signal-cli can't receive messages from new users (PreKey decryption fails)

[guillaumedebavelaere]

Hi,

For a few days now, my signal-cli bot can't receive messages from new users (it still works fine for existing users).

I saw rate limit errors with a challenge that I resolved with submitRateLimitChallenge, but since then I still get these decryption errors:

org.signal.libsignal.metadata.ProtocolInvalidMessageException: invalid PreKey message: decryption failed

This happens consistently when a new user sends their first message to the bot

The retry receipt mechanism does fire (no more rate limit), but each retry from the user fails the same way: the session never gets re-established.

Context:

For several days my bot was running signal-cli native (GraalVM) with frequent OOMKills (~2-4 times/day) due to a memory leak under load. I suspect these forced restarts left the PreKey store in an inconsistent state.

I then migrated to JVM (Eclipse Temurin 25) which fixed the memory issue. The service is now stable, but the new-user decryption errors continue.

What I've tried:

• register --reregister succeeded, but issue persists
• submitRateLimitChallenge fixed the rate limit, retry receipts now go through, but decryption still fails
• Pod restarts no effect

Sample log:

2026-05-03T12:17:25.422Z DEBUG IncomingMessageHandler - Failed to decrypt incoming message
org.signal.libsignal.metadata.ProtocolInvalidMessageException: invalid PreKey message: decryption failed
    at SignalServiceCipher.decryptInternal(SignalServiceCipher.java:246)
    at IncomingMessageHandler.handleEnvelope(IncomingMessageHandler.java:154)
    ...
Caused by: org.signal.libsignal.protocol.InvalidMessageException: invalid PreKey message: decryption failed
    at Native.SessionCipher_DecryptPreKeySignalMessage(Native Method)

Envelope from: f1248176-... (device: 1) to +33******99
Exception: invalid PreKey message: decryption failed (ProtocolInvalidMessageException)

2026-05-03T12:17:25.423Z DEBUG ReceiveHelper - Executing action SendRetryMessageRequestAction
2026-05-03T12:17:25.532Z DEBUG ReceiveHelper - Executing action RenewSessionAction
2026-05-03T12:17:25.792Z DEBUG ReceiveHelper - Retrieved 1 envelopes!
... user retries ...
2026-05-03T12:18:31.229Z DEBUG IncomingMessageHandler - Failed to decrypt incoming message
(same error, repeats until user gives up)

Environment:

• signal-cli version: 0.14.3
• libsignal-client: 0.92.1 (ARM64 native lib from exquo/signal-libs-build)
• JRE: Eclipse Temurin 25
• Linux ARM64
• Daemon mode: --http 0.0.0.0:3000 --receive-mode=manual

I'm not sure what to try next. Any help would be appreciated.
Is there a known contact/recipient limit per Signal account that could trigger this kind of issue under load?

Thanks for any guidance!

[AloisHofstaetter]

Hi

I observed the same behavior.
signal-cli version 0.14.3 from https://github.com/AsamK/signal-cli/releases
JRE: OpenJDK 25.0.2 2026-01-20

Downgrading did help.

BR

[guillaumedebavelaere]

Hi,

Thanks a lot for sharing this! Your hint was exactly what I needed.

I downgraded to signal-cli 0.14.2 (libsignal-client 0.90.0) yesterday evening, and several previously-blocked users have now confirmed they can successfully establish sessions again.

[orion-ob1]

It's related to this change in the upstream
https://github.com/signalapp/libsignal/blob/6e5a0466b35e23925ad4b3a31a8c6572471c33d9/rust/protocol/src/protocol.rs#L213

Instead of PNI address, signal-cli always sends ACI and address verification fails.

