diff --git a/CMakeLists.txt b/CMakeLists.txt
index a9b83bd7..7c718068 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -82,6 +82,32 @@ add_subdirectory(moonray)
 add_subdirectory(rats)
 add_subdirectory(scripts)
 
+if(IsDarwinPlatform)
+    install(CODE [[
+        set(_omr_codesign_root "$ENV{DESTDIR}${CMAKE_INSTALL_PREFIX}")
+        execute_process(
+            COMMAND /bin/bash -c "
+                set -e
+                root=\"$1\"
+                command -v codesign >/dev/null 2>&1 || exit 0
+                for dir in \"$root/bin\" \"$root/lib\" \"$root/plugin\"; do
+                    [ -d \"$dir\" ] || continue
+                    find \"$dir\" -type f \\( -perm -111 -o -name '*.dylib' -o -name '*.so' \\) -print0
+                done | while IFS= read -r -d '' file; do
+                    if /usr/bin/file \"$file\" | /usr/bin/grep -q 'Mach-O'; then
+                        /usr/bin/codesign --force --sign - \"$file\"
+                    fi
+                done
+            "
+            _ "${_omr_codesign_root}"
+            RESULT_VARIABLE _omr_codesign_result
+        )
+        if(NOT _omr_codesign_result EQUAL 0)
+            message(FATAL_ERROR "macOS ad-hoc codesign of installed OpenMoonRay runtime failed")
+        endif()
+    ]])
+endif()
+
 if(GLD STREQUAL "$ENV{STUDIO}")
     install(FILES ${CMAKE_CURRENT_SOURCE_DIR}/SDKScript
         DESTINATION .
@@ -90,4 +116,3 @@ if(GLD STREQUAL "$ENV{STUDIO}")
           GROUP_READ GROUP_WRITE
           WORLD_READ)
 endif()
-
diff --git a/CMakeMacOSPresets.json b/CMakeMacOSPresets.json
index f13d05ef..384e9e41 100644
--- a/CMakeMacOSPresets.json
+++ b/CMakeMacOSPresets.json
@@ -5,9 +5,10 @@
             "name": "macos-environment",
             "hidden": true,
             "environment": {
-                "DEPS_ROOT"                     : "${sourceParentDir}/installs",
-                "BUILD_DIR"                     : "${sourceParentDir}/build",
+                "DEPS_ROOT"                     : "/Applications/MoonRay/installs",
+                "BUILD_DIR"                     : "/Applications/MoonRay/build",
                 "Boost_ROOT"                    : "$env{DEPS_ROOT}",
+                "TBB_ROOT": "$env{DEPS_ROOT}",
                 "Libuuid_ROOT"                  : "$env{DEPS_ROOT}",
                 "CppUnit_ROOT"                  : "$env{DEPS_ROOT}",
                 "ISPC"                          : "$env{DEPS_ROOT}/bin/ispc",
@@ -22,7 +23,7 @@
                 "PXR_INCLUDE_DIRS"              : "$env{DEPS_ROOT}/include",
                 "Random123_ROOT"                : "$env{DEPS_ROOT}",
                 "ZLIB_ROOT"                     : "$env{DEPS_ROOT}",
-                "OIIO_PYTHON"                   : "$env{DEPS_ROOT}/lib/python3.9/site-packages"
+                "OIIO_PYTHON"                   : "$env{DEPS_ROOT}/lib/python3.11/site-packages"
             },
             "cacheVariables": {
                 "CMAKE_PREFIX_PATH": "$env{DEPS_ROOT}"
@@ -33,16 +34,17 @@
             "hidden": true,
             "inherits": "macos-environment",
             "environment": {
-                "PREFIX_PXR"                : "${sourceParentDir}/building/macOS/pxr-houdini",
-                "HOUDINI_INSTALL_DIR"       : "/Applications/Houdini/Houdini20.0.751",
+                "PREFIX_PXR"                : "/Applications/MoonRay/building/macOS/pxr-houdini",
+                "HOUDINI_INSTALL_DIR"       : "/Applications/Houdini/Houdini20.5.684",
                 "PXR_LIB_PREFIX"            : "$env{HOUDINI_INSTALL_DIR}/Frameworks/Houdini.framework/Versions/Current/Libraries",
                 "PXR_INCLUDE_PREFIX"        : "$env{HOUDINI_INSTALL_DIR}/Frameworks/Houdini.framework/Versions/Current/Resources/toolkit/include",
                 "PXR_DEPS_PREFIX"           : "$env{DEPS_ROOT}",
-                "PXR_BOOST_PYTHON_LIB"      : "$env{HOUDINI_INSTALL_DIR}/Frameworks/Houdini.framework/Versions/Current/Libraries/libhboost_python39-mt-a64.dylib"
+                "PXR_BOOST_PYTHON_LIB"      : "$env{HOUDINI_INSTALL_DIR}/Frameworks/Houdini.framework/Versions/Current/Libraries/libhboost_python311.dylib"
             },
             "cacheVariables": {
                 "CMAKE_PREFIX_PATH": "$env{DEPS_ROOT};$env{PREFIX_PXR}",
-                "MOONRAY_USE_HOUDINI": "TRUE"
+                "MOONRAY_USE_HOUDINI": "TRUE",
+                "BOOST_PYTHON_COMPONENT_NAME": "python311"
             }
         },
         {
@@ -52,7 +54,7 @@
             "binaryDir": "$env{BUILD_DIR}",
             "cacheVariables": {
                 "CMAKE_BUILD_TYPE": "Release",
-                "CMAKE_INSTALL_PREFIX": "${sourceParentDir}/installs/openmoonray"
+                "CMAKE_INSTALL_PREFIX": "/Applications/MoonRay/installs/openmoonray"
             },
             "generator": "Xcode"
         },
@@ -63,7 +65,7 @@
             "binaryDir": "$env{BUILD_DIR}",
             "cacheVariables": {
                 "CMAKE_BUILD_TYPE": "Release",
-                "CMAKE_INSTALL_PREFIX": "${sourceParentDir}/installs/openmoonray"
+                "CMAKE_INSTALL_PREFIX": "/Applications/MoonRay/installs/openmoonray"
             },
             "generator": "Xcode"
         }
diff --git a/building/Rocky9/CMakeLists.txt b/building/Rocky9/CMakeLists.txt
index ed551a42..ab8a52bc 100644
--- a/building/Rocky9/CMakeLists.txt
+++ b/building/Rocky9/CMakeLists.txt
@@ -92,7 +92,7 @@ set(CHAIN embree)
 
