AcademySoftwareFoundation · lgritz · Jul 27, 2026
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -489,8 +489,8 @@ jobs:
                              BUILD_PNG_VERSION=1.6.0
                              PIP_SUFFIX=.9
                              PIP_INSTALLS=numpy
-                             Robinmap_BUILD_VERSION=1.2.0
-                             Robinmap_GIT_COMMIT=68ff7325b3898fca267a103bad5c509e8861144d
+                             Robinmap_BUILD_VERSION=1.3.0
+                             Robinmap_GIT_COMMIT=188c45569cc2a5dd768077c193830b51d33a5020
                              TIFF_BUILD_VERSION=4.0.0
                              TIFF_GIT_COMMIT=f7b79dc7dc86ccbaabe9882e2b9ffa5ee8dac917
                             #  OpenJPEG_BUILD_VERSION=2.2.0
@@ -519,8 +519,8 @@ jobs:
                             PIP_INSTALLS=numpy
                             OIIO_CC=clang
                             OIIO_CXX=clang++
-                            Robinmap_BUILD_VERSION=1.2.0
-                            Robinmap_GIT_COMMIT=68ff7325b3898fca267a103bad5c509e8861144d
+                            Robinmap_BUILD_VERSION=1.3.0
+                            Robinmap_GIT_COMMIT=188c45569cc2a5dd768077c193830b51d33a5020
                             TIFF_BUILD_VERSION=4.0.0
                             TIFF_GIT_COMMIT=f7b79dc7dc86ccbaabe9882e2b9ffa5ee8dac917
                             openjph_CMAKE_C_COMPILER=gcc
@@ -560,8 +560,8 @@ jobs:
                              BUILD_PNG_VERSION=1.6.0
                              PIP_SUFFIX=.9
                              PIP_INSTALLS=numpy
-                             Robinmap_BUILD_VERSION=1.2.0
-                             Robinmap_GIT_COMMIT=68ff7325b3898fca267a103bad5c509e8861144d
+                             Robinmap_BUILD_VERSION=1.3.0
+                             Robinmap_GIT_COMMIT=188c45569cc2a5dd768077c193830b51d33a5020
                              TIFF_BUILD_VERSION=4.0.0
                              TIFF_GIT_COMMIT=f7b79dc7dc86ccbaabe9882e2b9ffa5ee8dac917
             required_deps: none
@@ -706,12 +706,14 @@ jobs:
             python_ver: "3.12"
             ctest_test_timeout: "240"
             setenvs: export OPENIMAGEIO_PYTHON_LOAD_DLLS_FROM_PATH=1
+                            OIIO_PYTHON_BINDINGS_BACKEND=nanobind
           - desc: Windows-2025 VS2026
             runner: windows-2025-vs2026
             nametag: windows-2025-vs2026
             generator: "Visual Studio 18 2026"
             python_ver: "3.12"
             ctest_test_timeout: "240"
             setenvs: export OPENIMAGEIO_PYTHON_LOAD_DLLS_FROM_PATH=1
+                            OIIO_PYTHON_BINDINGS_BACKEND=nanobind
             benchmark: 1
             oiio_python_bindings_backend: both
diff --git a/src/build-scripts/ci-startup.bash b/src/build-scripts/ci-startup.bash
@@ -53,6 +53,9 @@ export TESTSUITE_CLEANUP_ON_SUCCESS=${TESTSUITE_CLEANUP_ON_SUCCESS:=1}
 # For CI, default to building missing dependencies automatically
 export OpenImageIO_BUILD_MISSING_DEPS=${OpenImageIO_BUILD_MISSING_DEPS:=all}
 
+# Build both set of python bindings in main/3.2 for now
+export OIIO_PYTHON_BINDINGS_BACKEND=both
+
 # Sonar
 export BUILD_WRAPPER_OUT_DIR="${PWD}/bw_output"
 export BW_OUTPUT_DIR="${PWD}/bw_output"

diff --git a/src/build-scripts/gh-installdeps.bash b/src/build-scripts/gh-installdeps.bash
@@ -234,16 +234,5 @@ fi
 df -h .
 df -h /host/root || true
 
