diff --git a/.github/workflows/rtools-make.yml b/.github/workflows/rtools-make.yml
new file mode 100644
index 00000000000..60311376772
--- /dev/null
+++ b/.github/workflows/rtools-make.yml
@@ -0,0 +1,186 @@
+name: Windows Rtools40
+
+on:
+  pull_request:
+    branches: [ develop, master ]
+  push:
+    branches: [ tbb-rtools-make ]
+    paths-ignore:
+      - 'doygen/**'
+      - 'hooks/**'
+      - 'licenses/**'
+      - 'LICENSE.md'
+      - 'README.md'
+      - 'RELEASE-NOTES.txt'
+permissions:
+  contents: read
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  prim-rev:
+    name: prim and rev tests
+    runs-on: windows-latest
+
+    steps:
+    - uses: actions/checkout@v4
+    - uses: actions/setup-python@v5
+      with:
+        python-version: '3.x'
+    - uses: r-lib/actions/setup-r@v2
+      with:
+        r-version: 4.1.3
+
+    - name: Set path for Rtools40
+      if: runner.os == 'Windows'
+      run: echo "C:/rtools40/usr/bin;C:/rtools40/mingw64/bin" | Out-File -Append -FilePath $env:GITHUB_PATH -Encoding utf8
+
+    - name: Build Math libs
+      shell: powershell
+      run: |
+        Add-Content make\local "O=1`n"
+        make -f make/standalone math-libs -j2
+    - name: Add TBB to PATH
+      shell: powershell
+      run: echo "D:/a/math/math/lib/tbb" | Out-File -Append -FilePath $env:GITHUB_PATH -Encoding utf8
+    - name: Run prim and rev unit tests
+      shell: powershell
+      run: |
+        python.exe runTests.py -j2 test/unit/*_test.cpp
+        python.exe runTests.py -j2 test/unit/math/*_test.cpp
+        python.exe runTests.py -j2 test/unit/math/prim
+        python.exe runTests.py -j2 test/unit/math/rev
+        python.exe runTests.py -j2 test/unit/math/memory
+
+    - name: Upload gtest_output xml
+      uses: actions/upload-artifact@v4
+      if: failure()
+      with:
+        name: gtest_outputs_xml
+        path: '**/*_test.xml'
+
+  fwd-non-fun-mix:
+    name: fwd tests and non-fun mix tests
+    runs-on: windows-latest
+
+    steps:
+    - uses: actions/checkout@v4
+    - uses: actions/setup-python@v5
+      with:
+        python-version: '3.x'
+    - uses: r-lib/actions/setup-r@v2
+      with:
+        r-version: 4.1.3
+
+    - name: Set path for Rtools40
+      if: runner.os == 'Windows'
+      run: echo "C:/rtools40/usr/bin;C:/rtools40/mingw64/bin" | Out-File -Append -FilePath $env:GITHUB_PATH -Encoding utf8
+
+    - name: Build Math libs
+      shell: powershell
+      run: |
+        Add-Content make\local "O=1`n"
+        make -f make/standalone math-libs -j2
+    - name: Add TBB to PATH
+      shell: powershell
+      run: echo "D:/a/math/math/lib/tbb" | Out-File -Append -FilePath $env:GITHUB_PATH -Encoding utf8
+    - name: Disable running fwd/mix tests
+      shell: powershell
+      run: echo "CXXFLAGS+= -DSTAN_MATH_TESTS_REV_ONLY" | Out-File -Append -FilePath make/local -Encoding utf8
+    - name: Run fwd unit tests and all the mix tests except those in mix/fun
+      shell: powershell
+      run: |
+        python.exe runTests.py test/unit/math/fwd -j2
+        python.exe runTests.py test/unit/math/mix/core -j2
+        python.exe runTests.py test/unit/math/mix/functor -j2
+        python.exe runTests.py test/unit/math/mix/meta -j2
+        python.exe runTests.py test/unit/math/mix/prob -j2
+        python.exe runTests.py test/unit/math/mix/*_test.cpp -j2
+
+    - name: Upload gtest_output xml
+      uses: actions/upload-artifact@v4
+      if: failure()
+      with:
+        name: gtest_outputs_xml
+        path: '**/*_test.xml'
+
+  mix-fun-1:
+    name: mix/fun tests 1
+    runs-on: windows-latest
+
+    steps:
+    - uses: actions/checkout@v4
+    - uses: actions/setup-python@v5
+      with:
+        python-version: '3.x'
+    - uses: r-lib/actions/setup-r@v2
