diff --git a/native/native_rust_library/src/farcaster.rs b/native/native_rust_library/src/farcaster.rs
new file mode 100644
--- /dev/null
+++ b/native/native_rust_library/src/farcaster.rs
@@ -0,0 +1,7 @@
+pub fn farcaster_id_string_to_option(input: &str) -> Option<String> {
+  if input.is_empty() {
+    None
+  } else {
+    Some(input.to_string())
+  }
+}
diff --git a/native/native_rust_library/src/lib.rs b/native/native_rust_library/src/lib.rs
--- a/native/native_rust_library/src/lib.rs
+++ b/native/native_rust_library/src/lib.rs
@@ -4,6 +4,7 @@
 use exact_user_search::{
   find_user_id_for_username, find_user_id_for_wallet_address,
 };
+use farcaster::farcaster_id_string_to_option;
 use ffi::{bool_callback, string_callback, void_callback};
 use future_manager::ffi::*;
 use grpc_clients::identity::protos::auth::{
@@ -34,6 +35,7 @@
 mod backup;
 mod constants;
 mod exact_user_search;
+mod farcaster;
 mod future_manager;
 mod wallet_registration;
 
@@ -75,6 +77,7 @@
       notif_prekey_signature: String,
       content_one_time_keys: Vec<String>,
       notif_one_time_keys: Vec<String>,
+      farcaster_id: String, // TODO: move params to serde struct
       promise_id: u32,
     );
 
@@ -103,6 +106,7 @@
       notif_prekey_signature: String,
       content_one_time_keys: Vec<String>,
       notif_one_time_keys: Vec<String>,
+      farcaster_id: String, // TODO: move params to serde struct
       promise_id: u32,
     );
 
@@ -544,6 +548,7 @@
   notif_prekey_signature: String,
   content_one_time_keys: Vec<String>,
   notif_one_time_keys: Vec<String>,
+  farcaster_id: String,
   promise_id: u32,
 ) {
   RUNTIME.spawn(async move {
@@ -558,6 +563,7 @@
       notif_prekey_signature,
       content_one_time_keys,
       notif_one_time_keys,
+      farcaster_id: farcaster_id_string_to_option(&farcaster_id),
     };
     let result = register_password_user_helper(password_user_info).await;
     handle_string_result_as_callback(result, promise_id);
@@ -575,6 +581,7 @@
   notif_prekey_signature: String,
   content_one_time_keys: Vec<String>,
   notif_one_time_keys: Vec<String>,
+  farcaster_id: Option<String>,
 }
 
 #[derive(Serialize)]
@@ -626,7 +633,7 @@
       one_time_notif_prekeys: password_user_info.notif_one_time_keys,
       device_type: DEVICE_TYPE.into(),
     }),
-    farcaster_id: None,
+    farcaster_id: password_user_info.farcaster_id,
   };
 
   let mut identity_client = get_unauthenticated_client(
@@ -686,6 +693,7 @@
       notif_prekey_signature,
       content_one_time_keys: Vec::new(),
       notif_one_time_keys: Vec::new(),
+      farcaster_id: None,
     };
     let result = log_in_password_user_helper(password_user_info).await;
     handle_string_result_as_callback(result, promise_id);
@@ -765,6 +773,7 @@
   notif_prekey_signature: String,
   content_one_time_keys: Vec<String>,
   notif_one_time_keys: Vec<String>,
+  farcaster_id: Option<String>,
 }
 
 #[instrument]
@@ -791,6 +800,7 @@
       notif_prekey_signature,
       content_one_time_keys: Vec::new(),
       notif_one_time_keys: Vec::new(),
+      farcaster_id: None,
     };
     let result = log_in_wallet_user_helper(wallet_user_info).await;
     handle_string_result_as_callback(result, promise_id);
diff --git a/native/native_rust_library/src/wallet_registration.rs b/native/native_rust_library/src/wallet_registration.rs
--- a/native/native_rust_library/src/wallet_registration.rs
+++ b/native/native_rust_library/src/wallet_registration.rs
@@ -1,6 +1,7 @@
 use crate::{
-  handle_string_result_as_callback, Error, UserIDAndDeviceAccessToken,
-  WalletUserInfo, CODE_VERSION, DEVICE_TYPE, IDENTITY_SOCKET_ADDR, RUNTIME,
+  farcaster::farcaster_id_string_to_option, handle_string_result_as_callback,
+  Error, UserIDAndDeviceAccessToken, WalletUserInfo, CODE_VERSION, DEVICE_TYPE,
+  IDENTITY_SOCKET_ADDR, RUNTIME,
 };
 use grpc_clients::identity::{
   get_unauthenticated_client,
@@ -22,6 +23,7 @@
   notif_prekey_signature: String,
   content_one_time_keys: Vec<String>,
   notif_one_time_keys: Vec<String>,
+  farcaster_id: String,
   promise_id: u32,
 ) {
   RUNTIME.spawn(async move {
@@ -36,6 +38,7 @@
       notif_prekey_signature,
       content_one_time_keys,
       notif_one_time_keys,
+      farcaster_id: farcaster_id_string_to_option(&farcaster_id),
     };
     let result = register_wallet_user_helper(wallet_user_info).await;
     handle_string_result_as_callback(result, promise_id);
@@ -66,7 +69,7 @@
       one_time_notif_prekeys: wallet_user_info.notif_one_time_keys,
       device_type: DEVICE_TYPE.into(),
     }),
-    farcaster_id: None,
+    farcaster_id: wallet_user_info.farcaster_id,
   };
 
   let mut identity_client = get_unauthenticated_client(