diff --git a/db/migrations/uniform_canonical_ids_test.go b/db/migrations/uniform_canonical_ids_test.go
index ee547c64d..345579931 100644
--- a/db/migrations/uniform_canonical_ids_test.go
+++ b/db/migrations/uniform_canonical_ids_test.go
@@ -71,8 +71,8 @@ var _ = Describe("upUniformCanonicalIds", func() {
 		seed(`INSERT INTO media_file VALUES (?, ?, ?, ?, '', '', ?)`, legacyOld, legacyOld, hashID, legacyOld, uuidOld)
 		seed(`INSERT INTO album VALUES (?, ?)`, legacyOld, hashID)
 		seed(`INSERT INTO user VALUES (?)`, randOld)
-		// uuid id, random owner, smart-playlist rules with an embedded inPlaylist id
-		seed(`INSERT INTO playlist VALUES (?, ?, ?)`, uuidOld, randOld, `{"all":[{"inPlaylist":{"id":"`+uuidOld+`"}}]}`)
+		// uuid id, random owner, smart-playlist rules with an embedded inPlaylist id and a sibling operator
+		seed(`INSERT INTO playlist VALUES (?, ?, ?)`, uuidOld, randOld, `{"all":[{"inPlaylist":{"id":"`+uuidOld+`"}},{"inTheLast":{"lastPlayed":30}}]}`)
 		seed(`INSERT INTO annotation VALUES (?, ?, 'media_file')`, randOld, legacyOld)
 		seed(`INSERT INTO playqueue VALUES (?, ?, ?)`, randOld, randOld, legacyOld+","+hashID)
 		seed(`INSERT INTO share VALUES (?, ?, ?, 'Album Foo...')`, shareID, randOld, legacyOld+","+uuidOld)
@@ -83,6 +83,9 @@ var _ = Describe("upUniformCanonicalIds", func() {
 		seed(`INSERT INTO library_tag VALUES (?, 1)`, hashID)
 		seed(`INSERT INTO plugin VALUES ('lastfm', ?)`, `["`+randOld+`","`+hashID+`"]`)
 		seed(`INSERT INTO plugin VALUES ('empty', '[]')`) // exempt: empty user list untouched
+		// malformed JSON in both a plugin list and a playlist rule: must pass through byte-for-byte
+		seed(`INSERT INTO plugin VALUES ('broken', 'not-json')`)
+		seed(`INSERT INTO playlist VALUES (?, ?, '{broken')`, hashID, hashID)
 
 		tx, err = db.Begin()
 		Expect(err).ToNot(HaveOccurred())
@@ -103,8 +106,8 @@ var _ = Describe("upUniformCanonicalIds", func() {
 		Expect(get(`SELECT album_id FROM media_file`)).To(Equal(legacyNew))
 		Expect(get(`SELECT id FROM album`)).To(Equal(legacyNew))
 		Expect(get(`SELECT id FROM user`)).To(Equal(randNew))
-		Expect(get(`SELECT id FROM playlist`)).To(Equal(uuidNew))
-		Expect(get(`SELECT owner_id FROM playlist`)).To(Equal(randNew))
+		Expect(get(`SELECT id FROM playlist WHERE owner_id='` + randNew + `'`)).To(Equal(uuidNew))
+		Expect(get(`SELECT owner_id FROM playlist WHERE id='` + uuidNew + `'`)).To(Equal(randNew))
 		Expect(get(`SELECT item_id FROM annotation`)).To(Equal(legacyNew))
 		Expect(get(`SELECT user_id FROM annotation`)).To(Equal(randNew))
 	})
@@ -136,15 +139,40 @@ var _ = Describe("upUniformCanonicalIds", func() {
 		Expect(get(`SELECT id FROM plugin WHERE id='lastfm'`)).To(Equal("lastfm")) // plugin name, untouched
 
 		var rules map[string]any
-		Expect(json.Unmarshal([]byte(get(`SELECT rules FROM playlist`)), &rules)).To(Succeed())
+		Expect(json.Unmarshal([]byte(get(`SELECT rules FROM playlist WHERE id='`+uuidNew+`'`)), &rules)).To(Succeed())
 		all, ok := rules["all"].([]any)
 		Expect(ok).To(BeTrue())
-		Expect(all).To(HaveLen(1))
+		Expect(all).To(HaveLen(2))
 		inPl := all[0].(map[string]any)["inPlaylist"].(map[string]any)
 		Expect(inPl["id"]).To(Equal(uuidNew))
 	})
 
