diff --git a/build.sbt b/build.sbt
index 4dfebca..6b4686f 100644
--- a/build.sbt
+++ b/build.sbt
@@ -5,7 +5,7 @@ import sbtversionpolicy.withsbtrelease.ReleaseVersion
 
 // dependency versions
 val contentEntityVersion = "4.0.0"
-val contentAtomVersion = "12.0.1"
+val contentAtomVersion = "13.1.0-PREVIEW.glspike-multimedia-atom.2026-08-03T1406.314057f2"
 val storyPackageVersion = "2.2.0"
 val thriftVersion = "0.24.0"
 val scroogeVersion = "22.1.0" // update plugins too if this version changes
@@ -25,6 +25,11 @@ val snapshotReleaseSuffix = "-SNAPSHOT"
 
 lazy val artifactProductionSettings = Seq(
   scalaVersion := "2.13.14",
+  // A newer scala-library (2.13.18) is pulled in transitively via content-atom, but the 2.13.18
+  // compiler crashes on the fezziwig/circe macro-generated trees (scala.MatchError in RefChecks'
+  // isSimpleCaseApply). We stay on the 2.13.14 compiler, which compiles cleanly, and demote the
+  // SIP-51 check since all 2.13.x are binary compatible.
+  allowUnsafeScalaLibUpgrade := true,
   // This old attempt to downgrade scrooge reserved word clashes is now insufficient... https://github.com/twitter/scrooge/issues/259#issuecomment-1900743695
   Compile / scroogeDisableStrict := true,
   // scrooge 21.3.0: Builds are now only supported for Scala 2.12+
diff --git a/json/src/main/scala/com/gu/contentapi/json/CirceDecoders.scala b/json/src/main/scala/com/gu/contentapi/json/CirceDecoders.scala
index fce68bc..0300923 100644
--- a/json/src/main/scala/com/gu/contentapi/json/CirceDecoders.scala
+++ b/json/src/main/scala/com/gu/contentapi/json/CirceDecoders.scala
@@ -203,6 +203,10 @@ object CirceDecoders {
   implicit val audioAtomDecoder: Decoder[audio.AudioAtom] = deriveDecoder
   implicit val offPlatformDecoder: Decoder[audio.OffPlatform] = deriveDecoder
   implicit val emailSignUpAtomDecoder: Decoder[emailsignup.EmailSignUpAtom] = deriveDecoder
+  implicit val multimediaSlideshowMediaReferenceDecoder: Decoder[multimediaslideshow.MediaReference] = deriveDecoder
+  implicit val multimediaSlideshowSlideContentDecoder: Decoder[multimediaslideshow.SlideContent] = deriveDecoder
+  implicit val multimediaSlideshowSlideDecoder: Decoder[multimediaslideshow.Slide] = deriveDecoder
+  implicit val multimediaSlideshowAtomDecoder: Decoder[multimediaslideshow.MultimediaSlideshowAtom] = deriveDecoder
   implicit val atomDecoder: Decoder[contentatom.Atom] = deriveDecoder
   implicit val contentChangeDetailsDecoder: Decoder[contentatom.ContentChangeDetails] = deriveDecoder
   implicit val changeRecordDecoder: Decoder[contentatom.ChangeRecord] = deriveDecoder
diff --git a/json/src/main/scala/com/gu/contentapi/json/CirceEncoders.scala b/json/src/main/scala/com/gu/contentapi/json/CirceEncoders.scala
index 70e1f65..3cf2c2c 100644
--- a/json/src/main/scala/com/gu/contentapi/json/CirceEncoders.scala
+++ b/json/src/main/scala/com/gu/contentapi/json/CirceEncoders.scala
@@ -152,6 +152,10 @@ object CirceEncoders {
   implicit val audioAtomEncoder: Encoder[audio.AudioAtom] = deriveEncoder
   implicit val offPlatformEncoder: Encoder[audio.OffPlatform] = deriveEncoder
   implicit val emailSignUpAtomEncoder: Encoder[emailsignup.EmailSignUpAtom] = deriveEncoder
+  implicit val multimediaSlideshowMediaReferenceEncoder: Encoder[multimediaslideshow.MediaReference] = deriveEncoder
+  implicit val multimediaSlideshowSlideContentEncoder: Encoder[multimediaslideshow.SlideContent] = deriveEncoder
+  implicit val multimediaSlideshowSlideEncoder: Encoder[multimediaslideshow.Slide] = deriveEncoder
+  implicit val multimediaSlideshowAtomEncoder: Encoder[multimediaslideshow.MultimediaSlideshowAtom] = deriveEncoder
   implicit val atomEncoder: Encoder[contentatom.Atom] = deriveEncoder
   implicit val contentChangeDetailsEncoder: Encoder[contentatom.ContentChangeDetails] = deriveEncoder
   implicit val changeRecordEncoder: Encoder[contentatom.ChangeRecord] = deriveEncoder
diff --git a/models/src/main/thrift/content/v1.thrift b/models/src/main/thrift/content/v1.thrift
index 9057a0e..5ff21a3 100644
--- a/models/src/main/thrift/content/v1.thrift
+++ b/models/src/main/thrift/content/v1.thrift
@@ -1857,6 +1857,8 @@ struct Atoms {
     16: optional list<contentatom.Atom> audios
 
     17: optional list<contentatom.Atom> emailsignups
+
+    18: optional list<contentatom.Atom> multimediaslideshows
 }
 
 struct ContentStats {