Merge ef2f421f344d2a4b401d19469000b8adb13bec51 into e1d7bc5587ea0d82a9ac9ec27fa88464f2dde751

README.md

@@ -5,6 +5,7 @@ It supports registering, verifying, sending and receiving messages.
 signal-cli uses a [patched libsignal-service-java](https://github.com/Turasa/libsignal-service-java),
 extracted from the [Signal-Android source code](https://github.com/signalapp/Signal-Android/tree/main/lib/libsignal-service).
 For registering you need a phone number where you can receive SMS or incoming calls.
+Existing accounts without a phone number can be linked from a compatible Signal mobile app.
 
 signal-cli is primarily intended to be used on servers to notify admins of important events.
 For this use-case, it has a daemon mode with JSON-RPC interface ([man page](https://github.com/AsamK/signal-cli/blob/master/man/signal-cli-jsonrpc.5.adoc))
@@ -60,14 +61,16 @@ For a complete usage overview please read
 the [man page](https://github.com/AsamK/signal-cli/blob/master/man/signal-cli.1.adoc) and
 the [wiki](https://github.com/AsamK/signal-cli/wiki).
 
-Important: The ACCOUNT is your phone number in international format and must include the country calling code. Hence it
+For a numbered account, ACCOUNT is your phone number in international format and must include the country calling code. Hence it
 should start with a "+" sign. (See [Wikipedia](https://en.wikipedia.org/wiki/List_of_country_calling_codes) for a list
 of all country codes.)
+For a linked account without a phone number, use its ACI (Account ID) instead.
+See [numberless accounts](doc/numberless-accounts.md) for details.
 
 * Link to an existing account
 
-  If you have an existing Signal account associated
-  with a number, you can link signal-cli to it with:
+  If you have an existing Signal account, with or without a phone number,
+  you can link signal-cli to it with:
 
       signal-cli link
 

doc/numberless-accounts.md

@@ -0,0 +1,73 @@
+# Linking an account without a phone number
+
+signal-cli can link as a secondary device to an account registered without a phone
+number, such as those created in Signal Android 8.28. Creating or recovering a
+primary numberless account using an Account Key is not supported.
+
+Run `signal-cli link -n signal-cli`, then scan the QR code from the mobile app's
+Linked devices screen. The linking URI advertises `capabilities=nopni`. If linking
+completes, the CLI prints the account's ACI instead of a phone number.
+
+Use that ACI with `-a` for subsequent commands:
+
+```sh
+signal-cli -a YOUR_ACCOUNT_ACI receive
+signal-cli -a YOUR_ACCOUNT_ACI listGroups
+signal-cli -a YOUR_ACCOUNT_ACI send --note-to-self -m 'Numberless account test'
+```
+
+When only one local account exists, `-a` can be omitted. Numbered accounts continue
+to accept their phone number or ACI. A numberless account cannot infer a country
+code for a recipient's phone number; use a complete international number beginning
+with `+`, an ACI, or a Signal username.
+
+In JSON-RPC, use the ACI in the `account` parameter. `listAccounts` and `finishLink`
+return an `aci` field alongside `number`; `number` is null for a numberless account.
+Receive events use the ACI in their `account` field when there is no phone number.
+REST wrappers must understand those nullable numbers and ACI selectors before they
+can be assumed compatible.
+
+Numberless accounts are also supported through D-Bus. Start
+`signal-cli daemon --dbus`, then use the ACI with the D-Bus client:
+
+```sh
+signal-cli --dbus -a YOUR_ACCOUNT_ACI listGroups
+signal-cli --dbus -a YOUR_ACCOUNT_ACI send --note-to-self -m 'Numberless account test'
+```
+
+In multi-account mode, D-Bus exports numberless accounts under
+`/org/asamk/Signal/ACI`, with the ACI's hyphens replaced by underscores. Numbered
+accounts retain their phone-number-based paths. Use `SignalControl.listAccounts`
+or `SignalControl.getAccount` to discover paths; `getAccount` accepts either a
+phone number or an ACI. `Signal.getSelfNumber` returns an empty string when the
+account has no phone number, and `Signal.getSelfACI` returns the ACI.
+`Signal.listRecipientIdentifiers` includes contacts without a phone number;
+`Signal.listNumbers` continues to return only phone numbers.
+
+## Validation
+
+Run `./gradlew test installDist` with JDK 25. Regression tests cover the linking
+request (including ACI authentication and omission of PNI keys), numbered-account
+linking, missing group credential salts, persisted account reload, account discovery
+(including superseded accounts and legacy indexes), group membership lookup,
+recipient-number formatting, and JSON account identifiers.
+
+D-Bus transport tests require a session bus. To run them on an isolated bus, use
+`dbus-run-session -- ./gradlew --no-daemon :test --tests '*NumberlessDbusTest*' --rerun-tasks`.
+These tests exercise the D-Bus server and client with a local test backend, including
+mixed accounts, direct and group messages, self-directed operations, and account
+removal. They do not contact Signal. Without a session bus, only the D-Bus unit
+tests run and the transport tests are skipped.
+
+Live acceptance requires a real mobile account and is separate from these tests:
+
+1. Link a newly created secondary device using the numberless mobile account.
+2. Restart signal-cli and verify that `listAccounts` still reports the ACI.
+3. Send and receive a Note to Self message and a DM with a second account.
+4. Receive a group message, list the group, and send a reply to that test group.
+5. Run the JSON-RPC daemon, restart it, and repeat receiving and sending by ACI.
+6. Repeat with `daemon --dbus` and the `--dbus -a YOUR_ACCOUNT_ACI` client, checking
+   direct messages, group messages, and Note to Self.
+
+Only one signal-cli process may open an account's state at a time. Stop the daemon
+before running one-off commands against the same configuration directory.

lib/src/main/java/org/asamk/signal/manager/Manager.java

@@ -98,6 +98,14 @@ public interface Manager extends Closeable {
 
     String getSelfACI();
 
+    /**
+     * Returns the phone number for numbered accounts, or the ACI for numberless accounts.
+     */
+    default String getSelfIdentifier() {
+        final var number = getSelfNumber();
+        return number != null ? number : getSelfACI();
+    }
+
     /**
      * This is used for checking a set of phone numbers for registration on Signal
      *

lib/src/main/java/org/asamk/signal/manager/ProvisioningManager.java

@@ -10,5 +10,8 @@ public interface ProvisioningManager {
 
     URI getDeviceLinkUri() throws TimeoutException, IOException;
 
+    /**
+     * Completes linking and returns the account's phone number, or ACI if it has no number.
+     */
     String finishDeviceLink(String deviceName) throws IOException, TimeoutException, UserAlreadyExistsException;
 }

lib/src/main/java/org/asamk/signal/manager/SignalAccountFiles.java

@@ -25,6 +25,7 @@ import java.io.IOException;
 import java.util.Objects;
 import java.util.Set;
 import java.util.function.Consumer;
+import java.util.stream.Collectors;
 
 public class SignalAccountFiles {
 
@@ -65,15 +66,26 @@ public class SignalAccountFiles {
         return accountsStore.getAllNumbers();
     }
 
+    public Set<String> getAllLocalAccountIdentifiers() throws IOException {
+        return accountsStore.getAllAccounts()
+                .stream()
+                .map(a -> a.number() != null ? a.number() : a.uuid())
+                .collect(Collectors.toSet());
+    }
+
     public MultiAccountManager initMultiAccountManager() throws IOException {
         final var managerPairs = accountsStore.getAllAccounts().parallelStream().map(a -> {
+            final var identifier = a.number() != null ? a.number() : a.uuid();
             try {
-                return new Pair<Manager, Throwable>(initManagerByNumber(a.number(), a.path()), null);
+                final var manager = a.number() != null
+                        ? initManagerByNumber(a.number(), a.path())
+                        : initManagerByAci(ACI.parseOrThrow(a.uuid()), a.path());
+                return new Pair<Manager, Throwable>(manager, null);
             } catch (NotRegisteredException e) {
-                logger.warn("Ignoring {}: {} ({})", a.number(), e.getMessage(), e.getClass().getSimpleName());
+                logger.warn("Ignoring {}: {} ({})", identifier, e.getMessage(), e.getClass().getSimpleName());
                 return null;
             } catch (AccountCheckException | IOException e) {
-                logger.error("Failed to load {}: {} ({})", a.number(), e.getMessage(), e.getClass().getSimpleName());
+                logger.error("Failed to load {}: {} ({})", identifier, e.getMessage(), e.getClass().getSimpleName());
                 return new Pair<Manager, Throwable>(null, e);
             }
         }).filter(Objects::nonNull).toList();

lib/src/main/java/org/asamk/signal/manager/helper/AccountHelper.java

@@ -18,6 +18,7 @@ import org.signal.core.models.ServiceId.ACI;
 import org.signal.core.models.ServiceId.PNI;
 import org.signal.core.util.Base64;
 import org.signal.core.util.crypto.DeviceNameCipher;
+import org.signal.libsignal.net.RequestResult;
 import org.signal.libsignal.protocol.IdentityKeyPair;
 import org.signal.libsignal.protocol.InvalidKeyException;
 import org.signal.libsignal.protocol.NoSessionException;
@@ -27,6 +28,8 @@ import org.signal.libsignal.protocol.state.SignedPreKeyRecord;
 import org.signal.libsignal.protocol.util.KeyHelper;
 import org.signal.libsignal.usernames.BaseUsernameException;
 import org.signal.libsignal.usernames.Username;
+import org.signal.network.api.AccountApiV2;
+import org.signal.network.api.AccountApiV2.SetAccountAttributesError;
 import org.signal.network.exceptions.NonSuccessfulResponseCodeException;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -57,11 +60,13 @@ import java.util.Objects;
 import java.util.UUID;
 import java.util.concurrent.TimeUnit;
 
+import kotlin.Unit;
 import okio.ByteString;
 
 import static org.asamk.signal.manager.config.ServiceConfig.PREKEY_MAXIMUM_ID;
 import static org.asamk.signal.manager.util.Utils.handleResponseException;
 import static org.asamk.signal.manager.util.Utils.handleResponseExceptionSuspend;
+import static org.asamk.signal.manager.util.Utils.runSuspendBlocking;
 import static org.whispersystems.signalservice.internal.util.Util.isEmpty;
 
 public class AccountHelper {
@@ -96,10 +101,10 @@ public class AccountHelper {
             } else {
                 context.getPreKeyHelper().refreshPreKeysIfNecessary();
             }
-            if (account.getPni() == null) {
+            if (account.getPni() == null && account.getNumber() != null) {
                 checkWhoAmiI();
             }
-            if (!account.isPrimaryDevice() && account.getPniIdentityKeyPair() == null) {
+            if (!account.isPrimaryDevice() && account.getPni() != null && account.getPniIdentityKeyPair() == null) {
                 throw new IOException("Missing PNI identity key, relinking required");
             }
             if (account.getPreviousStorageVersion() < 10
@@ -138,8 +143,9 @@ public class AccountHelper {
         final var whoAmI = dependencies.getAccountManager().getWhoAmI();
         final var number = whoAmI.getNumber();
         final var aci = ACI.parseOrThrow(whoAmI.getAci());
-        final var pni = PNI.parseOrThrow(whoAmI.getPni());
-        if (number.equals(account.getNumber()) && aci.equals(account.getAci()) && pni.equals(account.getPni())) {
+        final var pni = whoAmI.getPni() == null ? null : PNI.parseOrThrow(whoAmI.getPni());
+        if (Objects.equals(number, account.getNumber()) && aci.equals(account.getAci()) && Objects.equals(pni,
+                account.getPni())) {
             return;
         }
 
@@ -150,7 +156,7 @@ public class AccountHelper {
         account.setNumber(number);
         account.setAci(aci);
         account.setPni(pni);
-        if (account.isPrimaryDevice() && account.getPniIdentityKeyPair() == null) {
+        if (pni != null && account.isPrimaryDevice() && account.getPniIdentityKeyPair() == null) {
             account.setPniIdentityKeyPair(KeyUtils.generateIdentityKeyPair());
         }
         account.getRecipientTrustedResolver().resolveSelfRecipientTrusted(account.getSelfRecipientAddress());
@@ -564,7 +570,22 @@ public class AccountHelper {
     }
 
     public void updateAccountAttributes() throws IOException {
-        handleResponseException(dependencies.getAccountApi().setAccountAttributes(account.getAccountAttributes(null)));
+        if (account.getNumber() != null) {
+            handleResponseException(dependencies.getAccountApi()
+                    .setAccountAttributes(account.getAccountAttributes(null)));
+            return;
+        }
+        final var api = new AccountApiV2(dependencies.getAuthenticatedSignalWebSocket());
+        final RequestResult<Unit, ? extends SetAccountAttributesError> result = runSuspendBlocking(cont -> api.setAccountAttributes(
+                account.getAccountAttributesV2(),
+                cont));
+        if (result instanceof RequestResult.NonSuccess<?> failure) {
+            if (failure.getError() instanceof SetAccountAttributesError.Unauthorized) {
+                throw new AuthorizationFailedException(401, "Authorization failed!");
+            }
+            throw new IOException("Account attribute update rate limited; try again later");
+        }
+        handleResponseException(result);
     }
 
     public void addDevice(DeviceLinkUrl deviceLinkInfo) throws IOException, org.asamk.signal.manager.api.DeviceLimitExceededException {

lib/src/main/java/org/asamk/signal/manager/helper/GroupV2Helper.java

@@ -136,7 +136,7 @@ class GroupV2Helper {
 
     int findRevisionWeWereAdded(DecryptedGroup partialDecryptedGroup) {
         ByteString aciBytes = getSelfAci().toByteString();
-        ByteString pniBytes = getSelfPni().toByteString();
+        ByteString pniBytes = getSelfPni() == null ? null : getSelfPni().toByteString();
         for (DecryptedMember decryptedMember : partialDecryptedGroup.members) {
             if (decryptedMember.aciBytes.equals(aciBytes) || decryptedMember.pniBytes.equals(pniBytes)) {
                 return decryptedMember.joinedAtRevision;
@@ -264,7 +264,7 @@ class GroupV2Helper {
         var pendingMembersList = groupInfoV2.getGroup().pendingMembers;
         final var selfAci = getSelfAci();
         var selfPendingMember = DecryptedGroupUtil.findPendingByServiceId(pendingMembersList, selfAci);
-        if (selfPendingMember.isEmpty()) {
+        if (selfPendingMember.isEmpty() && getSelfPni() != null) {
             selfPendingMember = DecryptedGroupUtil.findPendingByServiceId(pendingMembersList, getSelfPni());
         }
 

lib/src/main/java/org/asamk/signal/manager/helper/IncomingMessageHandler.java

@@ -339,7 +339,7 @@ public final class IncomingMessageHandler {
             throw new AssertionError(e);
         }
 
