From 38e86b58d8088e5d36f376a4c3b8f48c7347ae09 Mon Sep 17 00:00:00 2001
From: Lanre Shittu <136805224+Shizoqua@users.noreply.github.com>
Date: Mon, 8 Jun 2026 19:49:24 +0100
Subject: [PATCH] docs: add Windows BUILD_MONAI instructions to installation
 guide

The installation guide only documents the POSIX inline form `BUILD_MONAI=1 pip install ...` for building the C++/CUDA extensions. That `VAR=value command` syntax is not supported by Windows cmd.exe or PowerShell, so the documented commands fail out of the box for Windows users.

Add cmd.exe and PowerShell snippets to both the system-wide (Option 1) and editable (Option 2) install sections: set the environment variable first, then run the install command.

Closes #6119

Signed-off-by: Lanre Shittu <136805224+Shizoqua@users.noreply.github.com>
---
 docs/source/installation.md | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/docs/source/installation.md b/docs/source/installation.md
index 5123bc3e6b..bbb04b2706 100644
--- a/docs/source/installation.md
+++ b/docs/source/installation.md
@@ -117,6 +117,22 @@ To build the extensions, if the system environment already has a version of Pyto
 BUILD_MONAI=1 pip install --no-build-isolation git+https://github.com/Project-MONAI/MONAI
 ```
 
+On Windows the inline `BUILD_MONAI=1 pip install ...` form is not supported by
+`cmd.exe` or PowerShell. Set the environment variable first, then run either
+install command shown above:
+
+```bat
+:: cmd.exe
+set BUILD_MONAI=1
+pip install --no-build-isolation git+https://github.com/Project-MONAI/MONAI
+```
+
+```powershell
+# PowerShell
+$env:BUILD_MONAI="1"
+pip install --no-build-isolation git+https://github.com/Project-MONAI/MONAI
+```
+
 this command will download and install the current `dev` branch of [MONAI from
 GitHub](https://github.com/Project-MONAI/MONAI).
 
@@ -147,6 +163,22 @@ BUILD_MONAI=1 pip install -e .
 BUILD_MONAI=1 CC=clang CXX=clang++ pip install -e .
 ```
 
+On Windows set the environment variable before running `pip install -e .`:
+
+```bat
+:: cmd.exe
+cd MONAI/
+set BUILD_MONAI=1
+pip install -e .
+```
+
+```powershell
+# PowerShell
+cd MONAI/
+$env:BUILD_MONAI="1"
+pip install -e .
+```
+
 To uninstall the package please run:
 
 ```bash