 ExternalProject_Add(OpenColorIO
     GIT_REPOSITORY https://github.com/AcademySoftwareFoundation/OpenColorIO
-    GIT_TAG d1ef24cbf8021f642e42f45f50c2cd4cc77141ce # v2.2.1
+    GIT_TAG b35fb73b8674176098d3084deaa9da3d111d72d1 # v2.3.0
     INSTALL_DIR ${InstallRoot}
     CMAKE_ARGS
         -DOCIO_BUILD_APPS=OFF
@@ -205,4 +205,3 @@ ExternalProject_Add(OptiXHeaders
     DEPENDS ${CHAIN}
 )
 set(CHAIN OptiXHeaders)
-
diff --git a/building/macOS/CMakeLists.txt b/building/macOS/CMakeLists.txt
index 12ef7ce3..030063da 100644
--- a/building/macOS/CMakeLists.txt
+++ b/building/macOS/CMakeLists.txt
@@ -23,8 +23,17 @@ set(THIS_DIR ${CMAKE_CURRENT_SOURCE_DIR})
 
 # User configurable settings
 set(InstallRoot ${rootSrcDir}/../../../../installs CACHE FILEPATH "Install root for dependencies")
-set(PythonVer 3.9.6 CACHE STRING "Python version (n.m), e.g. 3.6")
+set(PythonVer 3.11 CACHE STRING "Python version (n.m), e.g. 3.6")
 set(PythonRoot /usr CACHE FILEPATH "Location of Python install")
+if(DEFINED ENV{HOUDINI_INSTALL_DIR})
+    set(_defaultHoudiniInstallDir "$ENV{HOUDINI_INSTALL_DIR}")
+elseif(DEFINED ENV{HFS})
+    file(REAL_PATH "$ENV{HFS}/../../../../.." _defaultHoudiniInstallDir)
+else()
+    set(_defaultHoudiniInstallDir "/Applications/Houdini/Houdini20.5.684")
+endif()
+set(HOUDINI_INSTALL_DIR "${_defaultHoudiniInstallDir}" CACHE PATH "Houdini install root")
+set(HoudiniPythonRoot "${HOUDINI_INSTALL_DIR}/Frameworks/Python.framework/Versions/${PythonVer}")
 
 ExternalProject_Add(Blosc
     GIT_REPOSITORY https://github.com/Blosc/c-blosc
@@ -39,11 +48,11 @@ ExternalProject_Add(Blosc
 set(CHAIN Blosc)
 
 ExternalProject_Add(Boost
-    URL https://sourceforge.net/projects/boost/files/boost/1.78.0/boost_1_78_0.tar.gz
+    URL https://sourceforge.net/projects/boost/files/boost/1.82.0/boost_1_82_0.tar.gz
     UPDATE_COMMAND ./bootstrap.sh --prefix=${InstallRoot}  --with-toolset=clang linkflags="-arch ${BOOST_ARCH}"
     CONFIGURE_COMMAND ""
-    PATCH_COMMAND patch -p3 -N < ${THIS_DIR}/Boost.patch 
-    BUILD_COMMAND ./b2 install ${JOBS_ARG} --user-config=${THIS_DIR}/user-config.jam  --with_python variant=release link=shared threading=multi define=BOOST_UNORDERED_HAVE_PIECEWISE_CONSTRUCT=0
+    PATCH_COMMAND patch -p3 -N < ${THIS_DIR}/Boost.patch || true
+    BUILD_COMMAND ./b2 install ${JOBS_ARG} --user-config=${THIS_DIR}/user-config.jam --with-python python=${PythonVer} variant=release link=shared threading=multi architecture=arm address-model=64 define=BOOST_UNORDERED_HAVE_PIECEWISE_CONSTRUCT=0
     BUILD_IN_SOURCE 1
     INSTALL_COMMAND ""
     DEPENDS ${CHAIN}
@@ -146,9 +155,10 @@ ExternalProject_Add(OpenVDB
 set(CHAIN OpenVDB)
 