-        if (account.getPni().equals(destination.serviceId)) {
+        if (destination.serviceId.equals(account.getPni())) {
             account.getRecipientStore().markNeedsPniSignature(sender, true);
         } else if (account.getAci().equals(destination.serviceId)) {
             account.getRecipientStore().markNeedsPniSignature(sender, false);
@@ -1124,7 +1124,7 @@ public final class IncomingMessageHandler {
         if (destination == null || destination.isUnknown()) {
             throw new InvalidMessageException("Missing destination");
         }
-        if (!account.getAci().equals(destination) && !account.getPni().equals(destination)) {
+        if (!destination.equals(account.getAci()) && !destination.equals(account.getPni())) {
             throw new InvalidMessageException("Message not intended for this account");
         }
         return new DeviceAddress(account.getRecipientResolver().resolveRecipient(destination),

lib/src/main/java/org/asamk/signal/manager/helper/SendHelper.java

@@ -886,7 +886,8 @@ public class SendHelper {
 
         var address = context.getRecipientHelper().resolveSignalServiceAddress(recipientId);
         try {
-            final boolean includePniSignature = account.getRecipientStore().needsPniSignature(recipientId);
+            final boolean includePniSignature = account.getPni() != null && account.getRecipientStore()
+                    .needsPniSignature(recipientId);
             try {
                 return s.send(messageSender,
                         address,

lib/src/main/java/org/asamk/signal/manager/internal/MultiAccountManagerImpl.java

@@ -121,7 +121,7 @@ public class MultiAccountManagerImpl implements MultiAccountManager {
             } else {
                 // Phone number — check already loaded managers
                 var existing = managers.stream()
-                        .filter(m -> m.getSelfNumber().equals(identifier))
+                        .filter(m -> identifier.equals(m.getSelfNumber()))
                         .findFirst()
                         .orElse(null);
                 if (existing != null) {

lib/src/main/java/org/asamk/signal/manager/internal/ProvisioningManagerImpl.java

@@ -20,7 +20,6 @@ import org.asamk.signal.manager.Manager;
 import org.asamk.signal.manager.ProvisioningManager;
 import org.asamk.signal.manager.Settings;
 import org.asamk.signal.manager.api.UserAlreadyExistsException;
-import org.asamk.signal.manager.config.ServiceConfig;
 import org.asamk.signal.manager.config.ServiceEnvironmentConfig;
 import org.asamk.signal.manager.storage.SignalAccount;
 import org.asamk.signal.manager.storage.accounts.AccountsStore;
@@ -30,17 +29,20 @@ import org.signal.core.models.ServiceId.ACI;
 import org.signal.core.models.ServiceId.PNI;
 import org.signal.core.models.backup.MediaRootBackupKey;
 import org.signal.core.util.crypto.DeviceNameCipher;
+import org.signal.libsignal.net.RequestResult;
 import org.signal.libsignal.protocol.IdentityKey;
 import org.signal.libsignal.protocol.IdentityKeyPair;
 import org.signal.libsignal.protocol.ecc.ECPrivateKey;
 import org.signal.libsignal.zkgroup.profiles.ProfileKey;
+import org.signal.network.api.RegistrationApiV2;
+import org.signal.network.api.RegistrationApiV2.LinkDeviceResponse;
+import org.signal.network.api.RegistrationApiV2.RegisterAsLinkedDeviceError;
+import org.signal.network.rest.SignalRestClient;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import org.whispersystems.signalservice.api.SignalServiceAccountManager;
-import org.whispersystems.signalservice.api.account.DeviceAttributes;
+import org.whispersystems.signalservice.api.account.PreKeyCollection;
 import org.whispersystems.signalservice.api.provisioning.ProvisioningSocket;
 import org.whispersystems.signalservice.api.push.ServiceIdType;
-import org.whispersystems.signalservice.api.push.SignalServiceAddress;
 import org.whispersystems.signalservice.api.push.exceptions.AuthorizationFailedException;
 import org.whispersystems.signalservice.internal.crypto.SecondaryProvisioningCipher;
 import org.whispersystems.signalservice.internal.push.ProvisionMessage;
@@ -68,6 +70,7 @@ import kotlinx.coroutines.CoroutineScope;
 
 import static org.asamk.signal.manager.util.KeyUtils.generatePreKeysForType;
 import static org.asamk.signal.manager.util.Utils.handleResponseException;
+import static org.asamk.signal.manager.util.Utils.runSuspendBlocking;
 
 public class ProvisioningManagerImpl implements ProvisioningManager, Closeable {
 
@@ -114,7 +117,8 @@ public class ProvisioningManagerImpl implements ProvisioningManager, Closeable {
     public URI getDeviceLinkUri() throws TimeoutException, IOException {
         try {
             var url = urlFuture.get(30, TimeUnit.SECONDS);
-            return new URI(url);
+            // Mode.Link(false) does not advertise any capabilities itself.
+            return new URI(url + "&capabilities=nopni");
         } catch (java.util.concurrent.TimeoutException e) {
             throw new TimeoutException("Timed out waiting for provisioning URL");
         } catch (InterruptedException e) {
@@ -148,18 +152,20 @@ public class ProvisioningManagerImpl implements ProvisioningManager, Closeable {
 
         var number = msg.number;
         var aci = ACI.parseOrThrow(msg.aci, msg.aciBinary);
-        var pni = PNI.parseOrThrow(msg.pni, msg.pniBinary);
+        var pni = parsePni(msg);
+        var identifier = number != null ? number : aci.toString();
 
-        logger.info("Received link information from {}, linking in progress ...", number);
+        logger.info("Received link information from {}, linking in progress ...", identifier);
 
         var accountPath = accountsStore.getPathByAci(aci);
-        if (accountPath == null) {
+        if (accountPath == null && number != null) {
             accountPath = accountsStore.getPathByNumber(number);
         }
         final var accountExists = accountPath != null && SignalAccount.accountFileExists(pathConfig.dataPath(),
                 accountPath);
         if (accountExists && !canRelinkExistingAccount(accountPath)) {
-            throw new UserAlreadyExistsException(number, SignalAccount.getFileName(pathConfig.dataPath(), accountPath));
+            throw new UserAlreadyExistsException(identifier,
+                    SignalAccount.getFileName(pathConfig.dataPath(), accountPath));
         }
         if (accountPath == null) {
             accountPath = accountsStore.addAccount(number, aci);
@@ -173,8 +179,10 @@ public class ProvisioningManagerImpl implements ProvisioningManager, Closeable {
         try {
             aciIdentity = new IdentityKeyPair(new IdentityKey(msg.aciIdentityKeyPublic.toByteArray()),
                     new ECPrivateKey(msg.aciIdentityKeyPrivate.toByteArray()));
-            pniIdentity = new IdentityKeyPair(new IdentityKey(msg.pniIdentityKeyPublic.toByteArray()),
-                    new ECPrivateKey(msg.pniIdentityKeyPrivate.toByteArray()));
+            pniIdentity = pni == null
+                    ? null
+                    : new IdentityKeyPair(new IdentityKey(msg.pniIdentityKeyPublic.toByteArray()),
+                            new ECPrivateKey(msg.pniIdentityKeyPrivate.toByteArray()));
             profileKey = msg.profileKey == null
                     ? KeyUtils.createProfileKey()
                     : new ProfileKey(msg.profileKey.toByteArray());
@@ -222,28 +230,19 @@ public class ProvisioningManagerImpl implements ProvisioningManager, Closeable {
             }
 
             final var aciPreKeys = generatePreKeysForType(account.getAccountData(ServiceIdType.ACI));
-            final var pniPreKeys = generatePreKeysForType(account.getAccountData(ServiceIdType.PNI));
+            final var pniPreKeys = pni == null
+                    ? null
+                    : generatePreKeysForType(account.getAccountData(ServiceIdType.PNI));
 
             logger.debug("Finishing new device registration");
-            final var attrs = account.getAccountAttributes(null);
-            final var deviceAttributes = new DeviceAttributes(attrs.getFetchesMessages(),
-                    attrs.getRegistrationId(),
-                    attrs.getPniRegistrationId(),
-                    attrs.getName(),
-                    attrs.getCapabilities());
-            final var unauthAccountManager = SignalServiceAccountManager.createWithStaticCredentials(
-                    serviceEnvironmentConfig.signalServiceConfiguration(),
-                    null,
-                    null,
-                    number,
-                    SignalServiceAddress.DEFAULT_DEVICE_ID,
-                    password,
-                    userAgent,
-                    ServiceConfig.AUTOMATIC_NETWORK_RETRY,
-                    ServiceConfig.GROUP_MAX_SIZE);
-            final var registerResponse = handleResponseException(unauthAccountManager.getRegistrationApi()
-                    .registerAsSecondaryDevice(msg.provisioningCode, deviceAttributes, aciPreKeys, pniPreKeys, null));
-            final var deviceId = Integer.parseInt(registerResponse.getDeviceId());
+            final var restClient = new SignalRestClient(serviceEnvironmentConfig.signalServiceConfiguration(),
+                    userAgent);
+            final var registrationApi = new RegistrationApiV2(restClient, false);
+            final var deviceId = registerLinkedDevice(registrationApi,
+                    account,
+                    msg.provisioningCode,
+                    aciPreKeys,
+                    pniPreKeys);
 
             account.finishLinking(deviceId, aciPreKeys, pniPreKeys);
             linkingFinished = true;
@@ -277,7 +276,7 @@ public class ProvisioningManagerImpl implements ProvisioningManager, Closeable {
                     newManagerListener.accept(m);
                     m = null;
                 }
-                return number;
+                return identifier;
             } finally {
                 if (m != null) {
                     m.close();
@@ -296,6 +295,76 @@ public class ProvisioningManagerImpl implements ProvisioningManager, Closeable {
         }
     }
 
+    static PNI parsePni(final ProvisionMessage message) throws IOException {
+        if (message.number != null) {
+            return PNI.parseOrThrow(message.pni, message.pniBinary);
+        }
+        if (message.pni != null
+                || message.pniBinary != null
+                || message.pniIdentityKeyPublic != null
+                || message.pniIdentityKeyPrivate != null) {
+            throw new IOException("Provisioning message has PNI material without a phone number");
+        }
+        if (message.authCredentialSalt == null || message.authCredentialSalt.size() == 0) {
+            throw new IOException("Numberless provisioning message is missing the group auth credential salt");
+        }
+        return null;
+    }
+
+    static int registerLinkedDevice(
+            final RegistrationApiV2 registrationApi,
+            final SignalAccount account,
+            final String provisioningCode,
+            final PreKeyCollection aciPreKeys,
+            final PreKeyCollection pniPreKeys
+    ) throws IOException {
+        final var attrs = account.getAccountAttributesV2();
+        final var deviceAttributes = new RegistrationApiV2.DeviceAttributes(attrs.getFetchesMessages(),
+                attrs.getRegistrationId(),
+                attrs.getPniRegistrationId(),
+                attrs.getName(),
+                attrs.getCapabilities());
+        final RequestResult<LinkDeviceResponse, ? extends RegisterAsLinkedDeviceError> result = runSuspendBlocking(cont -> registrationApi.registerAsSecondaryDevice(
+                account.getAci(),
+                account.getPassword(),
+                provisioningCode,
+                deviceAttributes,
+                toRegistrationPreKeys(aciPreKeys),
+                toRegistrationPreKeys(pniPreKeys),
+                null,
+                cont));
+        return getLinkedDeviceId(result);
+    }
+
+    static int getLinkedDeviceId(
+            final RequestResult<LinkDeviceResponse, ? extends RegisterAsLinkedDeviceError> result
+    ) throws IOException {
+        if (result instanceof RequestResult.NonSuccess<?> failure) {
+            throw switch (failure.getError()) {
+                case RegisterAsLinkedDeviceError.IncorrectVerification ignored ->
+                        new AuthorizationFailedException(403, "Device verification failed");
+                case RegisterAsLinkedDeviceError.MissingCapability ignored ->
+                        new IOException("Linked device is missing a required account capability");
+                case RegisterAsLinkedDeviceError.MaxLinkedDevices ignored ->
+                        new IOException("Account has reached its linked device limit");
+                case RegisterAsLinkedDeviceError.InvalidRequest ignored ->
+                        new IOException("Signal rejected the device linking request");
+                case RegisterAsLinkedDeviceError.RateLimited ignored ->
+                        new IOException("Device linking rate limited; try again later");
+                default -> new IOException("Unexpected device linking response");
+            };
+        }
+        return handleResponseException(result).getDeviceId();
+    }
+
+    static RegistrationApiV2.PreKeyCollection toRegistrationPreKeys(final PreKeyCollection preKeys) {
+        return preKeys == null
+                ? null
+                : new RegistrationApiV2.PreKeyCollection(preKeys.getIdentityKey(),
+                        preKeys.getSignedPreKey(),
+                        preKeys.getLastResortKyberPreKey());
+    }
+
     @Override
     public void close() throws IOException {
         socketHandle.close();

lib/src/main/java/org/asamk/signal/manager/storage/SignalAccount.java

@@ -71,6 +71,7 @@ import org.signal.libsignal.protocol.state.SignedPreKeyRecord;
 import org.signal.libsignal.protocol.util.KeyHelper;
 import org.signal.libsignal.zkgroup.InvalidInputException;
 import org.signal.libsignal.zkgroup.profiles.ProfileKey;
+import org.signal.network.api.RegistrationApiV2;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.whispersystems.signalservice.api.SignalServiceAccountDataStore;
@@ -350,7 +351,9 @@ public class SignalAccount implements Closeable {
         this.registered = true;
         this.deviceId = deviceId;
         setPreKeys(ServiceIdType.ACI, aciPreKeys);
-        setPreKeys(ServiceIdType.PNI, pniPreKeys);
+        if (pniPreKeys != null) {
+            setPreKeys(ServiceIdType.PNI, pniPreKeys);
+        }
         save();
     }
 
