diff --git a/lib/agent/handlers.go b/lib/agent/handlers.go
index 66801cd..4c32b31 100644
--- a/lib/agent/handlers.go
+++ b/lib/agent/handlers.go
@@ -409,7 +409,7 @@ func (a *Agent) handleKey(w http.ResponseWriter, r *http.Request) {
 			helpers.WriteError(w, http.StatusBadRequest, err.Error())
 			return
 		}
-		helpers.Log.Printf("key: %v", err)
+		helpers.Log.Printf("key %q action=%s mods=%v: %v", request.Key, action, request.Modifiers, err)
 		helpers.WriteError(w, http.StatusInternalServerError, "could not send key")
 		return
 	}
diff --git a/lib/input/input.go b/lib/input/input.go
index 258ea79..ac362e1 100644
--- a/lib/input/input.go
+++ b/lib/input/input.go
@@ -2,6 +2,7 @@ package input
 
 import (
 	"errors"
+	"fmt"
 	"runtime"
 	"strings"
 	"syscall"
@@ -10,46 +11,69 @@ import (
 	"unsafe"
 
 	"tea.chunkbyte.com/kato/go-worm/lib/config"
+	"tea.chunkbyte.com/kato/go-worm/lib/helpers"
 )
 
 const (
-	inputMouse    = 0
+	inputMouse  = 0
 	inputKeyboard = 1
 
-	mouseMove          = 0x0001
-	mouseLeftDown      = 0x0002
-	mouseLeftUp        = 0x0004
-	mouseRightDown     = 0x0008
-	mouseRightUp       = 0x0010
-	mouseAbsolute      = 0x8000
-	mouseVirtualDesk   = 0x4000
-	desktopAllAccess   = 0x01FF
-	keyeventfKeyup       = 0x0002
-	keyeventfUnicode     = 0x0004
-	smXVirtualScreen     = 76
-	smYVirtualScreen     = 77
-	smCXVirtualScreen    = 78
-	smCYVirtualScreen    = 79
+	mouseMove        = 0x0001
+	mouseLeftDown    = 0x0002
+	mouseLeftUp      = 0x0004
+	mouseRightDown   = 0x0008
+	mouseRightUp     = 0x0010
+	mouseAbsolute    = 0x8000
+	mouseVirtualDesk = 0x4000
+	desktopAllAccess = 0x01FF
+
+	keyeventfExtended = 0x0001
+	keyeventfKeyup    = 0x0002
+	keyeventfUnicode  = 0x0004
+
+	smXVirtualScreen  = 76
+	smYVirtualScreen  = 77
+	smCXVirtualScreen = 78
+	smCYVirtualScreen = 79
 )
 
 var (
 	ErrBadButton = errors.New("button must be left or right")
 	ErrEmptyText = errors.New("text must not be empty")
 
-	user32               = syscall.NewLazyDLL("user32.dll")
-	procSetCursorPos     = user32.NewProc("SetCursorPos")
-	procSendInput        = user32.NewProc("SendInput")
+	user32                 = syscall.NewLazyDLL("user32.dll")
+	procSetCursorPos       = user32.NewProc("SetCursorPos")
+	procSendInput          = user32.NewProc("SendInput")
 	procSetProcessDPIAware = user32.NewProc("SetProcessDPIAware")
-	procOpenInputDesktop = user32.NewProc("OpenInputDesktop")
-	procSetThreadDesktop = user32.NewProc("SetThreadDesktop")
-	procCloseDesktop     = user32.NewProc("CloseDesktop")
-	procGetSystemMetrics = user32.NewProc("GetSystemMetrics")
+	procOpenInputDesktop   = user32.NewProc("OpenInputDesktop")
+	procSetThreadDesktop   = user32.NewProc("SetThreadDesktop")
+	procCloseDesktop       = user32.NewProc("CloseDesktop")
+	procGetSystemMetrics   = user32.NewProc("GetSystemMetrics")
+
+	inputStructSize = int(unsafe.Sizeof(winInput{}))
 )
 
