From 5acb200c02d1a4f884dd6f609c027d9187c17f29 Mon Sep 17 00:00:00 2001
From: fmarcac <188743521+fmarcac@users.noreply.github.com>
Date: Sat, 5 Sep 2026 14:23:37 +0200
Subject: Drop SyncPlay requests from sessions that left the group

---
 Emby.Server.Implementations/SyncPlay/SyncPlayManager.cs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

(limited to 'Emby.Server.Implementations')

diff --git a/Emby.Server.Implementations/SyncPlay/SyncPlayManager.cs b/Emby.Server.Implementations/SyncPlay/SyncPlayManager.cs
index b45d754554..9b12c68ec1 100644
--- a/Emby.Server.Implementations/SyncPlay/SyncPlayManager.cs
+++ b/Emby.Server.Implementations/SyncPlay/SyncPlayManager.cs
@@ -332,8 +332,11 @@ namespace Emby.Server.Implementations.SyncPlay
                 // Group lock required as Group is not thread-safe.
                 lock (group)
                 {
-                    // Make sure that session still belongs to this group.
-                    if (_sessionToGroupMap.TryGetValue(session.Id, out var checkGroup) && !checkGroup.GroupId.Equals(group.GroupId))
+                    // Make sure that session still belongs to this group. The lookup can fail
+                    // outright when the session left while this request was waiting on the group
+                    // lock, which is exactly the case this re-check exists to catch.
+                    if (!_sessionToGroupMap.TryGetValue(session.Id, out var checkGroup)
+                        || !checkGroup.GroupId.Equals(group.GroupId))
                     {
                         // Drop request.
                         return;
-- 
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