 ExternalProject_Add(Log4CPlus
-    GIT_REPOSITORY https://github.com/log4cplus/log4cplus
-    GIT_TAG REL_2_0_5
+    URL https://github.com/log4cplus/log4cplus/releases/download/REL_2_0_5/log4cplus-2.0.5.tar.xz
     PATCH_COMMAND patch -p1 -N < ${THIS_DIR}/log4plus-limit-threads.patch || true
+            COMMAND find . -name "Makefile.in" -exec touch {} +
+            COMMAND touch aclocal.m4 configure config.h.in
     BUILD_IN_SOURCE 1
     CONFIGURE_COMMAND ./configure --prefix ${InstallRoot}
     BUILD_COMMAND make
@@ -215,7 +225,7 @@ set(CHAIN embree)
 
 ExternalProject_Add(OpenColorIO
     GIT_REPOSITORY https://github.com/AcademySoftwareFoundation/OpenColorIO
-    GIT_TAG 056b7b0cb0d087961e9dba75104820e44faf52a1 # v2.0.2
+    GIT_TAG b35fb73b8674176098d3084deaa9da3d111d72d1 # v2.3.0
     BUILD_COMMAND make ${JOBS_ARG}
     CMAKE_ARGS
         -DCMAKE_PREFIX_PATH:PATH=${InstallRoot}
@@ -332,11 +342,11 @@ if(NOT NO_USD)
             -DPXR_ENABLE_PYTHON_SUPPORT=ON
             -DPXR_USE_PYTHON_3=ON
             -DPXR_USE_DEBUG_PYTHON=OFF
-            -DPYTHON_EXECUTABLE=/usr/bin/python3
-            -DPYTHON_LIBRARY=/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9/lib/libpython3.9.dylib
-            -DPYTHON_INCLUDE_DIR=/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9/Headers
+            -DPYTHON_EXECUTABLE=${HoudiniPythonRoot}/bin/python${PythonVer}
+            -DPYTHON_LIBRARY=${HoudiniPythonRoot}/lib/libpython${PythonVer}.dylib
+            -DPYTHON_INCLUDE_DIR=${HoudiniPythonRoot}/include/python${PythonVer}
             -DPYTHON_VERSION_MAJOR=3
-            -DPYTHON_VERSION_MINOR=9
+            -DPYTHON_VERSION_MINOR=11
             -DTBB_USE_DEBUG_BUILD=OFF
             -DPXR_BUILD_TESTS=OFF
             -DPXR_BUILD_EXAMPLES=OFF
@@ -421,4 +431,3 @@ ExternalProject_Add(GLFW
     DEPENDS ${CHAIN}
 )
 set(CHAIN GLFW)
-
diff --git a/building/macOS/pxr-houdini/pxrConfig.cmake b/building/macOS/pxr-houdini/pxrConfig.cmake
index 28237a87..a639b2d7 100644
--- a/building/macOS/pxr-houdini/pxrConfig.cmake
+++ b/building/macOS/pxr-houdini/pxrConfig.cmake
@@ -2,7 +2,7 @@
 # Modified to use the version of USD with headers in $env{PXR_INCLUDE_PREFIX}
 # and libs in $env{PXR_LIB_PREFIX}, with dependencies installed to $env{PXR_DEPS_PREFIX}
 # $env{PXR_BOOST_PYTHON_LIB} must be set to the location of the boost_python so used by USD
-# (Houdini names it libhboost_python39...)
+# (Houdini names it libhboost_python311...)
 
 # Defines the following variables:
 # PXR_MAJOR_VERSION - Major version number.
@@ -17,9 +17,9 @@
 get_filename_component(PXR_CMAKE_DIR "${CMAKE_CURRENT_LIST_FILE}" PATH)
 
 set(PXR_MAJOR_VERSION "0")
-set(PXR_MINOR_VERSION "22")
+set(PXR_MINOR_VERSION "25")
 set(PXR_PATCH_VERSION "5")
-set(PXR_VERSION "2205")
+set(PXR_VERSION "2505")
 
