diff --git a/.github/workflows/dev.yml b/.github/workflows/dev.yml
index 37b5071..8fcd549 100644
--- a/.github/workflows/dev.yml
+++ b/.github/workflows/dev.yml
@@ -23,10 +23,10 @@ jobs:
       image: datadog/docker-library:httpd-datadog-ci-28219c0ef3e00f1e3d5afcab61a73a5e9bd2a9b957d7545556711cce2a6262cd
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
-        with:
-          submodules: true
       - name: Add cloned repo as safe
         run: sh -c "git config --global --add safe.directory $PWD"
+      - name: Init required submodules
+        run: git submodule update --init --depth=1 deps/dd-trace-cpp deps/nginx-datadog
       - name: Configure
         run: cmake --preset=ci-dev -B build .
       - name: Build
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 0d58326..7a7539b 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -9,10 +9,10 @@ jobs:
       image: datadog/docker-library:httpd-datadog-ci-28219c0ef3e00f1e3d5afcab61a73a5e9bd2a9b957d7545556711cce2a6262cd
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
-        with:
-          submodules: true
       - name: Add cloned repo as safe
         run: sh -c "git config --global --add safe.directory $PWD"
+      - name: Init required submodules
+        run: git submodule update --init --depth=1 deps/dd-trace-cpp deps/nginx-datadog
       - name: Configure
         run: cmake --preset ci-release -B build .
       - name: Build
diff --git a/.github/workflows/system-tests.yml b/.github/workflows/system-tests.yml
index b9b0051..72414ee 100644
--- a/.github/workflows/system-tests.yml
+++ b/.github/workflows/system-tests.yml
@@ -23,10 +23,10 @@ jobs:
       image: datadog/docker-library:httpd-datadog-ci-28219c0ef3e00f1e3d5afcab61a73a5e9bd2a9b957d7545556711cce2a6262cd
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
-        with:
-          submodules: true
       - name: Add cloned repo as safe
         run: sh -c "git config --global --add safe.directory $PWD"
+      - name: Init required submodules
+        run: git submodule update --init --depth=1 deps/dd-trace-cpp deps/nginx-datadog
       - name: Configure
         run: cmake --preset=ci-dev -B build .
       - name: Build
diff --git a/.gitmodules b/.gitmodules
index d88c1b8..52a8a84 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -5,3 +5,6 @@
 	path = deps/nginx-datadog
 	url = ../httpd-datadog.git
 	branch = mirror-nginx-datadog
+[submodule "deps/inject-browser-sdk"]
+	path = deps/inject-browser-sdk
+	url = ../inject-browser-sdk.git
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7f0afad..59ef466 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -23,23 +23,6 @@ if (NOT HTTPD_SRC_DIR)
 endif ()
 
 include(cmake/utils.cmake)
-include(cmake/deps/fmt.cmake)
-
-if (HTTPD_DATADOG_ENABLE_RUM)
-  include(FetchContent)
-
-  set(INJECT_BROWSER_SDK_GIT_REF "49245e1c6ed8275990bb910125187e0aaad09e3d" CACHE STRING
-      "Git tag/branch for inject-browser-sdk")
-
-  FetchContent_Declare(
-    InjectBrowserSDK
-    GIT_REPOSITORY https://github.com/DataDog/inject-browser-sdk.git
-    GIT_TAG        ${INJECT_BROWSER_SDK_GIT_REF}
-  )
-  FetchContent_MakeAvailable(InjectBrowserSDK)
-
-  include(cmake/deps/rapidjson.cmake)
-endif ()
 
 add_library(httpd INTERFACE)
 target_include_directories(
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 0794211..63d4b27 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -2,12 +2,14 @@
 
 ## Fork, Clone, Branch and Create your PR
 
-When cloning the repo, you have to initialize the submodules:
+When cloning the repo, initialize the submodules you need. For a standard build:
 
 ```sh
-git submodule update --init --recursive
+git submodule update --init deps/dd-trace-cpp deps/nginx-datadog
 ```
 
+The `deps/inject-browser-sdk` submodule is a private repo and is only required when building with `-DHTTPD_DATADOG_ENABLE_RUM=ON`. If you have access, use `--recursive` instead to pull it as well.
+
 ### Rules
 - Follow the pattern of what you already see in the code.
 - Follow the coding style.
diff --git a/cmake/deps/fmt.cmake b/cmake/deps/fmt.cmake
index 829b9aa..6563674 100644
--- a/cmake/deps/fmt.cmake
+++ b/cmake/deps/fmt.cmake
@@ -4,15 +4,9 @@ FetchContent_Declare(
   fmt
   GIT_REPOSITORY https://github.com/fmtlib/fmt.git
   GIT_TAG        10.2.1
+  EXCLUDE_FROM_ALL
 )
 
-FetchContent_GetProperties(fmt)
-if(NOT fmt_POPULATED)
-  FetchContent_Populate(fmt)
-
-  set(BUILD_SHARED_LIBS OFF)
-  set(CMAKE_POSITION_INDEPENDENT_CODE ON)
-
-  add_subdirectory(${fmt_SOURCE_DIR} ${fmt_BINARY_DIR} EXCLUDE_FROM_ALL)
-endif()
-
+set(BUILD_SHARED_LIBS OFF)
+set(CMAKE_POSITION_INDEPENDENT_CODE ON)
+FetchContent_MakeAvailable(fmt)
diff --git a/deps/CMakeLists.txt b/deps/CMakeLists.txt
index 1181b4d..da207da 100644
--- a/deps/CMakeLists.txt
+++ b/deps/CMakeLists.txt
@@ -1,6 +1,22 @@
+include(${CMAKE_SOURCE_DIR}/cmake/deps/fmt.cmake)
+
 add_subdirectory(dd-trace-cpp)
 
 # Force POSITION_INDEPENDENT_CODE (PIC) because mod_datadog.so is loaded via
 # dlopen, but dd-trace-cpp sets this based on BUILD_SHARED_LIBS, whereas we
 # link with the static library.
 set_target_properties(dd-trace-cpp-objects PROPERTIES POSITION_INDEPENDENT_CODE ON)
+
+if (HTTPD_DATADOG_ENABLE_RUM)
+  if (NOT EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/inject-browser-sdk/CMakeLists.txt")
+    message(FATAL_ERROR
+      "deps/inject-browser-sdk submodule is not initialized. "
+      "Run: git submodule update --init --recursive")
+  endif ()
+  # mod_datadog/CMakeLists.txt references ${injectbrowsersdk_SOURCE_DIR}, which
+  # FetchContent used to set; replicate it for the submodule layout.
+  set(injectbrowsersdk_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/inject-browser-sdk" CACHE INTERNAL "")
+  add_subdirectory(inject-browser-sdk EXCLUDE_FROM_ALL)
+
+  include(${CMAKE_SOURCE_DIR}/cmake/deps/rapidjson.cmake)
+endif ()
diff --git a/deps/inject-browser-sdk b/deps/inject-browser-sdk
new file mode 160000
index 0000000..49245e1
--- /dev/null
+++ b/deps/inject-browser-sdk
@@ -0,0 +1 @@
+Subproject commit 49245e1c6ed8275990bb910125187e0aaad09e3d