diff --git a/verifycache/script_cache.go b/verifycache/script_cache.go
index 51d84dd..e337700 100644
--- a/verifycache/script_cache.go
+++ b/verifycache/script_cache.go
@@ -28,8 +28,9 @@ func SignVersionScripts(versionDir string) error {
 }
 
 // SignScript force-resigns one delegated .cmd/.bat/.js launcher, bypassing the
-// TrustedModules gate. Used after the user accepts a trust prompt so VerifyCache
-// can be refreshed before the next launch retry.
+// TrustedModules gate. In-process callers (nvm firewall trust module) use this
+// directly. The --sign-script CLI flag is gated separately: signed proxy parent
+// plus an inherited pipe. Do not treat argv as a trust source.
 func SignScript(scriptPath string) error {
 	scriptPath = strings.TrimSpace(scriptPath)
 	if scriptPath == "" {
diff --git a/verifycache/sign_script_auth.go b/verifycache/sign_script_auth.go
new file mode 100644
index 0000000..626b030
--- /dev/null
+++ b/verifycache/sign_script_auth.go
@@ -0,0 +1,216 @@
+//go:build windows
+
+package verifycache
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"unsafe"
+
+	"common/settings"
+	"common/verify"
+
+	"golang.org/x/sys/windows"
+)
+
+const maxSignScriptPathBytes = 32 * 1024
+
+var (
+	parentPIDFn             = func() uint32 { return uint32(os.Getppid()) }
+	stdinPipeServerPIDFn    = stdinPipeServerPID
+	verifyParentPublisherFn = verifyParentPublisher
+
+	procGetNamedPipeServerProcessId = windows.NewLazySystemDLL("kernel32.dll").NewProc("GetNamedPipeServerProcessId")
+)
+
+func verifyParentPublisher(parent string) error {
+	return verify.VerifySamePublisherAsExecutable(parent)
+}
+
+func stdinPipeServerPID() (uint32, bool) {
+	h := windows.Handle(os.Stdin.Fd())
+	ft, err := windows.GetFileType(h)
+	if err != nil || ft != windows.FILE_TYPE_PIPE {
+		return 0, false
+	}
+	var pid uint32
+	r1, _, _ := procGetNamedPipeServerProcessId.Call(uintptr(h), uintptr(unsafe.Pointer(&pid)))
+	if r1 == 0 || pid == 0 {
+		return 0, false
+	}
+	return pid, true
+}
+
+// AuthorizeSignScriptFromParent is the --sign-script gate. The caller must be
+// nvm.exe spawned by a signed proxy image, with the path on an anonymous pipe
+// whose server PID is that parent. argv is not a trust source.
+func AuthorizeSignScriptFromParent() error {
+	dataRoot, err := dataRootFromSettings()
+	if err != nil {
+		return fmt.Errorf("sign-script refused: %w", err)
+	}
+	parent := parentImagePathFn()
+	if !parentIsNvmProxy(parent, dataRoot) {
+		return fmt.Errorf("sign-script refused: parent is not proxy")
+	}
+	if err := verifyParentPublisherFn(parent); err != nil {
+		return fmt.Errorf("sign-script refused: %w", err)
+	}
+	pipePID, ok := stdinPipeServerPIDFn()
+	if !ok {
+		return fmt.Errorf("sign-script refused: missing proxy pipe")
+	}
+	if pipePID != parentPIDFn() {
+		return fmt.Errorf("sign-script refused: pipe is not from parent")
+	}
+	return nil
+}
+
+// ReadSignScriptPath reads one launcher path from the proxy pipe. Extra
+// command-line arguments are ignored by design; this is the only path source.
+func ReadSignScriptPath(r io.Reader) (string, error) {
+	limited := io.LimitReader(r, maxSignScriptPathBytes+1)
+	raw, err := io.ReadAll(limited)
+	if err != nil {
+		return "", fmt.Errorf("sign-script refused: %w", err)
+	}
+	if len(raw) > maxSignScriptPathBytes {
+		return "", fmt.Errorf("sign-script refused: path too long")
+	}
+	scriptPath := strings.TrimSpace(string(raw))
+	if scriptPath == "" {
+		return "", fmt.Errorf("sign-script refused: empty path")
+	}
+	if strings.ContainsAny(scriptPath, "\x00\n\r") {
+		return "", fmt.Errorf("sign-script refused: invalid path")
+	}
+	return scriptPath, nil
+}
+
+// IsDelegatedLauncherPath is true for .cmd/.bat/.js files NVM proxy would
+// launch: under the installs root, Yarn Classic global bin, pnpm home bin,
+// or the roaming npm prefix.
