diff --git a/native/utils/farcaster-utils.js b/native/utils/farcaster-utils.js
--- a/native/utils/farcaster-utils.js
+++ b/native/utils/farcaster-utils.js
@@ -19,10 +19,7 @@
       try {
         await linkFID(newFID);
       } catch (e) {
-        if (
-          getMessageForException(e) ===
-          'farcaster ID already associated with different user'
-        ) {
+        if (getMessageForException(e) === 'fid_taken') {
           const { title, message } =
             getFarcasterAccountAlreadyLinkedAlertDetails();
           Alert.alert(title, message);
diff --git a/services/identity/src/client_service.rs b/services/identity/src/client_service.rs
--- a/services/identity/src/client_service.rs
+++ b/services/identity/src/client_service.rs
@@ -284,7 +284,9 @@
       };
       Ok(Response::new(response))
     } else {
-      Err(tonic::Status::not_found("session not found"))
+      Err(tonic::Status::not_found(
+        tonic_status_messages::SESSION_NOT_FOUND,
+      ))
     }
   }
 
@@ -434,7 +436,9 @@
       };
       Ok(Response::new(response))
     } else {
-      Err(tonic::Status::not_found("session not found"))
+      Err(tonic::Status::not_found(
+        tonic_status_messages::SESSION_NOT_FOUND,
+      ))
     }
   }
 
@@ -1063,7 +1067,7 @@
       .is_empty();
     if fid_already_registered {
       return Err(tonic::Status::already_exists(
-        "farcaster ID already associated with different user",
+        tonic_status_messages::FID_TAKEN,
       ));
     }
     Ok(())
diff --git a/services/identity/src/constants.rs b/services/identity/src/constants.rs
--- a/services/identity/src/constants.rs
+++ b/services/identity/src/constants.rs
@@ -231,6 +231,13 @@
   pub const USER_NOT_FOUND: &str = "user_not_found";
   pub const INVALID_NONCE: &str = "invalid_nonce";
   pub const NONCE_EXPIRED: &str = "nonce_expired";
+  pub const FID_TAKEN: &str = "fid_taken";
+  pub const CANNOT_LINK_FID: &str = "cannot_link_fid";
+  pub const INVALID_PLATFORM_METADATA: &str = "invalid_platform_metadata";
+  pub const MISSING_CREDENTIALS: &str = "missing_credentials";
+  pub const BAD_CREDENTIALS: &str = "bad_credentials";
+  pub const SESSION_NOT_FOUND: &str = "session_not_found";
+  pub const INVALID_TIMESTAMP: &str = "invalid_timestamp";
 }
 
 // Tunnelbroker
diff --git a/services/identity/src/grpc_services/authenticated.rs b/services/identity/src/grpc_services/authenticated.rs
--- a/services/identity/src/grpc_services/authenticated.rs
+++ b/services/identity/src/grpc_services/authenticated.rs
@@ -50,8 +50,10 @@
 ) -> Result<Request<()>, Status> {
   trace!("Intercepting request to check auth info: {:?}", req);
 
-  let (user_id, device_id, access_token) = get_auth_info(&req)
-    .ok_or_else(|| Status::unauthenticated("Missing credentials"))?;
+  let (user_id, device_id, access_token) =
+    get_auth_info(&req).ok_or_else(|| {
+      Status::unauthenticated(tonic_status_messages::MISSING_CREDENTIALS)
+    })?;
 
   let handle = tokio::runtime::Handle::current();
   let new_db_client = db_client.clone();
@@ -69,7 +71,7 @@
   })?;
 
   if !valid_token {
-    return Err(Status::aborted("Bad Credentials"));
+    return Err(Status::aborted(tonic_status_messages::BAD_CREDENTIALS));
   }
 
   Ok(req)
@@ -293,7 +295,9 @@
       .await
       .map_err(handle_db_error)?
     else {
-      return Err(tonic::Status::not_found("session not found"));
+      return Err(tonic::Status::not_found(
+        tonic_status_messages::SESSION_NOT_FOUND,
+      ));
     };
 
     let server_registration = comm_opaque2::server::Registration::new();
@@ -470,7 +474,9 @@
       .await
       .map_err(handle_db_error)?
     else {
-      return Err(tonic::Status::not_found("session not found"));
+      return Err(tonic::Status::not_found(
+        tonic_status_messages::SESSION_NOT_FOUND,
+      ));
     };
 
     let mut server_login = state.opaque_server_login;
@@ -500,8 +506,11 @@
 
     let since = since_timestamp
       .map(|timestamp| {
-        DateTime::from_timestamp_millis(timestamp)
-          .ok_or_else(|| tonic::Status::invalid_argument("Invalid timestamp"))
+        DateTime::from_timestamp_millis(timestamp).ok_or_else(|| {
+          tonic::Status::invalid_argument(
+            tonic_status_messages::INVALID_TIMESTAMP,
+          )
+        })
       })
       .transpose()?;
 
@@ -656,16 +665,16 @@
         errorType = error_types::GRPC_SERVICES_LOG,
         "multiple users associated with the same Farcaster ID"
       );
-      return Err(Status::failed_precondition("cannot link Farcaster ID"));
+      return Err(Status::failed_precondition(
+        tonic_status_messages::CANNOT_LINK_FID,
+      ));
     }
 
     if let Some(u) = get_farcaster_users_response.pop() {
       if u.0.user_id == user_id {
         return Ok(Response::new(Empty {}));
       } else {
-        return Err(Status::already_exists(
-          "farcaster ID already associated with different user",
-        ));
+        return Err(Status::already_exists(tonic_status_messages::FID_TAKEN));
       }
     }
 
@@ -728,7 +737,11 @@
     let (user_id, device_id) = get_user_and_device_id(&request)?;
     let platform_metadata = get_platform_metadata(&request)?;
     let platform_details = PlatformDetails::new(platform_metadata, None)
-      .map_err(|_| Status::invalid_argument("Invalid platform metadata"))?;
+      .map_err(|_| {
+        Status::invalid_argument(
+          tonic_status_messages::INVALID_PLATFORM_METADATA,
+        )
+      })?;
 
     self
       .db_client