diff --git a/cmake/build_options.cmake b/cmake/build_options.cmake
index f774253..b723a65 100644
--- a/cmake/build_options.cmake
+++ b/cmake/build_options.cmake
@@ -4,7 +4,14 @@
 # `.github/workflows/ci.yml` and the composition-root validator in
 # `src/gps_denied_onboard/runtime_root.py`.
 
-option(BUILD_OKVIS2                 "Build C1 OKVIS2 VIO strategy"              ON)
+# BUILD_OKVIS2 default OFF: AZ-332's pybind11 binding requires apt-installed
+# Eigen + Ceres + Brisk + DBoW2 + opengv on the host (`USE_SYSTEM_*` flags in
+# `cpp/okvis2/CMakeLists.txt`). Tier-1 / Tier-2 CI explicitly opts in via
+# `-DBUILD_OKVIS2=ON` from `.github/workflows/ci.yml`; macOS dev hosts don't
+# carry those system deps and would fail at the OpenGV/Eigen `find_package`
+# step otherwise. The C1 fake binding fixture (tests/unit/c1_vio/conftest.py)
+# keeps unit tests green without the native build.
+option(BUILD_OKVIS2                 "Build C1 OKVIS2 VIO strategy"             OFF)
 option(BUILD_VINS_MONO              "Build C1 VINS-Mono VIO strategy"          OFF)
 option(BUILD_KLT_RANSAC             "Build C1 KLT/RANSAC simple baseline"      ON)