diff --git a/lib/components/keyserver-connection-handler.js b/lib/components/keyserver-connection-handler.js
--- a/lib/components/keyserver-connection-handler.js
+++ b/lib/components/keyserver-connection-handler.js
@@ -161,7 +161,7 @@
               : logInActionSources.keyserverAuthFromNative,
             keyserverData: {
               [keyserverID]: {
-                initialContentEncryptedMessage: contentSession,
+                initialContentEncryptedMessage: contentSession.message,
                 initialNotificationsEncryptedMessage: notifsSession,
               },
             },
diff --git a/lib/handlers/peer-to-peer-message-handler.js b/lib/handlers/peer-to-peer-message-handler.js
--- a/lib/handlers/peer-to-peer-message-handler.js
+++ b/lib/handlers/peer-to-peer-message-handler.js
@@ -17,7 +17,7 @@
   const { olmAPI } = getConfig();
   if (message.type === peerToPeerMessageTypes.OUTBOUND_SESSION_CREATION) {
     try {
-      const { senderInfo, encryptedContent } = message;
+      const { senderInfo, encryptedData } = message;
       const { keys } = await identityClient.getInboundKeysForUser(
         senderInfo.userID,
       );
@@ -33,7 +33,7 @@
       await olmAPI.initializeCryptoAccount();
       const result = await olmAPI.contentInboundSessionCreator(
         deviceKeys.identityKeysBlob.primaryIdentityPublicKeys,
-        encryptedContent,
+        encryptedData,
       );
       console.log(
         'Created inbound session with device ' +
diff --git a/lib/types/crypto-types.js b/lib/types/crypto-types.js
--- a/lib/types/crypto-types.js
+++ b/lib/types/crypto-types.js
@@ -144,12 +144,12 @@
   +decrypt: (encryptedData: EncryptedData, deviceID: string) => Promise<string>,
   +contentInboundSessionCreator: (
     contentIdentityKeys: OLMIdentityKeys,
-    initialEncryptedContent: string,
+    initialEncryptedData: EncryptedData,
   ) => Promise<string>,
   +contentOutboundSessionCreator: (
     contentIdentityKeys: OLMIdentityKeys,
     contentInitializationInfo: OlmSessionInitializationInfo,
-  ) => Promise<string>,
+  ) => Promise<EncryptedData>,
   +notificationsSessionCreator: (
     cookie: ?string,
     notificationsIdentityKeys: OLMIdentityKeys,
diff --git a/lib/types/tunnelbroker/peer-to-peer-message-types.js b/lib/types/tunnelbroker/peer-to-peer-message-types.js
--- a/lib/types/tunnelbroker/peer-to-peer-message-types.js
+++ b/lib/types/tunnelbroker/peer-to-peer-message-types.js
@@ -30,13 +30,13 @@
 export type OutboundSessionCreation = {
   +type: 'OutboundSessionCreation',
   +senderInfo: SenderInfo,
-  +encryptedContent: string,
+  +encryptedData: EncryptedData,
 };
 export const outboundSessionCreationValidator: TInterface<OutboundSessionCreation> =
   tShape<OutboundSessionCreation>({
     type: tString(peerToPeerMessageTypes.OUTBOUND_SESSION_CREATION),
     senderInfo: senderInfoValidator,
-    encryptedContent: t.String,
+    encryptedData: encryptedDataValidator,
   });
 
 export type EncryptedMessage = {
diff --git a/lib/utils/crypto-utils.js b/lib/utils/crypto-utils.js
--- a/lib/utils/crypto-utils.js
+++ b/lib/utils/crypto-utils.js
@@ -78,7 +78,7 @@
       continue;
     }
     try {
-      const encryptedContent = await olmAPI.contentOutboundSessionCreator(
+      const encryptedData = await olmAPI.contentOutboundSessionCreator(
         primaryIdentityPublicKeys,
         keys.contentInitializationInfo,
       );
@@ -89,7 +89,7 @@
           userID,
           deviceID,
         },
-        encryptedContent,
+        encryptedData,
       };
 
       await sendMessage({
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
@@ -6,6 +6,8 @@
   type OneTimeKeysResultValues,
   type OlmAPI,
   type OLMIdentityKeys,
+  type EncryptedData,
+  olmEncryptedMessageTypes,
 } from 'lib/types/crypto-types.js';
 import type { OlmSessionInitializationInfo } from 'lib/types/request-types.js';
 