+func IsDelegatedLauncherPath(scriptPath string) bool {
+	scriptPath = filepath.Clean(strings.TrimSpace(scriptPath))
+	if scriptPath == "" || scriptPath == "." {
+		return false
+	}
+	ext := strings.ToLower(filepath.Ext(scriptPath))
+	if ext != ".cmd" && ext != ".bat" && ext != ".js" {
+		return false
+	}
+	installRoot := filepath.Clean(strings.TrimSpace(settings.Global().Root))
+	if installRoot != "" && installRoot != "." && pathUnderDir(scriptPath, installRoot) {
+		return true
+	}
+	if dir := yarnClassicGlobalBinDir(); dir != "" && pathUnderDir(scriptPath, dir) {
+		return true
+	}
+	if dir := pnpmGlobalBinDir(); dir != "" && pathUnderDir(scriptPath, dir) {
+		return true
+	}
+	if dir := npmRoamingBinDir(); dir != "" && pathUnderDir(scriptPath, dir) {
+		return true
+	}
+	return false
+}
+
+func parentIsNvmProxy(parent, dataRoot string) bool {
+	parent = filepath.Clean(strings.TrimSpace(parent))
+	dataRoot = filepath.Clean(strings.TrimSpace(dataRoot))
+	if parent == "" || dataRoot == "" || dataRoot == "." {
+		return false
+	}
+	proxy := filepath.Join(dataRoot, "proxy.exe")
+	if strings.EqualFold(parent, proxy) {
+		return true
+	}
+	shim := filepath.Join(dataRoot, ".shim")
+	if !pathUnderDir(parent, shim) {
+		return false
+	}
+	if strings.EqualFold(filepath.Base(parent), "node.exe") {
+		return false
+	}
+	if !strings.EqualFold(filepath.Ext(parent), ".exe") {
+		return false
+	}
+	return filesHaveSameContents(parent, proxy)
+}
+
+func yarnClassicGlobalBinDir() string {
+	local := strings.TrimSpace(os.Getenv("LOCALAPPDATA"))
+	if local == "" {
+		return ""
+	}
+	return filepath.Join(local, "Yarn", "bin")
+}
+
+func pnpmGlobalBinDir() string {
+	home := strings.TrimSpace(os.Getenv("PNPM_HOME"))
+	if home == "" {
+		return ""
+	}
+	return filepath.Join(home, "bin")
+}
+
+func npmRoamingBinDir() string {
+	appdata, err := os.UserConfigDir()
+	if err != nil {
+		return ""
+	}
+	appdata = strings.TrimSpace(appdata)
+	if appdata == "" {
+		return ""
+	}
+	return filepath.Join(appdata, "npm")
+}
+
+func filesHaveSameContents(leftPath, rightPath string) bool {
+	left, err := os.Open(leftPath)
+	if err != nil {
+		return false
+	}
+	defer left.Close()
+	right, err := os.Open(rightPath)
+	if err != nil {
+		return false
+	}
+	defer right.Close()
+	leftInfo, err := left.Stat()
+	if err != nil {
+		return false
+	}
+	rightInfo, err := right.Stat()
+	if err != nil {
+		return false
+	}
+	if leftInfo.Size() != rightInfo.Size() {
+		return false
+	}
+	bufL := make([]byte, 8192)
+	bufR := make([]byte, 8192)
+	for {
+		nL, errL := left.Read(bufL)
+		nR, errR := right.Read(bufR)
+		if nL != nR || !bytes.Equal(bufL[:nL], bufR[:nR]) {
+			return false
+		}
+		if errL == io.EOF && errR == io.EOF {
+			return true
+		}
+		if errL != nil && errL != io.EOF {
+			return false
+		}
+		if errR != nil && errR != io.EOF {
+			return false
+		}
+		if (errL == io.EOF) != (errR == io.EOF) {
+			return false
+		}
+	}
+}
diff --git a/verifycache/sign_script_auth_test.go b/verifycache/sign_script_auth_test.go
new file mode 100644
index 0000000..8d254dc
--- /dev/null
+++ b/verifycache/sign_script_auth_test.go
@@ -0,0 +1,158 @@
+//go:build windows
+
+package verifycache
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestParentIsNvmProxy(t *testing.T) {
+	dataRoot := t.TempDir()
+	proxy := filepath.Join(dataRoot, "proxy.exe")
+	shim := filepath.Join(dataRoot, ".shim")
+	if err := os.MkdirAll(shim, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	payload := []byte("proxy-bytes")
+	if err := os.WriteFile(proxy, payload, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	vue := filepath.Join(shim, "vue.exe")
+	if err := os.WriteFile(vue, payload, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	node := filepath.Join(shim, "node.exe")
+	if err := os.WriteFile(node, []byte("node-shim"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	evil := filepath.Join(shim, "evil.exe")
+	if err := os.WriteFile(evil, []byte("not-proxy"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	if !parentIsNvmProxy(proxy, dataRoot) {