@@ -1426,6 +1429,29 @@ public class SignalAccount implements Closeable {
         return getCapabilities(isPrimaryDevice());
     }
 
+    public RegistrationApiV2.AccountAttributes getAccountAttributesV2() {
+        final var attributes = getAccountAttributes(null);
+        final var capabilities = attributes.getCapabilities();
+        return new RegistrationApiV2.AccountAttributes(attributes.getSignalingKey(),
+                attributes.getRegistrationId(),
+                attributes.getVoice(),
+                attributes.getVideo(),
+                attributes.getFetchesMessages(),
+                attributes.getRegistrationLock(),
+                attributes.getUnidentifiedAccessKey(),
+                attributes.getUnrestrictedUnidentifiedAccess(),
+                number == null ? null : attributes.getDiscoverableByPhoneNumber(),
+                new RegistrationApiV2.AccountAttributes.Capabilities(capabilities.getStorage(),
+                        capabilities.getVersionedExpirationTimer(),
+                        capabilities.getAttachmentBackfill(),
+                        capabilities.getSpqr(),
+                        capabilities.getUsernameChangeSyncMessage(),
+                        capabilities.getOptionalPhoneNumber()),
+                attributes.getName(),
+                getPni() == null ? null : attributes.getPniRegistrationId(),
+                attributes.getRecoveryPassword());
+    }
+
     public ServiceId getAccountId(ServiceIdType serviceIdType) {
         return getAccountData(serviceIdType).getServiceId();
     }

lib/src/main/java/org/asamk/signal/manager/storage/accounts/AccountsStorage.java

@@ -4,5 +4,6 @@ import java.util.List;
 
 public record AccountsStorage(List<Account> accounts, Integer version) {
 
-    public record Account(String path, String environment, String number, String uuid) {}
+    // Older indexes omit this flag; entries with only a UUID must then be checked against their account state.
+    public record Account(String path, String environment, String number, String uuid, Boolean numberless) {}
 }

lib/src/main/java/org/asamk/signal/manager/storage/accounts/AccountsStore.java

@@ -63,11 +63,14 @@ public class AccountsStore {
     public synchronized Set<AccountsStorage.Account> getAllAccounts() throws IOException {
         return readAccounts().stream()
                 .filter(a -> a.environment() == null || serviceEnvironment.equals(a.environment()))
-                .filter(a -> a.number() != null)
+                .filter(a -> a.number() != null || (a.uuid() != null && Boolean.TRUE.equals(a.numberless())))
                 .collect(Collectors.toSet());
     }
 
     public synchronized String getPathByNumber(String number) throws IOException {
+        if (number == null) {
+            return null;
+        }
         return readAccounts().stream()
                 .filter(a -> a.environment() == null || serviceEnvironment.equals(a.environment()))
                 .filter(a -> number.equals(a.number()))
@@ -95,14 +98,15 @@ public class AccountsStore {
                 return new AccountsStorage.Account(a.path(),
                         serviceEnvironment,
                         number,
-                        aci == null ? null : aci.toString());
+                        aci == null ? null : aci.toString(),
+                        number == null && aci != null);
             }
 
             if (number != null && number.equals(a.number())) {
-                return new AccountsStorage.Account(a.path(), a.environment(), null, a.uuid());
+                return new AccountsStorage.Account(a.path(), a.environment(), null, a.uuid(), false);
             }
-            if (aci != null && aci.toString().equals(a.toString())) {
-                return new AccountsStorage.Account(a.path(), a.environment(), a.number(), null);
+            if (aci != null && aci.toString().equals(a.uuid())) {
+                return new AccountsStorage.Account(a.path(), a.environment(), a.number(), null, false);
             }
 
             return a;
@@ -114,7 +118,8 @@ public class AccountsStore {
         final var account = new AccountsStorage.Account(accountPath,
                 serviceEnvironment,
                 number,
-                aci == null ? null : aci.toString());
+                aci == null ? null : aci.toString(),
+                number == null && aci != null);
         updateAccounts(accounts -> {
             final var existingAccounts = accounts.stream().map(a -> {
                 if (a.environment() != null && !serviceEnvironment.equals(a.environment())) {
@@ -122,10 +127,10 @@ public class AccountsStore {
                 }
 
                 if (number != null && number.equals(a.number())) {
-                    return new AccountsStorage.Account(a.path(), a.environment(), null, a.uuid());
+                    return new AccountsStorage.Account(a.path(), a.environment(), null, a.uuid(), false);
                 }
                 if (aci != null && aci.toString().equals(a.uuid())) {
-                    return new AccountsStorage.Account(a.path(), a.environment(), a.number(), null);
+                    return new AccountsStorage.Account(a.path(), a.environment(), a.number(), null, false);
                 }
 
                 return a;
@@ -156,7 +161,7 @@ public class AccountsStore {
     private void createInitialAccounts() throws IOException {
         final var legacyAccountPaths = getLegacyAccountPaths();
         final var accountsStorage = new AccountsStorage(legacyAccountPaths.stream()
-                .map(number -> new AccountsStorage.Account(number, null, number, null))
+                .map(number -> new AccountsStorage.Account(number, null, number, null, false))
                 .toList(), CURRENT_STORAGE_VERSION);
 
         IOUtils.createPrivateDirectories(dataPath);
@@ -188,7 +193,7 @@ public class AccountsStore {
     private List<AccountsStorage.Account> readAccounts() throws IOException {
         final var pair = openFileChannel(getAccountsFile());
         try (final var fileChannel = pair.first(); final var lock = pair.second()) {
-            final var storage = readAccountsLocked(fileChannel);
+            var storage = readAccountsLocked(fileChannel);
 
             var accountsVersion = storage.version() == null ? 1 : storage.version();
             if (accountsVersion > CURRENT_STORAGE_VERSION) {
@@ -197,12 +202,36 @@ public class AccountsStore {
                 throw new IOException("Accounts file was created by a no longer supported older version: "
                         + accountsVersion);
             } else if (accountsVersion < CURRENT_STORAGE_VERSION) {
-                return upgradeAccountsFile(fileChannel, storage, accountsVersion).accounts();
+                storage = upgradeAccountsFile(fileChannel, storage, accountsVersion);
             }
-            return storage.accounts();
+            final var accounts = storage.accounts().stream().map(this::resolveNumberlessAccount).toList();
+            if (!accounts.equals(storage.accounts())) {
+                saveAccountsLocked(fileChannel, new AccountsStorage(accounts, storage.version()));
+            }
+            return accounts;
         }
     }
 
+    private AccountsStorage.Account resolveNumberlessAccount(final AccountsStorage.Account entry) {
+        if (entry.numberless() != null) {
+            return entry;
+        }
+
+        var numberless = false;
+        if (entry.number() == null && entry.uuid() != null) {
+            // Older entries also lose their number when another account takes it over.
+            try (final var account = accountLoader.loadAccountOrNull(entry.path())) {
+                if (account == null) {
+                    // Keep the entry unresolved so a locked or unavailable account can be checked later.
+                    return entry;
+                }
+                numberless = account.getNumber() == null && account.getAci() != null && entry.uuid()
+                        .equals(account.getAci().toString());
+            }
+        }
+        return new AccountsStorage.Account(entry.path(), entry.environment(), entry.number(), entry.uuid(), numberless);
+    }
+
     private AccountsStorage upgradeAccountsFile(
             final FileChannel fileChannel,
             final AccountsStorage storage,
@@ -223,7 +252,8 @@ public class AccountsStore {
                         return new AccountsStorage.Account(a.path(),
                                 getServiceEnvironmentString(account.getServiceEnvironment()),
                                 a.number(),
-                                a.uuid());
+                                a.uuid(),
+                                a.numberless());
                     }
                 }).toList();
             }

lib/src/main/java/org/asamk/signal/manager/util/PhoneNumberFormatter.java

@@ -42,6 +42,19 @@ public class PhoneNumberFormatter {
             throw new InvalidNumberException("No valid characters found.");
         }
 
+        if (localNumber == null) {
+            if (!number.startsWith("+")) {
+                throw new InvalidNumberException(
+                        "Use an international number including the country code for a numberless account.");
+            }
+            try {
+                final var util = PhoneNumberUtil.getInstance();
+                return util.format(util.parse(number, null), PhoneNumberFormat.E164);
+            } catch (NumberParseException e) {
+                throw new InvalidNumberException("Invalid international phone number.");
+            }
+        }
+
         try {
             PhoneNumberUtil util = PhoneNumberUtil.getInstance();
             PhoneNumber localNumberObject = util.parse(localNumber, null);

lib/src/test/java/org/asamk/signal/manager/helper/NumberlessGroupTest.java

@@ -0,0 +1,57 @@
+package org.asamk.signal.manager.helper;
+
+import org.asamk.signal.manager.Settings;
+import org.asamk.signal.manager.api.ServiceEnvironment;
+import org.asamk.signal.manager.storage.SignalAccount;
+import org.asamk.signal.manager.util.KeyUtils;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import org.signal.core.models.ServiceId.ACI;
+import org.signal.storageservice.storage.protos.groups.local.DecryptedGroup;
+import org.signal.storageservice.storage.protos.groups.local.DecryptedMember;
+
+import java.nio.file.Path;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class NumberlessGroupTest {
+
+    @TempDir
+    Path directory;
+
+    @Test
+    void findsOurGroupMembershipByAciWhenPniIsAbsent() throws Exception {
+        final var aci = ACI.parseOrThrow("11111111-1111-4111-8111-111111111111");
+        final var otherAci = ACI.parseOrThrow("22222222-2222-4222-8222-222222222222");
+        try (final var account = SignalAccount.createLinkedAccount(directory.toFile(),
+                "account",
+                ServiceEnvironment.STAGING,
+                Settings.DEFAULT); final var context = new Context(account, null, null, null, null, null)) {
+            account.setProvisioningData(null,
+                    aci,
+                    null,
+                    "test-password",
+                    new byte[]{1},
+                    KeyUtils.generateIdentityKeyPair(),
+                    null,
+                    KeyUtils.createProfileKey(),
+                    null,
+                    new byte[32],
+                    null);
+            final var otherMember = new DecryptedMember.Builder().aciBytes(otherAci.toByteString())
+                    .joinedAtRevision(1)
+                    .build();
+            final var selfMember = new DecryptedMember.Builder().aciBytes(aci.toByteString())
+                    .joinedAtRevision(4)
+                    .build();
+            final var group = new DecryptedGroup.Builder().revision(9)
+                    .members(List.of(otherMember, selfMember))
+                    .build();
+            assertEquals(4, context.getGroupV2Helper().findRevisionWeWereAdded(group));
+            assertEquals(9,
+                    context.getGroupV2Helper()
+                            .findRevisionWeWereAdded(group.newBuilder().members(List.of(otherMember)).build()));
+        }
+    }
+}

lib/src/test/java/org/asamk/signal/manager/internal/NumberlessProvisioningTest.java

