diff --git a/AnkiDroid/src/main/java/com/ichi2/anki/pages/PostRequestHandler.kt b/AnkiDroid/src/main/java/com/ichi2/anki/pages/PostRequestHandler.kt
index 29adaec145f0..ed1e09ca9fcb 100644
--- a/AnkiDroid/src/main/java/com/ichi2/anki/pages/PostRequestHandler.kt
+++ b/AnkiDroid/src/main/java/com/ichi2/anki/pages/PostRequestHandler.kt
@@ -128,8 +128,8 @@ val collectionMethods =
         "getIgnoredBeforeCount" to { bytes -> getIgnoredBeforeCountRaw(bytes) },
         "getRetentionWorkload" to { bytes -> getRetentionWorkloadRaw(bytes) },
         "simulateFsrsWorkload" to { bytes -> simulateFsrsWorkloadRaw(bytes) },
-        // https://github.com/ankitects/anki/pull/4326 -> saveCustomColours should be no-op in mobile clients
-        "saveCustomColours" to { bytes -> backendIdentity(bytes) },
+        "saveCustomColours" to { bytes -> saveCustomColoursRaw(bytes) },
+        "getCustomColours" to { bytes -> getCustomColoursRaw(bytes) },
     )
 
 suspend fun handleCollectionPostRequest(
diff --git a/AnkiDroid/src/main/java/com/ichi2/anki/scheduling/Fsrs.kt b/AnkiDroid/src/main/java/com/ichi2/anki/scheduling/Fsrs.kt
index 67c093b1c5fe..ce1542755533 100644
--- a/AnkiDroid/src/main/java/com/ichi2/anki/scheduling/Fsrs.kt
+++ b/AnkiDroid/src/main/java/com/ichi2/anki/scheduling/Fsrs.kt
@@ -43,7 +43,7 @@ value class FsrsVersion(
         when (libraryVersion) {
             "0.6.4" -> "FSRS 4.5"
             "1.4.3", "2.0.3" -> "FSRS 5"
-            "4.1.1", "5.1.0" -> "FSRS 6"
+            "4.1.1", "5.1.0", "5.2.0" -> "FSRS 6"
             else -> null
         }
 }
diff --git a/AnkiDroid/src/test/java/com/ichi2/anki/TranslationTest.kt b/AnkiDroid/src/test/java/com/ichi2/anki/TranslationTest.kt
index 0cb3dca14bb5..08394ab17fed 100644
--- a/AnkiDroid/src/test/java/com/ichi2/anki/TranslationTest.kt
+++ b/AnkiDroid/src/test/java/com/ichi2/anki/TranslationTest.kt
@@ -39,7 +39,9 @@ class TranslationTest : RobolectricTest() {
     @Test
     fun `translatable strings do not duplicate GeneratedTranslations`() =
         runTest {
-            val backendStrings = getBackendNonArgStrings()
+            val backendStrings =
+                getBackendNonArgStrings()
+                    .filterNot { it.methodName in IGNORED_BACKEND_TRANSLATIONS }
             val backendByText = backendStrings.groupBy { it.text }
             val backendByTextLower = backendStrings.groupBy { it.text.lowercase() }
             val xmlStrings = getTranslatableXmlStrings()
@@ -363,5 +365,16 @@ class TranslationTest : RobolectricTest() {
                 // TR.studyingShowAnswer()
                 // TR.deckConfigQuestionActionShowAnswer()
             )
+
+        /**
+         * Backend translation method names (e.g. `TR.xx()`) excluded from the
+         * duplicate check as the strings are unrelated conceptually.
+         *
+         * Do not remove this set when empty.
+         */
+        private val IGNORED_BACKEND_TRANSLATIONS =
+            setOf(
+                "launcherOff", // "Off" - unrelated to R.string.full_screen_off
+            )
     }
 }
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index a2c9a9014b8c..b24e41e49e78 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -64,7 +64,7 @@ androidxWebkit = "1.15.0"
 # https://developer.android.com/jetpack/androidx/releases/work
 androidxWork = "2.11.2"
 # https://github.com/ankidroid/Anki-Android-Backend/
-ankiBackend = '0.1.64-anki25.09.2'
+ankiBackend = '0.1.65-anki26.05b1'
 autoService = "1.1.1"
 autoServiceAnnotations = "1.1.1"
 # https://github.com/skydoves/ColorPickerView/releases
diff --git a/libanki/src/main/java/com/ichi2/anki/libanki/Collection.kt b/libanki/src/main/java/com/ichi2/anki/libanki/Collection.kt
index e8131fbcec4a..d32b7ccd213f 100644
--- a/libanki/src/main/java/com/ichi2/anki/libanki/Collection.kt
+++ b/libanki/src/main/java/com/ichi2/anki/libanki/Collection.kt
@@ -1493,6 +1493,12 @@ class Collection(
 
     @NotInPyLib
     fun evaluateParamsLegacyRaw(input: ByteArray): ByteArray = backend.evaluateParamsLegacyRaw(input = input)
+
+    @NotInPyLib
+    fun saveCustomColoursRaw(input: ByteArray): ByteArray = backend.saveCustomColoursRaw(input = input)
+
+    @NotInPyLib
+    fun getCustomColoursRaw(input: ByteArray): ByteArray = backend.getCustomColoursRaw(input = input)
 }
 
 @NotInPyLib
diff --git a/libanki/src/main/java/com/ichi2/anki/libanki/Deck.kt b/libanki/src/main/java/com/ichi2/anki/libanki/Deck.kt
index 668bd6a15989..44a78695ada1 100644
--- a/libanki/src/main/java/com/ichi2/anki/libanki/Deck.kt
+++ b/libanki/src/main/java/com/ichi2/anki/libanki/Deck.kt
@@ -135,6 +135,7 @@ fun Order.toDisplayString(translations: Translations) =
         Order.REVERSE_ADDED -> translations.decksLatestAddedFirst()
         Order.RETRIEVABILITY_ASCENDING -> translations.deckConfigSortOrderRetrievabilityAscending()
         Order.RETRIEVABILITY_DESCENDING -> translations.deckConfigSortOrderRetrievabilityDescending()
+        Order.RELATIVE_OVERDUENESS -> translations.decksRelativeOverdueness()
         Order.UNRECOGNIZED -> throw IllegalArgumentException("Can't display an unknown enum value.")
     }