() {
     };
 
     const ready = document.fonts?.ready;
-    if (ready) ready.then(compute).catch(compute);
+    if (ready !== undefined) ready.then(compute).catch(compute);
     else compute();
     const ro = new ResizeObserver(compute);
     ro.observe(box);
diff --git a/frontend/apps/artcraft-website-next/src/components/ruler/heading-flow.tsx b/frontend/apps/artcraft-website-next/src/components/ruler/heading-flow.tsx
--- a/frontend/apps/artcraft-website-next/src/components/ruler/heading-flow.tsx
+++ b/frontend/apps/artcraft-website-next/src/components/ruler/heading-flow.tsx
@@ -167,7 +167,7 @@ export default function HeadingFlow({
       setMetrics(measureLabels(sections.map((s) => s.label)));
     };
     const ready = document.fonts?.ready;
-    if (ready) ready.then(run).catch(run);
+    if (ready !== undefined) ready.then(run).catch(run);
     else run();
     return () => {
       cancelled = true;
diff --git a/frontend/libs/components/create-3d-modal/src/lib/create-3d-modal.tsx b/frontend/libs/components/create-3d-modal/src/lib/create-3d-modal.tsx
--- a/frontend/libs/components/create-3d-modal/src/lib/create-3d-modal.tsx
+++ b/frontend/libs/components/create-3d-modal/src/lib/create-3d-modal.tsx
@@ -38,7 +38,7 @@ export const Create3dModal = ({ onModelComplete }: Create3dModalProps = {}) => {
   // Listen for generation complete events
   useEffect(() => {
     let isUnmounted = false;
-    let unlisten: Promise<UnlistenFn>;
+    let unlisten: Promise<UnlistenFn> | undefined;
 
     const setup = async () => {
       unlisten = listen("generation-complete-event", (event: any) => {
@@ -102,7 +102,7 @@ export const Create3dModal = ({ onModelComplete }: Create3dModalProps = {}) => {
 
     return () => {
       isUnmounted = true;
-      if (unlisten) {
+      if (unlisten !== undefined) {
         unlisten.then((f) => f());
       }
     };
diff --git a/frontend/libs/components/pagescene/src/lib/DragAndDrop/DndAsset.ts b/frontend/libs/components/pagescene/src/lib/DragAndDrop/DndAsset.ts
--- a/frontend/libs/components/pagescene/src/lib/DragAndDrop/DndAsset.ts
+++ b/frontend/libs/components/pagescene/src/lib/DragAndDrop/DndAsset.ts
@@ -273,7 +273,7 @@ class DndAsset {
       return;
     }
     const inspection = this.clipNodeNamesCache.get(item.media_id);
-    if (!inspection) {
+    if (inspection === undefined) {
       // No inspection in flight (shouldn't happen — pointer-down starts
       // one): add unvalidated, matching the ungated click-to-add path.
       this.completeAnimationDrop(editor, item, target, undefined);
diff --git a/frontend/libs/components/pagescene/src/lib/engine/ammoLoader.ts b/frontend/libs/components/pagescene/src/lib/engine/ammoLoader.ts
--- a/frontend/libs/components/pagescene/src/lib/engine/ammoLoader.ts
+++ b/frontend/libs/components/pagescene/src/lib/engine/ammoLoader.ts
@@ -8,7 +8,7 @@
 let ammoLoadPromise: Promise<void> | null = null;
 
 export const ensureAmmoLoaded = (): Promise<void> => {
-  if (ammoLoadPromise) return ammoLoadPromise;
+  if (ammoLoadPromise !== null) return ammoLoadPromise;
 
   ammoLoadPromise = new Promise<void>((resolve, reject) => {
     if (typeof document === "undefined") {
diff --git a/frontend/libs/components/pagescene/src/lib/engine/scene.ts b/frontend/libs/components/pagescene/src/lib/engine/scene.ts
--- a/frontend/libs/components/pagescene/src/lib/engine/scene.ts
+++ b/frontend/libs/components/pagescene/src/lib/engine/scene.ts
@@ -1026,22 +1026,21 @@ class Scene {
     onComplete: () => void,
     signal?: AbortSignal,
   ): Promise<GLTF> {
-    return new Promise<GLTF>(async (resolve, reject) => {
-      let buffer;
-      try {
-        // Host-supplied CORS-bypassed binary fetch (FetchProxy under
-        // Tauri; plain fetch under web hosts that allow it).
-        buffer = await (
-          await this.deps.fetchAsset(media_url, { signal })
-        ).arrayBuffer();
-      } catch (error) {
-        if ((error as { name?: string })?.name !== "AbortError") {
-          console.error("load GLB from Tauri error:", error);
-        }
-        reject(error);
-        return;
+    let buffer;
+    try {
+      // Host-supplied CORS-bypassed binary fetch (FetchProxy under
+      // Tauri; plain fetch under web hosts that allow it).
+      buffer = await (
+        await this.deps.fetchAsset(media_url, { signal })
+      ).arrayBuffer();
+    } catch (error) {
+      if ((error as { name?: string })?.name !== "AbortError") {
+        console.error("load GLB from Tauri error:", error);
       }
-      const glbLoader = new GLTFLoader();
+      throw error;
+    }
+    const glbLoader = new GLTFLoader();
+    return new Promise<GLTF>((resolve, reject) => {
       glbLoader.parse(
         buffer,
         "", // NB: No relative path to load additional assets!
@@ -1068,22 +1067,21 @@ class Scene {
     onComplete: () => void,
     signal?: AbortSignal,
   ): Promise<SplatMesh> {
-    return new Promise(async (resolve, reject) => {
-      let buffer;
-      try {
-        // Host-supplied CORS-bypassed binary fetch (FetchProxy under
-        // Tauri; plain fetch under web hosts that allow it).
-        buffer = await (
-          await this.deps.fetchAsset(media_url, { signal })
-        ).arrayBuffer();
-      } catch (error) {
-        if ((error as { name?: string })?.name !== "AbortError") {
-          console.error("load Splat from Tauri error:", error);
-        }
-        reject(error);
-        return;
+    let buffer;
+    try {
+      // Host-supplied CORS-bypassed binary fetch (FetchProxy under
+      // Tauri; plain fetch under web hosts that allow it).
+      buffer = await (
+        await this.deps.fetchAsset(media_url, { signal })
+      ).arrayBuffer();
+    } catch (error) {
+      if ((error as { name?: string })?.name !== "AbortError") {
+        console.error("load Splat from Tauri error:", error);
       }
+      throw error;
+    }
 
