diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b5802371f..784a54b23 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -525,7 +525,7 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - desc: MacOS-15-Intel aclang17/C++17/py3.13 llvm17 oiio-release
+          - desc: MacOS-15-Intel aclang17/C++17/py3.13 llvm18 oiio-release
             runner: macos-15-intel
             nametag: macos15
             cc_compiler: clang
@@ -535,8 +535,8 @@ jobs:
             python_ver: "3.13"
             ctest_test_timeout: 120
             setenvs: export HOMEBREW_PREFIX=/usr/local
-                            LLVMBREWVER="@17"
-                            USE_OPENVDB=0
+                            LLVMBREWVER="@18"
+                            INSTALL_OPENVDB=0 INSTALL_QT=0
           - desc: MacOS-14-ARM llvm19 oiio-release
             runner: macos-14
             nametag: macos14-arm
diff --git a/src/build-scripts/ci-startup.bash b/src/build-scripts/ci-startup.bash
index 8115d8cab..901106c68 100755
--- a/src/build-scripts/ci-startup.bash
+++ b/src/build-scripts/ci-startup.bash
@@ -38,6 +38,7 @@ export PYTHON_VERSION=${PYTHON_VERSION:="3.7"}
 export PYTHONPATH=$DISTDIR/lib/python${PYTHON_VERSION}/site-packages:$PYTHONPATH
 cmake --version
 export OSL_CI=true
+export OpenImageIO_CI=true
 export USE_NINJA=${USE_NINJA:=1}
 export CMAKE_GENERATOR=${CMAKE_GENERATOR:=Ninja}
 export CMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE:=Release}
diff --git a/src/build-scripts/install_homebrew_deps.bash b/src/build-scripts/install_homebrew_deps.bash
index b506eb28a..573035cc2 100755
--- a/src/build-scripts/install_homebrew_deps.bash
+++ b/src/build-scripts/install_homebrew_deps.bash
@@ -28,33 +28,37 @@ echo ""
 echo "Before my brew installs:"
 brew list --versions
 
-if [[ "${BREW_UNLINK_PACKAGES}" != "" ]] ; then
-    brew unlink ${BREW_UNLINK_PACKAGES} || true
-fi
-
-
-if [[ "${DO_BREW_CMAKE_INSTALL:=1}" != "0" ]] ; then
-    brew install --display-times -q cmake || true
-fi
-brew install --display-times -q gcc ccache ninja || true
-brew link --overwrite gcc
-brew install --display-times -q python@${PYTHON_VERSION} || true
-brew link --overwrite --force python@${PYTHON_VERSION} || true
-brew install --display-times -q imath openexr opencolorio || true
-#brew install --display-times -q freetype
-brew install --display-times -q partio pugixml || true
-brew install --display-times -q pybind11 numpy || true
-brew install --display-times -q tbb || true
-brew install --display-times -q openvdb || true
-brew install --display-times -q flex bison
-brew install --display-times -q fmt
-brew install --display-times -q llvm${LLVMBREWVER}
-if [[ "${USE_QT}" != "0" ]] ; then
-    brew install --display-times -q qt${QT_VERSION}
-fi
-if [[ "${EXTRA_BREW_PACKAGES}" != "" ]] ; then
-    brew install --display-times -q ${EXTRA_BREW_PACKAGES}
+if [[ "$OSL_BREW_INSTALL_PACKAGES" == "" ]] ; then
+    OSL_BREW_INSTALL_PACKAGES=" \
+        bison \
+        ccache \
+        expat \
+        flex \
+        fmt \
+        imath \
+        llvm${LLVMBREWVER} \
+        ninja \
+        numpy \
+        opencolorio \
+        openexr \
+        partio \
+        ptex \
+        pugixml \
+        pybind11 \
+        robin-map \
+        tbb \
+        "
+    if [[ "${USE_OPENVDB:=1}" != "0" ]] && [[ "${INSTALL_OPENVDB:=1}" != "0" ]] ; then
+        OSL_BREW_INSTALL_PACKAGES+=" openvdb"
+    fi
+    if [[ "${USE_QT:=1}" != "0" ]] && [[ "${INSTALL_QT:=1}" != "0" ]] ; then
+        OSL_BREW_INSTALL_PACKAGES+=" qt${QT_VERSION}"
+    fi
+    if [[ "${EXTRA_BREW_PACKAGES}" != "" ]] ; then
+        brew install --display-times -q ${EXTRA_BREW_PACKAGES}
+    fi
 fi
+brew install --display-times -q $OSL_BREW_INSTALL_PACKAGES $OSL_BREW_EXTRA_INSTALL_PACKAGES || true
 
 echo ""
 echo "After brew installs:"