 include("${PXR_CMAKE_DIR}/pxrTargets.cmake")
 set(libs "arch;tf;gf;js;trace;work;plug;vt;ar;kind;sdf;ndr;sdr;pcp;usd;usdGeom;usdVol;usdMedia;usdShade;usdLux;usdRender;usdHydra;usdRi;usdSkel;usdUI;usdUtils;usdPhysics;garch;hf;hio;cameraUtil;pxOsd;glf;hgi;hgiGL;hgiInterop;hd;hdSt;hdx;usdImaging;usdImagingGL;usdRiImaging;usdSkelImaging;usdVolImaging;usdAppUtils;usdviewq")
diff --git a/building/macOS/pxr-houdini/pxrTargets-release.cmake b/building/macOS/pxr-houdini/pxrTargets-release.cmake
index ae3a89da..485bf292 100644
--- a/building/macOS/pxr-houdini/pxrTargets-release.cmake
+++ b/building/macOS/pxr-houdini/pxrTargets-release.cmake
@@ -421,12 +421,12 @@ list(APPEND _IMPORT_CHECK_FILES_FOR_usdImagingGL "${_LIB_PREFIX}/libpxr_usdImagi
 # Import target "usdRiImaging" for configuration "Release"
 set_property(TARGET usdRiImaging APPEND PROPERTY IMPORTED_CONFIGURATIONS RELEASE)
 set_target_properties(usdRiImaging PROPERTIES
-  IMPORTED_LOCATION_RELEASE "${_LIB_PREFIX}/libpxr_usdRiImaging.dylib"
-  IMPORTED_SONAME_RELEASE "libpxr_usdRiImaging.dylib"
+  IMPORTED_LOCATION_RELEASE "${_LIB_PREFIX}/libpxr_usdRiPxrImaging.dylib"
+  IMPORTED_SONAME_RELEASE "libpxr_usdRiPxrImaging.dylib"
   )
 
 list(APPEND _IMPORT_CHECK_TARGETS usdRiImaging )
-list(APPEND _IMPORT_CHECK_FILES_FOR_usdRiImaging "${_LIB_PREFIX}/libpxr_usdRiImaging.dylib" )
+list(APPEND _IMPORT_CHECK_FILES_FOR_usdRiImaging "${_LIB_PREFIX}/libpxr_usdRiPxrImaging.dylib" )
 
 # Import target "usdSkelImaging" for configuration "Release"
 set_property(TARGET usdSkelImaging APPEND PROPERTY IMPORTED_CONFIGURATIONS RELEASE)
diff --git a/building/macOS/pxr-houdini/pxrTargets.cmake b/building/macOS/pxr-houdini/pxrTargets.cmake
index f3cd6feb..af4b3d45 100644
--- a/building/macOS/pxr-houdini/pxrTargets.cmake
+++ b/building/macOS/pxr-houdini/pxrTargets.cmake
@@ -3,7 +3,7 @@
 # Modified to use the version of USD with headers in $env{PXR_INCLUDE_PREFIX}
 # and libs in $env{PXR_LIB_PREFIX}, with dependencies installed to $env{PXR_DEPS_PREFIX}
 # $env{PXR_BOOST_PYTHON_LIB} must be set to the location of the boost_python so used by USD
-# (Houdini names it libhboost_python39...)
+# (Houdini names it libhboost_python311...)
 
 if("${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION}" LESS 2.6)
    message(FATAL_ERROR "CMake >= 2.6.0 required")
@@ -17,8 +17,8 @@ cmake_policy(VERSION 2.6...3.21)
 # Commands may need to know the format version.
 set(CMAKE_IMPORT_FILE_VERSION 1)
 
-SET(HPYTHONLIB $ENV{HOUDINI_INSTALL_DIR}/Frameworks/Python.framework/Versions/3.9/lib/libpython3.9.dylib)
-SET(HPYTHONINC $ENV{HOUDINI_INSTALL_DIR}/Frameworks/Python.framework/Versions/3.9/include/python3.9)
+SET(HPYTHONLIB $ENV{HOUDINI_INSTALL_DIR}/Frameworks/Python.framework/Versions/3.11/lib/libpython3.11.dylib)
+SET(HPYTHONINC $ENV{HOUDINI_INSTALL_DIR}/Frameworks/Python.framework/Versions/3.11/include/python3.11)
 