+      with:
+        r-version: 4.1.3
+
+    - name: Set path for Rtools40
+      if: runner.os == 'Windows'
+      run: echo "C:/rtools40/usr/bin;C:/rtools40/mingw64/bin" | Out-File -Append -FilePath $env:GITHUB_PATH -Encoding utf8
+
+    - name: Build Math libs
+      shell: powershell
+      run: |
+        Add-Content make\local "O=1`n"
+        make -f make/standalone math-libs -j2
+    - name: Add TBB to PATH
+      shell: powershell
+      run: echo "D:/a/math/math/lib/tbb" | Out-File -Append -FilePath $env:GITHUB_PATH -Encoding utf8
+    - name: Run mix/fun unit tests
+      shell: powershell
+      run: |
+        $MixFunTests = Get-ChildItem -Path test\unit\math\mix\fun\* -Include *.cpp | Resolve-Path -Relative
+        $NumberTests = $MixFunTests.Length
+        $HalfNumberTests = [math]::Floor($NumberTests / 2)
+        python.exe runTests.py $MixFunTests[0..$HalfNumberTests]
+
+    - name: Upload gtest_output xml
+      uses: actions/upload-artifact@v4
+      if: failure()
+      with:
+        name: gtest_outputs_xml
+        path: '**/*_test.xml'
+
+  mix-fun-2:
+    name: mix/fun tests 2
+    runs-on: windows-latest
+
+    steps:
+    - uses: actions/checkout@v4
+    - uses: actions/setup-python@v5
+      with:
+        python-version: '3.x'
+    - uses: r-lib/actions/setup-r@v2
+      with:
+        r-version: 4.1.3
+
+    - name: Set path for Rtools40
+      if: runner.os == 'Windows'
+      run: echo "C:/rtools40/usr/bin;C:/rtools40/mingw64/bin" | Out-File -Append -FilePath $env:GITHUB_PATH -Encoding utf8
+
+    - name: Build Math libs
+      shell: powershell
+      run: |
+        Add-Content make\local "O=1`n"
+        make -f make/standalone math-libs -j2
+    - name: Add TBB to PATH
+      shell: powershell
+      run: echo "D:/a/math/math/lib/tbb" | Out-File -Append -FilePath $env:GITHUB_PATH -Encoding utf8
+    - name: Run mix/fun unit tests
+      shell: powershell
+      run: |
+        $MixFunTests = Get-ChildItem -Path test\unit\math\mix\fun\* -Include *.cpp | Resolve-Path -Relative
+        $NumberTests = $MixFunTests.Length
+        $HalfNumberTests = [math]::Floor($NumberTests / 2)
+        python.exe runTests.py $MixFunTests[($HalfNumberTests + 1)..($NumberTests - 1)]
+
+    - name: Upload gtest_output xml
+      uses: actions/upload-artifact@v4
+      if: failure()
+      with:
+        name: gtest_outputs_xml
+        path: '**/*_test.xml'
diff --git a/lib/tbb_2020.3/build/windows.inc b/lib/tbb_2020.3/build/windows.inc
index dafd8928523..ed74edb07b6 100644
--- a/lib/tbb_2020.3/build/windows.inc
+++ b/lib/tbb_2020.3/build/windows.inc
@@ -22,7 +22,7 @@ endif
 
 # A convenience wrapper for calls to detect.js.
 # $(1) is the full command line for the script, e.g. /minversion icl 12
-detect_js = $(shell cmd /C "cscript /nologo /E:jscript $(tbb_root)/build/detect.js $(1)")
+detect_js = $(shell $(CMD) "cscript //NoLogo //E:jscript $(tbb_root)/build/detect.js $(1)")
 
 # TODO give an error if archs doesn't match
 ifndef arch
diff --git a/make/libraries b/make/libraries
index 516318cdfcf..be3bba7c849 100644
--- a/make/libraries
+++ b/make/libraries
@@ -158,11 +158,11 @@ ifeq ($(OS),Windows_NT)
 ifneq ($(MAKE),$(MAKE_ESCAPED))
 $(error '$nError:$n$nThe RTools toolchain is installed in a path with spaces or brackets.$nPlease reinstall the toolchain.$n$n')
 else
-	if ! [[ $(MAKE) =~ mingw32 ]]; then \
-		echo "ERROR: Please use mingw32-make on Windows to build the Intel TBB library."; \
-		echo "This is packaged with RTools, for example."; \
-		exit 1; \
-	fi
+#	if ! [[ $(MAKE) =~ mingw32 ]]; then \
+#		echo "ERROR: Please use mingw32-make on Windows to build the Intel TBB library."; \
+#		echo "This is packaged with RTools, for example."; \
+#		exit 1; \
+#	fi
 endif
 endif
 	@mkdir -p $(TBB_BIN)