diff --git a/native/cpp/CommonCpp/NativeModules/CommCoreModule.h b/native/cpp/CommonCpp/NativeModules/CommCoreModule.h
--- a/native/cpp/CommonCpp/NativeModules/CommCoreModule.h
+++ b/native/cpp/CommonCpp/NativeModules/CommCoreModule.h
@@ -121,7 +121,7 @@
   virtual jsi::Value initializeContentInboundSession(
       jsi::Runtime &rt,
       jsi::String identityKeys,
-      jsi::String encryptedMessage,
+      jsi::Object encryptedDataJSI,
       jsi::String deviceID) override;
   virtual jsi::Value
   encrypt(jsi::Runtime &rt, jsi::String message, jsi::String deviceID) override;
diff --git a/native/cpp/CommonCpp/NativeModules/CommCoreModule.cpp b/native/cpp/CommonCpp/NativeModules/CommCoreModule.cpp
--- a/native/cpp/CommonCpp/NativeModules/CommCoreModule.cpp
+++ b/native/cpp/CommonCpp/NativeModules/CommCoreModule.cpp
@@ -1122,7 +1122,7 @@
       rt, [=](jsi::Runtime &innerRt, std::shared_ptr<Promise> promise) {
         taskType job = [=, &innerRt]() {
           std::string error;
-          crypto::EncryptedData initialEncryptedMessage;
+          crypto::EncryptedData initialEncryptedData;
           try {
             this->contentCryptoModule->initializeOutboundForSendingSession(
                 deviceIDCpp,
@@ -1135,8 +1135,9 @@
                     oneTimeKeyCpp.begin(), oneTimeKeyCpp.end()));
 
             const std::string initMessage = "{\"type\": \"init\"}";
-            initialEncryptedMessage =
+            initialEncryptedData =
                 contentCryptoModule->encrypt(deviceIDCpp, initMessage);
+
             this->persistCryptoModules(true, false);
           } catch (const std::exception &e) {
             error = e.what();
@@ -1146,11 +1147,18 @@
               promise->reject(error);
               return;
             }
-            promise->resolve(jsi::String::createFromUtf8(
+            auto initialEncryptedDataJSI = jsi::Object(innerRt);
+            auto message = std::string{
+                initialEncryptedData.message.begin(),
+                initialEncryptedData.message.end()};
+            auto messageJSI = jsi::String::createFromUtf8(innerRt, message);
+            initialEncryptedDataJSI.setProperty(innerRt, "message", messageJSI);
+            initialEncryptedDataJSI.setProperty(
                 innerRt,
-                std::string{
-                    initialEncryptedMessage.message.begin(),
-                    initialEncryptedMessage.message.end()}));
+                "messageType",
+                static_cast<int>(initialEncryptedData.messageType));
+
+            promise->resolve(std::move(initialEncryptedDataJSI));
           });
         };
         this->cryptoThread->scheduleTask(job);
@@ -1160,10 +1168,13 @@
 jsi::Value CommCoreModule::initializeContentInboundSession(
     jsi::Runtime &rt,
     jsi::String identityKeys,
-    jsi::String encryptedMessage,
+    jsi::Object encryptedDataJSI,
     jsi::String deviceID) {
   auto identityKeysCpp{identityKeys.utf8(rt)};
-  auto encryptedMessageCpp{encryptedMessage.utf8(rt)};
+  size_t messageType =
+      std::lround(encryptedDataJSI.getProperty(rt, "messageType").asNumber());
+  std::string encryptedMessageCpp =
+      encryptedDataJSI.getProperty(rt, "message").asString(rt).utf8(rt);
   auto deviceIDCpp{deviceID.utf8(rt)};
   return createPromiseAsJSIValue(
       rt, [=](jsi::Runtime &innerRt, std::shared_ptr<Promise> promise) {
@@ -1177,8 +1188,10 @@
                     encryptedMessageCpp.begin(), encryptedMessageCpp.end()),
                 std::vector<uint8_t>(
                     identityKeysCpp.begin(), identityKeysCpp.end()));
-            crypto::EncryptedData encryptedData{std::vector<uint8_t>(
-                encryptedMessageCpp.begin(), encryptedMessageCpp.end())};
+            crypto::EncryptedData encryptedData{
+                std::vector<uint8_t>(
+                    encryptedMessageCpp.begin(), encryptedMessageCpp.end()),
+                messageType};
             decryptedMessage =
                 this->contentCryptoModule->decrypt(deviceIDCpp, encryptedData);
             this->persistCryptoModules(true, false);
diff --git a/native/cpp/CommonCpp/_generated/commJSI-generated.cpp b/native/cpp/CommonCpp/_generated/commJSI-generated.cpp
--- a/native/cpp/CommonCpp/_generated/commJSI-generated.cpp
+++ b/native/cpp/CommonCpp/_generated/commJSI-generated.cpp
@@ -103,7 +103,7 @@
   return static_cast<CommCoreModuleSchemaCxxSpecJSI *>(&turboModule)->initializeContentOutboundSession(rt, args[0].asString(rt), args[1].asString(rt), args[2].asString(rt), args[3].asString(rt), args[4].asString(rt));
 }
 static jsi::Value __hostFunction_CommCoreModuleSchemaCxxSpecJSI_initializeContentInboundSession(jsi::Runtime &rt, TurboModule &turboModule, const jsi::Value* args, size_t count) {
-  return static_cast<CommCoreModuleSchemaCxxSpecJSI *>(&turboModule)->initializeContentInboundSession(rt, args[0].asString(rt), args[1].asString(rt), args[2].asString(rt));
+  return static_cast<CommCoreModuleSchemaCxxSpecJSI *>(&turboModule)->initializeContentInboundSession(rt, args[0].asString(rt), args[1].asObject(rt), args[2].asString(rt));
 }
 static jsi::Value __hostFunction_CommCoreModuleSchemaCxxSpecJSI_encrypt(jsi::Runtime &rt, TurboModule &turboModule, const jsi::Value* args, size_t count) {
   return static_cast<CommCoreModuleSchemaCxxSpecJSI *>(&turboModule)->encrypt(rt, args[0].asString(rt), args[1].asString(rt));
diff --git a/native/cpp/CommonCpp/_generated/commJSI.h b/native/cpp/CommonCpp/_generated/commJSI.h
--- a/native/cpp/CommonCpp/_generated/commJSI.h
+++ b/native/cpp/CommonCpp/_generated/commJSI.h
@@ -49,7 +49,7 @@
   virtual jsi::Value removeKeyserverDataFromNotifStorage(jsi::Runtime &rt, jsi::Array keyserverIDsToDelete) = 0;
   virtual jsi::Value getKeyserverDataFromNotifStorage(jsi::Runtime &rt, jsi::Array keyserverIDs) = 0;
   virtual jsi::Value initializeContentOutboundSession(jsi::Runtime &rt, jsi::String identityKeys, jsi::String prekey, jsi::String prekeySignature, jsi::String oneTimeKey, jsi::String deviceID) = 0;
-  virtual jsi::Value initializeContentInboundSession(jsi::Runtime &rt, jsi::String identityKeys, jsi::String encryptedMessage, jsi::String deviceID) = 0;
+  virtual jsi::Value initializeContentInboundSession(jsi::Runtime &rt, jsi::String identityKeys, jsi::Object encryptedContent, jsi::String deviceID) = 0;
   virtual jsi::Value encrypt(jsi::Runtime &rt, jsi::String message, jsi::String deviceID) = 0;
   virtual jsi::Value decrypt(jsi::Runtime &rt, jsi::Object encryptedData, jsi::String deviceID) = 0;
   virtual jsi::Value signMessage(jsi::Runtime &rt, jsi::String message) = 0;
@@ -327,13 +327,13 @@
       return bridging::callFromJs<jsi::Value>(
           rt, &T::initializeContentOutboundSession, jsInvoker_, instance_, std::move(identityKeys), std::move(prekey), std::move(prekeySignature), std::move(oneTimeKey), std::move(deviceID));
     }
-    jsi::Value initializeContentInboundSession(jsi::Runtime &rt, jsi::String identityKeys, jsi::String encryptedMessage, jsi::String deviceID) override {
+    jsi::Value initializeContentInboundSession(jsi::Runtime &rt, jsi::String identityKeys, jsi::Object encryptedContent, jsi::String deviceID) override {
       static_assert(
           bridging::getParameterCount(&T::initializeContentInboundSession) == 4,
           "Expected initializeContentInboundSession(...) to have 4 parameters");
 