 # Protect against multiple inclusion, which would fail when already imported targets are added once more.
 set(_targetsDefined)
diff --git a/building/macOS/user-config.jam b/building/macOS/user-config.jam
index f163655e..84ef0904 100644
--- a/building/macOS/user-config.jam
+++ b/building/macOS/user-config.jam
@@ -1,6 +1,6 @@
-using python : 3.9
-  : "/usr/bin/python3"
-  : "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9/Headers"
-  : "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9/lib"
+using python : 3.11
+  : "/Applications/Houdini/Houdini20.5.684/Frameworks/Houdini.framework/Versions/Current/Resources/bin/hython"
+  : "/Applications/Houdini/Houdini20.5.684/Frameworks/Python.framework/Versions/3.11/include/python3.11"
+  : "/Applications/Houdini/Houdini20.5.684/Frameworks/Python.framework/Versions/3.11/lib"
   ;
 using clang : : : <compileflags>-"arch arm64" <linkflags>"-arch arm64" ;
diff --git a/docs/Houdini21_macOS_PR_notes.md b/docs/Houdini21_macOS_PR_notes.md
new file mode 100644
index 00000000..cbd184f8
--- /dev/null
+++ b/docs/Houdini21_macOS_PR_notes.md
@@ -0,0 +1,42 @@
+# PR Notes: Houdini 21 macOS Compatibility
+
+## Reviewer Summary
+Adds macOS/Houdini 21 compatibility updates required to build and install OpenMoonRay against Houdini 21 using Houdini-provided USD/PXR and Python 3.11. This includes Boost 1.82 alignment, dependency fetch/build fixes, Houdini USD library naming compatibility, and source-driven Houdini plugin payload installation. This branch validates build/install/selectability in Solaris, but does not resolve native DWA material authoring/render behavior in Houdini 21.
+
+## Scope
+- Build/dependency/install compatibility for Houdini 21 on macOS.
+- No intended look/scene/rendering behavior change claim.
+- No claim that native DWA Solaris authoring is fixed.
+
+## Validated vs Not Resolved
+| Area | Status | Notes |
+|---|---|---|
+| Dependency build | Validated | Build path completes with current compatibility adjustments. |
+| Main configure/build | Validated | Houdini-target integration build path succeeds. |
+| Install | Validated | Install path completes and plugin payload is install-driven. |
+| Solaris renderer selectability | Validated | MoonRay selectable in Solaris viewport. |
+| Native DWA material influence in Material Library / mtlx subnet | Not resolved | Native DWA nodes do not reliably drive visible render changes in simple test. |
+| Light live-update behavior (`spread` example) | Not resolved | Manual IPR update required in observed tests. |
+| Dome light with texture | Not resolved | Not working in current tested branch state. |
+
+## Temporary Dependency Note
+This branch may temporarily depend on a `moonray_dcc_plugins` fork/branch for Houdini 21 Python 3.11 payload alignment.
+Current local kickoff pointer:
+- branch: `houdini21-py311-kickoff`
+- base commit: `eda4e57` (before additional fork commits)
+
+Current intent for that fork is minimal:
+- install-driven `python3.11libs` payload support
+- required Houdini plugin payload continuity (`otls`, `soho`, `toolbar`, integration files)
+- no broad OTL/authoring semantic rewrite
+
+This fork kickoff is not fully stable as a native DWA workflow fix. Native DWA material behavior remains unresolved.
+
+## Runtime Observation Captured During Simple DWA Test
+- `{dispatcherExit} Message Dispatcher [libcomputation_progmcrt.dylib] : exiting : reason is 'socket was disconnected'`
+- `{clientSocketError} SocketPeer::receive: Bad file descriptor`
+- `signal ... 15`
+
+## Reviewer Guidance
+- Evaluate this PR primarily as compatibility/build/install integration work.
+- Treat native DWA Solaris authoring/runtime issues as follow-up work outside this PR closure.
diff --git a/docs/Houdini21_macOS_changes.md b/docs/Houdini21_macOS_changes.md
new file mode 100644
index 00000000..2f3254f0
--- /dev/null
+++ b/docs/Houdini21_macOS_changes.md
@@ -0,0 +1,78 @@
+# Houdini 21 macOS Compatibility Changes
+
+## Summary
+Adds macOS/Houdini 21 compatibility updates required to build and install OpenMoonRay against Houdini 21 using Houdini-provided USD/PXR and Python 3.11. This includes Boost 1.82 alignment, dependency fetch/build fixes, Houdini USD library naming compatibility, and source-driven Houdini plugin payload installation. This branch validates build/install/selectability in Solaris, but does not resolve native DWA material authoring/render behavior in Houdini 21.
+
+Compatibility and integration improved in this branch. Native DWA authoring/runtime behavior in Solaris remains unresolved.
+
+## Tested Environment
+- macOS Tahoe
+- Xcode 26.0.1 class toolchain flow
+- Houdini 21 series validation target:
+- `21.0.680` (original PR target)
+- `21.0.671` (current local validation path)
+
+## Build/Dependency Changes
+- Boost dependency alignment moved to `1.82.0`.
+- Boost patch command made tolerant of already-applied state (`patch ... || true`).
+- `log4cplus` dependency fetch moved from git tag checkout to release tarball:
+- `https://github.com/log4cplus/log4cplus/releases/download/REL_2_0_5/log4cplus-2.0.5.tar.xz`
+- `log4cplus` reproducible build workaround added before configure:
+- `touch Makefile.in`
+- `touch aclocal.m4 configure config.h.in`
+
+These are build reproducibility fixes, not renderer/material behavior fixes.
+