@@ -0,0 +1,165 @@
+package org.asamk.signal.manager.internal;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import org.asamk.signal.manager.Settings;
+import org.asamk.signal.manager.api.ServiceEnvironment;
+import org.asamk.signal.manager.config.ServiceConfig;
+import org.asamk.signal.manager.storage.SignalAccount;
+import org.asamk.signal.manager.util.KeyUtils;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import org.signal.core.models.ServiceId.ACI;
+import org.signal.core.models.ServiceId.PNI;
+import org.signal.libsignal.net.RequestResult;
+import org.signal.network.api.RegistrationApiV2;
+import org.signal.network.api.RegistrationApiV2.RegisterAsLinkedDeviceError;
+import org.signal.network.rest.SignalRestClient;
+import org.whispersystems.signalservice.api.push.ServiceIdType;
+import org.whispersystems.signalservice.api.push.exceptions.AuthorizationFailedException;
+import org.whispersystems.signalservice.internal.push.ProvisionMessage;
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.security.SecureRandom;
+import java.util.concurrent.atomic.AtomicReference;
+
+import okhttp3.Credentials;
+import okhttp3.MediaType;
+import okhttp3.OkHttpClient;
+import okhttp3.Protocol;
+import okhttp3.Request;
+import okhttp3.Response;
+import okhttp3.ResponseBody;
+import okio.Buffer;
+import okio.ByteString;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class NumberlessProvisioningTest {
+
+    private static final ACI ACI_ID = ACI.parseOrThrow("11111111-1111-4111-8111-111111111111");
+    private static final PNI PNI_ID = PNI.parseOrThrow("22222222-2222-4222-8222-222222222222");
+
+    @TempDir
+    Path directory;
+
+    @Test
+    void numberlessProvisioningRequiresGroupCredentialSalt() {
+        assertThrows(IOException.class, () -> ProvisioningManagerImpl.parsePni(new ProvisionMessage.Builder().build()));
+        final var emptySalt = new ProvisionMessage.Builder().authCredentialSalt(ByteString.EMPTY).build();
+        assertThrows(IOException.class, () -> ProvisioningManagerImpl.parsePni(emptySalt));
+        assertNull(ProvisioningManagerImpl.toRegistrationPreKeys(null));
+    }
+
+    @Test
+    void acceptsNumberlessProvisioningButRejectsInconsistentPhoneIdentity() throws Exception {
+        final var message = new ProvisionMessage.Builder().authCredentialSalt(ByteString.of(new byte[32]));
+        assertNull(ProvisioningManagerImpl.parsePni(message.build()));
+        assertThrows(IOException.class, () -> ProvisioningManagerImpl.parsePni(message.pni(PNI_ID.toString()).build()));
+        assertThrows(IllegalArgumentException.class,
+                () -> ProvisioningManagerImpl.parsePni(new ProvisionMessage.Builder().number("+12025550123").build()));
+        assertEquals(PNI_ID,
+                ProvisioningManagerImpl.parsePni(new ProvisionMessage.Builder().number("+12025550123")
+                        .pni(PNI_ID.toString())
+                        .build()));
+    }
+
+    @Test
+    void numberlessLinkRequestOmitsPniAndAuthenticatesWithAci() throws Exception {
+        checkLinkRequest(null, null);
+    }
+
+    @Test
+    void numberedLinkRequestStillIncludesPniKeys() throws Exception {
+        checkLinkRequest("+12025550123", PNI_ID);
+    }
+
+    private void checkLinkRequest(final String number, final PNI pni) throws Exception {
+        final var request = new AtomicReference<Request>();
+        final var body = new AtomicReference<JsonNode>();
+        final var mapper = new ObjectMapper();
+        final var client = new OkHttpClient.Builder().addInterceptor(chain -> {
+            request.set(chain.request());
+            final var buffer = new Buffer();
+            chain.request().body().writeTo(buffer);
+            body.set(mapper.readTree(buffer.readUtf8()));
+            return new Response.Builder().request(chain.request())
+                    .protocol(Protocol.HTTP_1_1)
+                    .code(200)
+                    .message("OK")
+                    .body(ResponseBody.create("{\"deviceId\":2}", MediaType.get("application/json")))
+                    .build();
+        }).build();
+        final var config = ServiceConfig.getServiceEnvironmentConfig(ServiceEnvironment.STAGING, "signal-cli-test");
+        final var restClient = new SignalRestClient(config.signalServiceConfiguration(),
+                "signal-cli-test",
+                null,
+                false,
+                1000L,
+                new SecureRandom(),
+                client);
+        final var api = new RegistrationApiV2(restClient, false);
+
+        try (final var account = SignalAccount.createLinkedAccount(directory.toFile(),
+                "account",
+                ServiceEnvironment.STAGING,
+                Settings.DEFAULT)) {
+            account.setProvisioningData(number,
+                    ACI_ID,
+                    pni,
+                    "test-password",
+                    new byte[]{1},
+                    KeyUtils.generateIdentityKeyPair(),
+                    pni == null ? null : KeyUtils.generateIdentityKeyPair(),
+                    KeyUtils.createProfileKey(),
+                    null,
+                    new byte[32],
+                    null);
+            final var aciKeys = KeyUtils.generatePreKeysForType(account.getAccountData(ServiceIdType.ACI));
+            final var pniKeys = pni == null
+                    ? null
+                    : KeyUtils.generatePreKeysForType(account.getAccountData(ServiceIdType.PNI));
+            final var deviceId = ProvisioningManagerImpl.registerLinkedDevice(api,
+                    account,
+                    "test-code",
+                    aciKeys,
+                    pniKeys);
+
+            assertEquals(2, deviceId);
+            assertEquals("PUT", request.get().method());
+            assertEquals("/v1/devices/link", request.get().url().encodedPath());
+            assertEquals(Credentials.basic(ACI_ID.toString(), "test-password"), request.get().header("Authorization"));
+            assertTrue(body.get()
+                    .path("accountAttributes")
+                    .path("capabilities")
+                    .path("optionalPhoneNumber")
+                    .asBoolean());
+            assertTrue(body.get().hasNonNull("aciSignedPreKey"));
+            assertTrue(body.get().hasNonNull("aciPqLastResortPreKey"));
+            assertEquals(pni != null, body.get().has("pniSignedPreKey"));
+            assertEquals(pni != null, body.get().has("pniPqLastResortPreKey"));
+            assertEquals(pni != null, body.get().path("accountAttributes").has("pniRegistrationId"));
+        } finally {
+            client.dispatcher().executorService().shutdown();
+            client.connectionPool().evictAll();
+        }
+    }
+
+    @Test
+    @SuppressWarnings("unchecked")
+    void linkingErrorsAreReportedWithoutCrashingOrIncludingServerBody() {
+        final var incorrectVerification = RegisterAsLinkedDeviceError.IncorrectVerification.INSTANCE;
+        assertThrows(AuthorizationFailedException.class,
+                () -> ProvisioningManagerImpl.getLinkedDeviceId(new RequestResult.NonSuccess<>(incorrectVerification)));
+        final var invalidRequest = new RegisterAsLinkedDeviceError.InvalidRequest("secret payload");
+        final var error = assertThrows(IOException.class,
+                () -> ProvisioningManagerImpl.getLinkedDeviceId(new RequestResult.NonSuccess<>(invalidRequest)));
+        assertFalse(error.getMessage().contains("secret payload"));
+    }
+}

lib/src/test/java/org/asamk/signal/manager/storage/NumberlessAccountTest.java

@@ -0,0 +1,64 @@
+package org.asamk.signal.manager.storage;
+
+import org.asamk.signal.manager.Settings;
+import org.asamk.signal.manager.api.ServiceEnvironment;
+import org.asamk.signal.manager.util.KeyUtils;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import org.signal.core.models.ServiceId.ACI;
+import org.whispersystems.signalservice.api.push.ServiceIdType;
+
+import java.nio.file.Path;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class NumberlessAccountTest {
+
+    @TempDir
+    Path directory;
+
+    @Test
+    void numberlessLinkedAccountSurvivesReload() throws Exception {
+        final var aci = ACI.parseOrThrow("11111111-1111-4111-8111-111111111111");
+        final var identity = KeyUtils.generateIdentityKeyPair();
+        final var salt = new byte[32];
+        salt[0] = 42;
+        try (final var account = SignalAccount.createLinkedAccount(directory.toFile(),
+                "account",
+                ServiceEnvironment.STAGING,
+                Settings.DEFAULT)) {
+            account.setProvisioningData(null,
+                    aci,
+                    null,
+                    "test-password",
+                    new byte[]{1},
+                    identity,
+                    null,
+                    KeyUtils.createProfileKey(),
+                    null,
+                    salt,
+                    null);
+            account.finishLinking(2, KeyUtils.generatePreKeysForType(account.getAccountData(ServiceIdType.ACI)), null);
+        }
+
+        try (final var account = SignalAccount.load(directory.toFile(), "account", true, Settings.DEFAULT)) {
+            assertTrue(account.isRegistered());
+            assertFalse(account.isPrimaryDevice());
+            assertEquals(2, account.getDeviceId());
+            assertEquals(aci, account.getAci());
+            assertNull(account.getNumber());
+            assertNull(account.getPni());
+            assertNull(account.getPniIdentityKeyPair());
+            assertNull(account.getSignalServiceDataStore().pniOrNull());
+            assertArrayEquals(identity.serialize(), account.getAciIdentityKeyPair().serialize());
+            assertArrayEquals(salt, account.getAuthCredentialSalt());
+            assertNull(account.getAccountAttributesV2().getPniRegistrationId());
+            assertNull(account.getAccountAttributesV2().getDiscoverableByPhoneNumber());
+            assertTrue(account.getAccountAttributesV2().getCapabilities().getOptionalPhoneNumber());
+        }
+    }
+}

lib/src/test/java/org/asamk/signal/manager/storage/accounts/AccountsStoreTest.java

@@ -0,0 +1,208 @@
+package org.asamk.signal.manager.storage.accounts;
+
+import org.asamk.signal.manager.Settings;
+import org.asamk.signal.manager.api.ServiceEnvironment;
+import org.asamk.signal.manager.storage.SignalAccount;
+import org.asamk.signal.manager.storage.Utils;
+import org.asamk.signal.manager.util.KeyUtils;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+import org.signal.core.models.ServiceId.ACI;
+
+import java.io.IOException;
+import java.nio.channels.OverlappingFileLockException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class AccountsStoreTest {
+
+    private static final ACI OLD_ACI = ACI.parseOrThrow("11111111-1111-4111-8111-111111111111");
+    private static final ACI NEW_ACI = ACI.parseOrThrow("22222222-2222-4222-8222-222222222222");
+
+    @TempDir
+    Path directory;
+
+    @Test
+    void discoversNumberlessAccountsByAciAndKeepsEnvironmentsSeparate() throws Exception {
+        final var store = new AccountsStore(directory.toFile(), ServiceEnvironment.STAGING, path -> null);
+        final var aci = ACI.parseOrThrow("11111111-1111-4111-8111-111111111111");
+        final var path = store.addAccount(null, aci);
+        store.addAccount("+12025550123", null);
+
+        final var reopened = new AccountsStore(directory.toFile(), ServiceEnvironment.STAGING, ignored -> null);
+        assertEquals(2, reopened.getAllAccounts().size());
+        assertEquals(path, reopened.getPathByAci(aci));
+        assertNull(reopened.getPathByNumber(null));
+        assertEquals(Set.of("+12025550123"), reopened.getAllNumbers());
+        assertTrue(new AccountsStore(directory.toFile(), ServiceEnvironment.LIVE, ignored -> null).getAllAccounts()
+                .isEmpty());
+    }
+
+    @Test
+    void updatingAnAciDoesNotLeaveDuplicateNumberlessAccounts() throws Exception {
+        final var store = new AccountsStore(directory.toFile(), ServiceEnvironment.STAGING, path -> null);
+        final var aci = ACI.parseOrThrow("11111111-1111-4111-8111-111111111111");
+        final var oldPath = store.addAccount(null, aci);
+        Files.createFile(directory.resolve(oldPath));
+        final var newPath = store.addAccount(null, null);
+        store.updateAccount(newPath, null, aci);
+
+        assertEquals(newPath, store.getPathByAci(aci));
+        assertEquals(1, store.getAllAccounts().size());
+    }
+
+    @ParameterizedTest
+    @ValueSource(booleans = {false, true})
+    void replacingANumberDoesNotRediscoverTheOldAccountAsNumberless(final boolean update) throws Exception {
+        final var store = new AccountsStore(directory.toFile(), ServiceEnvironment.STAGING, path -> null);
+        final var oldPath = store.addAccount("+12025550123", OLD_ACI);
+        Files.createFile(directory.resolve(oldPath));
+        final String newPath;
+        if (update) {
+            newPath = store.addAccount("+12025550124", NEW_ACI);
+            store.updateAccount(newPath, "+12025550123", NEW_ACI);
+        } else {
+            newPath = store.addAccount("+12025550123", NEW_ACI);
+        }
+
+        final var reopened = new AccountsStore(directory.toFile(), ServiceEnvironment.STAGING, path -> {
+            throw new AssertionError("New entries should not require loading account state for discovery");
+        });
+        assertEquals(Set.of(newPath), getAccountPaths(reopened));
+        assertEquals(newPath, reopened.getPathByNumber("+12025550123"));
+        assertEquals(oldPath, reopened.getPathByAci(OLD_ACI));
+
+        // Only an explicit account update should turn the old entry into a numberless account.
+        reopened.updateAccount(oldPath, null, OLD_ACI);
+        assertEquals(Set.of(oldPath, newPath), getAccountPaths(reopened));
+    }
+
+    @ParameterizedTest
+    @ValueSource(ints = {1, 2})
+    void legacyIndexesDistinguishNumberlessAccountsFromSupersededNumberedAccounts(final int version) throws Exception {
+        createSavedAccount("old", "+12025550123", OLD_ACI);
+        createSavedAccount("numberless", null, NEW_ACI);
+        final var legacyIndex = """
+                                {
+                                  "version": %d,
+                                  "accounts": [
+                                    {"path": "old", "environment": %s, "number": null, "uuid": "%s"},
+                                    {"path": "numberless", "environment": %s, "number": null, "uuid": "%s"},
+                                    {"path": "current", "environment": "STAGING", "number": "+12025550123", "uuid": null}
+                                  ]
+                                }
+                                """.formatted(version,
+                version == 1 ? "null" : "\"STAGING\"",
+                OLD_ACI,
+                version == 1 ? "null" : "\"STAGING\"",
+                NEW_ACI);
+        Files.writeString(directory.resolve("accounts.json"), legacyIndex);
+
+        final var store = new AccountsStore(directory.toFile(), ServiceEnvironment.STAGING, this::loadAccountOrNull);
+        assertEquals(Set.of("numberless", "current"), getAccountPaths(store));
+        assertEquals("old", store.getPathByAci(OLD_ACI));
+        assertEquals("numberless", store.getPathByAci(NEW_ACI));
+        assertEquals(Set.of("+12025550123"), store.getAllNumbers());
+
+        final var reopened = new AccountsStore(directory.toFile(), ServiceEnvironment.STAGING, path -> {
+            throw new AssertionError("Resolved entries should not require loading account state again");
+        });
+        assertEquals(Set.of("numberless", "current"), getAccountPaths(reopened));
+        assertTrue(new AccountsStore(directory.toFile(),
+                ServiceEnvironment.LIVE,
+                this::loadAccountOrNull).getAllAccounts().isEmpty());
+    }
+
+    @Test
+    void retriesLockedLegacyAccountsAndPersistsSuccessfulClassification() throws Exception {
+        createSavedAccount("numberless", null, NEW_ACI);
+        writeLegacyNumberlessEntry(NEW_ACI);
+        final var store = new AccountsStore(directory.toFile(), ServiceEnvironment.STAGING, this::loadAccountOrNull);
+
+        try (final var account = SignalAccount.load(directory.toFile(), "numberless", false, Settings.DEFAULT)) {
+            assertTrue(store.getAllAccounts().isEmpty());
+            assertEquals("numberless", store.getPathByAci(NEW_ACI));
+            final var storage = Utils.createStorageObjectMapper()
+                    .readValue(directory.resolve("accounts.json").toFile(), AccountsStorage.class);
+            assertNull(storage.accounts().getFirst().numberless());
+        }
+
+        assertEquals(Set.of("numberless"), getAccountPaths(store));
+        try (final var account = SignalAccount.load(directory.toFile(), "numberless", false, Settings.DEFAULT)) {
+            final var reopened = new AccountsStore(directory.toFile(), ServiceEnvironment.STAGING, path -> {
+                throw new AssertionError("A classified account should remain discoverable while locked");
+            });
+            assertEquals(Set.of("numberless"), getAccountPaths(reopened));
+        }
+    }
+
+    @Test
+    void retriesLegacyAccountsAfterMissingStateIsRestored() throws Exception {
+        writeLegacyNumberlessEntry(NEW_ACI);
+        final var store = new AccountsStore(directory.toFile(), ServiceEnvironment.STAGING, this::loadAccountOrNull);
+        assertTrue(store.getAllAccounts().isEmpty());
+        assertEquals("numberless", store.getPathByAci(NEW_ACI));
+
+        createSavedAccount("numberless", null, NEW_ACI);
+        assertEquals(Set.of("numberless"), getAccountPaths(store));
+    }
+
+    @Test
+    void doesNotDiscoverLegacyEntriesWithAMismatchedAci() throws Exception {
+        createSavedAccount("numberless", null, NEW_ACI);
+        writeLegacyNumberlessEntry(OLD_ACI);
+        final var store = new AccountsStore(directory.toFile(), ServiceEnvironment.STAGING, this::loadAccountOrNull);
+        assertTrue(store.getAllAccounts().isEmpty());
+        assertEquals("numberless", store.getPathByAci(OLD_ACI));
+    }
+
+    private Set<String> getAccountPaths(final AccountsStore store) throws IOException {
+        return store.getAllAccounts().stream().map(AccountsStorage.Account::path).collect(Collectors.toSet());
+    }
+
+    private void writeLegacyNumberlessEntry(final ACI aci) throws IOException {
+        final var legacyIndex = """
+                                {
+                                  "version": 2,
+                                  "accounts": [
+                                    {"path": "numberless", "environment": "STAGING", "number": null, "uuid": "%s"}
+                                  ]
+                                }
+                                """.formatted(aci);
+        Files.writeString(directory.resolve("accounts.json"), legacyIndex);
+    }
+
+    private void createSavedAccount(final String path, final String number, final ACI aci) throws IOException {
+        // Account creation needs a number until the ACI has been assigned.
+        try (final var account = SignalAccount.create(directory.toFile(),
+                path,
+                "+12025550123",
+                ServiceEnvironment.STAGING,
+                KeyUtils.generateIdentityKeyPair(),
+                KeyUtils.generateIdentityKeyPair(),
+                KeyUtils.createProfileKey(),
+                Settings.DEFAULT)) {
+            account.setAci(aci);
+            account.setNumber(number);
+        }
+    }
+
+    private SignalAccount loadAccountOrNull(final String path) {
+        if (!SignalAccount.accountFileExists(directory.toFile(), path)) {
+            return null;
+        }
+        try {
+            return SignalAccount.load(directory.toFile(), path, false, Settings.DEFAULT);
+        } catch (IOException | OverlappingFileLockException e) {
+            return null;
+        }
+    }
+}

