diff --git a/.gitattributes b/.gitattributes
index 3fbc0933c..92f72e59a 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -23,3 +23,7 @@ script/pre-commit export-ignore
 # Scorecard entirely
 # no export of website-specific content
 doc/talk export-ignore
+# these Windows batch scripts intentionally use CRLF line endings, do not
+# flag the CR as a trailing whitespace error
+script/INSTALL.bat whitespace=cr-at-eol
+script/UNINSTALL.bat whitespace=cr-at-eol
diff --git a/.github/workflows/windows_tests.yaml b/.github/workflows/windows_tests.yaml
index 2a47e407e..c26f15db7 100644
--- a/.github/workflows/windows_tests.yaml
+++ b/.github/workflows/windows_tests.yaml
@@ -48,7 +48,31 @@ jobs:
         run: |
           jar xvf %DIST_WIN%.zip
           cd %DIST_WIN%
-          INSTALL.bat
+          :: replace (rather than extend) the inherited PATH with a
+          :: controlled value that is still past the legacy 1024-character
+          :: limit of the 'setx' tool previously used here, to simulate a
+          :: large pre-existing PATH such as found in a Visual Studio
+          :: Developer Prompt (see GH-654), while staying safely under the
+          :: 8191-character command line length limit of cmd.exe
+          setlocal enabledelayedexpansion
+          set "PATH=%SYSTEMROOT%\system32;%SYSTEMROOT%"
+          for /L %%i in (1,1,50) do set "PATH=!PATH!;C:\dummy-path-segment-%%i"
+          set "PATH=!PATH!;C:\marker-end-of-long-path"
+          call INSTALL.bat
+      - name: Check persisted PATH is not truncated
+        shell: cmd
+        run: |
+          reg query "HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environment" /v PATH > persisted-path.txt
+          %SYSTEMROOT%\system32\find /i "marker-end-of-long-path" persisted-path.txt >nul
+          if errorlevel 1 (
+              echo "persisted system PATH truncated: marker entry not found"
+              exit /b 1
+          )
+          %SYSTEMROOT%\system32\find /i "%MODULE_DIR%" persisted-path.txt >nul
+          if errorlevel 1 (
+              echo "installation 'bin' directory not found in persisted system PATH"
+              exit /b 1
+          )
       - name: Test Modules installation
         shell: cmd
         run: |
diff --git a/.hunspell.en.dic b/.hunspell.en.dic
index 8d8de51a5..617915391 100644
--- a/.hunspell.en.dic
+++ b/.hunspell.en.dic
@@ -736,6 +736,7 @@ setState
 setenv
 setgid
 setq
+setx
 severities
 sexualized
 sgr
diff --git a/NEWS.rst b/NEWS.rst
index 8e97a6a68..7af7124cd 100644
--- a/NEWS.rst
+++ b/NEWS.rst
@@ -173,6 +173,12 @@ Modules 5.7.0 (not yet released)
   white matte color instead of black.
 * Doc: document Windows Terminal profile setup as an alternative way to
   initialize Modules on Windows without an install script. (fix issue #634)
+* Install: use ``reg add`` instead of ``setx /M`` to persist the system-wide
+  ``PATH`` environment variable in :file:`INSTALL.bat` and
+  :file:`UNINSTALL.bat`, as ``setx`` silently truncates the value it writes
+  to 1024 characters, which could corrupt the system ``PATH`` when installing
+  from a shell with an already long inherited ``PATH`` (e.g. a Visual Studio
+  Developer Prompt). (fix issue #654)
 
 
 .. _5.6 release notes:
diff --git a/doc/source/devel/ci.rst b/doc/source/devel/ci.rst
index 3d73609ca..ca078e8c4 100644
--- a/doc/source/devel/ci.rst
+++ b/doc/source/devel/ci.rst
@@ -107,7 +107,10 @@ on Windows:
     <https://www.bawt.tcl3d.org/>`_), built via ``make dist-win`` and
     installed/tested/uninstalled through the generated
     :file:`INSTALL.bat`/:file:`TESTINSTALL.bat`/:file:`UNINSTALL.bat`
-    scripts, driven from a ``cmd`` shell.
+    scripts, driven from a ``cmd`` shell. Before installing, the inherited
+    ``PATH`` is padded past the legacy 1024-character limit of the
+    ``setx`` tool (mimicking a Visual Studio Developer Prompt) to guard
+    against the persisted system ``PATH`` getting silently truncated.
 ``native-pwsh``
     Same native Windows install, but through the PowerShell variant
     (:file:`INSTALL_PWSH.bat`/:file:`TESTINSTALL_PWSH.ps1`).
diff --git a/script/INSTALL.bat b/script/INSTALL.bat
index e3c742205..d9a4e8285 100644
--- a/script/INSTALL.bat
+++ b/script/INSTALL.bat
@@ -23,7 +23,9 @@ set FIND=%SYSTEMROOT%\system32\find
 echo %PATH% | %FIND% /i "%binpath:"=%">nul || set "NEWPATH=%binpath%;%PATH%"
 if not "%NEWPATH%" == "" (
    set "PATH=%NEWPATH%"
-   setx /M PATH "%NEWPATH%"
+   :: 'reg add' is used instead of 'setx /M' as the latter silently
+   :: truncates the value it persists to 1024 characters
+   reg add "HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environment" /v PATH /t REG_EXPAND_SZ /d "%NEWPATH%" /f
 )
 if errorlevel 1 ( exit /b 3 )
 
diff --git a/script/UNINSTALL.bat b/script/UNINSTALL.bat
index 9527e3f10..9e4ea6079 100644
--- a/script/UNINSTALL.bat
+++ b/script/UNINSTALL.bat
@@ -13,7 +13,9 @@ setlocal enableextensions enabledelayedexpansion
 set "NEWPATH=!PATH:%binpath%;=!"
 if not "%NEWPATH%" == "%PATH%" (
    set "PATH=%NEWPATH%"
-   setx /M PATH "%NEWPATH%"
+   :: 'reg add' is used instead of 'setx /M' as the latter silently
+   :: truncates the value it persists to 1024 characters
+   reg add "HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environment" /v PATH /t REG_EXPAND_SZ /d "%NEWPATH%" /f
 )
 if errorlevel 1 ( exit /b 1 )