-# nanobind's CMake config is discovered via `python -m nanobind --cmake_dir`.
-# Version + wheel hash: src/build-scripts/ci-requirements-nanobind.txt (CodeQL / supply chain).
-if [[ "${OIIO_PYTHON_BINDINGS_BACKEND:-}" == "both" || "${OIIO_PYTHON_BINDINGS_BACKEND:-}" == "nanobind" ]] ; then
-    _oiio_nanobind_requirements_file="$PWD/src/build-scripts/ci-requirements-nanobind.txt"
-    if [[ "$ASWF_ORG" != ""  ]] ; then
-        time pip3 install -r "$_oiio_nanobind_requirements_file" --require-hashes || true
-    else
-        time pip3${PIP_SUFFIX} install -r "$_oiio_nanobind_requirements_file" --require-hashes
-    fi
-fi
-
 # Save the env for use by other stages
 src/build-scripts/save-env.bash
diff --git a/src/build-scripts/gh-win-installdeps.bash b/src/build-scripts/gh-win-installdeps.bash
@@ -39,11 +39,6 @@ elif [[ "$PYTHON_VERSION" == "3.14" ]] ; then
 fi
 pip install numpy
 
-if [[ "${OIIO_PYTHON_BINDINGS_BACKEND:-}" == "both" || "${OIIO_PYTHON_BINDINGS_BACKEND:-}" == "nanobind" ]] ; then
-    _oiio_nanobind_requirements_file="$PWD/src/build-scripts/ci-requirements-nanobind.txt"
-    "${Python_EXECUTABLE:-python}" -m pip install -r "$_oiio_nanobind_requirements_file" --require-hashes
-fi
-
 
 # In case we need vcpkg, example:
 # echo "All pre-installed VCPkg installs:"

diff --git a/src/cmake/build_Robinmap.cmake b/src/cmake/build_Robinmap.cmake
@@ -6,10 +6,10 @@
 # Robinmap by hand!
 ######################################################################
 
-set_cache (Robinmap_BUILD_VERSION 1.4.0 "Robinmap version for local builds")
+set_cache (Robinmap_BUILD_VERSION 1.4.1 "Robinmap version for local builds")
 set (Robinmap_GIT_REPOSITORY "https://github.com/Tessil/robin-map")
 set (Robinmap_GIT_TAG "v${Robinmap_BUILD_VERSION}")
-set_cache (Robinmap_GIT_COMMIT "4ec1bf19c6a96125ea22062f38c2cf5b958e448e"
+set_cache (Robinmap_GIT_COMMIT "bd14e6830a1474fed9d2d03f5c3b0683d818d540"
            "commit hash to verify tag against")
 
 build_dependency_with_cmake(Robinmap
@@ -23,9 +23,10 @@ build_dependency_with_cmake(Robinmap
         -D CMAKE_POLICY_VERSION_MINIMUM=3.5
     )
 
