Accept prerelease private media payloads

app/src/main/java/com/bitchat/android/model/NoiseEncrypted.kt

@@ -27,8 +27,17 @@ enum class NoisePayloadType(val value: UByte) {
 
 
     companion object {
+        // #1434 prerelease iOS builds briefly emitted private files as 0x09. Keep this
+        // decode-only: every NoisePayload constructed by Android still encodes FILE_TRANSFER as
+        // its canonical 0x20 value, so the compatibility alias cannot leak into new traffic.
+        private val PRERELEASE_FILE_TRANSFER_RAW_VALUE = 0x09u.toUByte()
+
         fun fromValue(value: UByte): NoisePayloadType? {
-            return values().find { it.value == value }
+            return if (value == PRERELEASE_FILE_TRANSFER_RAW_VALUE) {
+                FILE_TRANSFER
+            } else {
+                values().find { it.value == value }
+            }
         }
     }
 }

app/src/test/kotlin/com/bitchat/android/mesh/MessageHandlerTest.kt

@@ -210,6 +210,40 @@ class MessageHandlerTest {
         }
     }
 
+    @Test
+    fun `encrypted prerelease iOS Noise 0x09 private media is delivered`() {
+        runBlocking {
+            val file = BitchatFilePacket(
+                fileName = "prerelease-ios.pdf",
+                fileSize = 4,
+                mimeType = "application/pdf",
+                content = byteArrayOf(1, 2, 3, 4)
+            )
+            val prereleasePlaintext = byteArrayOf(0x09) + file.encode()!!
+            val ciphertext = byteArrayOf(0x41, 0x42, 0x43)
+            whenever(delegate.decryptFromPeer(any(), eq(peerID))).thenReturn(prereleasePlaintext)
+            whenever(delegate.getPeerNickname(peerID)).thenReturn(nickname)
+            whenever(delegate.getMyNickname()).thenReturn("me")
+            whenever(delegate.encryptForPeer(any(), eq(peerID))).thenReturn(byteArrayOf(0x55))
+
+            val outerPacket = BitchatPacket(
+                version = 2u,
+                type = MessageType.NOISE_ENCRYPTED.value,
+                senderID = peerID.hexToBytes(),
+                recipientID = myPeerID.hexToBytes(),
+                timestamp = System.currentTimeMillis().toULong(),
+                payload = ciphertext,
+                signature = signature,
+                ttl = 7u
+            )
+
+            handler.handleNoiseEncrypted(RoutedPacket(outerPacket, peerID, "direct-link"))
+
+            verify(delegate).decryptFromPeer(ciphertext, peerID)
+            verify(delegate).onMessageReceived(any())
+        }
+    }
+
     private fun announcePacket(
         ageMs: Long,
         ttl: UByte = (AppConstants.MESSAGE_TTL_HOPS.toInt() - 1).toUByte(),

app/src/test/kotlin/com/bitchat/android/mesh/PrivateMediaTransferPreparerTest.kt

@@ -47,6 +47,18 @@ class PrivateMediaTransferPreparerTest {
         assertEquals(0x20u.toUByte(), encryptedPlaintext!![0].toUByte())
     }
 
+    @Test
+    fun `prerelease iOS Noise 0x09 decodes as file transfer but re-encodes canonical 0x20`() {
+        val filePayload = file(3).encode()!!
+        val prereleasePayload = byteArrayOf(0x09) + filePayload
+
+        val decoded = NoisePayload.decode(prereleasePayload)
+
+        assertEquals(NoisePayloadType.FILE_TRANSFER, decoded?.type)
+        assertTrue(filePayload.contentEquals(decoded?.data))
+        assertEquals(0x20u.toUByte(), decoded!!.encode()[0].toUByte())
+    }
+
     @Test
     fun `legacy mode requires consent and signing failure aborts`() {
         val noConsent = preparer(policy = PrivateMediaPolicyDecision.RequiresLegacyConsent)

docs/PRIVATE_MEDIA_V1.md

@@ -11,7 +11,15 @@ for the recipient, and only then fragments the final outer packet.
 - Noise payload data: one complete encoded `BitchatFilePacket`.
 - Outer recipient: the target peer ID; never broadcast for private media.
 
-Do not allocate a second Noise payload type for this format.
+Prerelease iOS builds of #1434 briefly emitted the inner file type as `0x09`.
+Android accepts that value on decode and immediately canonicalizes it to
+`NoisePayloadType.FILE_TRANSFER`; every Android encode remains `0x20`. Do not
+allocate or emit a second Noise payload type for this format.
+
+The decode-only `0x09` alias may be removed only after every TestFlight/internal
+build that emitted it has expired and the project's minimum-supported-client
+policy excludes those builds. Track that release criterion explicitly; do not
+remove the alias on an arbitrary calendar date.
 
 ## Capability announcement
 
@@ -96,6 +104,8 @@ capability and bounded streaming design.
 
 - New Android to new iOS/Android: encrypted Noise `0x20` after authenticated
   capability promotion.
+- Prerelease iOS to new Android: encrypted Noise `0x09` is decoded,
+  canonicalized to `0x20`, and delivered during the migration window.
 - New Android to a verified older client: blocked until the user explicitly
   accepts one relay-visible signed raw `0x22` transfer.
 - Old clients receiving a new announcement: ignore TLV `0x05` and continue