diff --git a/lib/src/main/java/org/asamk/signal/manager/SignalAccountFiles.java b/lib/src/main/java/org/asamk/signal/manager/SignalAccountFiles.java
index 82b73495..9ce9e313 100644
--- a/lib/src/main/java/org/asamk/signal/manager/SignalAccountFiles.java
+++ b/lib/src/main/java/org/asamk/signal/manager/SignalAccountFiles.java
@@ -5,6 +5,7 @@ import org.asamk.signal.manager.api.NotRegisteredException;
 import org.asamk.signal.manager.api.Pair;
 import org.asamk.signal.manager.api.ServiceEnvironment;
 import org.asamk.signal.manager.config.ServiceConfig;
+import org.signal.core.models.ServiceId.ACI;
 import org.asamk.signal.manager.config.ServiceEnvironmentConfig;
 import org.asamk.signal.manager.internal.AccountFileUpdaterImpl;
 import org.asamk.signal.manager.internal.ManagerImpl;
@@ -95,6 +96,30 @@ public class SignalAccountFiles {
         return this.initManager(number, accountPath);
     }
 
+    public String getAccountNumberByAci(final String aciStr) throws IOException {
+        final var accounts = accountsStore.getAllAccounts();
+        final var account = accounts.stream()
+                .filter(a -> aciStr.equals(a.uuid()))
+                .findFirst()
+                .orElse(null);
+        if (account == null || account.number() == null) {
+            return null;
+        }
+        return account.number();
+    }
+
+    public Manager initManagerByAci(String aciStr) throws IOException, NotRegisteredException, AccountCheckException {
+        final var phoneNumber = getAccountNumberByAci(aciStr);
+        if (phoneNumber == null) {
+            throw new NotRegisteredException();
+        }
+        final var accountPath = accountsStore.getPathByNumber(phoneNumber);
+        if (accountPath == null) {
+            throw new NotRegisteredException();
+        }
+        return this.initManager(phoneNumber, accountPath);
+    }
+
     private Manager initManager(
             String number,
             String accountPath
diff --git a/lib/src/main/java/org/asamk/signal/manager/internal/MultiAccountManagerImpl.java b/lib/src/main/java/org/asamk/signal/manager/internal/MultiAccountManagerImpl.java
index 24ecae61..3adefbef 100644
--- a/lib/src/main/java/org/asamk/signal/manager/internal/MultiAccountManagerImpl.java
+++ b/lib/src/main/java/org/asamk/signal/manager/internal/MultiAccountManagerImpl.java
@@ -8,6 +8,7 @@ import org.asamk.signal.manager.SignalAccountFiles;
 import org.asamk.signal.manager.api.AccountCheckException;
 import org.asamk.signal.manager.api.NotRegisteredException;
 import org.slf4j.Logger;
+import org.signal.core.util.UuidUtil;
 import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
@@ -95,23 +96,54 @@ public class MultiAccountManagerImpl implements MultiAccountManager {
     }
 
     @Override
-    public Manager getManager(final String number) {
+    public Manager getManager(final String identifier) {
         synchronized (managers) {
-            final var manager = managers.stream()
-                    .filter(m -> m.getSelfNumber().equals(number))
-                    .findFirst()
-                    .orElse(null);
-            if (manager != null) {
-                return manager;
-            }
-            try {
-                final var newManager = signalAccountFiles.initManager(number);
-                managers.add(newManager);
-                return newManager;
-            } catch (IOException | NotRegisteredException | AccountCheckException e) {
-                logger.warn("Failed to load new manager", e);
-                return null;
+            if (UuidUtil.INSTANCE.isUuid(identifier)) {
+                // Check if UUID corresponds to an already-loaded manager
+                try {
+                    final var phoneNumber = signalAccountFiles.getAccountNumberByAci(identifier);
+                    if (phoneNumber != null) {
+                        final var existing = managers.stream()
+                                .filter(m -> m.getSelfNumber().equals(phoneNumber))
+                                .findFirst()
+                                .orElse(null);
+                        if (existing != null) {
+                            logger.debug("Found already loaded manager for ACI: {}", identifier);
+                            return existing;
+                        }
+                    }
+                } catch (IOException e) {
+                    logger.warn("Failed to lookup ACI in accounts: {}", identifier, e);
+                }
+                // Load by ACI
+                try {
+                    final var newManager = signalAccountFiles.initManagerByAci(identifier);
+                    managers.add(newManager);
+                    return newManager;
+                } catch (NotRegisteredException e) {
+                    logger.debug("Manager not found by ACI: {}", identifier);
+                } catch (IOException | IllegalArgumentException | AccountCheckException e) {
+                    logger.warn("Failed to load new manager by ACI: {}", identifier, e);
+                }
+            } else {
+                // Phone number — check already loaded managers
+                var existing = managers.stream()
+                        .filter(m -> m.getSelfNumber().equals(identifier))
+                        .findFirst()
+                        .orElse(null);
+                if (existing != null) {
+                    return existing;
+                }
+                // Load by phone number
+                try {
+                    final var newManager = signalAccountFiles.initManager(identifier);
+                    managers.add(newManager);
+                    return newManager;
+                } catch (NotRegisteredException | IOException | IllegalArgumentException | AccountCheckException e) {
+                    logger.warn("Failed to load manager by number: {}", identifier, e);
+                }
             }
+            return null;
         }
     }
 
diff --git a/src/main/java/org/asamk/signal/http/HttpServerHandler.java b/src/main/java/org/asamk/signal/http/HttpServerHandler.java
index a6fc9f9e..c797e22a 100644
--- a/src/main/java/org/asamk/signal/http/HttpServerHandler.java
+++ b/src/main/java/org/asamk/signal/http/HttpServerHandler.java
@@ -262,6 +262,9 @@ public class HttpServerHandler implements AutoCloseable {
             } else {
                 final var manager = c.getManager(account);
                 if (manager == null) {
+                    // Account not found by the given identifier (number or ACI/UUID)
+                    // Log the available accounts to help debug
+                    logger.warn("Account not found for identifier: {}", account);
                     return null;
                 }
                 return List.of(manager);
diff --git a/src/main/java/org/asamk/signal/util/Util.java b/src/main/java/org/asamk/signal/util/Util.java
index 585c5690..76e41fa7 100644
--- a/src/main/java/org/asamk/signal/util/Util.java
+++ b/src/main/java/org/asamk/signal/util/Util.java
@@ -79,7 +79,7 @@ public class Util {
         for (var param : params) {
             final var paramParts = param.split("=", 2);
             var name = URLDecoder.decode(paramParts[0], StandardCharsets.UTF_8);
-            var value = paramParts.length == 1 ? null : URLDecoder.decode(paramParts[1], StandardCharsets.UTF_8);
+            var value = paramParts.length == 1 ? null : URLDecoder.decode(paramParts[1].replace("+", "%2B"), StandardCharsets.UTF_8);
             map.put(name, value);
         }
         return map;