Upstream logic to decrypt message
https://github.com/signalapp/Signal-Android/blob/d68e541ee6888f82f13a5aa5486857f25704f833/app/src/main/java/org/thoughtcrime/securesms/messages/MessageDecryptor.kt#L107

A variant of a potential fix:

diff --git a/lib/src/main/java/org/asamk/signal/manager/helper/IncomingMessageHandler.java b/lib/src/main/java/org/asamk/signal/manager/helper/IncomingMessageHandler.java
index 92014fa3..3cd8bced 100644
--- a/lib/src/main/java/org/asamk/signal/manager/helper/IncomingMessageHandler.java
+++ b/lib/src/main/java/org/asamk/signal/manager/helper/IncomingMessageHandler.java
@@ -111,8 +111,7 @@ public final class IncomingMessageHandler {
             account.getIdentityKeyStore().setRetryingDecryption(true);
             final var destination = getDestination(envelope).serviceId();
             try {
-                final var cipherResult = dependencies.getCipher(destination == null
-                                || destination.equals(account.getAci()) ? ServiceIdType.ACI : ServiceIdType.PNI)
+                final var cipherResult = dependencies.getCipher(destination)
                         .decrypt(envelope.getProto(), envelope.getServerDeliveredTimestamp());
                 content = validate(envelope.getProto(), cipherResult, envelope.getServerDeliveredTimestamp());
                 if (content == null) {
@@ -149,8 +148,7 @@ public final class IncomingMessageHandler {
         if (!envelope.isReceipt()) {
             final var destination = getDestination(envelope).serviceId();
             try {
-                final var cipherResult = dependencies.getCipher(destination == null
-                                || destination.equals(account.getAci()) ? ServiceIdType.ACI : ServiceIdType.PNI)
+                final var cipherResult = dependencies.getCipher(destination)
                         .decrypt(envelope.getProto(), envelope.getServerDeliveredTimestamp());
                 content = validate(envelope.getProto(), cipherResult, envelope.getServerDeliveredTimestamp());
                 if (content == null) {
diff --git a/lib/src/main/java/org/asamk/signal/manager/internal/SignalDependencies.java b/lib/src/main/java/org/asamk/signal/manager/internal/SignalDependencies.java
index 77068eaa..e9efd1fa 100644
--- a/lib/src/main/java/org/asamk/signal/manager/internal/SignalDependencies.java
+++ b/lib/src/main/java/org/asamk/signal/manager/internal/SignalDependencies.java
@@ -3,11 +3,13 @@ package org.asamk.signal.manager.internal;
 import org.asamk.signal.manager.config.ServiceConfig;
 import org.asamk.signal.manager.config.ServiceEnvironmentConfig;
 import org.asamk.signal.manager.util.Utils;
+import org.signal.core.models.ServiceId;
 import org.signal.libsignal.metadata.certificate.CertificateValidator;
 import org.signal.libsignal.net.Network;
 import org.signal.libsignal.zkgroup.profiles.ClientZkProfileOperations;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import org.whispersystems.signalservice.api.SignalServiceAccountDataStore;
 import org.whispersystems.signalservice.api.SignalServiceAccountManager;
 import org.whispersystems.signalservice.api.SignalServiceDataStore;
 import org.whispersystems.signalservice.api.SignalServiceMessageReceiver;
@@ -366,13 +368,24 @@ public class SignalDependencies {
                         getUnauthenticatedSignalWebSocket()));
     }

-    public SignalServiceCipher getCipher(ServiceIdType serviceIdType) {
+    public SignalServiceCipher getCipher(ServiceId destination) {
+        final var selfAci = credentialsProvider.getAci();
+        final var selfPni = credentialsProvider.getPni();
+        final ServiceId localServiceId;
+        final SignalServiceAccountDataStore  store;
+        if (destination.equals(selfPni)){
+            localServiceId = selfPni;
+            store = dataStore.pni();
+        } else {
+            localServiceId = selfAci;
+            store = dataStore.aci();
+        }
         final var certificateValidator = new CertificateValidator(serviceEnvironmentConfig.unidentifiedSenderTrustRoots());
-        final var address = new SignalServiceAddress(credentialsProvider.getAci(), credentialsProvider.getE164());
+        final var address = new SignalServiceAddress(localServiceId, credentialsProvider.getE164());
         final var deviceId = credentialsProvider.getDeviceId();
         return new SignalServiceCipher(address,
                 deviceId,
-                serviceIdType == ServiceIdType.ACI ? dataStore.aci() : dataStore.pni(),
+                store,
                 sessionLock,
                 certificateValidator);
     }

It's incomplete and doesn't have other address checks upstream has.

[AsamK]

Thanks for analyzing!
I've pushed a fix for the incorrect SignalServiceCipher initialization (b427541) and also added more address checks.