-# Set some things up that we'll need for a subsequent find_package to work
-set (Robinmap_ROOT ${Robinmap_INSTALL_DIR})
-
-# Signal to caller that we need to find again at the installed location
+# Signal to caller that we need to find again at the installed location,
+# this time via the real upstream package name (see the NAMES tsl-robin-map
+# on the checked_find_package call in externalpackages.cmake) so that we
+# get the genuine tsl::robin_map target -- the same one nanobind looks for.
 set (Robinmap_REFIND TRUE)
-set (Robinmap_VERSION ${Robinmap_BUILD_VERSION})
+set (Robinmap_REFIND_ARGS CONFIG NAMES tsl-robin-map)
+set (Robinmap_REFIND_VERSION ${Robinmap_BUILD_VERSION})
diff --git a/src/cmake/build_nanobind.cmake b/src/cmake/build_nanobind.cmake
@@ -0,0 +1,68 @@
+# Copyright Contributors to the OpenImageIO project.
+# SPDX-License-Identifier: Apache-2.0
+# https://github.com/AcademySoftwareFoundation/OpenImageIO
+
+######################################################################
+# nanobind by hand!
+#
+# Unlike most of our other bundled dependencies, nanobind isn't a library
+# to compile and install -- it's a source tree plus a set of CMake helper
+# functions (nanobind_add_module(), etc.) that get pulled into whichever
+# project actually builds Python extension modules. Its own top-level
+# CMakeLists.txt, configured standalone with NB_TEST=OFF, does nothing
+# but copy its headers/sources/cmake helpers to an install prefix and
+# generate a version file -- there's nothing to actually compile. That's
+# the (unusually light) local build performed below.
+######################################################################
+
+set_cache (nanobind_BUILD_VERSION 2.13.0 "nanobind version for local builds")
+set (nanobind_GIT_REPOSITORY "https://github.com/wjakob/nanobind")
+set_cache (nanobind_GIT_TAG "v${nanobind_BUILD_VERSION}"
+           "nanobind git tag to checkout")
+set_cache (nanobind_GIT_COMMIT "e2dc00f7a34f935c6cf91948776d59c4709e9fe6"
+           "nanobind commit hash to verify tag against")
+
+set (nanobind_LOCAL_SOURCE_DIR "${${PROJECT_NAME}_LOCAL_DEPS_ROOT}/nanobind")
+
+# nanobind vendors tsl::robin_map as a git submodule (ext/robin_map), and
+# its CMakeLists.txt hard-errors if that submodule isn't checked out.
+# build_dependency_with_cmake()'s plain `git clone` doesn't init submodules,
+# so fetch the source and its submodule ourselves before handing off to the
+# shared helper below (which will find the directory already present and
+# just checkout/verify the pinned tag against it).
+if (NOT IS_DIRECTORY "${nanobind_LOCAL_SOURCE_DIR}")
+    find_package (Git REQUIRED)
+    message (STATUS "Cloning ${nanobind_GIT_REPOSITORY} @ ${nanobind_GIT_TAG}")
+    execute_process (COMMAND ${GIT_EXECUTABLE} clone -q
+                        -b ${nanobind_GIT_TAG} --depth 1
+                        ${nanobind_GIT_REPOSITORY} ${nanobind_LOCAL_SOURCE_DIR})
+    execute_process (COMMAND ${GIT_EXECUTABLE} submodule update --init --depth 1
+                        -- ext/robin_map
+                      WORKING_DIRECTORY ${nanobind_LOCAL_SOURCE_DIR})
+endif ()
+
+build_dependency_with_cmake(nanobind
+    VERSION         ${nanobind_BUILD_VERSION}
+    GIT_REPOSITORY  ${nanobind_GIT_REPOSITORY}
+    GIT_TAG         ${nanobind_GIT_TAG}
+    GIT_COMMIT      ${nanobind_GIT_COMMIT}
+    CMAKE_ARGS
+        # Skip nanobind's own test suite -- we only want its install
+        # rules (headers, sources, and CMake helper functions), not a
+        # build of its tests, which would otherwise need Python at
+        # configure time and a lot of unnecessary compilation.
+        -D NB_TEST=OFF
+    )
+
+# nanobind installs its CMake package config to <prefix>/nanobind/cmake, a
+# layout that generic find_package() prefix search doesn't check, so point
+# straight at it. (This is the same trick externalpackages.cmake's
+# discover_nanobind_cmake_dir() uses for a pip install, via
+# `python -m nanobind --cmake_dir`.)
+set (nanobind_DIR "${nanobind_LOCAL_INSTALL_DIR}/nanobind/cmake" CACHE PATH
+     "Path to the nanobind CMake package" FORCE)
+
+# Signal to caller that we need to find again at the installed location
+set (nanobind_REFIND TRUE)
+set (nanobind_REFIND_ARGS CONFIG)
+set (nanobind_REFIND_VERSION ${nanobind_BUILD_VERSION})
diff --git a/src/cmake/externalpackages.cmake b/src/cmake/externalpackages.cmake
@@ -124,7 +124,9 @@ if (USE_PYTHON AND OIIO_BUILD_PYTHON_PYBIND11)
 endif ()
 if (USE_PYTHON AND OIIO_BUILD_PYTHON_NANOBIND)
     discover_nanobind_cmake_dir()
-    checked_find_package (nanobind CONFIG REQUIRED)
+    checked_find_package (nanobind CONFIG REQUIRED
+                          VERSION_MIN 2.8.0
+                          BUILD_LOCAL missing)
 endif ()
 
 
@@ -237,9 +239,15 @@ if (OIIO_USE_HWY)
     checked_find_package (hwy)
 endif ()
 
-# Tessil/robin-map
-checked_find_package (Robinmap REQUIRED
-                      VERSION_MIN 1.2.0
+# Tessil/robin-map. Use its own exported CMake config (target tsl::robin_map)
+# rather than a bespoke Find module. This also means that when the nanobind
+# Python backend is enabled, nanobind's own CMake code will detect and reuse
+# this exact target/version instead of compiling against its private vendored
+# copy (see nanobind_build_library()'s `NOT TARGET tsl::robin_map` check).
+checked_find_package (Robinmap CONFIG REQUIRED
+                      NAMES tsl-robin-map
+                      VERSION_MIN 1.3.0
+                      NO_FP_RANGE_CHECK
                       BUILD_LOCAL missing
                      )
 

