fix(local): use native shell on Windows

adk/backend/local/local.go

@@ -262,11 +262,10 @@ var defaultValidateCommand = func(string) error {
 
 // NewBackend creates a new local filesystem Local instance.
 //
-// IMPORTANT - System Compatibility:
-//   - Supported: Unix/MacOS only
-//   - NOT Supported: Windows (requires custom implementation of filesystem.Backend)
-//   - Command Execution: Uses /bin/sh by default for Execute method
-//   - If /bin/sh does not meet your requirements, please implement your own filesystem.Backend
+// IMPORTANT - Command Execution:
+//   - Unix/macOS use /bin/sh.
+//   - Windows uses cmd.exe.
+//   - If the system shell does not meet your requirements, implement your own filesystem.Backend.
 func NewBackend(_ context.Context, cfg *Config) (*Local, error) {
 	if cfg == nil {
 		return nil, errors.New("config is required")
@@ -987,7 +986,7 @@ func (s *Local) Execute(ctx context.Context, input *filesystem.ExecuteRequest) (
 		return nil, err
 	}
 
-	cmd := exec.CommandContext(ctx, "/bin/sh", "-c", input.Command)
+	cmd := newShellCmd(ctx, input.Command)
 
 	var stdoutBuf, stderrBuf strings.Builder
 	cmd.Stdout = &stdoutBuf
@@ -1023,7 +1022,7 @@ func (s *Local) Execute(ctx context.Context, input *filesystem.ExecuteRequest) (
 
 // initStreamingCmd creates command with stdout and stderr pipes.
 func (s *Local) initStreamingCmd(ctx context.Context, command string) (*exec.Cmd, io.ReadCloser, io.ReadCloser, error) {
-	cmd := exec.CommandContext(ctx, "/bin/sh", "-c", command)
+	cmd := newShellCmd(ctx, command)
 
 	stdout, err := cmd.StdoutPipe()
 	if err != nil {
@@ -1039,6 +1038,13 @@ func (s *Local) initStreamingCmd(ctx context.Context, command string) (*exec.Cmd
 	return cmd, stdout, stderr, nil
 }
 
+func newShellCmd(ctx context.Context, command string) *exec.Cmd {
+	if runtime.GOOS == "windows" {
+		return exec.CommandContext(ctx, "cmd.exe", "/C", command)
+	}
+	return exec.CommandContext(ctx, "/bin/sh", "-c", command)
+}
+
 // runCmdInBackground executes command in background without waiting for completion.
 // The caller controls timeout/cancellation via ctx.Done().
 func (s *Local) runCmdInBackground(ctx context.Context, cmd *exec.Cmd, stdout, stderr io.ReadCloser, w *schema.StreamWriter[*filesystem.ExecuteResponse]) {

adk/backend/local/local_test.go

@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"testing"
 	"time"
@@ -793,6 +794,21 @@ func TestExecuteStreaming(t *testing.T) {
 	})
 }
 
+func TestNewShellCmd(t *testing.T) {
+	command := "echo hello"
+	cmd := newShellCmd(context.Background(), command)
+
+	if runtime.GOOS == "windows" {
+		assert.Equal(t, []string{"cmd.exe", "/C", command}, cmd.Args)
+	} else {
+		assert.Equal(t, []string{"/bin/sh", "-c", command}, cmd.Args)
+	}
+
+	output, err := cmd.Output()
+	require.NoError(t, err)
+	assert.Equal(t, "hello", strings.TrimSpace(string(output)))
+}
+
 func TestExecute(t *testing.T) {
 	ctx := context.Background()
 	s, err := NewBackend(ctx, &Config{})