diff --git a/docs/msys2.md b/docs/msys2.md
index 7f00bc07e4c..15181fc647e 100644
--- a/docs/msys2.md
+++ b/docs/msys2.md
@@ -7,8 +7,7 @@ MSYS2
 Installing msys2
 ----------------
 
-First, install MSYS2 using the [one-click installer](https://msys2.github.io/) or
-directly unzipping the archive from their [repository](http://sourceforge.net/projects/msys2/files/Base/x86_64/)
+First, install MSYS2 from [https://www.msys2.org/](https://www.msys2.org/).
 
 If you have an old install of MSYS2 (before 2018), it's recommended to do a fresh install.
 
diff --git a/scripts/msys2/install_dependencies.sh b/scripts/msys2/install_dependencies.sh
index 05a44afe431..bee10afba16 100755
--- a/scripts/msys2/install_dependencies.sh
+++ b/scripts/msys2/install_dependencies.sh
@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-script_dir="$( dirname "$(readlink -f "$0")" )"
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 
 function usage {
     echo usage:
@@ -13,16 +13,16 @@ function usage {
 }
 
 #Analyse script arguments
-confirm="yes"
+FORCE_YES=0
 while [[ $# > 0 ]] ; do
 	arg=$1
 	shift
 	if [ "$arg" == "--noconfirm" ]; then
-		confirm="no"
+		FORCE_YES=1
 		continue
 	fi
 	if [ "$arg" == "--confirm" ]; then
-		confirm="yes"
+		FORCE_YES=0
 		continue
 	fi
 	if [ "$arg" == "--help" ]; then
@@ -38,46 +38,165 @@ while [[ $# > 0 ]] ; do
 	exit 1
 done
 
+resolveMsystem(){
+	if [[ -z "${msystem:-}" ]]; then
+		msystem=$(echo "${MSYSTEM:-ucrt64}" | tr '[:upper:]' '[:lower:]')
+	fi
+	# MSYS shell has no MinGW prefix (pacman would see -assimp)
+	if [[ "$msystem" == "msys" ]]; then
+		echo "MSYS shell detected — use Start Menu → MSYS2 UCRT64 to compile. https://www.msys2.org/"
+		echo "Installing ucrt64 packages anyway."
+		msystem="ucrt64"
+		FROM_MSYS_SHELL=1
+	fi
+	case "$msystem" in
+		clang64)    MINGW_PACKAGE_PREFIX="mingw-w64-clang-x86_64" ;;
+		clangarm64) MINGW_PACKAGE_PREFIX="mingw-w64-clang-aarch64" ;;
+		ucrt64)     MINGW_PACKAGE_PREFIX="mingw-w64-ucrt-x86_64" ;;
+		mingw64)    MINGW_PACKAGE_PREFIX="mingw-w64-x86_64" ;;
+		mingw32)    MINGW_PACKAGE_PREFIX="mingw-w64-i686" ;;
+		*)
+			msystem="ucrt64"
+			MINGW_PACKAGE_PREFIX="mingw-w64-ucrt-x86_64"
+			;;
+	esac
+	export MINGW_PACKAGE_PREFIX
+}
+
+# Git Bash often has no execute bit on .exe; -f is the reliable exists check.
+msys2PacmanAt(){
+	local root="$1" p
+	[[ -n "$root" ]] || return 1
+	for p in "$root/usr/bin/pacman.exe" "$root/usr/bin/pacman"; do
+		[[ -f "$p" ]] && { printf '%s' "$p"; return 0; }
+	done
+	return 1
+}
+
+findPacman(){
+	local p root
+	if command -v pacman >/dev/null 2>&1; then
+		command -v pacman
+		return 0
+	fi
+	if command -v pacman.exe >/dev/null 2>&1; then
+		command -v pacman.exe
+		return 0
+	fi
+	# MSYS2 installed, but this is Git Bash / cmd so pacman is not on PATH
+	for root in \
+		"${MSYS2_ROOT:-}" \
+		"${MSYS2_PATH:-}" \
+		/c/msys64 \
+		/d/msys64 \
+		/e/msys64 \
+		/c/msys32 \
+		/c/tools/msys64 \
+		"/c/Program Files/MSYS2" \
+		"/c/Program Files/msys64" \
+		"$HOME/msys64" \
+		"$HOME/scoop/apps/msys2/current" \
+		"${LOCALAPPDATA:-}/Programs/MSYS2" \
+		"${LOCALAPPDATA:-}/msys64"
+	do
+		p=$(msys2PacmanAt "$root") || continue
+		printf '%s' "$p"
+		return 0
+	done
+	return 1
+}
+
+isWindowsHost(){
+	case "$(uname -s 2>/dev/null)" in
+		MINGW*|MSYS*|CYGWIN*) return 0 ;;
+	esac
+	[[ "${OS:-}" == "Windows_NT" ]]
+}
+
+resolveMsystem
+
+PACMAN=$(findPacman) || PACMAN=""
+if [[ -z "$PACMAN" ]]; then
+	echo "pacman is not on PATH in this shell (Git Bash / cmd / PowerShell)."
+	echo "MSYS2 may already be installed — open a UCRT64 / MINGW64 / CLANG64 terminal"
+	echo "from the Start menu and re-run:"
+	echo "  scripts/msys2/install_dependencies.sh"
+	echo
+	echo "If MSYS2 is not installed yet: https://www.msys2.org/"
+	echo
+	echo "Visual Studio / Git Bash does not need pacman:"
+	echo "  scripts/vs/install_dependencies.sh"
+	echo "  scripts/vs/download_libs.sh"
+	echo
+	if isWindowsHost && [[ -f "$SCRIPT_DIR/../vs/install_dependencies.sh" ]]; then
+		echo "Falling back to the Windows VS/Git-Bash helper (optional gum via winget/scoop)."
+		VS_ARGS=()
+		[[ "$FORCE_YES" == "1" ]] && VS_ARGS+=(-y)
+		exec bash "$SCRIPT_DIR/../vs/install_dependencies.sh" "${VS_ARGS[@]}"
+	fi
+	exit 1
+fi
+# Off-PATH pacman.exe still needs usr/bin for msys-2.0.dll
+PACMAN_DIR=$(dirname "$PACMAN")
+case ":$PATH:" in
+	*":${PACMAN_DIR}:"*) ;;
+	*) export PATH="${PACMAN_DIR}:$PATH" ;;
+esac
+echo "using pacman: $PACMAN"
+
 # List of MSYS packages to be installed
-# msyspackages="make rsync zip unzip wget"
-msyspackages="unzip make"
+# MSYS_PACKAGES="make rsync zip unzip wget"
+MSYS_PACKAGES="unzip make"
 