lib/src/test/java/org/asamk/signal/manager/util/PhoneNumberFormatterTest.java

@@ -0,0 +1,25 @@
+package org.asamk.signal.manager.util;
+
+import org.asamk.signal.manager.api.InvalidNumberException;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class PhoneNumberFormatterTest {
+
+    @Test
+    void numberlessAccountsCanAddressInternationalPhoneNumbers() throws Exception {
+        assertEquals("+12025550123", PhoneNumberFormatter.formatNumber("+1 (202) 555-0123", null));
+    }
+
+    @Test
+    void numberlessAccountsCannotInferACountryCode() {
+        assertThrows(InvalidNumberException.class, () -> PhoneNumberFormatter.formatNumber("2025550123", null));
+    }
+
+    @Test
+    void numberedAccountsStillInferTheirCountryCode() throws Exception {
+        assertEquals("+12025550123", PhoneNumberFormatter.formatNumber("2025550123", "+12025550124"));
+    }
+}

man/signal-cli-dbus.5.adoc

@@ -15,9 +15,13 @@ signal-cli-dbus - A commandline and dbus interface for the Signal messenger
 
 *signal-cli* [--verbose] [--data-dir DATA_DIR] [-a ACCOUNT] [-o {plain-text,json}] daemon [--dbus] [--dbus-system]
 
-*dbus-send* [--system | --session] [--print-reply] --type=method_call --dest="org.asamk.Signal" /org/asamk/Signal[/_<phonenumber>] org.asamk.Signal.<method> [string:<string argument>] [array:<type>:<array argument>]
+*dbus-send* [--system | --session] [--print-reply] --type=method_call --dest="org.asamk.Signal" /org/asamk/Signal[/<account-id>] org.asamk.Signal.<method> [string:<string argument>] [array:<type>:<array argument>]
 
-Note: when daemon was started without explicit `-a ACCOUNT`, the `dbus-send` command requires adding the phone number in `/org/asamk/Signal/_<phonenumber>`.
+Note: when daemon was started without explicit `-a ACCOUNT`, use the account's
+object path returned by `org.asamk.SignalControl.listAccounts` or
+`org.asamk.SignalControl.getAccount`. Numbered accounts use
+`/org/asamk/Signal/_<phonenumber>`. Accounts without a phone number use
+`/org/asamk/Signal/<ACI>`, with hyphens replaced by underscores.
 
 == Description
 
@@ -49,6 +53,11 @@ All Exceptions begin with "org.asamk.Signal.Error." which is omitted here for be
 
 Phone numbers always have the format +<countrycode><regional number>
 
+For an account without a phone number, use its ACI (Account ID) with the
+`signal-cli --dbus -a ACCOUNT` client. ACI selectors also work for numbered accounts.
+An account without a phone number cannot infer the country code of a recipient;
+use a complete international phone number, an ACI, or a Signal username.
+
 == Methods
 
 === SignalControl interface
@@ -73,11 +82,29 @@ For example:
 dbus-send --session --dest=org.asamk.Signal --type=method_call --print-reply /org/asamk/Signal org.asamk.Signal.link string:"My secondary client" | tr '\n' '\0' | sed 's/.*string //g' | sed 's/\"//g' | qrencode -s10 -tANSI256
 ----
 
-listAccounts() -> accountList<as>::
+listAccounts() -> accountList<ao>::
 * accountList : Array of all attached accounts in DBus object path form
 
 Exceptions: None
 
+getAccount(identifier<s>) -> account<o>::
+* identifier : Phone number or ACI of an attached account
+* account : DBus object path of the account
+
+Exceptions: org.asamk.SignalControl.Error.Failure if the account is unknown
+
+startLink() -> deviceLinkUri<s>::
+* deviceLinkUri : Provisioning URI to scan with the primary Signal device
+
+finishLink(deviceLinkUri<s>, newDeviceName<s>) -> identifier<s>::
+* deviceLinkUri : URI returned by startLink
+* newDeviceName : Name for the linked device
+* identifier : Phone number of the linked account, or its ACI when it has no phone number
+
+Both linking methods support accounts with or without a phone number.
+
+Exceptions: org.asamk.SignalControl.Error.Failure
+
 register(number<s>, voiceVerification<b>) -> <>::
 * number : Phone number
 * voiceVerification : true = use voice verification; false = use SMS verification
@@ -115,9 +142,10 @@ Exceptions: None
 
 The following methods listen to the account's object path, which is constructed as follows:
 
-- for single-account mode: "/org/asamk/Signal/"
-- for multi-account mode: "/org/asamk/Signal/" + DBusNumber
-* DBusNumber: account's phone number, with underscore (_) replacing plus (+)
+- for single-account mode: "/org/asamk/Signal"
+- for multi-account mode: "/org/asamk/Signal/" + DBusIdentifier
+* DBusIdentifier: account's phone number with underscore (_) replacing plus (+),
+  or its ACI with underscores replacing hyphens when there is no phone number
 
 getContactName(number<s>) -> name<s>::
 * number : Phone number
@@ -135,7 +163,12 @@ May result in e.g. two entries if a contact and profile name is set.
 Exceptions: None
 
 getSelfNumber() -> number<s>::
-* number : Your phone number
+* number : Your phone number, or an empty string for an account without a phone number
+
+Exceptions: None
+
+getSelfACI() -> aci<s>::
+* aci : Your account's ACI (Account ID), available with or without a phone number
 
 Exceptions: None
 
@@ -167,6 +200,14 @@ This is a concatenated list of all defined contacts as well of profiles known (e
 
 Exceptions: None
 
+listRecipientIdentifiers() -> identifiers<as>::
+* identifiers : String array of known recipient identifiers, including recipients without a phone number
+
+Uses phone numbers where known and includes ACIs for recipients without a phone
+number. Unlike `listNumbers`, this method also includes numberless recipients.
+
+Exceptions: None
+
 removePin() -> <>::
 
 Removes registration PIN protection.

man/signal-cli-jsonrpc.5.adoc

@@ -76,6 +76,9 @@ Messages are then sent similar to the automatic mode, but wrapped in a subscript
 When the daemon/jsonRpc command is started without an account parameter (-a), signal-cli will provide all local accounts and additional commands to register (`register`) and link (`startLink`, `finishLink`) new accounts.
 
 In multi-account mode, requests for a single account require an additional `account` param.
+For an account without a phone number, this parameter must be its ACI (Account ID).
+`listAccounts` returns the ACI in `aci` and a null `number` for these accounts.
+Receive events identify them by ACI in the `account` field.
 
 REQUEST: `{"jsonrpc":"2.0","method":"listGroups","id":"my special mark","params":{"account":"+33123456789"}}`
 
@@ -132,7 +135,10 @@ Params:
 
 REQUEST: `{"jsonrpc":"2.0","method":"finishLink","id":"6","params":{"deviceLinkUri":"sgnl://linkdevice?uuid=X&pub_key=X","deviceName":"new-name"}}`
 
-RESPONSE: `{"jsonrpc":"2.0","result":{"deviceLinkUri":"sgnl://linkdevice?uuid=X&pub_key=X"},"id":"6"}`
+RESPONSE: `{"jsonrpc":"2.0","result":{"number":null,"aci":"11111111-1111-4111-8111-111111111111"},"id":"6"}`
+
+The `number` field contains the phone number for a numbered account. Linking a numberless
+account uses the same QR flow; no Account Key is supplied to `finishLink`.
 
 == Examples
 

man/signal-cli.1.adoc

@@ -65,6 +65,7 @@ Make sure you have full read/write access to the given directory.
 *-a* ACCOUNT, *--account* ACCOUNT::
 Specify your phone number, that will be your identifier.
 The phone number must include the country calling code, i.e. the number must start with a "+" sign.
+An ACI (Account ID) can also select an existing account and is required for an account without a phone number.
 
 This flag must not be given for the `link` command.
 It is optional for the `daemon` command.

src/main/java/org/asamk/Signal.java

@@ -20,6 +20,9 @@ import java.util.Map;
  */
 public interface Signal extends DBusInterface {
 
+    /**
+     * Returns the account's phone number, or an empty string for a numberless account.
+     */
     String getSelfNumber();
 
     String getSelfACI();
@@ -186,6 +189,8 @@ public interface Signal extends DBusInterface {
 
     List<String> listNumbers();
 
+    List<String> listRecipientIdentifiers();
+
     List<String> getContactNumber(final String name) throws Error.Failure;
 
     @Deprecated

src/main/java/org/asamk/SignalControl.java

@@ -37,7 +37,10 @@ public interface SignalControl extends DBusInterface {
 
     List<DBusPath> listAccounts();
 
-    DBusPath getAccount(String number);
+    /**
+     * Resolves a phone number or ACI to an exported account's object path.
+     */
+    DBusPath getAccount(String identifier) throws Error.Failure;
 
     interface Error {
 

src/main/java/org/asamk/signal/App.java

@@ -208,14 +208,15 @@ public class App {
     private static String getAccountIfOnlyOne(final SignalAccountFiles signalAccountFiles) throws IOErrorException, UserErrorException {
         Set<String> accounts;
         try {
-            accounts = signalAccountFiles.getAllLocalAccountNumbers();
+            accounts = signalAccountFiles.getAllLocalAccountIdentifiers();
         } catch (IOException e) {
             throw new IOErrorException("Failed to load local accounts file", e);
         }
         if (accounts.isEmpty()) {
             throw new UserErrorException("No local users found, you first need to register or link an account");
         } else if (accounts.size() > 1) {
-            throw new UserErrorException("Multiple users found, you need to specify an account (phone number) with -a");
+            throw new UserErrorException(
+                    "Multiple users found, you need to specify an account (phone number or ACI) with -a");
         }
         return accounts.stream().findFirst().get();
     }

src/main/java/org/asamk/signal/ReceiveMessageHandler.java

@@ -39,7 +39,7 @@ public class ReceiveMessageHandler implements Manager.ReceiveMessageHandler {
         writer.println("Envelope from: {} (device: {}) to {}",
                 source.map(this::formatContact).orElse("unknown source"),
                 envelope.sourceDevice(),
-                m.getSelfNumber());
+                m.getSelfIdentifier());
         writer.println("Timestamp: {}", DateUtils.formatTimestamp(envelope.timestamp()));
         writer.println("Server timestamps: received: {} delivered: {}",
                 DateUtils.formatTimestamp(envelope.serverReceivedTimestamp()),
@@ -55,13 +55,13 @@ public class ReceiveMessageHandler implements Manager.ReceiveMessageHandler {
                 final var recipientName = e.getSender().getLegacyIdentifier();
                 writer.println(
                         "Use 'signal-cli -a {} listIdentities -n {}', verify the key and run 'signal-cli -a {} trust -v \"FINGER_PRINT\" {}' to mark it as trusted",
-                        m.getSelfNumber(),
+                        m.getSelfIdentifier(),
                         recipientName,
-                        m.getSelfNumber(),
+                        m.getSelfIdentifier(),
                         recipientName);
                 writer.println(
                         "If you don't care about security, use 'signal-cli -a {} trust -a {}' to trust it without verification",
-                        m.getSelfNumber(),
+                        m.getSelfIdentifier(),
                         recipientName);
             } else {
                 writer.println("Exception: {} ({})", exception.getMessage(), exception.getClass().getSimpleName());

src/main/java/org/asamk/signal/commands/FinishLinkCommand.java

@@ -54,9 +54,9 @@ public class FinishLinkCommand implements JsonRpcMultiCommand<FinishLinkCommand.
         if (deviceName == null) {
             deviceName = "cli";
         }
-        final String number;
+        final String identifier;
         try {
-            number = provisioningManager.finishDeviceLink(deviceName);
+            identifier = provisioningManager.finishDeviceLink(deviceName);
         } catch (TimeoutException e) {
             throw new UserErrorException("Link request timed out, please try again.");
         } catch (IOException e) {
@@ -73,10 +73,11 @@ public class FinishLinkCommand implements JsonRpcMultiCommand<FinishLinkCommand.
                     + "\" before trying again.");
         }
 