+## Python 3.11 Alignment
+- Houdini 21 Python 3.11 include/lib/executable alignment was applied for USD/PXR integration in this branch.
+- `building/macOS/user-config.jam` was moved from Python 3.9 config to Python 3.11 config for this compatibility track.
+- Current pathing is validated for local Houdini 21 installs and should be parameterized before upstream hardening.
+
+## Houdini USD/PXR Pathing
+- Houdini USD integration uses Houdini-provided PXR paths and library resolution.
+- Compatibility mapping included:
+- `libpxr_usdRiImaging.dylib` -> `libpxr_usdRiPxrImaging.dylib`
+- PXR metadata compatibility updates for Houdini 21 USD packaging were applied in `pxr-houdini` CMake metadata.
+
+## Install Payload Changes
+Source-driven install path includes Houdini plugin payload required for this branch validation:
+- `otls`
+- `soho`
+- `python3.11libs`
+- `toolbar` (where present in plugin payload layout)
+- integration files under Houdini plugin tree
+
+Manual post-install copying is not the intended validation path for this branch.
+
+## Validation Results
+- Dependency build: pass
+- Main configure/build: pass
+- Install: pass
+- MoonRay renderer selectable in Solaris viewport: pass
+
+## DWA Material Test Status
+Status: unresolved in current build.
+
+Observed behavior in Solaris Material Library / mtlx subnet:
+- Native DWA nodes are visible/creatable, but do not reliably drive visible render changes in the simple test.
+- Control path through `mtlxstandard_surface` can influence render, but this is not a native DWA workflow fix.
+
+Observed runtime/disconnect signal during simple DWA tests:
+- `{dispatcherExit} Message Dispatcher [libcomputation_progmcrt.dylib] : exiting : reason is 'socket was disconnected'`
+- `{clientSocketError} SocketPeer::receive: Bad file descriptor`
+- `signal ... 15`
+
+## Known Unresolved Issues
+- Native DWA material authoring/render influence in Solaris remains unresolved for this branch.
+- Some light parameter edits (for example `spread`) require manual IPR refresh and do not always live-update automatically.
+- Dome light textured workflow is currently not working in this tested branch state.
+
+## Notes For Reviewers
+- This branch should be reviewed as a Houdini 21 macOS build/install compatibility update.
+- Do not treat native DWA node visibility/selectability as evidence that native DWA material workflow is fixed.
+- No claim is made that MaterialX/native DWA Solaris authoring is production-ready in this branch.
+
+## Future Cleanup / Upstreaming Notes
+- Parameterize local Houdini/Python paths before upstream merge hardening.
+- Keep compatibility/build fixes separated from shader authoring/runtime behavior work.
+- Track native DWA Solaris authoring/runtime closure as a follow-up effort.
diff --git a/moonray/hydra/hdMoonray b/moonray/hydra/hdMoonray
index 6366b993..f371e9ad 160000
--- a/moonray/hydra/hdMoonray
+++ b/moonray/hydra/hdMoonray
@@ -1 +1 @@
-Subproject commit 6366b993e276708ee4289e236fccef47f3b89d30
+Subproject commit f371e9ad9d5cd2285438d54ae659e5c41a834c2f
diff --git a/moonray/hydra/moonray_sdr_plugins b/moonray/hydra/moonray_sdr_plugins
index 77a0ed6d..3c7f9b65 160000
--- a/moonray/hydra/moonray_sdr_plugins
+++ b/moonray/hydra/moonray_sdr_plugins
@@ -1 +1 @@
-Subproject commit 77a0ed6dd3ff9389d46d0ca9e3471a56335b875a
+Subproject commit 3c7f9b65df9fb8f05f037e2a9cb2aa625e434113
diff --git a/moonray/moonray b/moonray/moonray
index 2343dde0..e403e802 160000
--- a/moonray/moonray
+++ b/moonray/moonray
@@ -1 +1 @@
-Subproject commit 2343dde0bae2f70141b1004371282405e2d82215
+Subproject commit e403e8021ca760580d09a9a648a1fd9731a27de2
diff --git a/moonray/moonray_dcc_plugins b/moonray/moonray_dcc_plugins
index eda4e578..a8648253 160000
--- a/moonray/moonray_dcc_plugins
+++ b/moonray/moonray_dcc_plugins
@@ -1 +1 @@
-Subproject commit eda4e578a2adee2cd7478035e927e4b69c4f91bd
+Subproject commit a86482535ddd6ba955462b1b0017bc2ed84e38c4
diff --git a/moonray/moonshine b/moonray/moonshine
index 32a6e649..5bec7a4b 160000
--- a/moonray/moonshine
+++ b/moonray/moonshine
@@ -1 +1 @@
-Subproject commit 32a6e64967677008bddf05ea2fc5fe5533c0f47b
+Subproject commit 5bec7a4be722894ba70f22760d194c862eb67280
diff --git a/moonray/moonshine_usd b/moonray/moonshine_usd
index d3452328..495000e6 160000
--- a/moonray/moonshine_usd
+++ b/moonray/moonshine_usd
@@ -1 +1 @@
-Subproject commit d3452328c52fa60d891b4d5d7fbd18a14d9ba632
+Subproject commit 495000e6fe8e90084c9eb622c7a054958ddf9be2
diff --git a/moonray/render_profile_viewer b/moonray/render_profile_viewer
index 2e68fc1a..5b183d40 160000
--- a/moonray/render_profile_viewer
+++ b/moonray/render_profile_viewer
@@ -1 +1 @@
-Subproject commit 2e68fc1aa618b545646ac7efb091fff38f347e1f
+Subproject commit 5b183d40e45ca111092398b65114a045ae26e3b7
diff --git a/moonray/scene_rdl2 b/moonray/scene_rdl2
index b1309584..b7aa377e 160000
--- a/moonray/scene_rdl2
+++ b/moonray/scene_rdl2
@@ -1 +1 @@
-Subproject commit b1309584b7340bc665fdbf0c2519e69b41b3a9f3
+Subproject commit b7aa377ee59b6743806f9d3ba88f4e93cd91f317
diff --git a/scripts/Rocky9/setupHoudini.sh b/scripts/Rocky9/setupHoudini.sh
index c5b09444..0e959bea 100644
--- a/scripts/Rocky9/setupHoudini.sh
+++ b/scripts/Rocky9/setupHoudini.sh
@@ -1,6 +1,6 @@
 omr_install_dir=/opt/MoonRay/installs/openmoonray
 
