diff --git a/backend/cpp/ik-llama-cpp/grpc-server.cpp b/backend/cpp/ik-llama-cpp/grpc-server.cpp
index 578d69034..96eea3b58 100644
--- a/backend/cpp/ik-llama-cpp/grpc-server.cpp
+++ b/backend/cpp/ik-llama-cpp/grpc-server.cpp
@@ -45,7 +45,9 @@ using backend::HealthMessage;
 
 ///// LLAMA.CPP server code below
 
-using json = nlohmann::json;
+// Match mtmd.h and ik_llama's server/common headers, which all use
+// nlohmann::ordered_json; a plain nlohmann::json alias collides at global scope.
+using json = nlohmann::ordered_json;
 
 struct server_params
 {
diff --git a/backend/cpp/ik-llama-cpp/utils.hpp b/backend/cpp/ik-llama-cpp/utils.hpp
index 4427d4b91..f0e599212 100644
--- a/backend/cpp/ik-llama-cpp/utils.hpp
+++ b/backend/cpp/ik-llama-cpp/utils.hpp
@@ -13,7 +13,10 @@
 
 #include "mtmd.h"
 
-using json = nlohmann::json;
+// mtmd.h and ik_llama's entire server/common stack (chat.h, server-common.h,
+// server-task.h, ...) declare `using json = nlohmann::ordered_json`, so match it
+// here: a plain `nlohmann::json` alias collides with mtmd.h's at global scope.
+using json = nlohmann::ordered_json;
 
 extern bool server_verbose;