 # List of MINGW packages to be installed (without prefix)
 # opencv is pinned separately below (ofxOpenCv isn't ported to OpenCV 5's C++-only API yet)
-mingwPackages="assimp cairo curl freeimage \
+MINGW_PACKAGES="assimp cairo curl freeimage \
 	glew glfw glm fmt zlib brotli libpng \
 	harfbuzz libsndfile libusb libxml2 mpg123 \
 	nlohmann-json openal \
 	pkgconf pugixml rtaudio \
 	uriparser utf8cpp "
 if [[ "$msystem" == "clang64" ]] || [[ "$msystem" == "clangarm64" ]] ; then
-    mingwPackages="clang $mingwPackages"
+    MINGW_PACKAGES="clang $MINGW_PACKAGES"
 elif [[ "$msystem" == "ucrt64" ]]; then
-    mingwPackages="gcc $mingwPackages"
+    MINGW_PACKAGES="gcc $MINGW_PACKAGES"
 elif [[ "$msystem" == "mingw64" ]]; then
-    mingwPackages="gcc $mingwPackages"
+    MINGW_PACKAGES="gcc $MINGW_PACKAGES"
 fi
 # gdb zlib ntldd-git
 # boost poco tools
 # Build the full list of packages adding prefix to MINGW packages
-packages=${msyspackages}
-for pkg in ${mingwPackages}; do
-	packages="$packages  $MINGW_PACKAGE_PREFIX-$pkg"
+PACKAGES=${MSYS_PACKAGES}
+for pkg in ${MINGW_PACKAGES}; do
+	PACKAGES="$PACKAGES ${MINGW_PACKAGE_PREFIX}-${pkg}"
 done
+if [[ "$PACKAGES" == *" -"* ]] || [[ -z "$MINGW_PACKAGE_PREFIX" ]]; then
+	echo "MINGW_PACKAGE_PREFIX is empty — refusing to pass '-package' names to pacman."
+	echo "Open an MSYS2 UCRT64 terminal: https://www.msys2.org/"
+	exit 1
+fi
 
-# Install packages
-if [[ "${confirm}" == "yes" ]]; then
-	pacman -Su --confirm --needed ${packages}
-	# for pkg in ${packages}; do
-		# pacman -Su --confirm --needed ${pkg}
-	# done
-else
-	pacman -Su --noconfirm --needed ${packages}
+# pacman has --noconfirm, not --confirm. -S installs; do not -Su (full upgrade).
+# -Sy first so we don't request deleted files (stale DB → fmt-10.2.1-1 404s).
+SYNC_FLAGS=(-Sy)
+[[ "$FORCE_YES" == "1" ]] && SYNC_FLAGS+=(--noconfirm)
+echo "Refreshing package databases…"
+"$PACMAN" "${SYNC_FLAGS[@]}"
+exit_code=$?
+if [ $exit_code != 0 ]; then
+	echo "error refreshing pacman databases (mirrors may be unreachable)"
+	echo "try: pacman -Syu   then re-run this script"
+	exit $exit_code
 fi
 
+PACMAN_FLAGS=(-S --needed)
+[[ "$FORCE_YES" == "1" ]] && PACMAN_FLAGS+=(--noconfirm)
+
+"$PACMAN" "${PACMAN_FLAGS[@]}" ${PACKAGES}
+
 
