diff --git a/src/common/pages/code.js b/src/common/pages/code.js
index b763f079..8dc1a455 100644
--- a/src/common/pages/code.js
+++ b/src/common/pages/code.js
@@ -222,7 +222,7 @@ export function handleBuildFormSubmit() {
   const importBtn = document.querySelector("#import-button");
   const importInput = document.querySelector("#import-input");
 
-  importBtn?.addEventListener("click", () => importInput?.click());
+  importBtn?.addEventListener("click", () => /** @type {HTMLElement} */ (importInput)?.click());
 
   importInput?.addEventListener("change", async (event) => {
     const file = /** @type {HTMLInputElement} */ (event.target).files?.[0];
diff --git a/src/components/engine/audio/element.js b/src/components/engine/audio/element.js
index 9bcc105a..d75d8455 100644
--- a/src/components/engine/audio/element.js
+++ b/src/components/engine/audio/element.js
@@ -623,6 +623,9 @@ class AudioEngineItem extends BroadcastableDiffuseElement {
 
   /**
    * @override
+   * @param {string} name
+   * @param {string} oldValue
+   * @param {string} newValue
    */
   attributeChangedCallback(name, oldValue, newValue) {
     super.attributeChangedCallback(name, oldValue, newValue);
diff --git a/src/components/orchestrator/media-session/element.js b/src/components/orchestrator/media-session/element.js
index 9c5565aa..5750a50b 100644
--- a/src/components/orchestrator/media-session/element.js
+++ b/src/components/orchestrator/media-session/element.js
@@ -8,6 +8,8 @@ import {
 /**
  * @import {OutputElement} from "~/components/output/types.d.ts"
  * @import ArtworkOrchestrator from "~/components/orchestrator/artwork/element.js"
+ * @import {default as AudioEngine} from "~/components/engine/audio/element.js"
+ * @import {default as QueueEngine} from "~/components/engine/queue/element.js"
  */
 
 ////////////////////////////////////////////
@@ -36,9 +38,13 @@ class MediaSessionOrchestrator extends BroadcastableDiffuseElement {
 
     if (!("mediaSession" in navigator)) return;
 
+    /** @type {AudioEngine} */
     this.audio = query(this, "audio-engine-selector");
+    /** @type {QueueEngine} */
     this.queue = query(this, "queue-engine-selector");
+    /** @type {OutputElement | null} */
     this.output = queryOptional(this, "output-selector");
+    /** @type {ArtworkOrchestrator | null} */
     this.artwork = queryOptional(this, "artwork-selector");
 
     await Promise.all([
diff --git a/src/facets/themes/winamp/window-manager/element.js b/src/facets/themes/winamp/window-manager/element.js
index d10c2a34..14c9b38a 100644
--- a/src/facets/themes/winamp/window-manager/element.js
+++ b/src/facets/themes/winamp/window-manager/element.js
@@ -88,7 +88,7 @@ class WindowManager extends DiffuseElement {
         const target = mutation.target;
         if (!(target instanceof HTMLElement) || !target.id) continue;
         const isOpen = target.hasAttribute("open");
-        const state = this.#loadState(target.id) ?? {};
+        const state = this.#loadState(target.id) ?? /** @type {{ left: string; top: string; width?: string; height?: string; open?: boolean }} */ ({});
         this.#saveState(
           target.id,
           state.left ?? target.style.left,
@@ -120,7 +120,7 @@ class WindowManager extends DiffuseElement {
         if (!initialized) { initialized = true; return; }
         const { width, height } = body.getBoundingClientRect();
         if (width === 0 || height === 0) return;
-        const state = this.#loadState(w.id) ?? {};
+        const state = this.#loadState(w.id) ?? /** @type {{ left: string; top: string; width?: string; height?: string; open?: boolean }} */ ({});
         this.#saveState(
           w.id,
           state.left ?? w.style.left,
@@ -251,7 +251,7 @@ class WindowManager extends DiffuseElement {
 
       const target = ogEvent.detail.element;
       if (target instanceof HTMLElement && target.id) {
-        const state = this.#loadState(target.id) ?? {};
+        const state = this.#loadState(target.id) ?? /** @type {{ left: string; top: string; width?: string; height?: string; open?: boolean }} */ ({});
         this.#saveState(target.id, target.style.left, target.style.top, state.width, state.height, state.open);
       }
     };
@@ -302,7 +302,7 @@ class WindowManager extends DiffuseElement {
           const stagger = index * 12;
           w.style.left = `${Math.round(Math.max(0, (window.innerWidth - width) / 2) + stagger)}px`;
           w.style.top = `${Math.round(Math.max(0, (window.innerHeight - height) / 2) + stagger)}px`;
-          const state = this.#loadState(id) ?? {};
+          const state = this.#loadState(id) ?? /** @type {{ left: string; top: string; width?: string; height?: string; open?: boolean }} */ ({});
           this.#saveState(id, w.style.left, w.style.top, state.width, state.height, state.open);
         };
         requestAnimationFrame(placeWindow);
diff --git a/src/oauth/lock.js b/src/oauth/lock.js
index 3a62a47f..d0cc8448 100644
--- a/src/oauth/lock.js
+++ b/src/oauth/lock.js
@@ -9,6 +9,7 @@
 // This lock serialises all library operations so only one module at a time
 // owns the global state.
 
+/** @type {Promise<unknown>} */
 let _chain = Promise.resolve();
 
 /**