From b59759638c1ecd86b13b2284906e4e65a7b5292c Mon Sep 17 00:00:00 2001
From: Gauvain <contact@uruk.dev>
Date: Wed, 8 Jul 2026 18:14:07 +0200
Subject: [PATCH] fix(subtitles): normalize local subtitle sentinel to -1 in
 stream re-negotiation URLs

---
 app/(auth)/player/direct-player.tsx                 | 13 ++++++++++---
 .../video-player/controls/contexts/VideoContext.tsx |  9 ++++++++-
 components/video-player/controls/types.ts           |  8 ++++++++
 3 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/app/(auth)/player/direct-player.tsx b/app/(auth)/player/direct-player.tsx
index 27d9bf0c7..b68bac4c3 100644
--- a/app/(auth)/player/direct-player.tsx
+++ b/app/(auth)/player/direct-player.tsx
@@ -25,7 +25,10 @@ import { Controls } from "@/components/video-player/controls/Controls";
 import { Controls as TVControls } from "@/components/video-player/controls/Controls.tv";
 import { PlayerProvider } from "@/components/video-player/controls/contexts/PlayerContext";
 import { VideoProvider } from "@/components/video-player/controls/contexts/VideoContext";
-import { LOCAL_SUBTITLE_INDEX_START } from "@/components/video-player/controls/types";
+import {
+  LOCAL_SUBTITLE_INDEX_START,
+  toServerSubtitleIndex,
+} from "@/components/video-player/controls/types";
 import {
   PlaybackSpeedScope,
   updatePlaybackSpeedSettings,
@@ -888,7 +891,9 @@ export default function DirectPlayerPage() {
         const queryParams = new URLSearchParams({
           itemId: item?.Id ?? "",
           audioIndex: String(index),
-          subtitleIndex: String(currentSubtitleIndex),
+          // A local (client-downloaded) sub only exists in the dying mpv
+          // instance — the server must be asked for "none" (-1) instead.
+          subtitleIndex: String(toServerSubtitleIndex(currentSubtitleIndex)),
           mediaSourceId: stream?.mediaSource?.Id ?? "",
           bitrateValue: bitrateValue?.toString() ?? "",
           playbackPosition: msToTicks(progress.get()).toString(),
@@ -954,7 +959,9 @@ export default function DirectPlayerPage() {
       const queryParams = new URLSearchParams({
         itemId: item?.Id ?? "",
         audioIndex: params.audioIndex ?? String(currentAudioIndex ?? ""),
-        subtitleIndex: params.subtitleIndex ?? String(currentSubtitleIndex),
+        subtitleIndex:
+          params.subtitleIndex ??
+          String(toServerSubtitleIndex(currentSubtitleIndex)),
         mediaSourceId: stream?.mediaSource?.Id ?? "",
         bitrateValue: bitrateValue?.toString() ?? "",
         playbackPosition: msToTicks(progress.get()).toString(),
diff --git a/components/video-player/controls/contexts/VideoContext.tsx b/components/video-player/controls/contexts/VideoContext.tsx
index 4aee779f8..c42c7dca0 100644
--- a/components/video-player/controls/contexts/VideoContext.tsx
+++ b/components/video-player/controls/contexts/VideoContext.tsx
@@ -126,10 +126,17 @@ export const VideoProvider: React.FC<{ children: ReactNode }> = ({
     audioIndex?: string;
     subtitleIndex?: string;
   }) => {
+    // The URL param can hold a local-sub sentinel (selected via setParams) that
+    // only exists in the dying player — the server must get "none" (-1) instead.
+    // NaN (missing/blank param) fails the comparison and passes through as-is.
+    const fallbackSubtitleIndex =
+      Number.parseInt(subtitleIndex, 10) <= LOCAL_SUBTITLE_INDEX_START
+        ? "-1"
+        : subtitleIndex;
     const queryParams = new URLSearchParams({
       itemId: itemId ?? "",
       audioIndex: params.audioIndex ?? audioIndex,
-      subtitleIndex: params.subtitleIndex ?? subtitleIndex,
+      subtitleIndex: params.subtitleIndex ?? fallbackSubtitleIndex,
       mediaSourceId: mediaSource?.Id ?? "",
       bitrateValue: bitrateValue,
       playbackPosition: playbackPosition,
diff --git a/components/video-player/controls/types.ts b/components/video-player/controls/types.ts
index 470b0f084..ff6ddeab0 100644
--- a/components/video-player/controls/types.ts
+++ b/components/video-player/controls/types.ts
@@ -36,4 +36,12 @@ type Track = {
  */
 export const LOCAL_SUBTITLE_INDEX_START = -100;
 
+/**
+ * Map a client-side subtitle index to what the Jellyfin stream API understands.
+ * Local sentinel indexes have no matching MediaStream on the server, which
+ * expects -1 ("no subtitles") when re-negotiating a stream.
+ */
+export const toServerSubtitleIndex = (index: number): number =>
+  index <= LOCAL_SUBTITLE_INDEX_START ? -1 : index;
+
 export type { EmbeddedSubtitle, ExternalSubtitle, Track, TranscodedSubtitle };