diff --git a/src/cmake/modules/FindRobinmap.cmake b/src/cmake/modules/FindRobinmap.cmake
diff --git a/src/cmake/pythonutils.cmake b/src/cmake/pythonutils.cmake
@@ -8,8 +8,8 @@ set (PYTHON_VERSION "" CACHE STRING "Target version of python to find")
 option (PYLIB_INCLUDE_SONAME "If ON, soname/soversion will be set for Python module library" OFF)
 option (PYLIB_LIB_PREFIX "If ON, prefix the Python module with 'lib'" OFF)
 set (PYMODULE_SUFFIX "" CACHE STRING "Suffix to add to Python module init namespace")
-set (OIIO_PYTHON_BINDINGS_BACKEND "pybind11" CACHE STRING
-     "Which Python binding backend(s) to build: pybind11, nanobind, or both")
+set_cache (OIIO_PYTHON_BINDINGS_BACKEND "pybind11"
+     "Which Python binding backend(s) to build: pybind11, nanobind, or both" VERBOSE)
 set_property (CACHE OIIO_PYTHON_BINDINGS_BACKEND PROPERTY STRINGS
               pybind11 nanobind both)
 
@@ -112,8 +112,18 @@ endmacro()
 
 
 # Help CMake locate nanobind when it was installed as a Python package.
-macro (discover_nanobind_cmake_dir)
-    if (nanobind_DIR OR nanobind_ROOT OR "$ENV{nanobind_DIR}" OR "$ENV{nanobind_ROOT}")
+# This is a function (not a macro) deliberately: its early return must
+# not escape into whatever file happens to include pythonutils.cmake and
+# call this at file scope (a macro's return() would abort that entire
+# caller file, silently skipping everything after it).
+function (discover_nanobind_cmake_dir)
+    # Cached from a previous configure. Trust it only if it still points to
+    # a real nanobind install -- e.g. it may be stale if nanobind was
+    # uninstalled/upgraded since the cache was written.
+    if (nanobind_DIR AND EXISTS "${nanobind_DIR}/nanobind-config.cmake")
+        return()
+    endif ()
+    if (nanobind_ROOT OR "$ENV{nanobind_DIR}" OR "$ENV{nanobind_ROOT}")
         return()
     endif ()
 
@@ -132,7 +142,7 @@ macro (discover_nanobind_cmake_dir)
         set (nanobind_DIR "${_oiio_nanobind_cmake_dir}" CACHE PATH
              "Path to the nanobind CMake package" FORCE)
     endif ()
-endmacro()
+endfunction()
 
 
 ###########################################################################
@@ -239,12 +249,13 @@ macro (setup_python_module_nanobind)
 
     if (NOT COMMAND nanobind_add_module)
         discover_nanobind_cmake_dir()
-        find_package (nanobind CONFIG REQUIRED)
     endif ()
 
     nanobind_add_module(${target_name} ${lib_SOURCES})
-    if (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND TARGET nanobind-static)
-        target_compile_options (nanobind-static PRIVATE -Wno-error=format-nonliteral)
+    if (TARGET nanobind-static AND (CMAKE_CXX_COMPILER_ID MATCHES "Clang"
+                                    OR CMAKE_CXX_COMPILER_ID MATCHES "Apple"
+                                    OR CMAKE_CXX_COMPILER_ID MATCHES "IntelLLVM"))
+        target_compile_options (nanobind-static PUBLIC -Wno-format-nonliteral)
     endif ()
 