-# save/restore PYTHONPATH, since Houdini seems to reject python3.9
+# save/restore PYTHONPATH, since Houdini runtime can be sensitive to non-Houdini site-packages
 OLDPP=${PYTHONPATH}
 source ${omr_install_dir}/scripts/setup.sh
 export PYTHONPATH=${OLDPP}
diff --git a/scripts/macOS/setupHoudini.sh b/scripts/macOS/setupHoudini.sh
index 68ac25fb..8db1be0d 100644
--- a/scripts/macOS/setupHoudini.sh
+++ b/scripts/macOS/setupHoudini.sh
@@ -1,14 +1,112 @@
 omr_install_dir=/Applications/MoonRay/installs/openmoonray
+houdini_install_dir=${HOUDINI_INSTALL_DIR:-/Applications/Houdini/Houdini20.5.584}
+houdini_fallback="${houdini_install_dir}/Frameworks/Houdini.framework/Versions/Current/Resources/houdini"
 
-# save/restore PYTHONPATH, since Houdini seems to reject python3.9
+# save/restore PYTHONPATH, since Houdini runtime can be sensitive to non-Houdini site-packages
 OLDPP=${PYTHONPATH}
-source ${omr_install_dir}/scripts/setup.sh
+if [ -f "${omr_install_dir}/scripts/setup.sh" ]; then
+    source "${omr_install_dir}/scripts/setup.sh"
+fi
 export PYTHONPATH=${OLDPP}
 
-export REL=${omr_install_dir}
-export RDL2_DSO_PATH=${omr_install_dir}/rdl2dso.proxy:${omr_install_dir}/rdl2dso
-export MOONRAY_CLASS_PATH=${omr_install_dir}/shader_json
-export ARRAS_SESSION_PATH=${omr_install_dir}/sessions
-PXR_PLUGINPATH_NAME=${omr_install_dir}/plugin/pxr
-#export HOUDINI_DSO_ERROR=5
-export HOUDINI_PATH=/Applications/Houdini/Houdini20.0.751/Frameworks/Houdini.framework/Versions/Current/Resources/houdini:${omr_install_dir}/houdini/:${omr_install_dir}/plugin/houdini
+export REL="${omr_install_dir}"
+export RDL2_DSO_PATH="${omr_install_dir}/rdl2dso.proxy:${omr_install_dir}/rdl2dso"
+export MOONRAY_CLASS_PATH="${omr_install_dir}/shader_json"
+export ARRAS_SESSION_PATH="${omr_install_dir}/sessions"
+
+prepend_unique_path() {
+    local add_path="$1"
+    local current="${2:-}"
+    case ":${current}:" in
+        *":${add_path}:"*) echo "${current}" ;;
+        *)
+            if [ -n "${current}" ]; then
+                echo "${add_path}:${current}"
+            else
+                echo "${add_path}"
+            fi
+            ;;
+    esac
+}
+
+prepend_existing_path() {
+    local add_path="$1"
+    local current="${2:-}"
+    if [ -d "${add_path}" ]; then
+        prepend_unique_path "${add_path}" "${current}"
+    else
+        echo "${current}"
+    fi
+}
+
+resolve_ocio_package_value() {
+    local raw_value="$1"
+    local value="${raw_value}"
+
+    case "${value}" in
+        \${OCIO-*})
+            value="${value#\$\{OCIO-}"
+            value="${value%\}}"
+            ;;
+    esac
+
+    value="${value//\$HOME/${HOME}}"
+    case "${value}" in
+        "~/"*) value="${HOME}/${value#~/}" ;;
+    esac
+    echo "${value}"
+}
+
+set_ocio_from_houdini_packages() {
+    if [ -n "${OCIO:-}" ]; then
+        return
+    fi
+
+    local package_dirs="${HOUDINI_PACKAGE_DIR:-${HOME}/Library/Preferences/houdini/20.5/packages:${houdini_install_dir}/Frameworks/Houdini.framework/Versions/Current/Resources/packages}"
+    local package_dir
+    while IFS= read -r package_dir; do
+        if [ ! -d "${package_dir}" ]; then
+            continue
+        fi
+        local package_file
+        while IFS= read -r package_file; do
+            if [ ! -f "${package_file}" ] || ! grep -q '"OCIO"' "${package_file}"; then
+                continue
+            fi
+            local raw_value
+            raw_value="$(sed -nE 's/.*"OCIO"[[:space:]]*:[[:space:]]*"([^"]+)".*/\1/p' "${package_file}" | head -1)"
+            if [ -z "${raw_value}" ]; then
+                continue
+            fi
+            local candidate
+            candidate="$(resolve_ocio_package_value "${raw_value}")"
+            if [ -f "${candidate}" ]; then
+                export OCIO="$(realpath "${candidate}")"
+                return
+            fi
+        done < <(find "${package_dir}" -maxdepth 1 -type f -name '*.json' 2>/dev/null)
+    done < <(printf '%s\n' "${package_dirs}" | tr ':' '\n')
+}
+
+# Houdini loads package files itself, but standalone MoonRay tools launched from
+# this shell do not. Mirror a package-authored OCIO default without overriding an
+# explicitly supplied OCIO so husk/hd_usd2rdl use the same color config as Houdini.
+set_ocio_from_houdini_packages
+
+# Preserve any existing USD plugin search path while guaranteeing MoonRay plugin location is present.
+export PXR_PLUGINPATH_NAME="$(prepend_unique_path "${omr_install_dir}/plugin/pxr" "${PXR_PLUGINPATH_NAME}")"
+export PXR_PLUGIN_PATH="$(prepend_unique_path "${omr_install_dir}/plugin/pxr" "${PXR_PLUGIN_PATH}")"
+export PXR_PLUGINPATH_NAME="${PXR_PLUGINPATH_NAME%:}"
+export PXR_PLUGIN_PATH="${PXR_PLUGIN_PATH%:}"
+export PYTHONPATH="$(prepend_existing_path "${omr_install_dir}/lib/python" "${PYTHONPATH}")"
+
+# Prefer layering MoonRay onto an existing Houdini env (from houdini_setup).
+# If that wasn't sourced yet, fall back to the configured Houdini resources path.
+if [ -n "${HOUDINI_PATH}" ]; then
+    export HOUDINI_PATH="$(prepend_existing_path "${omr_install_dir}/plugin/houdini" "${HOUDINI_PATH}")"
+    export HOUDINI_PATH="$(prepend_existing_path "${omr_install_dir}/houdini" "${HOUDINI_PATH}")"
+else
+    export HOUDINI_PATH="${houdini_fallback}:&"
+    export HOUDINI_PATH="$(prepend_existing_path "${omr_install_dir}/plugin/houdini" "${HOUDINI_PATH}")"
+    export HOUDINI_PATH="$(prepend_existing_path "${omr_install_dir}/houdini" "${HOUDINI_PATH}")"
+fi
diff --git a/scripts/setup.sh b/scripts/setup.sh
index 999594db..d1124efe 100644
--- a/scripts/setup.sh
+++ b/scripts/setup.sh
@@ -8,10 +8,19 @@ omr_root="$(realpath ${sourcedir}/..)"
 
