diff --git a/.github/workflows/continuous.yaml b/.github/workflows/continuous.yaml
index bfa9289e..e243f364 100644
--- a/.github/workflows/continuous.yaml
+++ b/.github/workflows/continuous.yaml
@@ -153,7 +153,8 @@ jobs:
 
       - name: Select embree isa (macOS x64)
         if: runner.os == 'macOS' && runner.arch == 'X64'
-        run: echo "embree_max_isa=DEFAULT" >> $GITHUB_ENV
+        # Cap at SSE2: DEFAULT builds all ISAs, OOM-killing the 14 GB intel runner.
+        run: echo "embree_max_isa=SSE2" >> $GITHUB_ENV
 
       - name: Select embree isa (macOS arm64)
         if: runner.os == 'macOS' && runner.arch == 'ARM64'
@@ -202,7 +203,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [windows-2025]
+        os: [windows-2025, windows-11-arm]
         config: [Release, Debug]
     steps:
       - name: Show disk space
@@ -279,7 +280,6 @@ jobs:
             -DLAGRANGE_JENKINS=ON `
             -DLAGRANGE_ALL=ON `
             -DLAGRANGE_POLYSCOPE_MOCK_BACKEND=ON `
-            -DEMBREE_MAX_ISA=AVX2 `
             -B ${{ env.BUILD_DIR }} `
             -S .
 
diff --git a/cmake/recipes/external/Boost.cmake b/cmake/recipes/external/Boost.cmake
index ac371ef1..0d7a3b3e 100644
--- a/cmake/recipes/external/Boost.cmake
+++ b/cmake/recipes/external/Boost.cmake
@@ -79,23 +79,25 @@ option(BOOST_IOSTREAMS_ENABLE_BZIP2 "Boost.Iostreams: Enable BZip2 support" OFF)
 option(BOOST_IOSTREAMS_ENABLE_LZMA "Boost.Iostreams: Enable LZMA support" OFF)
 option(BOOST_IOSTREAMS_ENABLE_ZSTD "Boost.Iostreams: Enable Zstd support" OFF)
 
-set(BOOST_PATCHES "")
+set(BOOST_PATCHES)
 if(EMSCRIPTEN)
     # Wasm doesn't have rounding mode control yet, so we trick Boost::interval into thinking it has.
     # https://github.com/WebAssembly/rounding-mode-control
     # https://github.com/boostorg/interval/issues/44
-    set(BOOST_PATCHES PATCHES Boost.wasm.patch)
+    list(APPEND BOOST_PATCHES Boost.wasm.patch)
 endif()
 
 # Modern CMake target support was added in Boost 1.82.0
 # CMake support for boost::numeric_ublas was added in Boost 1.84.0
+# Windows ARM64 support in Boost.Context (formerly carried in Boost.winarm.patch) is upstream as of
+# Boost 1.89.0, so no local patch is needed anymore for that platform.
 include(CPM)
 CPMAddPackage(
     NAME Boost
-    URL https://github.com/boostorg/boost/releases/download/boost-1.84.0/boost-1.84.0.tar.xz
-    URL_HASH SHA256=2e64e5d79a738d0fa6fb546c6e5c2bd28f88d268a2a080546f74e5ff98f29d0e
+    URL https://github.com/boostorg/boost/releases/download/boost-1.91.0-1/boost-1.91.0-1-cmake.tar.xz
+    URL_HASH SHA256=cc5dc5006ecbdf0051f90979be31b4eee5987d9ae14ae9fb9c03cfa43fa3cdad
     EXCLUDE_FROM_ALL ON
-    ${BOOST_PATCHES}
+    PATCHES ${BOOST_PATCHES}
 )
 
 # Due to MKL, we may require the release runtime (/MD) even when compiling in Debug mode.
diff --git a/cmake/recipes/external/embree.cmake b/cmake/recipes/external/embree.cmake
index a323f51c..01f657b3 100644
--- a/cmake/recipes/external/embree.cmake
+++ b/cmake/recipes/external/embree.cmake
@@ -33,8 +33,10 @@ option(EMBREE_RAY_PACKETS    "Enable the usage packed ray."
 
 # Match embree's platform detection logic for arm
 if(APPLE AND CMAKE_SYSTEM_NAME STREQUAL "Darwin" AND (CMAKE_SYSTEM_PROCESSOR STREQUAL "arm64" AND CMAKE_OSX_ARCHITECTURES STREQUAL "") OR ("arm64" IN_LIST CMAKE_OSX_ARCHITECTURES))
+    message(STATUS "Setting arm version of Embree")
     set(EMBREE_ARM ON)
 elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL "aarch64" OR CMAKE_SYSTEM_PROCESSOR STREQUAL "ARM64")
+    message(STATUS "Setting arm version of Embree")
     set(EMBREE_ARM ON)
 endif()
 
@@ -120,9 +122,14 @@ function(embree_import_target)
         # https://github.com/RenderKit/embree/issues/486
         set(EMBREE_PATCHES PATCHES embree.patch)
     endif()
+    set(EMBREE_URL RenderKit/embree)
+    if(WIN32 AND CMAKE_SYSTEM_PROCESSOR STREQUAL "ARM64" AND EMBREE_VERSION STREQUAL "v4.4.0")
+        message(STATUS "Using winarm-compatible fork of embree 4")
+        set(EMBREE_VERSION 958014331b95bc6f23a82b8f2ea284ce7410febb)
+    endif()
     CPMAddPackage(
         NAME embree
-        GITHUB_REPOSITORY RenderKit/embree
+        GITHUB_REPOSITORY ${EMBREE_URL}
         GIT_TAG ${EMBREE_VERSION}
         ${EMBREE_PATCHES}
     )