-        jsonWriter.write(new JsonFinishLink(number));
+        final var manager = m.getManager(identifier);
+        jsonWriter.write(new JsonFinishLink(manager.getSelfNumber(), manager.getSelfACI()));
     }
 
     public record FinishLinkParams(String deviceLinkUri, String deviceName) {}
 
-    private record JsonFinishLink(String number) {}
+    private record JsonFinishLink(String number, String aci) {}
 }

src/main/java/org/asamk/signal/commands/ListAccountsCommand.java

@@ -27,19 +27,22 @@ public class ListAccountsCommand implements JsonRpcMultiLocalCommand {
             final MultiAccountManager c,
             final OutputWriter outputWriter
     ) throws CommandException {
-        final var accountNumbers = c.getAccountNumbers();
+        final var managers = c.getManagers();
         switch (outputWriter) {
             case JsonWriter jsonWriter -> {
-                final var jsonAccounts = accountNumbers.stream().map(JsonAccount::new).toList();
+                final var jsonAccounts = managers.stream()
+                        .map(m -> new JsonAccount(m.getSelfNumber(), m.getSelfACI()))
+                        .toList();
                 jsonWriter.write(jsonAccounts);
             }
             case PlainTextWriter plainTextWriter -> {
-                for (final var number : accountNumbers) {
-                    plainTextWriter.println("Number: {}", number);
+                for (final var manager : managers) {
+                    plainTextWriter.println(manager.getSelfNumber() != null ? "Number: {}" : "ACI: {}",
+                            manager.getSelfIdentifier());
                 }
             }
         }
     }
 
-    private record JsonAccount(String number) {}
+    private record JsonAccount(String number, String aci) {}
 }

src/main/java/org/asamk/signal/dbus/DbusCommandHandler.java

@@ -55,7 +55,7 @@ public class DbusCommandHandler {
         try {
             if (command instanceof ProvisioningCommand c) {
                 if (account != null) {
-                    throw new UserErrorException("You cannot specify a account (phone number) when linking");
+                    throw new UserErrorException("You cannot specify an account when linking");
                 }
 
                 handleProvisioningCommand(c, dBusConn, busname, commandHandler);
@@ -74,7 +74,9 @@ public class DbusCommandHandler {
                 throw new UserErrorException("Command only works in multi-account mode");
             }
 
-            var accountObjectPath = account == null ? tryGetSingleAccountObjectPath(dBusConn, busname) : null;
+            var accountObjectPath = account == null
+                    ? tryGetSingleAccountObjectPath(dBusConn, busname)
+                    : getAccountObjectPath(account, dBusConn, busname);
             if (accountObjectPath == null) {
                 accountObjectPath = DbusConfig.getObjectPath(account);
             }
@@ -86,6 +88,24 @@ public class DbusCommandHandler {
         }
     }
 
+    private static String getAccountObjectPath(
+            final String account,
+            final DBusConnection dBusConn,
+            final String busname
+    ) throws DBusException, CommandException {
+        final var control = dBusConn.getRemoteObject(busname, DbusConfig.getObjectPath(), SignalControl.class);
+        try {
+            return control.getAccount(account).getPath();
+        } catch (UnknownMethod e) {
+            // A single-account daemon exports Signal directly at the base path.
+            final var signal = dBusConn.getRemoteObject(busname, DbusConfig.getObjectPath(), Signal.class);
+            if (!account.equals(signal.getSelfNumber()) && !account.equals(signal.getSelfACI())) {
+                throw new UserErrorException("Unknown account: " + account);
+            }
+            return DbusConfig.getObjectPath();
+        }
+    }
+
     private static String tryGetSingleAccountObjectPath(
             final DBusConnection dBusConn,
             final String busname
@@ -97,7 +117,7 @@ public class DbusCommandHandler {
                 throw new UserErrorException("No local users found, you first need to register or link an account");
             } else if (accounts.size() > 1) {
                 throw new UserErrorException(
-                        "Multiple users found, you need to specify an account (phone number) with -a");
+                        "Multiple users found, you need to specify an account (phone number or ACI) with -a");
             }
 
             return accounts.getFirst().getPath();

src/main/java/org/asamk/signal/dbus/DbusHandler.java

@@ -67,7 +67,7 @@ public class DbusHandler implements AutoCloseable {
                 }
             });
             c.addOnManagerRemovedHandler(m -> {
-                final var path = DbusConfig.getObjectPath(m.getSelfNumber());
+                final var path = DbusConfig.getObjectPath(m.getSelfIdentifier());
                 try {
                     final var object = connection.getExportedObject(null, path);
                     if (object instanceof DbusSignalImpl dbusSignal) {
@@ -135,11 +135,11 @@ public class DbusHandler implements AutoCloseable {
         final var signal = new DbusSignalImpl(m, conn, objectPath, noReceiveOnStart);
         closeables.add(signal);
 
-        return Thread.ofPlatform().name("dbus-init-" + m.getSelfNumber()).start(signal::initObjects);
+        return Thread.ofPlatform().name("dbus-init-" + m.getSelfIdentifier()).start(signal::initObjects);
     }
 
     private Thread exportManager(final DBusConnection conn, final Manager m) {
-        final var objectPath = DbusConfig.getObjectPath(m.getSelfNumber());
+        final var objectPath = DbusConfig.getObjectPath(m.getSelfIdentifier());
         return exportDbusObject(conn, objectPath, m);
     }
 

src/main/java/org/asamk/signal/dbus/DbusManagerImpl.java

@@ -56,6 +56,7 @@ import org.asamk.signal.manager.api.UsernameLinkUrl;
 import org.asamk.signal.manager.api.UsernameStatus;
 import org.freedesktop.dbus.DBusPath;
 import org.freedesktop.dbus.connections.impl.DBusConnection;
+import org.freedesktop.dbus.errors.UnknownMethod;
 import org.freedesktop.dbus.exceptions.DBusException;
 import org.freedesktop.dbus.exceptions.DBusExecutionException;
 import org.freedesktop.dbus.interfaces.DBusInterface;
@@ -77,6 +78,7 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.Set;
+import java.util.UUID;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.function.Function;
@@ -110,7 +112,8 @@ public class DbusManagerImpl implements Manager {
 
     @Override
     public String getSelfNumber() {
-        return signal.getSelfNumber();
+        final var number = signal.getSelfNumber();
+        return number.isEmpty() ? null : number;
     }
 
     @Override
@@ -438,7 +441,7 @@ public class DbusManagerImpl implements Manager {
             numbers.forEach(n -> signal.sendTyping(n, action == TypingAction.STOP));
             return 0L;
         }, () -> {
-            signal.sendTyping(signal.getSelfNumber(), action == TypingAction.STOP);
+            signal.sendTyping(getSelfIdentifier(), action == TypingAction.STOP);
             return 0L;
         }, groupId -> {
             signal.sendGroupTyping(groupId, action == TypingAction.STOP);
@@ -486,7 +489,7 @@ public class DbusManagerImpl implements Manager {
     ) throws IOException, NotAGroupMemberException, GroupNotFoundException, GroupSendingNotAllowedException {
         return handleMessage(recipients,
                 numbers -> signal.sendRemoteDeleteMessage(targetSentTimestamp, numbers),
-                () -> signal.sendRemoteDeleteMessage(targetSentTimestamp, signal.getSelfNumber()),
+                () -> signal.sendRemoteDeleteMessage(targetSentTimestamp, getSelfIdentifier()),
                 groupId -> signal.sendGroupRemoteDeleteMessage(targetSentTimestamp, groupId));
     }
 
@@ -510,7 +513,7 @@ public class DbusManagerImpl implements Manager {
                         remove,
                         targetAuthor.getIdentifier(),
                         targetSentTimestamp,
-                        signal.getSelfNumber()),
+                        getSelfIdentifier()),
                 groupId -> signal.sendGroupMessageReaction(emoji,
                         remove,
                         targetAuthor.getIdentifier(),
@@ -809,43 +812,46 @@ public class DbusManagerImpl implements Manager {
             final Collection<RecipientIdentifier.Single> addresses,
             final Optional<String> name
     ) {
-        final var numbers = addresses.stream()
-                .filter(s -> s instanceof RecipientIdentifier.Number)
-                .map(s -> ((RecipientIdentifier.Number) s).number())
+        final var identifiers = addresses.stream()
+                .map(RecipientIdentifier.Single::getIdentifier)
                 .collect(Collectors.toSet());
-        return signal.listNumbers().stream().filter(n -> addresses.isEmpty() || numbers.contains(n)).map(n -> {
-            final var contactBlocked = signal.isContactBlocked(n);
-            if (blocked.isPresent() && blocked.get() != contactBlocked) {
-                return null;
-            }
-            final var contactName = signal.getContactName(n);
-            if (onlyContacts && contactName.isEmpty()) {
-                return null;
-            }
-            if (name.isPresent() && !name.get().equals(contactName)) {
-                return null;
-            }
-            return Recipient.newBuilder()
-                    .withAddress(new RecipientAddress(n))
-                    .withContact(new Contact(contactName,
-                            null,
-                            null,
-                            null,
-                            null,
-                            null,
-                            null,
-                            0,
-                            1,
-                            0,
-                            false,
-                            contactBlocked,
-                            0,
-                            false,
-                            false,
-                            false,
-                            null))
-                    .build();
-        }).filter(Objects::nonNull).toList();
+        return listRecipientIdentifiers().stream()
+                .filter(n -> addresses.isEmpty() || identifiers.contains(n))
+                .map(n -> {
+                    final var contactBlocked = signal.isContactBlocked(n);
+                    if (blocked.isPresent() && blocked.get() != contactBlocked) {
+                        return null;
+                    }
+                    final var contactName = signal.getContactName(n);
+                    if (onlyContacts && contactName.isEmpty()) {
+                        return null;
+                    }
+                    if (name.isPresent() && !name.get().equals(contactName)) {
+                        return null;
+                    }
+                    return Recipient.newBuilder()
+                            .withAddress(getRecipientAddress(n))
+                            .withContact(new Contact(contactName,
+                                    null,
+                                    null,
+                                    null,
+                                    null,
+                                    null,
+                                    null,
+                                    0,
+                                    1,
+                                    0,
+                                    false,
+                                    contactBlocked,
+                                    0,
+                                    false,
+                                    false,
+                                    false,
+                                    null))
+                            .build();
+                })
+                .filter(Objects::nonNull)
+                .toList();
     }
 
     @Override
@@ -870,16 +876,16 @@ public class DbusManagerImpl implements Manager {
                     (String) group.get("Description").getValue(),
                     GroupInviteLinkUrl.fromUri((String) group.get("GroupInviteLink").getValue()),
                     ((List<String>) group.get("Members").getValue()).stream()
-                            .map(m -> new GroupMember(new RecipientAddress(m), admins.contains(m), null, null))
+                            .map(m -> new GroupMember(getRecipientAddress(m), admins.contains(m), null, null))
                             .collect(Collectors.toSet()),
                     ((List<String>) group.get("PendingMembers").getValue()).stream()
-                            .map(RecipientAddress::new)
+                            .map(DbusManagerImpl::getRecipientAddress)
                             .collect(Collectors.toSet()),
                     ((List<String>) group.get("RequestingMembers").getValue()).stream()
-                            .map(RecipientAddress::new)
+                            .map(DbusManagerImpl::getRecipientAddress)
                             .collect(Collectors.toSet()),
                     ((List<String>) group.get("Banned").getValue()).stream()
-                            .map(RecipientAddress::new)
+                            .map(DbusManagerImpl::getRecipientAddress)
                             .collect(Collectors.toSet()),
                     (boolean) group.get("IsBlocked").getValue(),
                     (int) group.get("MessageExpirationTimer").getValue(),
@@ -910,7 +916,10 @@ public class DbusManagerImpl implements Manager {
         final var group = getRemoteObject(identityPath, Signal.Identity.class).GetAll("org.asamk.Signal.Identity");
         final var aci = (String) group.get("Uuid").getValue();
         final var number = (String) group.get("Number").getValue();
-        return new Identity(new RecipientAddress(aci, null, number, null),
+        return new Identity(new RecipientAddress(aci.isEmpty() ? null : aci,
+                null,
+                number.isEmpty() ? null : number,
+                null),
                 (byte[]) group.get("Fingerprint").getValue(),
                 (String) group.get("SafetyNumber").getValue(),
                 (byte[]) group.get("ScannableSafetyNumber").getValue(),
@@ -1073,6 +1082,23 @@ public class DbusManagerImpl implements Manager {
         return string == null ? "" : string;
     }
 
+    private static RecipientAddress getRecipientAddress(final String identifier) {
+        try {
+            return new RecipientAddress(UUID.fromString(identifier));
+        } catch (IllegalArgumentException e) {
+            return new RecipientAddress(identifier);
+        }
+    }
+
+    private List<String> listRecipientIdentifiers() {
+        try {
+            return signal.listRecipientIdentifiers();
+        } catch (UnknownMethod e) {
+            // Older daemons only expose recipients with a known phone number.
+            return signal.listNumbers();
+        }
+    }
+
     private <T extends DBusInterface> T getRemoteObject(final DBusPath path, final Class<T> type) {
         try {
             return connection.getRemoteObject(busname, path.getPath(), type);
@@ -1085,7 +1111,7 @@ public class DbusManagerImpl implements Manager {
         try {
             this.dbusMsgHandler = messageReceived -> {
                 final var extras = messageReceived.getExtras();
-                final var envelope = new MessageEnvelope(Optional.of(new RecipientAddress(messageReceived.getSender())),
+                final var envelope = new MessageEnvelope(Optional.of(getRecipientAddress(messageReceived.getSender())),
                         0,
                         messageReceived.getTimestamp(),
                         0,
@@ -1132,7 +1158,7 @@ public class DbusManagerImpl implements Manager {
             connection.addSigHandler(Signal.MessageReceivedV2.class, signal, this.dbusMsgHandler);
             this.dbusEditMsgHandler = messageReceived -> {
                 final var extras = messageReceived.getExtras();
-                final var envelope = new MessageEnvelope(Optional.of(new RecipientAddress(messageReceived.getSender())),
+                final var envelope = new MessageEnvelope(Optional.of(getRecipientAddress(messageReceived.getSender())),
                         0,
                         messageReceived.getTimestamp(),
                         0,
@@ -1186,7 +1212,7 @@ public class DbusManagerImpl implements Manager {
                     case "delivery" -> MessageEnvelope.Receipt.Type.DELIVERY;
                     default -> MessageEnvelope.Receipt.Type.UNKNOWN;
                 };
-                final var envelope = new MessageEnvelope(Optional.of(new RecipientAddress(receiptReceived.getSender())),
+                final var envelope = new MessageEnvelope(Optional.of(getRecipientAddress(receiptReceived.getSender())),
                         0,
                         receiptReceived.getTimestamp(),
                         0,
@@ -1207,7 +1233,7 @@ public class DbusManagerImpl implements Manager {
 
             this.dbusSyncHandler = syncReceived -> {
                 final var extras = syncReceived.getExtras();
-                final var envelope = new MessageEnvelope(Optional.of(new RecipientAddress(syncReceived.getSource())),
+                final var envelope = new MessageEnvelope(Optional.of(getRecipientAddress(syncReceived.getSource())),
                         0,
                         syncReceived.getTimestamp(),
                         0,
@@ -1221,7 +1247,7 @@ public class DbusManagerImpl implements Manager {
                                 syncReceived.getTimestamp(),
                                 syncReceived.getDestination().isEmpty()
                                         ? Optional.empty()
-                                        : Optional.of(new RecipientAddress(syncReceived.getDestination())),
+                                        : Optional.of(getRecipientAddress(syncReceived.getDestination())),
                                 Set.of(),
                                 Optional.of(new MessageEnvelope.Data(syncReceived.getTimestamp(),
                                         syncReceived.getGroupId().length > 0
@@ -1326,7 +1352,7 @@ public class DbusManagerImpl implements Manager {
 
         final List<Map<String, Variant<?>>> mentions = getValue(extras, "mentions");
         return mentions.stream()
-                .map(a -> new MessageEnvelope.Data.Mention(new RecipientAddress(this.<String>getValue(a, "recipient")),
+                .map(a -> new MessageEnvelope.Data.Mention(getRecipientAddress(this.<String>getValue(a, "recipient")),
                         getValue(a, "start"),
                         getValue(a, "length")))
                 .toList();

src/main/java/org/asamk/signal/dbus/DbusMultiAccountManagerImpl.java

@@ -45,10 +45,7 @@ public class DbusMultiAccountManagerImpl implements MultiAccountManager {
 
