ui/src/lib/audio.svelte.ts

@@ -85,11 +85,16 @@ class AudioStore {
 	nextChapter = $state<number | null>(null);
 
 	/**
-	 * Set to true by the layout's onended handler (when autoNext fires a
-	 * navigation).  The AudioPlayer on the new page checks this on mount
-	 * and, if true, immediately starts the play flow then clears the flag.
+	 * Set to the chapter number that should auto-start by the layout's onended
+	 * handler (when autoNext fires a navigation).  The AudioPlayer on the new
+	 * page checks this on mount: if it matches the component's own chapter prop
+	 * it starts playback and clears the value.
+	 *
+	 * Using the target chapter number (instead of a plain boolean) prevents the
+	 * still-mounted outgoing AudioPlayer from reacting to the flag before the
+	 * navigation completes — it only matches the incoming chapter's component.
 	 */
-	autoStartPending = $state(false);
+	autoStartChapter = $state<number | null>(null);
 
 	// ── Next-chapter pre-fetch state ─────────────────────────────────────────
 	/**

ui/src/lib/components/AudioPlayer.svelte

@@ -70,9 +70,11 @@
 	});
 
 	// Auto-start: if the layout navigated here via auto-next, kick off playback.
+	// We match against the chapter prop so the outgoing chapter's AudioPlayer
+	// (still mounted during the brief navigation window) never reacts to this.
 	$effect(() => {
-		if (audioStore.autoStartPending) {
-			audioStore.autoStartPending = false;
+		if (audioStore.autoStartChapter === chapter) {
+			audioStore.autoStartChapter = null;
 			startPlayback();
 		}
 	});

ui/src/routes/+layout.svelte

@@ -184,9 +184,11 @@
 			// we need.
 			const targetSlug = audioStore.slug;
 			const targetChapter = audioStore.nextChapter;
-			audioStore.autoStartPending = true;
+			// Store the target chapter number so only the newly-mounted AudioPlayer
+			// for that chapter reacts — not the outgoing chapter's component.
+			audioStore.autoStartChapter = targetChapter;
 			goto(`/books/${targetSlug}/chapters/${targetChapter}`).catch(() => {
-				audioStore.autoStartPending = false;
+				audioStore.autoStartChapter = null;
 			});
 		}
 	}}