+	It("preserves sibling operators alongside a rewritten inPlaylist id", func() {
+		var rules map[string]any
+		Expect(json.Unmarshal([]byte(get(`SELECT rules FROM playlist WHERE id='`+uuidNew+`'`)), &rules)).To(Succeed())
+		all := rules["all"].([]any)
+		var sawInPlaylist, sawInTheLast bool
+		for _, e := range all {
+			op := e.(map[string]any)
+			if pl, ok := op["inPlaylist"].(map[string]any); ok {
+				Expect(pl["id"]).To(Equal(uuidNew))
+				sawInPlaylist = true
+			}
+			if last, ok := op["inTheLast"].(map[string]any); ok {
+				Expect(last["lastPlayed"]).To(Equal(float64(30)))
+				sawInTheLast = true
+			}
+		}
+		Expect(sawInPlaylist).To(BeTrue())
+		Expect(sawInTheLast).To(BeTrue())
+	})
+
 	It("leaves exempt JSON rows untouched", func() {
 		Expect(get(`SELECT users FROM plugin WHERE id='empty'`)).To(Equal("[]"))
 	})
+
+	It("passes malformed JSON columns through byte-for-byte", func() {
+		Expect(get(`SELECT users FROM plugin WHERE id='broken'`)).To(Equal("not-json"))
+		Expect(get(`SELECT rules FROM playlist WHERE id='` + hashID + `'`)).To(Equal("{broken"))
+	})
 })
diff --git a/model/id/id.go b/model/id/id.go
index d94e7868b..61dc8d443 100644
--- a/model/id/id.go
+++ b/model/id/id.go
@@ -16,6 +16,9 @@ func NewRandom() string {
 
 // Encode128 renders a 16-byte value as the canonical 22-char zero-padded base62 id.
 func Encode128(b []byte) string {
+	if len(b) != 16 {
+		panic(fmt.Sprintf("id.Encode128: expected 16 bytes, got %d", len(b)))
+	}
 	return fmt.Sprintf("%022s", new(big.Int).SetBytes(b).Text(62))
 }
 
diff --git a/model/id/id_test.go b/model/id/id_test.go
index fc311016c..d3858af6b 100644
--- a/model/id/id_test.go
+++ b/model/id/id_test.go
@@ -22,6 +22,10 @@ var _ = Describe("Encode128/Decode128", func() {
 		Expect(id.Decode128(s)).To(Equal(b))
 	})
 
+	It("panics on non-16-byte input", func() {
+		Expect(func() { id.Encode128(make([]byte, 15)) }).To(Panic())
+	})
+
 	It("rejects invalid input", func() {
 		_, err := id.Decode128("short")
 		Expect(err).To(HaveOccurred())
diff --git a/model/metadata/persistent_ids_test.go b/model/metadata/persistent_ids_test.go
index 57bb47e08..57a5b1308 100644
--- a/model/metadata/persistent_ids_test.go
+++ b/model/metadata/persistent_ids_test.go
@@ -223,6 +223,16 @@ var _ = Describe("getPID", func() {
 			// md5("/music/a.mp3") = e3b7fc2ae9447bbec37a13bf916e3cf6 re-encoded as base62
 			Expect(legacyTrackID(mf, false)).To(Equal("6VHl3uR4kss6sUPKA8Cwnk"))
 		})
+		It("prepends the library id for a non-default library", func() {
+			mf := model.MediaFile{Path: "/music/a.mp3", LibraryID: 2}
+			// id.Encode128(md5.Sum([]byte("2\\/music/a.mp3")))
+			Expect(legacyTrackID(mf, true)).To(Equal("4EK5DHQBMeFuDHw6S3iooO"))
+		})
+		It("emits a canonical album id (golden)", func() {
+			mf := model.MediaFile{LibraryID: 1}
+			// id.Encode128(md5.Sum([]byte("[unknown artist]\\[unknown album]")))
+			Expect(legacyAlbumID(mf, Metadata{}, false)).To(Equal("6xBmxSAUFJSQuW7UvwCq8X"))
+		})
 		Context("track_legacy", func() {
 			When("library ID is default (1)", func() {
 				It("should not prepend library ID even when prependLibId is true", func() {
diff --git a/server/jellyfin/dto/ids_test.go b/server/jellyfin/dto/ids_test.go
index 26a957604..d85786d99 100644
--- a/server/jellyfin/dto/ids_test.go
+++ b/server/jellyfin/dto/ids_test.go
@@ -6,7 +6,7 @@ import (
 )
 
 var _ = Describe("id codec", func() {
-	It("round-trips a base62 nanoid through Encode/Decode", func() {
+	It("round-trips a base62 id", func() {
 		id := "5QFKvMsJrd57QE2Le2dKKo"
 		Expect(DecodeID(EncodeID(id))).To(Equal(id))
 	})
diff --git a/server/jellyfin/truncated_ids.go b/server/jellyfin/truncated_ids.go
index 822b696d5..bb3e4ce9b 100644
--- a/server/jellyfin/truncated_ids.go
+++ b/server/jellyfin/truncated_ids.go
@@ -11,7 +11,8 @@ import (
 )
 
 // truncatedIDLen is what Finamp's saved-queue persistence cuts item ids to (16 bytes, assuming
-// Jellyfin GUIDs). All Navidrome ids are 22 chars (share ids 10), so length alone flags a truncated id. See README.
+// Jellyfin GUIDs). All Navidrome ids are 22 chars (share ids 10), so length alone flags a
+// truncated id. See README.
 //
 // Handlers taking an item id resolve it via resolveItemID/resolveItemIDs; playlist-write handlers
 // and ParentId scoping don't (a restored queue never edits playlists or browses by container id).