Attempt to fix cmd quoting with quotes inside on first arg

CHANGELOG.md

@@ -28,6 +28,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- Windows CMD.EXE /C quoting now handles quoted commands with extra arguments (e.g., npm.cmd paths with spaces).
+
 ### Changed
 
 ## 0.9.0 - 2026-01-27

mshell/Pathbin_windows.go

@@ -245,6 +245,51 @@ func EscapeForCmd(allArgs []string) string {
 	return sb.String()
 }
 
+func BuildCmdExeLine(allArgs []string) string {
+	if len(allArgs) == 0 {
+		return ""
+	}
+	if len(allArgs) == 1 {
+		return allArgs[0]
+	}
+
+	// From `help cmd`
+	// If /C or /K is specified, then the remainder of the command line after
+	// the switch is processed as a command line, where the following logic is
+	// used to process quote (") characters:
+
+		// 1.  If all of the following conditions are met, then quote characters
+			// on the command line are preserved:
+
+			// - no /S switch
+			// - exactly two quote characters
+			// - no special characters between the two quote characters,
+			// where special is one of: &<>()@^|
+			// - there are one or more whitespace characters between the
+			// two quote characters
+			// - the string between the two quote characters is the name
+			// of an executable file.
+
+		// 2.  Otherwise, old behavior is to see if the first character is
+			// a quote character and if so, strip the leading character and
+			// remove the last quote character on the command line, preserving
+			// any text after the last quote character.
+
+	if strings.EqualFold(allArgs[1], "/C") || strings.EqualFold(allArgs[1], "/K") {
+		cmdStr := EscapeForCmd(allArgs[2:])
+		if len(allArgs) > 3 && strings.HasPrefix(cmdStr, "\"") {
+			// CMD.EXE needs an extra quote pair when the command starts with quotes and has extra args.
+			cmdStr = "\"" + cmdStr + "\""
+		}
+		if cmdStr == "" {
+			return allArgs[0] + " " + allArgs[1]
+		}
+		return allArgs[0] + " " + allArgs[1] + " " + cmdStr
+	}
+
+	return EscapeForCmd(allArgs)
+}
+
 func (pbm *PathBinManager) SetupCommand(allArgs []string) (*exec.Cmd) {
 	// Get basename of the command
 	if len(allArgs) == 0 {
@@ -254,7 +299,7 @@ func (pbm *PathBinManager) SetupCommand(allArgs []string) (*exec.Cmd) {
 	execName := filepath.Base(allArgs[0])
 	if strings.ToUpper(execName) == "CMD.EXE" {
 		// If the command is CMD.EXE, we need to escape the arguments properly
-		cmdStr := EscapeForCmd(allArgs)
+		cmdStr := BuildCmdExeLine(allArgs)
 
 		cmd := exec.Command("CMD.EXE")
 		cmd.SysProcAttr = &syscall.SysProcAttr{