+    return new Promise<SplatMesh>((resolve) => {
       new SplatMesh({
         fileBytes: buffer,
         onLoad: (mesh) => {
diff --git a/frontend/libs/components/pagescene/src/lib/engine/scene_manager_api.ts b/frontend/libs/components/pagescene/src/lib/engine/scene_manager_api.ts
--- a/frontend/libs/components/pagescene/src/lib/engine/scene_manager_api.ts
+++ b/frontend/libs/components/pagescene/src/lib/engine/scene_manager_api.ts
@@ -32,15 +32,21 @@ export type SceneObject = {
 };
 
 export interface SceneManagerAPI {
-  create(media_token: string, name: string, position: THREE.Vector3): void;
-  retrieve(object_uuid: string): void;
-  delete(object_uuid: string): void;
+  create(
+    media_token: string,
+    name: string,
+    position: THREE.Vector3,
+  ): Promise<THREE.Object3D<THREE.Object3DEventMap> | undefined>;
+  retrieve(
+    object_uuid: string,
+  ): Promise<THREE.Object3D<THREE.Object3DEventMap> | undefined>;
+  delete(object_uuid: string): Promise<void>;
   update(
     object_uuid: string,
     position: THREE.Vector3,
     rotation: THREE.Euler,
     scale: THREE.Vector3,
-  ): void;
+  ): Promise<void>;
   selected(): void;
   render_outliner(timeline_characters: { [key: string]: ClipGroup }): void;
   select_object(id: string): void;
diff --git a/frontend/libs/components/upload-modal/src/lib/UploadModal3D/utilities/convertFbxToGlb.worker.ts b/frontend/libs/components/upload-modal/src/lib/UploadModal3D/utilities/convertFbxToGlb.worker.ts
--- a/frontend/libs/components/upload-modal/src/lib/UploadModal3D/utilities/convertFbxToGlb.worker.ts
+++ b/frontend/libs/components/upload-modal/src/lib/UploadModal3D/utilities/convertFbxToGlb.worker.ts
@@ -23,26 +23,28 @@ const scope = self as unknown as {
   postMessage: (message: ConvertResponse, transfer?: Transferable[]) => void;
 };
 
-scope.onmessage = async (event) => {
-  const { id, buffer } = event.data;
-  try {
-    const group = new FBXLoader().parse(buffer, "");
-    const glb = await new Promise<ArrayBuffer>((resolve, reject) => {
-      new GLTFExporter().parse(
-        group,
-        (result) => {
-          if (result instanceof ArrayBuffer) {
-            resolve(result);
-          } else {
-            reject(new Error("GLTF export did not produce binary output."));
-          }
-        },
-        (error) => reject(error),
-        { binary: true, animations: group.animations ?? [] },
-      );
-    });
-    scope.postMessage({ id, ok: true, glb }, [glb]);
-  } catch (error) {
-    scope.postMessage({ id, ok: false, error: String(error) });
-  }
+scope.onmessage = (event) => {
+  void (async () => {
+    const { id, buffer } = event.data;
+    try {
+      const group = new FBXLoader().parse(buffer, "");
+      const glb = await new Promise<ArrayBuffer>((resolve, reject) => {
+        new GLTFExporter().parse(
+          group,
+          (result) => {
+            if (result instanceof ArrayBuffer) {
+              resolve(result);
+            } else {
+              reject(new Error("GLTF export did not produce binary output."));
+            }
+          },
+          (error) => reject(error),
+          { binary: true, animations: group.animations ?? [] },
+        );
+      });
+      scope.postMessage({ id, ok: true, glb }, [glb]);
+    } catch (error) {
+      scope.postMessage({ id, ok: false, error: String(error) });
+    }
+  })();
 };
diff --git a/frontend/libs/components/video-editor/src/lib/core/managers/audio-manager.ts b/frontend/libs/components/video-editor/src/lib/core/managers/audio-manager.ts
--- a/frontend/libs/components/video-editor/src/lib/core/managers/audio-manager.ts
+++ b/frontend/libs/components/video-editor/src/lib/core/managers/audio-manager.ts
@@ -539,7 +539,7 @@ export class AudioManager {
   }): Promise<AudioBuffer | null> {
     const cacheKey = this.buildPreparedClipCacheKey({ clip });
     const existing = this.preparedClipBuffers.get(cacheKey);
-    if (existing) {
+    if (existing !== undefined) {
       return existing;
     }
 