     @Override
     public List<String> getAccountNumbers() {
-        return signalControl.listAccounts()
-                .stream()
-                .map(a -> getRemoteObject(a, Signal.class).getSelfNumber())
-                .toList();
+        return getManagers().stream().map(Manager::getSelfNumber).toList();
     }
 
     @Override
@@ -74,8 +71,8 @@ public class DbusMultiAccountManagerImpl implements MultiAccountManager {
     }
 
     @Override
-    public Manager getManager(final String phoneNumber) {
-        return new DbusManagerImpl(getRemoteObject(signalControl.getAccount(phoneNumber), Signal.class),
+    public Manager getManager(final String identifier) {
+        return new DbusManagerImpl(getRemoteObject(signalControl.getAccount(identifier), Signal.class),
                 connection,
                 busname);
     }

src/main/java/org/asamk/signal/dbus/DbusSignalControlImpl.java

@@ -159,11 +159,19 @@ public class DbusSignalControlImpl implements org.asamk.SignalControl {
 
     @Override
     public List<DBusPath> listAccounts() {
-        return c.getAccountNumbers().stream().map(u -> new DBusPath(DbusConfig.getObjectPath(u))).toList();
+        return c.getManagers()
+                .stream()
+                .map(m -> new DBusPath(DbusConfig.getObjectPath(m.getSelfIdentifier())))
+                .toList();
     }
 
     @Override
-    public DBusPath getAccount(final String number) {
-        return new DBusPath(DbusConfig.getObjectPath(number));
+    public DBusPath getAccount(final String identifier) {
+        final var manager = c.getManagers()
+                .stream()
+                .filter(m -> identifier.equals(m.getSelfNumber()) || identifier.equals(m.getSelfACI()))
+                .findFirst()
+                .orElseThrow(() -> new Error.Failure("Unknown account: " + identifier));
+        return new DBusPath(DbusConfig.getObjectPath(manager.getSelfIdentifier()));
     }
 }

src/main/java/org/asamk/signal/dbus/DbusSignalImpl.java

@@ -138,7 +138,7 @@ public class DbusSignalImpl implements Signal, AutoCloseable {
 
     @Override
     public String getSelfNumber() {
-        return m.getSelfNumber();
+        return emptyIfNull(m.getSelfNumber());
     }
 
     @Override
@@ -803,6 +803,15 @@ public class DbusSignalImpl implements Signal, AutoCloseable {
                 .toList();
     }
 
+    @Override
+    public List<String> listRecipientIdentifiers() {
+        return m.getRecipients(false, Optional.empty(), Set.of(), Optional.empty())
+                .stream()
+                .map(r -> r.getAddress().getLegacyIdentifier())
+                .distinct()
+                .toList();
+    }
+
     @Override
     public List<String> getContactNumber(final String name) {
         return m.getRecipients(false, Optional.empty(), Set.of(), Optional.of(name))

src/main/java/org/asamk/signal/json/JsonReceiveMessageHandler.java

@@ -23,7 +23,7 @@ public class JsonReceiveMessageHandler implements Manager.ReceiveMessageHandler
     @Override
     public void handleMessage(MessageEnvelope envelope, Throwable exception) {
         final var object = new HashMap<String, Object>();
-        object.put("account", m.getSelfNumber());
+        object.put("account", m.getSelfIdentifier());
         if (exception != null) {
             object.put("exception", JsonError.from(exception));
         }

src/main/resources/META-INF/native-image/org.asamk/signal-cli/reachability-metadata.json

@@ -4012,7 +4012,8 @@
             "java.lang.String",
             "java.lang.String",
             "java.lang.String",
-            "java.lang.String"
+            "java.lang.String",
+            "java.lang.Boolean"
           ]
         },
         {
@@ -4023,6 +4024,10 @@
           "name": "number",
           "parameterTypes": []
         },
+        {
+          "name": "numberless",
+          "parameterTypes": []
+        },
         {
           "name": "path",
           "parameterTypes": []