+		t.Fatal("canonical proxy.exe must match")
+	}
+	if !parentIsNvmProxy(vue, dataRoot) {
+		t.Fatal(".shim vue.exe with proxy bytes must match")
+	}
+	if parentIsNvmProxy(node, dataRoot) {
+		t.Fatal(".shim node.exe must not match")
+	}
+	if parentIsNvmProxy(evil, dataRoot) {
+		t.Fatal("mismatched .shim exe must not match")
+	}
+	if parentIsNvmProxy(`C:\Windows\System32\cmd.exe`, dataRoot) {
+		t.Fatal("cmd.exe must not match")
+	}
+	if parentIsNvmProxy("", dataRoot) {
+		t.Fatal("empty parent must not match")
+	}
+}
+
+func TestAuthorizeSignScriptFromParent(t *testing.T) {
+	dataRoot := setupVerifyCacheTestProfile(t)
+	proxy := filepath.Join(dataRoot, "proxy.exe")
+	shim := filepath.Join(dataRoot, ".shim")
+	if err := os.MkdirAll(shim, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	payload := []byte("proxy-bytes")
+	if err := os.WriteFile(proxy, payload, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	vue := filepath.Join(shim, "vue.exe")
+	if err := os.WriteFile(vue, payload, 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	origParent := parentImagePathFn
+	origPID := parentPIDFn
+	origPipe := stdinPipeServerPIDFn
+	origPub := verifyParentPublisherFn
+	t.Cleanup(func() {
+		parentImagePathFn = origParent
+		parentPIDFn = origPID
+		stdinPipeServerPIDFn = origPipe
+		verifyParentPublisherFn = origPub
+	})
+
+	parentPIDFn = func() uint32 { return 4242 }
+	stdinPipeServerPIDFn = func() (uint32, bool) { return 4242, true }
+	verifyParentPublisherFn = func(string) error { return nil }
+	parentImagePathFn = func() string { return vue }
+
+	if err := AuthorizeSignScriptFromParent(); err != nil {
+		t.Fatalf("signed proxy parent + matching pipe: %v", err)
+	}
+
+	parentImagePathFn = func() string { return `C:\Windows\System32\cmd.exe` }
+	if err := AuthorizeSignScriptFromParent(); err == nil {
+		t.Fatal("cmd.exe parent must fail")
+	}
+
+	parentImagePathFn = func() string { return vue }
+	stdinPipeServerPIDFn = func() (uint32, bool) { return 0, false }
+	if err := AuthorizeSignScriptFromParent(); err == nil {
+		t.Fatal("console stdin must fail")
+	}
+
+	stdinPipeServerPIDFn = func() (uint32, bool) { return 99, true }
+	if err := AuthorizeSignScriptFromParent(); err == nil {
+		t.Fatal("pipe from another PID must fail")
+	}
+
+	stdinPipeServerPIDFn = func() (uint32, bool) { return 4242, true }
+	verifyParentPublisherFn = func(string) error { return os.ErrPermission }
+	if err := AuthorizeSignScriptFromParent(); err == nil {
+		t.Fatal("publisher mismatch must fail")
+	}
+}
+
+func TestReadSignScriptPath(t *testing.T) {
+	got, err := ReadSignScriptPath(strings.NewReader("  C:\\nvm\\installs\\v24\\vue.cmd \n"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != `C:\nvm\installs\v24\vue.cmd` {
+		t.Fatalf("got %q", got)
+	}
+	if _, err := ReadSignScriptPath(strings.NewReader("")); err == nil {
+		t.Fatal("empty path must fail")
+	}
+	if _, err := ReadSignScriptPath(strings.NewReader("a\nb")); err == nil {
+		t.Fatal("newline in path must fail")
+	}
+	if _, err := ReadSignScriptPath(bytes.NewReader(bytes.Repeat([]byte("x"), maxSignScriptPathBytes+1))); err == nil {
+		t.Fatal("oversize path must fail")
+	}
+}
+
+func TestIsDelegatedLauncherPath(t *testing.T) {
+	dataRoot := setupVerifyCacheTestProfile(t)
+	versionDir := filepath.Join(dataRoot, "installs", "v24.0.0")
+	ok := filepath.Join(versionDir, "vue.cmd")
+	nested := filepath.Join(versionDir, "node_modules", "npm", "bin", "npm-cli.js")
+	if !IsDelegatedLauncherPath(ok) {
+		t.Fatal("version-dir cmd must pass")
+	}
+	if !IsDelegatedLauncherPath(nested) {
+		t.Fatal("nested js under installs must pass")
+	}
+	if IsDelegatedLauncherPath(`C:\Temp\evil.cmd`) {
+		t.Fatal("temp cmd must fail")
+	}
+	if IsDelegatedLauncherPath(filepath.Join(versionDir, "vue.exe")) {
+		t.Fatal("exe must fail")
+	}
+
+	t.Setenv("LOCALAPPDATA", filepath.Join(dataRoot, "Local"))
+	yarn := filepath.Join(dataRoot, "Local", "Yarn", "bin", "vue.cmd")
+	if !IsDelegatedLauncherPath(yarn) {
+		t.Fatal("Yarn Classic bin must pass")
+	}
+}