@@ -574,7 +574,7 @@ export class AudioManager {
     clip: AudioClipSource;
   }): Promise<AudioBuffer | null> {
     const existing = this.decodedBuffers.get(clip.sourceKey);
-    if (existing) {
+    if (existing !== undefined) {
       return existing;
     }
 
diff --git a/frontend/libs/components/video-editor/src/lib/fonts/google-fonts.ts b/frontend/libs/components/video-editor/src/lib/fonts/google-fonts.ts
--- a/frontend/libs/components/video-editor/src/lib/fonts/google-fonts.ts
+++ b/frontend/libs/components/video-editor/src/lib/fonts/google-fonts.ts
@@ -26,7 +26,7 @@ export function clearFontAtlasCache(): void {
 
 export function loadFontAtlas(): Promise<FontAtlas | null> {
   if (cachedAtlas) return Promise.resolve(cachedAtlas);
-  if (atlasFetchPromise) return atlasFetchPromise;
+  if (atlasFetchPromise !== null) return atlasFetchPromise;
 
   atlasFetchPromise = fetch(FONT_ATLAS_PATH)
     .then(async (response) => {
diff --git a/frontend/libs/components/video-editor/src/lib/services/renderer/nodes/image-node.ts b/frontend/libs/components/video-editor/src/lib/services/renderer/nodes/image-node.ts
--- a/frontend/libs/components/video-editor/src/lib/services/renderer/nodes/image-node.ts
+++ b/frontend/libs/components/video-editor/src/lib/services/renderer/nodes/image-node.ts
@@ -35,7 +35,7 @@ export function loadImageSource({
   const cacheKey = `${url}::${maxSourceSize ?? "full"}`;
 
   const cached = imageSourceCache.get(cacheKey);
-  if (cached) return cached;
+  if (cached !== undefined) return cached;
 
   const promise = (async (): Promise<CachedImageSource> => {
     const image = new Image();
diff --git a/frontend/libs/components/video-editor/src/lib/services/renderer/nodes/sticker-node.ts b/frontend/libs/components/video-editor/src/lib/services/renderer/nodes/sticker-node.ts
--- a/frontend/libs/components/video-editor/src/lib/services/renderer/nodes/sticker-node.ts
+++ b/frontend/libs/components/video-editor/src/lib/services/renderer/nodes/sticker-node.ts
@@ -25,7 +25,7 @@ export function loadStickerSource({
   stickerId: string;
 }): Promise<CachedStickerSource> {
   const cached = stickerSourceCache.get(stickerId);
-  if (cached) return cached;
+  if (cached !== undefined) return cached;
 
   const promise = (async (): Promise<CachedStickerSource> => {
     const url = resolveStickerId({
diff --git a/frontend/libs/components/video-editor/src/lib/services/video-cache/service.ts b/frontend/libs/components/video-editor/src/lib/services/video-cache/service.ts
--- a/frontend/libs/components/video-editor/src/lib/services/video-cache/service.ts
+++ b/frontend/libs/components/video-editor/src/lib/services/video-cache/service.ts
@@ -170,7 +170,7 @@ export class VideoCache {
 
     try {
       while (true) {
-        if (sinkData.prefetching && sinkData.prefetchPromise) {
+        if (sinkData.prefetching && sinkData.prefetchPromise !== null) {
           await sinkData.prefetchPromise;
         }
 
@@ -215,7 +215,7 @@ export class VideoCache {
     time: number;
   }): Promise<WrappedCanvas | null> {
     try {
-      if (sinkData.prefetching && sinkData.prefetchPromise) {
+      if (sinkData.prefetching && sinkData.prefetchPromise !== null) {
         await sinkData.prefetchPromise;
       }
 
diff --git a/frontend/libs/components/video-editor/src/lib/services/waveform-cache/service.ts b/frontend/libs/components/video-editor/src/lib/services/waveform-cache/service.ts
--- a/frontend/libs/components/video-editor/src/lib/services/waveform-cache/service.ts
+++ b/frontend/libs/components/video-editor/src/lib/services/waveform-cache/service.ts
@@ -27,7 +27,7 @@ export class WaveformCache {
     audioUrl,
   }: GetSourceWaveformSummaryArgs): Promise<SourceWaveformSummary> {
     const existing = this.summaries.get(sourceKey);
-    if (existing) {
+    if (existing !== undefined) {
       return existing;
     }