-// ponytail: INPUT must be 40 bytes on amd64; wrong size yields SendInput failures.
-type mouseInput struct {
-	Type      uint32
+func init() {
+	if inputStructSize != 40 {
+		panic(fmt.Sprintf("winInput must be 40 bytes on this platform, got %d", inputStructSize))
+	}
+	if unsafe.Sizeof(winMouseInput{}) != 40 {
+		panic(fmt.Sprintf("winMouseInput must be 40 bytes on this platform, got %d", unsafe.Sizeof(winMouseInput{})))
+	}
+}
+
+// winInput matches the 40-byte INPUT struct on amd64 (8-byte header + 32-byte union).
+type keyboardData struct {
+	Vk        uint16
+	Scan      uint16
+	Flags     uint32
+	Time      uint32
 	_         uint32
+	ExtraInfo uintptr
+	_         [8]byte
+}
+
+type mouseData struct {
 	Dx        int32
 	Dy        int32
 	MouseData uint32
@@ -59,15 +83,16 @@ type mouseInput struct {
 	ExtraInfo uintptr
 }
 
-type keybdInput struct {
-	Type      uint32
-	_         uint32
-	Vk        uint16
-	Scan      uint16
-	Flags     uint32
-	Time      uint32
-	_         uint32
-	ExtraInfo uintptr
+type winInput struct {
+	Type uint32
+	_    uint32
+	Ki   keyboardData
+}
+
+type winMouseInput struct {
+	Type uint32
+	_    uint32
+	Mi   mouseData
 }
 
 func EnableDPIAwareness() {
@@ -87,16 +112,15 @@ func Click(x, y int, button string) error {
 	}
 
 	absX, absY := absoluteCoords(x, y)
-	inputs := []mouseInput{
-		{Type: inputMouse, Dx: absX, Dy: absY, Flags: mouseMove | mouseAbsolute | mouseVirtualDesk},
-		{Type: inputMouse, Flags: down},
-		{Type: inputMouse, Flags: up},
+	inputs := []winMouseInput{
+		{Type: inputMouse, Mi: mouseData{Dx: absX, Dy: absY, Flags: mouseMove | mouseAbsolute | mouseVirtualDesk}},
+		{Type: inputMouse, Mi: mouseData{Flags: down}},
+		{Type: inputMouse, Mi: mouseData{Flags: up}},
 	}
-	if err := sendMouse(inputs); err != nil {
+	if err := sendMouseInputs(inputs); err != nil {
 		return err
 	}
 
-	// ponytail: best-effort cursor sync for the local user; ignore denial after SendInput click.
 	_, _, _ = procSetCursorPos.Call(uintptr(x), uintptr(y))
 	return nil
 }
@@ -135,18 +159,17 @@ func resolveKeyDelay(ms int) int {
 	return ms
 }
 
-// ResolveKeyDelay returns the effective per-key delay for API responses.
 func ResolveKeyDelay(ms int) int {
 	return resolveKeyDelay(ms)
 }
 
 func sendUnicodeRune(r rune) error {
 	for _, unit := range utf16.Encode([]rune{r}) {
-		inputs := []keybdInput{
-			{Type: inputKeyboard, Scan: unit, Flags: keyeventfUnicode},
-			{Type: inputKeyboard, Scan: unit, Flags: keyeventfUnicode | keyeventfKeyup},
+		inputs := []winInput{
+			{Type: inputKeyboard, Ki: keyboardData{Scan: unit, Flags: keyeventfUnicode}},
+			{Type: inputKeyboard, Ki: keyboardData{Scan: unit, Flags: keyeventfUnicode | keyeventfKeyup}},
 		}
-		if err := sendKeys(inputs); err != nil {
+		if err := sendKeyboardInputs(inputs); err != nil {
 			return err
 		}
 	}
@@ -193,18 +216,29 @@ func mouseFlags(button string) (down, up uint32, err error) {
 	}
 }
 
-func sendMouse(inputs []mouseInput) error {
-	n, _, err := procSendInput.Call(uintptr(len(inputs)), uintptr(unsafe.Pointer(&inputs[0])), uintptr(unsafe.Sizeof(inputs[0])))
-	if n == 0 {
-		return err
-	}
-	return nil
+func sendMouseInputs(inputs []winMouseInput) error {
+	return sendInput(len(inputs), unsafe.Pointer(&inputs[0]), unsafe.Sizeof(inputs[0]), "mouse")
 }
 