@@ -20,7 +22,7 @@
   decrypt: commCoreModule.decrypt,
   async contentInboundSessionCreator(
     contentIdentityKeys: OLMIdentityKeys,
-    initialEncryptedContent: string,
+    initialEncryptedData: EncryptedData,
   ): Promise<string> {
     const identityKeys = JSON.stringify({
       curve25519: contentIdentityKeys.curve25519,
@@ -28,27 +30,31 @@
     });
     return commCoreModule.initializeContentInboundSession(
       identityKeys,
-      initialEncryptedContent,
+      initialEncryptedData.message,
       contentIdentityKeys.ed25519,
     );
   },
   async contentOutboundSessionCreator(
     contentIdentityKeys: OLMIdentityKeys,
     contentInitializationInfo: OlmSessionInitializationInfo,
-  ): Promise<string> {
+  ): Promise<EncryptedData> {
     const { prekey, prekeySignature, oneTimeKey } = contentInitializationInfo;
     const identityKeys = JSON.stringify({
       curve25519: contentIdentityKeys.curve25519,
       ed25519: contentIdentityKeys.ed25519,
     });
 
-    return commCoreModule.initializeContentOutboundSession(
+    const message = await commCoreModule.initializeContentOutboundSession(
       identityKeys,
       prekey,
       prekeySignature,
       oneTimeKey,
       contentIdentityKeys.ed25519,
     );
+    return {
+      message,
+      messageType: olmEncryptedMessageTypes.PREKEY,
+    };
   },
   notificationsSessionCreator(
     cookie: ?string,
diff --git a/web/shared-worker/worker/worker-crypto.js b/web/shared-worker/worker/worker-crypto.js
--- a/web/shared-worker/worker/worker-crypto.js
+++ b/web/shared-worker/worker/worker-crypto.js
@@ -7,7 +7,6 @@
 import { initialEncryptedMessageContent } from 'lib/shared/crypto-utils.js';
 import { hasMinCodeVersion } from 'lib/shared/version-utils.js';
 import {
-  olmEncryptedMessageTypes,
   type OLMIdentityKeys,
   type PickledOLMAccount,
   type IdentityKeysBlob,
@@ -407,7 +406,7 @@
   },
   async contentInboundSessionCreator(
     contentIdentityKeys: OLMIdentityKeys,
-    initialEncryptedContent: string,
+    initialEncryptedData: EncryptedData,
   ): Promise<string> {
     if (!cryptoStore) {
       throw new Error('Crypto account not initialized');
@@ -418,13 +417,13 @@
     session.create_inbound_from(
       contentAccount,
       contentIdentityKeys.curve25519,
-      initialEncryptedContent,
+      initialEncryptedData.message,
     );
 
     contentAccount.remove_one_time_keys(session);
     const initialEncryptedMessage = session.decrypt(
-      olmEncryptedMessageTypes.PREKEY,
-      initialEncryptedContent,
+      initialEncryptedData.messageType,
+      initialEncryptedData.message,
     );
 
     contentSessions[contentIdentityKeys.ed25519] = session;
@@ -435,7 +434,7 @@
   async contentOutboundSessionCreator(
     contentIdentityKeys: OLMIdentityKeys,
     contentInitializationInfo: OlmSessionInitializationInfo,
-  ): Promise<string> {
+  ): Promise<EncryptedData> {
     if (!cryptoStore) {
       throw new Error('Crypto account not initialized');
     }
@@ -450,14 +449,17 @@
       contentInitializationInfo.prekeySignature,
       contentInitializationInfo.oneTimeKey,
     );
-    const { body: initialContentEncryptedMessage } = session.encrypt(
+    const initialEncryptedData = session.encrypt(
       JSON.stringify(initialEncryptedMessageContent),
     );
 
     contentSessions[contentIdentityKeys.ed25519] = session;
     persistCryptoStore();
 
-    return initialContentEncryptedMessage;
+    return {
+      message: initialEncryptedData.body,
+      messageType: initialEncryptedData.type,
+    };
   },
   async notificationsSessionCreator(
     cookie: ?string,