 # Walk up to find the top-level install dir where the dependencies are installed
 install_root=${omr_root}
-while [ "$(basename ${install_root})" != "installs" ]
+while [ "$(basename ${install_root})" != "installs" ] && [ "${install_root}" != "/" ]
 do
     install_root=$(dirname ${install_root})
 done
+if [ "$(basename ${install_root})" != "installs" ]; then
+    sibling_installs="$(dirname "$(dirname "${omr_root}")")/installs"
+    if [ -d "${sibling_installs}" ]; then
+        install_root="$(realpath "${sibling_installs}")"
+    else
+        echo "Warning: could not find parent installs directory for ${omr_root}; using ${omr_root}"
+        install_root=${omr_root}
+    fi
+fi
 
 echo "Found install root at ${install_root}"
 echo "Setting up release in ${omr_root}"
@@ -19,8 +28,35 @@ echo "Setting up release in ${omr_root}"
 # NB required for Arras to function (it needs to find execComp)
 export PATH=${omr_root}/bin:${PATH}
 
-# need python modules for the USD interface and for the RATS tests
-export PYTHONPATH=${install_root}/lib/python:/usr/local/lib/python:${install_root}/lib64/python3.9/site-packages/:${PYTHONPATH}
+prepend_unique_path() {
+    add_path="$1"
+    current="${2:-}"
+    case ":${current}:" in
+        *":${add_path}:"*) echo "${current}" ;;
+        *)
+            if [ -n "${current}" ]; then
+                echo "${add_path}:${current}"
+            else
+                echo "${add_path}"
+            fi
+            ;;
+    esac
+}
+
+prepend_existing_path() {
+    add_path="$1"
+    current="${2:-}"
+    if [ -d "${add_path}" ]; then
+        prepend_unique_path "${add_path}" "${current}"
+    else
+        echo "${current}"
+    fi
+}
+
+# Need Python modules for the USD interface and for the RATS tests. Only add
+# paths that exist so source-tree setup does not inject stale system locations.
+export PYTHONPATH="$(prepend_existing_path "${omr_root}/lib/python" "${PYTHONPATH}")"
+export PYTHONPATH="$(prepend_existing_path "${omr_root}/lib64/python3.11/site-packages" "${PYTHONPATH}")"
 
 
 # tell moonray where to find dsos
@@ -43,7 +79,11 @@ export PXR_PLUGIN_PATH=${omr_root}/plugin/pxr:${PXR_PLUGIN_PATH} # for legacy DW
 # create shader descriptions if they don't exist
 if [ ! -d "${omr_root}/shader_json" ]
 then
-    echo "Building shader descriptions..."
-    ${omr_root}/bin/rdl2_json_exporter --out ${omr_root}/shader_json/ --sparse
-    echo "...done"
+    if [ -x "${omr_root}/bin/rdl2_json_exporter" ]; then
+        echo "Building shader descriptions..."
+        ${omr_root}/bin/rdl2_json_exporter --out ${omr_root}/shader_json/ --sparse
+        echo "...done"
+    else
+        echo "Warning: ${omr_root}/bin/rdl2_json_exporter not found; shader descriptions were not generated"
+    fi
 fi