From 2c88945e6b686acc71fd2ec50c7342f46967a495 Mon Sep 17 00:00:00 2001
From: Greyson Parrelli <greyson@signal.org>
Date: Thu, 4 Jun 2026 00:14:50 -0400
Subject: [PATCH] Fix sending messages to self when your session is deleted.

---
 .../api/SignalServiceMessageSender.java       | 20 ++++++++++---------
 .../signal/network/service/MessageService.kt  | 17 +++++++++-------
 .../network/service/MessageServiceTest.kt     | 17 ++++++++++++++++
 3 files changed, 38 insertions(+), 16 deletions(-)

diff --git a/lib/libsignal-service/src/main/java/org/whispersystems/signalservice/api/SignalServiceMessageSender.java b/lib/libsignal-service/src/main/java/org/whispersystems/signalservice/api/SignalServiceMessageSender.java
index 602e5ea811..2cca10b439 100644
--- a/lib/libsignal-service/src/main/java/org/whispersystems/signalservice/api/SignalServiceMessageSender.java
+++ b/lib/libsignal-service/src/main/java/org/whispersystems/signalservice/api/SignalServiceMessageSender.java
@@ -2808,22 +2808,24 @@ public class SignalServiceMessageSender {
                                                        boolean                      story)
       throws IOException, InvalidKeyException, UntrustedIdentityException
   {
-    List<OutgoingPushMessage> messages = new LinkedList<>();
+    List<OutgoingPushMessage> messages   = new LinkedList<>();
+    List<Integer>             subDevices = aciStore.getSubDeviceSessions(recipient.getIdentifier());
+    Set<Integer>              deviceIds  = subDevices.stream()
+                                                     .filter((id) -> aciStore.containsSession(new SignalProtocolAddress(recipient.getIdentifier(), id)))
+                                                     .collect(Collectors.toSet());
 
-    List<Integer> subDevices = aciStore.getSubDeviceSessions(recipient.getIdentifier());
-
-    List<Integer> deviceIds = new ArrayList<>(subDevices.size() + 1);
     deviceIds.add(SignalServiceAddress.DEFAULT_DEVICE_ID);
-    deviceIds.addAll(subDevices);
 
     if (recipient.matches(localAddress)) {
-      deviceIds.remove(Integer.valueOf(localDeviceId));
+      deviceIds.remove(localDeviceId);
+
+      if (deviceIds.isEmpty()) {
+        deviceIds.add(localDeviceId);
+      }
     }
 
     for (int deviceId : deviceIds) {
-      if (deviceId == SignalServiceAddress.DEFAULT_DEVICE_ID || aciStore.containsSession(new SignalProtocolAddress(recipient.getIdentifier(), deviceId))) {
-        messages.add(getEncryptedMessage(recipient, sealedSenderAccess, deviceId, plaintext, story));
-      }
+      messages.add(getEncryptedMessage(recipient, sealedSenderAccess, deviceId, plaintext, story));
     }
 
     return new OutgoingPushMessageList(recipient.getIdentifier(), timestamp, messages, online, urgent);
diff --git a/lib/network/src/main/java/org/signal/network/service/MessageService.kt b/lib/network/src/main/java/org/signal/network/service/MessageService.kt
index 91fc73bbfd..7e695c106e 100644
--- a/lib/network/src/main/java/org/signal/network/service/MessageService.kt
+++ b/lib/network/src/main/java/org/signal/network/service/MessageService.kt
@@ -396,17 +396,20 @@ open class MessageService(
   }
 
   private fun targetDeviceIds(serviceId: ServiceId): List<Int> {
-    val subDevices: MutableSet<Int> = (protocolStore.getSubDeviceSessions(serviceId.toString()) + SignalServiceAddress.DEFAULT_DEVICE_ID).toMutableSet()
+    val devices: MutableSet<Int> = protocolStore.getSubDeviceSessions(serviceId.toString())
+      .filter { protocolStore.containsSession(SignalProtocolAddress(serviceId.libSignalServiceId, it)) }
+      .toMutableSet()
+
+    devices += SignalServiceAddress.DEFAULT_DEVICE_ID
 
-    // When sending to self, skip our own device.
     if (serviceId == localAddress.serviceId) {
-      subDevices -= localDeviceId
+      devices -= localDeviceId
+      if (devices.isEmpty()) {
+        devices += localDeviceId
+      }
     }
 
-    return subDevices
-      .filter { it == SignalServiceAddress.DEFAULT_DEVICE_ID || protocolStore.containsSession(SignalProtocolAddress(serviceId.libSignalServiceId, it)) }
-      .sorted()
-      .toList()
+    return devices.sorted()
   }
 
   /**
diff --git a/lib/network/src/test/java/org/signal/network/service/MessageServiceTest.kt b/lib/network/src/test/java/org/signal/network/service/MessageServiceTest.kt
index ed980cee89..68c53c0a15 100644
--- a/lib/network/src/test/java/org/signal/network/service/MessageServiceTest.kt
+++ b/lib/network/src/test/java/org/signal/network/service/MessageServiceTest.kt
@@ -228,6 +228,23 @@ class MessageServiceTest {
     verify(exactly = 0) { cipher.encrypt(SignalProtocolAddress(recipientAci.libSignalServiceId, 3), any(), any()) }
   }
 
+  @Test
+  fun `local send with no other devices sends to own device`() = runTest {
+    val service = newService()
+    val localProtocolAddress = SignalProtocolAddress(localAci.libSignalServiceId, SignalServiceAddress.DEFAULT_DEVICE_ID)
+    every { protocolStore.getSubDeviceSessions(localAci.toString()) } returns emptyList()
+    every { cipher.encrypt(any(), any(), any()) } returns OutgoingPushMessage(1, 1, 100, "AAAA")
+
+    coEvery { messageApi.sendSealedSenderMessage(any(), any(), any(), any(), any(), any()) } returns
+      RequestResult.Success(Unit)
+
+    val result = service.sendMessage(localAci, envelopeContent, timestamp, sealedSenderAccess = null, story = true, isOnline = false)
+
+    val success = (result as Either.Right).value
+    assertThat(success.devices).isEqualTo(listOf(SignalServiceAddress.DEFAULT_DEVICE_ID))
+    verify { cipher.encrypt(localProtocolAddress, null, envelopeContent) }
+  }
+
   @Test
   fun `MismatchedDeviceException archives extras and fetches missing prekeys`() = runTest {
     val service = newService()