-func sendKeys(inputs []keybdInput) error {
-	n, _, err := procSendInput.Call(uintptr(len(inputs)), uintptr(unsafe.Pointer(&inputs[0])), uintptr(unsafe.Sizeof(inputs[0])))
-	if n == 0 {
+func sendKeyboardInputs(inputs []winInput) error {
+	return sendInput(len(inputs), unsafe.Pointer(&inputs[0]), unsafe.Sizeof(inputs[0]), "keyboard")
+}
+
+func sendInput(count int, ptr unsafe.Pointer, elemSize uintptr, kind string) error {
+	if count == 0 {
+		return nil
+	}
+	if int(elemSize) != inputStructSize {
+		return fmt.Errorf("input struct size mismatch: %s has %d bytes, want %d", kind, elemSize, inputStructSize)
+	}
+	n, _, err := procSendInput.Call(uintptr(count), uintptr(ptr), elemSize)
+	if n != 0 {
+		return nil
+	}
+	if err != nil && err.Error() != "The operation completed successfully." {
+		helpers.Log.Printf("SendInput %s count=%d cbSize=%d: %v", kind, count, elemSize, err)
 		return err
 	}
-	return nil
+	helpers.Log.Printf("SendInput %s count=%d cbSize=%d failed (n=0)", kind, count, elemSize)
+	return fmt.Errorf("SendInput failed")
 }
diff --git a/lib/input/key.go b/lib/input/key.go
index 5f04425..e43b6be 100644
--- a/lib/input/key.go
+++ b/lib/input/key.go
@@ -26,43 +26,48 @@ func PressKey(key, action string, modifiers []string) error {
 		modVKs = append(modVKs, modVK)
 	}
 
+	var inputs []winInput
 	for _, modVK := range modVKs {
-		if err := sendKeyEvent(modVK, false); err != nil {
-			return err
-		}
+		inputs = append(inputs, keyInput(modVK, false))
 	}
 
 	switch strings.ToLower(strings.TrimSpace(action)) {
 	case "down":
-		if err := sendKeyEvent(vk, false); err != nil {
-			return err
-		}
+		inputs = append(inputs, keyInput(vk, false))
 	case "up":
-		if err := sendKeyEvent(vk, true); err != nil {
-			return err
-		}
+		inputs = append(inputs, keyInput(vk, true))
 	default:
-		if err := sendKeyEvent(vk, false); err != nil {
-			return err
-		}
-		if err := sendKeyEvent(vk, true); err != nil {
-			return err
-		}
+		inputs = append(inputs, keyInput(vk, false), keyInput(vk, true))
 		for i := len(modVKs) - 1; i >= 0; i-- {
-			if err := sendKeyEvent(modVKs[i], true); err != nil {
-				return err
-			}
+			inputs = append(inputs, keyInput(modVKs[i], true))
 		}
-		return nil
 	}
-	return nil
+
+	return sendKeyboardInputs(inputs)
 }
 
-func sendKeyEvent(vk uint16, keyUp bool) error {
+func keyInput(vk uint16, keyUp bool) winInput {
 	flags := uint32(0)
 	if keyUp {
-		flags = keyeventfKeyup
+		flags |= keyeventfKeyup
+	}
+	if isExtendedVK(vk) {
+		flags |= keyeventfExtended
+	}
+	return winInput{
+		Type: inputKeyboard,
+		Ki: keyboardData{
+			Vk:    vk,
+			Flags: flags,
+		},
+	}
+}
+
+func isExtendedVK(vk uint16) bool {
+	switch vk {
+	case 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x2D, 0x2E, 0x5B, 0x5C, 0x5D:
+		return true
+	default:
+		return false
 	}
-	inputs := []keybdInput{{Type: inputKeyboard, Vk: vk, Flags: flags}}
-	return sendKeys(inputs)
 }
diff --git a/lib/input/keymap.go b/lib/input/keymap.go
index f95f8f8..fbf7862 100644
--- a/lib/input/keymap.go
+++ b/lib/input/keymap.go
@@ -12,10 +12,10 @@ var vkNames = map[string]uint16{
 	"backspace": 0x08,
 	"tab":       0x09,
 	"enter":     0x0D,
-	"shift":     0x10,
-	"ctrl":      0x11,
-	"control":   0x11,
-	"alt":       0x12,
+	"shift":     0xA0,
+	"ctrl":      0xA2,
+	"control":   0xA2,
+	"alt":       0xA4,
 	"pause":     0x13,
 	"capslock":  0x14,
 	"escape":    0x1B,
diff --git a/lib/input/keymap_test.go b/lib/input/keymap_test.go
index 9883e56..2ddc0a8 100644
--- a/lib/input/keymap_test.go
+++ b/lib/input/keymap_test.go
@@ -8,8 +8,8 @@ func TestVkCode(t *testing.T) {
 		"a":     0x41,
 		"A":     0x41,
 		"enter": 0x0D,
-		"ctrl":  0x11,
-		"win":   0x5B,
+	"ctrl":  0xA2,
+	"win":   0x5B,
 		"f5":    0x74,
 	}
 	for name, want := range cases {