src/test/java/org/asamk/signal/dbus/NumberlessDbusTest.java

@@ -0,0 +1,435 @@
+package org.asamk.signal.dbus;
+
+import org.asamk.Signal;
+import org.asamk.SignalControl;
+import org.asamk.signal.DbusConfig;
+import org.asamk.signal.commands.CommandHandler;
+import org.asamk.signal.commands.ListGroupsCommand;
+import org.asamk.signal.commands.LocalCommand;
+import org.asamk.signal.commands.exceptions.UserErrorException;
+import org.asamk.signal.manager.Manager;
+import org.asamk.signal.manager.api.Group;
+import org.asamk.signal.manager.api.GroupId;
+import org.asamk.signal.manager.api.GroupMember;
+import org.asamk.signal.manager.api.GroupPermission;
+import org.asamk.signal.manager.api.Identity;
+import org.asamk.signal.manager.api.MessageEnvelope;
+import org.asamk.signal.manager.api.Recipient;
+import org.asamk.signal.manager.api.RecipientAddress;
+import org.asamk.signal.manager.api.RecipientIdentifier;
+import org.asamk.signal.manager.api.SendMessageResults;
+import org.asamk.signal.manager.api.TrustLevel;
+import org.asamk.signal.manager.api.TypingAction;
+import org.asamk.signal.manager.internal.MultiAccountManagerImpl;
+import org.freedesktop.dbus.DBusPath;
+import org.freedesktop.dbus.connections.impl.DBusConnection;
+import org.freedesktop.dbus.connections.impl.DBusConnectionBuilder;
+import org.freedesktop.dbus.errors.UnknownMethod;
+import org.freedesktop.dbus.exceptions.DBusExecutionException;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.Timeout;
+import org.junit.jupiter.api.condition.EnabledIfEnvironmentVariable;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.NullSource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Proxy;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.UUID;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.stream.Collectors;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class NumberlessDbusTest {
+
+    private static final String NUMBER = "+12025550123";
+    private static final String ACI = "11111111-1111-4111-8111-111111111111";
+    private static final String OTHER_ACI = "22222222-2222-4222-8222-222222222222";
+    private static final String THIRD_ACI = "33333333-3333-4333-8333-333333333333";
+    private static final String NUMBERLESS_PATH = "/org/asamk/Signal/11111111_1111_4111_8111_111111111111";
+    private static final String NUMBERED_PATH = "/org/asamk/Signal/_12025550123";
+
+    @Test
+    void resolvesNumberlessAndNumberedAccountsWithoutChangingNumberedPaths() {
+        final var numberless = new TestAccount(null, ACI);
+        final var numbered = new TestAccount(NUMBER, OTHER_ACI);
+        final var accounts = new MultiAccountManagerImpl(List.of(numberless.manager, numbered.manager), null);
+        final var control = new DbusSignalControlImpl(accounts, DbusConfig.getObjectPath());
+
+        assertEquals(Set.of(new DBusPath(NUMBERLESS_PATH), new DBusPath(NUMBERED_PATH)),
+                Set.copyOf(control.listAccounts()));
+        assertEquals(NUMBERLESS_PATH, control.getAccount(ACI).getPath());
+        assertEquals(NUMBERED_PATH, control.getAccount(NUMBER).getPath());
+        assertEquals(NUMBERED_PATH, control.getAccount(OTHER_ACI).getPath());
+        assertThrows(SignalControl.Error.Failure.class, () -> control.getAccount(THIRD_ACI));
+    }
+
+    @ParameterizedTest
+    @NullSource
+    @ValueSource(strings = NUMBER)
+    void mapsOptionalPhoneNumbersAndAddressesSelfByAnAvailableIdentifier(final String number) throws Exception {
+        final var account = new TestAccount(number, ACI);
+        final var signal = new DbusSignalImpl(account.manager, null, DbusConfig.getObjectPath(), true);
+        final var client = new DbusManagerImpl(signal, null, "org.asamk.Signal.Test");
+
+        assertEquals(number == null ? "" : number, signal.getSelfNumber());
+        assertEquals(number, client.getSelfNumber());
+        assertEquals(number == null ? ACI : number, client.getSelfIdentifier());
+        checkSelfOperations(client,
+                account,
+                number == null
+                        ? new RecipientIdentifier.Uuid(UUID.fromString(ACI))
+                        : new RecipientIdentifier.Number(number));
+    }
+
+    @Test
+    void readsContactsFromOlderDaemonsWithoutTheNewRecipientListingMethod() {
+        final var account = new TestAccount(NUMBER, ACI);
+        account.recipients = List.of(Recipient.newBuilder().withAddress(new RecipientAddress(NUMBER)).build());
+        final var signal = new DbusSignalImpl(account.manager, null, DbusConfig.getObjectPath(), true) {
+            @Override
+            public List<String> listRecipientIdentifiers() {
+                throw new UnknownMethod("Not implemented by this daemon");
+            }
+        };
+        final var client = new DbusManagerImpl(signal, null, "org.asamk.Signal.Test");
+        assertEquals(NUMBER,
+                client.getRecipients(false, Optional.empty(), Set.of(), Optional.empty())
+                        .getFirst()
+                        .getAddress()
+                        .number()
+                        .orElseThrow());
+    }
+
+    // Run with: dbus-run-session -- ./gradlew --no-daemon :test --tests '*NumberlessDbusTest*' --rerun-tasks
+    @Nested
+    @Timeout(20)
+    @EnabledIfEnvironmentVariable(named = "DBUS_SESSION_BUS_ADDRESS", matches = ".+")
+    class SessionBus {
+
+        @Test
+        void exportsMixedAccountsRoutesAciSelectorsAndRemovesOnlyTheClosedAccount() throws Exception {
+            final var numberless = new TestAccount(null, ACI);
+            final var numbered = new TestAccount(NUMBER, OTHER_ACI);
+            final var secondNumberless = new TestAccount(null, THIRD_ACI);
+            final var accounts = new MultiAccountManagerImpl(List.of(numberless.manager,
+                    numbered.manager,
+                    secondNumberless.manager), null);
+            final var busname = newBusname();
+            try (final var server = new DbusHandler(false,
+                    busname,
+                    accounts,
+                    true); final var connection = DBusConnectionBuilder.forSessionBus().withShared(false).build()) {
+                server.init();
+                final var control = connection.getRemoteObject(busname,
+                        DbusConfig.getObjectPath(),
+                        SignalControl.class);
+                assertEquals(Set.of(NUMBERLESS_PATH, NUMBERED_PATH, DbusConfig.getObjectPath(THIRD_ACI)),
+                        control.listAccounts().stream().map(DBusPath::getPath).collect(Collectors.toSet()));
+                assertEquals(NUMBERED_PATH, control.getAccount(OTHER_ACI).getPath());
+                assertEquals(NUMBERED_PATH, control.getAccount(NUMBER).getPath());
+                assertEquals(NUMBERLESS_PATH, control.getAccount(ACI).getPath());
+                assertEquals(ACI, selectAccount(ACI, connection, busname));
+                assertEquals(OTHER_ACI, selectAccount(OTHER_ACI, connection, busname));
+                assertEquals(OTHER_ACI, selectAccount(NUMBER, connection, busname));
+                assertThrows(UserErrorException.class, () -> selectAccount(null, connection, busname));
+
+                final var client = new DbusMultiAccountManagerImpl(control, connection, busname);
+                assertEquals(3, client.getManagers().size());
+                assertEquals(2, client.getAccountNumbers().stream().filter(n -> n == null).count());
+                assertNull(client.getManager(ACI).getSelfNumber());
+                assertEquals(NUMBER, client.getManager(OTHER_ACI).getSelfNumber());
+
+                final var removed = connection.getRemoteObject(busname, NUMBERLESS_PATH, Signal.class);
+                numberless.manager.close();
+                assertEquals(2, control.listAccounts().size());
+                assertThrows(SignalControl.Error.Failure.class, () -> control.getAccount(ACI));
+                assertThrows(DBusExecutionException.class, removed::getSelfACI);
+                assertEquals(THIRD_ACI, client.getManager(THIRD_ACI).getSelfACI());
+                assertEquals(NUMBER, client.getManager(NUMBER).getSelfNumber());
+            }
+        }
+
+        @ParameterizedTest
+        @NullSource
+        @ValueSource(strings = NUMBER)
+        void selectsSingleAccountDaemonsImplicitlyAndByAci(final String number) throws Exception {
+            final var account = new TestAccount(number, ACI);
+            final var busname = newBusname();
+            try (final var server = new DbusHandler(false,
+                    busname,
+                    account.manager,
+                    true); final var connection = DBusConnectionBuilder.forSessionBus().withShared(false).build()) {
+                server.init();
+                assertEquals(ACI, selectAccount(null, connection, busname));
+                assertEquals(ACI, selectAccount(ACI, connection, busname));
+                if (number != null) {
+                    assertEquals(ACI, selectAccount(number, connection, busname));
+                }
+                assertThrows(UserErrorException.class, () -> selectAccount(OTHER_ACI, connection, busname));
+            }
+        }
+
+        @Test
+        void preservesAciAddressesInContactsGroupMembersAndIdentities() throws Exception {
+            final var account = new TestAccount(null, ACI);
+            final var contact = new RecipientAddress(UUID.fromString(OTHER_ACI));
+            final var numberedContact = new RecipientAddress(NUMBER);
+            account.recipients = List.of(Recipient.newBuilder().withAddress(contact).build(),
+                    Recipient.newBuilder().withAddress(numberedContact).build());
+            account.identities = List.of(new Identity(contact,
+                    new byte[]{1},
+                    "test",
+                    new byte[]{2},
+                    TrustLevel.TRUSTED_UNVERIFIED,
+                    123));
+            final var groupId = GroupId.unknownVersion(new byte[32]);
+            account.groups = List.of(new Group(groupId,
+                    "Test group",
+                    "",
+                    null,
+                    Set.of(new GroupMember(contact, true, null, null),
+                            new GroupMember(numberedContact, false, null, null)),
+                    Set.of(contact),
+                    Set.of(contact),
+                    Set.of(contact),
+                    false,
+                    0,
+                    GroupPermission.EVERY_MEMBER,
+                    GroupPermission.EVERY_MEMBER,
+                    GroupPermission.EVERY_MEMBER,
+                    true,
+                    true,
+                    false));
+            final var busname = newBusname();
+            try (final var server = new DbusHandler(false,
+                    busname,
+                    account.manager,
+                    true); final var connection = DBusConnectionBuilder.forSessionBus().withShared(false).build()) {
+                server.init();
+                final var signal = connection.getRemoteObject(busname, DbusConfig.getObjectPath(), Signal.class);
+                assertEquals(List.of(NUMBER), signal.listNumbers());
+                assertEquals(Set.of(OTHER_ACI, NUMBER), Set.copyOf(signal.listRecipientIdentifiers()));
+                try (final var client = new DbusManagerImpl(signal, connection, busname)) {
+                    final var contacts = client.getRecipients(false,
+                            Optional.empty(),
+                            Set.of(new RecipientIdentifier.Uuid(UUID.fromString(OTHER_ACI))),
+                            Optional.empty());
+                    assertEquals(1, contacts.size());
+                    assertEquals(contact, contacts.getFirst().getAddress());
+                    assertEquals(contact, client.getIdentities().getFirst().recipient());
+                    final var group = client.getGroups().getFirst();
+                    assertEquals(Set.of(contact, numberedContact),
+                            group.members().stream().map(GroupMember::recipientAddress).collect(Collectors.toSet()));
+                    assertEquals(Set.of(contact), group.pendingMembers());
+                    assertEquals(Set.of(contact), group.requestingMembers());
+                    assertEquals(Set.of(contact), group.bannedMembers());
+                }
+            }
+        }
+
+        @Test
+        void sendsAndReceivesNumberlessDirectGroupAndSelfMessagesOverDbus() throws Exception {
+            final var account = new TestAccount(null, ACI);
+            final var accounts = new MultiAccountManagerImpl(List.of(account.manager), null);
+            final var busname = newBusname();
+            try (final var server = new DbusHandler(false,
+                    busname,
+                    accounts,
+                    true); final var connection = DBusConnectionBuilder.forSessionBus().withShared(false).build()) {
+                server.init();
+                assertEquals(ACI, selectAccount(null, connection, busname));
+                final var signal = connection.getRemoteObject(busname, NUMBERLESS_PATH, Signal.class);
+                assertEquals("", signal.getSelfNumber());
+                final var groupId = GroupId.unknownVersion(new byte[32]);
+                assertEquals(42, signal.sendMessage("Direct", List.of(), OTHER_ACI));
+                assertEquals(42, signal.sendGroupMessage("Group", List.of(), groupId.serialize()));
+                assertEquals(42, signal.sendNoteToSelfMessage("Self", List.of()));
+                assertEquals(Set.of(new RecipientIdentifier.Uuid(UUID.fromString(OTHER_ACI))),
+                        account.calls.get(0).arguments().get(1));
+                assertEquals(Set.of(new RecipientIdentifier.Group(groupId)), account.calls.get(1).arguments().get(1));
+                assertEquals(Set.of(RecipientIdentifier.NoteToSelf.INSTANCE), account.calls.get(2).arguments().get(1));
+                assertThrows(Signal.Error.InvalidNumber.class,
+                        () -> signal.sendMessage("Invalid local number", List.of(), "2025550124"));
+
+                account.calls.clear();
+                try (final var client = new DbusManagerImpl(signal, connection, busname)) {
+                    checkSelfOperations(client, account, new RecipientIdentifier.Uuid(UUID.fromString(ACI)));
+                    final var received = new LinkedBlockingQueue<MessageEnvelope>();
+                    client.addReceiveHandler((envelope, error) -> received.add(envelope));
+                    for (final var group : List.of(Optional.<GroupId>empty(), Optional.of(groupId))) {
+                        account.emit(messageEnvelope(group));
+                        final var envelope = received.poll(5, TimeUnit.SECONDS);
+                        assertNotNull(envelope);
+                        assertEquals(OTHER_ACI, envelope.sourceAddress().orElseThrow().aci().orElseThrow());
+                        assertEquals(Optional.empty(), envelope.sourceAddress().orElseThrow().number());
+                        assertEquals("Incoming", envelope.data().orElseThrow().body().orElseThrow());
+                        assertEquals(Optional.of(ACI),
+                                envelope.data().orElseThrow().mentions().getFirst().recipient().aci());
+                        assertEquals(group,
+                                envelope.data()
+                                        .orElseThrow()
+                                        .groupContext()
+                                        .map(MessageEnvelope.Data.GroupContext::groupId));
+                    }
+                }
+                assertEquals(0, account.receivers.size());
+            }
+        }
+    }
+
+    private static void checkSelfOperations(
+            final Manager client,
+            final TestAccount account,
+            final RecipientIdentifier.Single self
+    ) throws Exception {
+        final Set<RecipientIdentifier> recipients = Set.of(RecipientIdentifier.NoteToSelf.INSTANCE);
+        client.sendTypingMessage(TypingAction.START, recipients);
+        client.sendRemoteDeleteMessage(123, recipients);
+        client.sendMessageReaction("\uD83D\uDC4D", false, self, 123, recipients, false, false);
+        assertEquals(List.of("sendTypingMessage", "sendRemoteDeleteMessage", "sendMessageReaction"),
+                account.calls.stream().map(Call::name).toList());
+        assertEquals(Set.of(self), account.calls.get(0).arguments().get(1));
+        assertEquals(Set.of(self), account.calls.get(1).arguments().get(1));
+        assertEquals(Set.of(self), account.calls.get(2).arguments().get(4));
+    }
+
+    private static String selectAccount(
+            final String account,
+            final DBusConnection connection,
+            final String busname
+    ) throws Exception {
+        final var selected = new AtomicReference<String>();
+        final var handler = new CommandHandler(null, null) {
+            @Override
+            public void handleLocalCommand(final LocalCommand command, final Manager manager) {
+                selected.set(manager.getSelfACI());
+            }
+        };
+        DbusCommandHandler.handleCommand(new ListGroupsCommand(), account, connection, busname, handler);
+        return selected.get();
+    }
+
+    private static String newBusname() {
+        return "org.asamk.Signal.Test" + UUID.randomUUID().toString().replace("-", "");
+    }
+
+    private static MessageEnvelope messageEnvelope(final Optional<GroupId> groupId) {
+        final var data = new MessageEnvelope.Data(123,
+                groupId.map(id -> new MessageEnvelope.Data.GroupContext(id, false, 0)),
+                Optional.empty(),
+                Optional.empty(),
+                Optional.of("Incoming"),
+                0,
+                false,
+                false,
+                false,
+                false,
+                false,
+                Optional.empty(),
+                Optional.empty(),
+                Optional.empty(),
+                List.of(),
+                Optional.empty(),
+                Optional.empty(),
+                List.of(),
+                Optional.empty(),
+                Optional.empty(),
+                Optional.empty(),
+                List.of(new MessageEnvelope.Data.Mention(new RecipientAddress(UUID.fromString(ACI)), 0, 1)),
+                List.of(),
+                List.of(),
+                Optional.empty(),
+                Optional.empty(),
+                Optional.empty());
+        return new MessageEnvelope(Optional.of(new RecipientAddress(UUID.fromString(OTHER_ACI))),
+                1,
+                123,
+                0,
+                0,
+                false,
+                Optional.empty(),
+                Optional.empty(),
+                Optional.of(data),
+                Optional.empty(),
+                Optional.empty(),
+                Optional.empty(),
+                Optional.empty());
+    }
+
+    private record Call(String name, List<Object> arguments) {}
+
+    private static final class TestAccount {
+
+        private final Manager manager;
+        private final List<Call> calls = new CopyOnWriteArrayList<>();
+        private final List<Runnable> closedListeners = new CopyOnWriteArrayList<>();
+        private final List<Manager.ReceiveMessageHandler> receivers = new CopyOnWriteArrayList<>();
+        private List<Recipient> recipients = List.of();
+        private List<Group> groups = List.of();
+        private List<Identity> identities = List.of();
+
+        private TestAccount(final String number, final String aci) {
+            manager = (Manager) Proxy.newProxyInstance(Manager.class.getClassLoader(),
+                    new Class<?>[]{Manager.class},
+                    (proxy, method, args) -> {
+                        if (method.isDefault()) {
+                            return InvocationHandler.invokeDefault(proxy, method, args);
+                        }
+                        return switch (method.getName()) {
+                            case "getSelfNumber" -> number;
+                            case "getSelfACI" -> aci;
+                            case "getLinkedDevices" -> List.of();
+                            case "getGroups" -> groups;
+                            case "getGroup" -> groups.getFirst();
+                            case "getIdentities" -> identities;
+                            case "getRecipients" -> recipients;
+                            case "isContactBlocked" -> false;
+                            case "getContactOrProfileName" -> "Test contact";
+                            case "addAddressChangedListener" -> null;
+                            case "addClosedListener" -> {
+                                closedListeners.add((Runnable) args[0]);
+                                yield null;
+                            }
+                            case "close" -> {
+                                closedListeners.forEach(Runnable::run);
+                                closedListeners.clear();
+                                yield null;
+                            }
+                            case "addReceiveHandler" -> {
+                                receivers.add((Manager.ReceiveMessageHandler) args[0]);
+                                yield null;
+                            }
+                            case "removeReceiveHandler" -> {
+                                receivers.remove(args[0]);
+                                yield null;
+                            }
+                            case "sendMessage", "sendTypingMessage", "sendRemoteDeleteMessage",
+                                 "sendMessageReaction" -> {
+                                calls.add(new Call(method.getName(), List.of(args)));
+                                yield new SendMessageResults(42, Map.of());
+                            }
+                            case "hashCode" -> System.identityHashCode(proxy);
+                            case "equals" -> proxy == args[0];
+                            default -> throw new UnsupportedOperationException(method.getName());
+                        };
+                    });
+        }
+
+        private void emit(final MessageEnvelope envelope) {
+            receivers.forEach(receiver -> receiver.handleMessage(envelope, null));
+        }
+    }
+}

src/test/java/org/asamk/signal/json/NumberlessAccountOutputTest.java

@@ -0,0 +1,71 @@
+package org.asamk.signal.json;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import org.asamk.signal.commands.ListAccountsCommand;
+import org.asamk.signal.manager.Manager;
+import org.asamk.signal.manager.internal.MultiAccountManagerImpl;
+import org.junit.jupiter.api.Test;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Proxy;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicReference;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertSame;
+
+class NumberlessAccountOutputTest {
+
+    private static final String ACI = "11111111-1111-4111-8111-111111111111";
+
+    @Test
+    void receiveEventsIdentifyNumberlessAccountByAci() {
+        final var output = new AtomicReference<Object>();
+        new JsonReceiveMessageHandler(manager(null), output::set).handleMessage(null, null);
+        assertEquals(ACI, ((Map<?, ?>) output.get()).get("account"));
+    }
+
+    @Test
+    void receiveEventsKeepNumberedAccountIdentifiers() {
+        final var output = new AtomicReference<Object>();
+        new JsonReceiveMessageHandler(manager("+12025550123"), output::set).handleMessage(null, null);
+        assertEquals("+12025550123", ((Map<?, ?>) output.get()).get("account"));
+    }
+
+    @Test
+    void listAccountsIncludesAciWithoutPuttingItInTheNumberField() throws Exception {
+        final var numberless = manager(null);
+        final var numbered = manager("+12025550123");
+        final var multi = new MultiAccountManagerImpl(List.of(numberless, numbered), null);
+        final var output = new AtomicReference<Object>();
+        new ListAccountsCommand().handleCommand(Map.of(), multi, output::set);
+        final var accounts = new ObjectMapper().valueToTree(output.get());
+        assertEquals(2, accounts.size());
+        for (final var account : accounts) {
+            assertEquals(ACI, account.path("aci").asText());
+            assertFalse(ACI.equals(account.path("number").asText()));
+        }
+        assertSame(numbered, multi.getManager("+12025550123"));
+    }
+
+    private static Manager manager(final String number) {
+        return (Manager) Proxy.newProxyInstance(Manager.class.getClassLoader(),
+                new Class<?>[]{Manager.class},
+                (proxy, method, args) -> {
+                    if (method.isDefault()) {
+                        return InvocationHandler.invokeDefault(proxy, method, args);
+                    }
+                    return switch (method.getName()) {
+                        case "getSelfNumber" -> number;
+                        case "getSelfACI" -> ACI;
+                        case "hashCode" -> System.identityHashCode(proxy);
+                        case "equals" -> proxy == args[0];
+                        case "addClosedListener" -> null;
+                        default -> throw new UnsupportedOperationException(method.getName());
+                    };
+                });
+    }
+}