 # this would install gstreamer which can be used in mingw too
-#pacman -Su ${MINGW_PACKAGE_PREFIX}-gst-libav ${MINGW_PACKAGE_PREFIX}-gst-plugins-bad ${MINGW_PACKAGE_PREFIX}-gst-plugins-base ${MINGW_PACKAGE_PREFIX}-gst-plugins-good ${MINGW_PACKAGE_PREFIX}-gst-plugins-ugly ${MINGW_PACKAGE_PREFIX}-gstreamer
+# "$PACMAN" -Su ${MINGW_PACKAGE_PREFIX}-gst-libav ${MINGW_PACKAGE_PREFIX}-gst-plugins-bad ${MINGW_PACKAGE_PREFIX}-gst-plugins-base ${MINGW_PACKAGE_PREFIX}-gst-plugins-good ${MINGW_PACKAGE_PREFIX}-gst-plugins-ugly ${MINGW_PACKAGE_PREFIX}-gstreamer
 
 exit_code=$?
 if [ $exit_code != 0 ]; then
@@ -89,31 +208,40 @@ fi
 # Pin OpenCV to the last 4.x build: ofxOpenCv still relies on OpenCV's legacy
 # C API, which OpenCV 5 removed entirely. MSYS2's "opencv" package now resolves
 # to 5.x, so install this specific 4.x build directly instead.
-opencv4_pkg_version="4.13.0-7"
-opencv4_pkg_file="${MINGW_PACKAGE_PREFIX}-opencv-${opencv4_pkg_version}-any.pkg.tar.zst"
-opencv4_pkg_url="https://repo.msys2.org/mingw/${msystem}/${opencv4_pkg_file}"
-if [[ "${confirm}" == "yes" ]]; then
-	pacman -U --confirm --needed "$opencv4_pkg_url"
-else
-	pacman -U --noconfirm --needed "$opencv4_pkg_url"
-fi
+OPENCV4_PKG_VERSION="4.13.0-7"
+OPENCV_REPO="${msystem:-ucrt64}"
+OPENCV4_PKG_FILE="${MINGW_PACKAGE_PREFIX}-opencv-${OPENCV4_PKG_VERSION}-any.pkg.tar.zst"
+OPENCV4_PKG_URL="https://repo.msys2.org/mingw/${OPENCV_REPO}/${OPENCV4_PKG_FILE}"
+echo "Installing pinned OpenCV 4 from $OPENCV4_PKG_URL"
+OPENCV_FLAGS=(-U --needed)
+[[ "$FORCE_YES" == "1" ]] && OPENCV_FLAGS+=(--noconfirm)
+"$PACMAN" "${OPENCV_FLAGS[@]}" "$OPENCV4_PKG_URL"
 exit_code=$?
 if [ $exit_code != 0 ]; then
-	echo "error installing pinned OpenCV 4 package from $opencv4_pkg_url"
-	exit $exit_code
+	echo "error installing pinned OpenCV 4 from $OPENCV4_PKG_URL"
+	echo "repo.msys2.org is up; that exact filename may have been removed."
+	echo "falling back to current ${MINGW_PACKAGE_PREFIX}-opencv from the synced database"
+	"$PACMAN" "${PACMAN_FLAGS[@]}" "${MINGW_PACKAGE_PREFIX}-opencv" || {
+		echo "error installing opencv — try: pacman -Syu"
+		exit 1
+	}
 fi
 
 
 # Update addon_config.mk files to use OpenCV 5, 4 or 3 depending on what's installed
-addons_dir="$(readlink -f "$script_dir/../../addons")"
-addon_config="$addons_dir/ofxOpenCv/addon_config.mk"
+ADDONS_DIR="$(cd "$SCRIPT_DIR/../../addons" && pwd)"
+ADDON_CONFIG="$ADDONS_DIR/ofxOpenCv/addon_config.mk"
 if pkg-config opencv5 --exists; then
 	echo "Updating ofxOpenCV to use openCV5"
-	sed -i -E 's/(ADDON_PKG_CONFIG_LIBRARIES =.*)\bopencv[45]?\b/\1opencv5/' "$addon_config"
+	sed -i -E 's/(ADDON_PKG_CONFIG_LIBRARIES =.*)\bopencv[45]?\b/\1opencv5/' "$ADDON_CONFIG"
 elif pkg-config opencv4 --exists; then
 	echo "Updating ofxOpenCV to use openCV4"
-	sed -i -E 's/(ADDON_PKG_CONFIG_LIBRARIES =.*)\bopencv[45]?\b/\1opencv4/' "$addon_config"
+	sed -i -E 's/(ADDON_PKG_CONFIG_LIBRARIES =.*)\bopencv[45]?\b/\1opencv4/' "$ADDON_CONFIG"
 else
 	echo "Updating ofxOpenCV to use openCV3"
-	sed -i -E 's/(ADDON_PKG_CONFIG_LIBRARIES =.*)\bopencv[45]?\b/\1opencv/' "$addon_config"
+	sed -i -E 's/(ADDON_PKG_CONFIG_LIBRARIES =.*)\bopencv[45]?\b/\1opencv/' "$ADDON_CONFIG"
+fi
+
+if [[ "${FROM_MSYS_SHELL:-0}" == "1" ]]; then
+	echo "done — open MSYS2 UCRT64 to compile"
 fi