From 1b72b8491c104b6abe8f8440de2a3da4d8de0981 Mon Sep 17 00:00:00 2001
From: Jason Dove <1695733+jasongdove@users.noreply.github.com>
Date: Wed, 31 Dec 2025 11:24:07 -0600
Subject: [PATCH] improve multi-episode grouping logic (#2744)

---
 CHANGELOG.md                                        |  2 ++
 ErsatzTV.Core/Scheduling/MultiPartEpisodeGrouper.cs | 10 +++++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4261fc412..6b1174f1e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -63,6 +63,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Fix startup error caused by duplicate smart collection names (and no longer allow duplicate smart collection names)
 - Fix erroneous downgrade health check failure with some installations that use MariaDB
 - Sequential schedules: fix `count` instruction validation to accept integer (constant) or string (expression)
+- Fix multi-part episode grouping logic so that it does NOT require release date metadata for episodes within a single show
+  - When **Treat Collections As Shows** is enabled (i.e. for crossover episodes) release date metadata is required for proper grouping
 
 ### Changed
 - No longer round framerate to nearest integer when normalizing framerate
diff --git a/ErsatzTV.Core/Scheduling/MultiPartEpisodeGrouper.cs b/ErsatzTV.Core/Scheduling/MultiPartEpisodeGrouper.cs
index 5d0e66ccd..fb7cebb9c 100644
--- a/ErsatzTV.Core/Scheduling/MultiPartEpisodeGrouper.cs
+++ b/ErsatzTV.Core/Scheduling/MultiPartEpisodeGrouper.cs
@@ -40,9 +40,17 @@ public static partial class MultiPartEpisodeGrouper
                 groups.Add(new GroupedMediaItem(item, null));
             }
 
+            // when treating multiple shows as a single "show" - we need to
+            // first sort by release date before looking for part 1, part 2, etc. to group
+            // otherwise, we can simply sort by season, episode number
+            // which does not require release date metadata
+            IComparer<MediaItem> comparer = treatCollectionsAsShows
+                ? new ChronologicalMediaComparer()
+                : new SeasonEpisodeMediaComparer();
+
             IEnumerable<Episode> sortedEpisodes = showId.Match(
                 id => episodes.Filter(e => e.Season.ShowId == id),
-                () => episodes).OrderBy(identity, new ChronologicalMediaComparer());
+                () => episodes).OrderBy(identity, comparer);
 
             foreach (Episode episode in sortedEpisodes)
             {