       return bridging::callFromJs<jsi::Value>(
-          rt, &T::initializeContentInboundSession, jsInvoker_, instance_, std::move(identityKeys), std::move(encryptedMessage), std::move(deviceID));
+          rt, &T::initializeContentInboundSession, jsInvoker_, instance_, std::move(identityKeys), std::move(encryptedContent), std::move(deviceID));
     }
     jsi::Value encrypt(jsi::Runtime &rt, jsi::String message, jsi::String deviceID) override {
       static_assert(
diff --git a/native/crypto/olm-api.js b/native/crypto/olm-api.js
--- a/native/crypto/olm-api.js
+++ b/native/crypto/olm-api.js
@@ -7,7 +7,6 @@
   type OlmAPI,
   type OLMIdentityKeys,
   type EncryptedData,
-  olmEncryptedMessageTypes,
 } from 'lib/types/crypto-types.js';
 import type { OlmSessionInitializationInfo } from 'lib/types/request-types.js';
 
@@ -30,7 +29,7 @@
     });
     return commCoreModule.initializeContentInboundSession(
       identityKeys,
-      initialEncryptedData.message,
+      initialEncryptedData,
       contentIdentityKeys.ed25519,
     );
   },
@@ -44,17 +43,13 @@
       ed25519: contentIdentityKeys.ed25519,
     });
 
-    const message = await commCoreModule.initializeContentOutboundSession(
+    return commCoreModule.initializeContentOutboundSession(
       identityKeys,
       prekey,
       prekeySignature,
       oneTimeKey,
       contentIdentityKeys.ed25519,
     );
-    return {
-      message,
-      messageType: olmEncryptedMessageTypes.PREKEY,
-    };
   },
   notificationsSessionCreator(
     cookie: ?string,
diff --git a/native/schema/CommCoreModuleSchema.js b/native/schema/CommCoreModuleSchema.js
--- a/native/schema/CommCoreModuleSchema.js
+++ b/native/schema/CommCoreModuleSchema.js
@@ -102,10 +102,10 @@
     prekeySignature: string,
     oneTimeKey: string,
     deviceID: string,
-  ) => Promise<string>;
+  ) => Promise<EncryptedData>;
   +initializeContentInboundSession: (
     identityKeys: string,
-    encryptedMessage: string,
+    encryptedContent: Object,
     deviceID: string,
   ) => Promise<string>;
   +encrypt: (message: string, deviceID: string) => Promise<EncryptedData>;
@@ -148,6 +148,11 @@
     backupID: string,
   ) => Promise<ArrayBuffer>;
   +decrypt: (encryptedData: EncryptedData, deviceID: string) => Promise<string>;
+  +initializeContentInboundSession: (
+    identityKeys: string,
+    encryptedContent: EncryptedData,
+    deviceID: string,
+  ) => Promise<string>;
 }
 
 export default (TurboModuleRegistry.getEnforcing<Spec>(