diff --git a/build-base/CLAUDE.md b/build-base/CLAUDE.md
index 8d7ecd6..27cb4fc 100644
--- a/build-base/CLAUDE.md
+++ b/build-base/CLAUDE.md
@@ -39,6 +39,7 @@ This base image is designed to create statically-linked C++ executables using:
 8. **fmt** (10.2.1) - Modern formatting library
 9. **spdlog** (1.13.0) - Fast C++ logging library
 10. **Drogon** (latest from git) - C++ web framework
+11. **nlohmann/json** (3.11.3) - Modern JSON library for C++
 
 ### Build Characteristics
 - All libraries installed in standard `/usr/local/` location
diff --git a/build-base/Dockerfile.dropshell-build-base b/build-base/Dockerfile.dropshell-build-base
index 57b1553..fa53086 100644
--- a/build-base/Dockerfile.dropshell-build-base
+++ b/build-base/Dockerfile.dropshell-build-base
@@ -228,3 +228,19 @@ RUN git clone --recurse-submodules https://github.com/drogonframework/drogon.git
     make -j$(nproc) && \
     make install && \
     cd / && rm -rf /tmp/drogon
+
+# Build nlohmann/json library (header-only, but we'll install it properly)
+ARG NLOHMANN_JSON_VERSION=3.11.3
+WORKDIR /tmp
+RUN curl -LO https://github.com/nlohmann/json/archive/refs/tags/v${NLOHMANN_JSON_VERSION}.tar.gz && \
+    tar xzf v${NLOHMANN_JSON_VERSION}.tar.gz && \
+    cd json-${NLOHMANN_JSON_VERSION} && \
+    mkdir build && cd build && \
+    cmake .. \
+      -DCMAKE_BUILD_TYPE=Release \
+      -DCMAKE_INSTALL_PREFIX=/usr/local \
+      -DJSON_BuildTests=OFF \
+      -DJSON_Install=ON && \
+    make -j$(nproc) && \
+    make install && \
+    cd / && rm -rf /tmp/json-${NLOHMANN_JSON_VERSION} /tmp/v${NLOHMANN_JSON_VERSION}.tar.gz
diff --git a/tests/ipdemo/CMakeLists.txt b/tests/ipdemo/CMakeLists.txt
index 2c1928d..abab72d 100644
--- a/tests/ipdemo/CMakeLists.txt
+++ b/tests/ipdemo/CMakeLists.txt
@@ -50,19 +50,11 @@ target_include_directories(${PROJECT_NAME} PRIVATE
     ${CMAKE_CURRENT_SOURCE_DIR}/src
 )
 
-# External dependencies
-include(FetchContent)
-FetchContent_Declare(
-    nlohmann_json
-    GIT_REPOSITORY https://github.com/nlohmann/json.git
-    GIT_TAG v3.12.0
-)
-FetchContent_MakeAvailable(nlohmann_json)
-
 # Find packages
 set(CMAKE_PREFIX_PATH /usr/local)
 find_package(OpenSSL REQUIRED)
 find_package(Drogon CONFIG REQUIRED)
+find_package(nlohmann_json REQUIRED)
 
 # Link libraries
 target_link_libraries(${PROJECT_NAME} PRIVATE