     target_include_directories (${target_name}

diff --git a/src/cmake/testing.cmake b/src/cmake/testing.cmake
@@ -259,11 +259,23 @@ macro (oiio_add_all_tests)
             oiio_tests_pythonpath_env_entry (_pybind_tests_pythonpath
                 "${CMAKE_BINARY_DIR}/lib/python/site-packages")
         endif ()
-        oiio_tests_pythonpath_env_entry (_nanobind_tests_pythonpath
-            "${CMAKE_BINARY_DIR}/lib/python/nanobind")
+        if (OIIO_PYTHON_BINDINGS_BACKEND STREQUAL "both")
+            # In "both" mode, the nanobind module is kept isolated under its
+            # own build-tree location so it doesn't clobber the pybind11
+            # module that also lives in lib/python/site-packages.
+            oiio_tests_pythonpath_env_entry (_nanobind_tests_pythonpath
+                "${CMAKE_BINARY_DIR}/lib/python/nanobind")
+        else ()
+            # nanobind-only builds install the module to the same location
+            # pybind11 would have used (see setup_python_module_nanobind()
+            # in pythonutils.cmake).
+            set (_nanobind_tests_pythonpath "${_pybind_tests_pythonpath}")
+        endif ()
         # Keep in sync with the pybind11 python-* tests below as dual-backend
         # coverage expands. imageinput/imagebufalgo also need oiio-images.
         set (nanobind_python_tests
+             docs-examples-python
+             filters
              python-colorconfig
              python-deep
              python-imagebuf
@@ -341,7 +353,18 @@ macro (oiio_add_all_tests)
         ENABLEVAR OIIO_USE_HWY  USE_PYTHON OIIO_BUILD_PYTHON_PYBIND11
         DISABLEVAR BUILD_OIIOUTIL_ONLY SANITIZE
         SUFFIX ".hwy"
-        ENVIRONMENT "OPENIMAGEIO_ENABLE_HWY=1"
+        ENVIRONMENT "OPENIMAGEIO_ENABLE_HWY=1" "${_pybind_tests_pythonpath}"
+        IMAGEDIR oiio-images
+        )
+
+    # Same test, run against the nanobind bindings (mirrors the pybind11
+    # variant above so hwy coverage isn't pybind11-only).
+    oiio_add_tests ( python-imagebufalgo
+        FOUNDVAR hwy_FOUND
+        ENABLEVAR OIIO_USE_HWY  USE_PYTHON OIIO_BUILD_PYTHON_NANOBIND
+        DISABLEVAR BUILD_OIIOUTIL_ONLY SANITIZE
+        SUFFIX "${nanobind_python_test_suffix}.hwy"
+        ENVIRONMENT "OPENIMAGEIO_ENABLE_HWY=1" "${_nanobind_tests_pythonpath}"
         IMAGEDIR oiio-images
         )
 
@@ -418,15 +441,18 @@ macro (oiio_add_all_tests)
         list (APPEND all_openexr_tests openexr-idmanifest)
     endif ()
     # Run all OpenEXR tests without core library
+    # (openexr-copy is Python-based, so pass along the site-packages
+    # PYTHONPATH -- it must not depend on the ambient shell environment
+    # already having it set, the way CI's ci-startup.bash does.)
     oiio_add_tests (${all_openexr_tests} openexr-luminance-chroma
-                    ENVIRONMENT OPENIMAGEIO_OPTIONS=openexr:core=0
+                    ENVIRONMENT OPENIMAGEIO_OPTIONS=openexr:core=0 "${_pybind_tests_pythonpath}"
                     IMAGEDIR openexr-images
                     URL http://github.com/AcademySoftwareFoundation/openexr-images)
     # For OpenEXR >= 3.1, be sure to test with the core option on
     if (OpenEXR_VERSION VERSION_GREATER_EQUAL 3.1)
         oiio_add_tests (${all_openexr_tests}
                         SUFFIX ".core"
-                        ENVIRONMENT OPENIMAGEIO_OPTIONS=openexr:core=1
+                        ENVIRONMENT OPENIMAGEIO_OPTIONS=openexr:core=1 "${_pybind_tests_pythonpath}"
                         IMAGEDIR openexr-images
                         URL http://github.com/AcademySoftwareFoundation/openexr-images)
     endif ()

diff --git a/src/libOpenImageIO/CMakeLists.txt b/src/libOpenImageIO/CMakeLists.txt
@@ -127,8 +127,6 @@ target_include_directories (OpenImageIO
                                 $<INSTALL_INTERFACE:include>
                             ${OPENIMAGEIO_IMATH_DEPENDENCY_VISIBILITY}
                                 ${OPENEXR_INCLUDES}
-                            PRIVATE
-                                ${ROBINMAP_INCLUDES}
                             )
 
 if (NOT BUILD_SHARED_LIBS)
@@ -147,6 +145,7 @@ target_link_libraries (OpenImageIO
             ${OPENIMAGEIO_IMATH_DEPENDENCY_VISIBILITY}
             ${OPENIMAGEIO_IMATH_TARGETS}
         PRIVATE
+            tsl::robin_map
             ${OPENIMAGEIO_OPENEXR_TARGETS}
             ${format_plugin_libs} # Add all the target link libraries from the plugins
             OpenColorIO::OpenColorIO
@@ -269,9 +268,9 @@ if (OIIO_BUILD_TESTS AND BUILD_TESTING)
 
     fancy_add_executable (NAME imagebufalgo_test SRC imagebufalgo_test.cpp
                           SYSTEM_INCLUDE_DIRS
-                                ${ROBINMAP_INCLUDES}
-                                ${OpenCV_INCLUDES}            
+                                ${OpenCV_INCLUDES}
                           LINK_LIBRARIES OpenImageIO
+                                         tsl::robin_map
                                          ${OpenCV_LIBRARIES}
                                          ${OPENIMAGEIO_IMATH_TARGETS}
                           FOLDER "Unit Tests" NO_INSTALL)