* Indicates that Windows does not support expos_paths, adding more mount paths for the Linux platform.

pkg/config/config.go

@@ -54,7 +54,7 @@ type IsolationConfig struct {
 }
 
 // ExposePath describes a host path that should remain visible inside the isolated
-// child-process environment.
+// child-process environment. This is currently implemented on Linux only.
 type ExposePath struct {
 	Source string `json:"source"`
 	Target string `json:"target,omitempty"`

pkg/isolation/README.md

@@ -46,7 +46,7 @@ Isolation lives under:
 Field meanings:
 
 - `enabled`: enables or disables subprocess isolation. Default: `false`.
-- `expose_paths`: explicitly exposes host paths inside the isolated environment. It only matters when `enabled=true`.
+- `expose_paths`: explicitly exposes host paths inside the isolated environment. It only matters when `enabled=true`. This is currently supported on Linux only.
 
 Example:
 
@@ -82,7 +82,7 @@ Rules for `expose_paths`:
 Platform note:
 
 - Linux uses a real `source -> target` mount view.
-- Windows currently keeps `target` for config shape, but access control is still based on `source`.
+- Windows does not currently support `expose_paths`.
 
 ## Instance Root And Directories
 
@@ -173,6 +173,10 @@ Disabling isolation increases the risk that child processes can access or modify
 
 ### Windows
 
+Windows isolation currently supports process-level restrictions such as restricted tokens, low integrity, job objects, and redirected user-environment directories.
+
+`expose_paths` is not currently supported on Windows. If it is configured, startup should fail instead of pretending the paths were exposed.
+
 The Windows backend currently uses:
 
 - a restricted primary token

pkg/isolation/README_CN.md

@@ -46,7 +46,7 @@
 字段说明：
 
 - `enabled`：是否启用子进程隔离。默认值：`false`。
-- `expose_paths`：显式把宿主路径带入隔离环境。仅在 `enabled=true` 时生效。
+- `expose_paths`：显式把宿主路径带入隔离环境。仅在 `enabled=true` 时生效。目前只在 Linux 上支持。
 
 示例：
 
@@ -82,7 +82,7 @@
 平台说明：
 
 - Linux 会真实使用 `source -> target` 挂载视图。
-- Windows 当前保留 `target` 结构，但权限控制仍以 `source` 为准。
+- Windows 当前不支持 `expose_paths`。
 
 ## 实例根与目录
 
@@ -173,6 +173,10 @@ Linux 后端当前依赖 `bwrap`（`bubblewrap`）。
 
 ### Windows
 
+Windows 隔离当前提供的是进程级限制，例如 restricted token、low integrity、job object，以及用户环境目录重定向。
+
+`expose_paths` 目前不支持 Windows。如果配置了该字段，启动应直接失败，而不是假装这些路径已经被暴露进隔离环境。
+
 Windows 后端当前使用：
 
 - 受限 primary token

pkg/isolation/platform_windows.go

@@ -39,11 +39,12 @@ func applyPlatformIsolation(cmd *exec.Cmd, isolation config.IsolationConfig, roo
 		cmd.SysProcAttr = &syscall.SysProcAttr{}
 	}
 	rules := BuildWindowsAccessRules(root, isolation.ExposePaths)
-	logger.InfoCF("isolation", "windows isolation access rules",
+	logger.InfoCF("isolation", "windows isolation process constraints",
 		map[string]any{
 			"root":    root,
 			"command": cmd.Path,
 			"rules":   formatWindowsAccessRules(rules),
+			"note":    "Windows currently enforces restricted token, low integrity, and job object limits; expose_paths filesystem remapping is rejected during preflight",
 		})
 	// Create the restricted token before the process starts so CreateProcess uses
 	// the reduced privilege set from the first instruction.

pkg/isolation/runtime.go

@@ -227,17 +227,33 @@ func DefaultExposePaths(root string) []config.ExposePath {
 		Mode:   "rw",
 	}}
 	if runtime.GOOS == "linux" {
-		items = append(items,
+		items = append(items, defaultLinuxSystemExposePaths()...)
-			config.ExposePath{Source: "/usr", Target: "/usr", Mode: "ro"},
-			config.ExposePath{Source: "/bin", Target: "/bin", Mode: "ro"},
-			config.ExposePath{Source: "/lib", Target: "/lib", Mode: "ro"},
-			config.ExposePath{Source: "/lib64", Target: "/lib64", Mode: "ro"},
-			config.ExposePath{Source: "/etc/resolv.conf", Target: "/etc/resolv.conf", Mode: "ro"},
-		)
 	}
 	return items
 }
 
+func defaultLinuxSystemExposePaths() []config.ExposePath {
+	return []config.ExposePath{
+		{Source: "/usr", Target: "/usr", Mode: "ro"},
+		{Source: "/bin", Target: "/bin", Mode: "ro"},
+		{Source: "/lib", Target: "/lib", Mode: "ro"},
+		{Source: "/lib64", Target: "/lib64", Mode: "ro"},
+		{Source: "/etc/resolv.conf", Target: "/etc/resolv.conf", Mode: "ro"},
+		{Source: "/etc/hosts", Target: "/etc/hosts", Mode: "ro"},
+		{Source: "/etc/nsswitch.conf", Target: "/etc/nsswitch.conf", Mode: "ro"},
+		{Source: "/etc/passwd", Target: "/etc/passwd", Mode: "ro"},
+		{Source: "/etc/group", Target: "/etc/group", Mode: "ro"},
+		{Source: "/etc/ssl", Target: "/etc/ssl", Mode: "ro"},
+		{Source: "/etc/pki", Target: "/etc/pki", Mode: "ro"},
+		{Source: "/etc/ca-certificates", Target: "/etc/ca-certificates", Mode: "ro"},
+		{Source: "/usr/share/ca-certificates", Target: "/usr/share/ca-certificates", Mode: "ro"},
+		{Source: "/usr/local/share/ca-certificates", Target: "/usr/local/share/ca-certificates", Mode: "ro"},
+		{Source: "/etc/alternatives", Target: "/etc/alternatives", Mode: "ro"},
+		{Source: "/usr/share/zoneinfo", Target: "/usr/share/zoneinfo", Mode: "ro"},
+		{Source: "/etc/localtime", Target: "/etc/localtime", Mode: "ro"},
+	}
+}
+
 // MergeExposePaths merges built-in rules with user overrides. Rules are keyed
 // by target path so later entries replace earlier ones for the same target.
 func MergeExposePaths(defaults []config.ExposePath, overrides []config.ExposePath) []config.ExposePath {
@@ -276,21 +292,19 @@ func BuildLinuxMountPlan(root string, overrides []config.ExposePath) []MountRule
 // Windows restricted-token backend.
 func BuildWindowsAccessRules(root string, overrides []config.ExposePath) []AccessRule {
 	rules := []AccessRule{{Path: root, Mode: "rw"}}
-	if userProfile := os.Getenv("USERPROFILE"); userProfile != "" {
-		rules = append(rules,
-			AccessRule{Path: filepath.Join(userProfile, ".ssh"), Mode: "deny"},
-			AccessRule{Path: filepath.Join(userProfile, ".gitconfig"), Mode: "deny"},
-			AccessRule{Path: filepath.Join(userProfile, "Documents"), Mode: "deny"},
-			AccessRule{Path: filepath.Join(userProfile, "Desktop"), Mode: "deny"},
-			AccessRule{Path: filepath.Join(userProfile, "Downloads"), Mode: "deny"},
-		)
-	}
 	for _, item := range MergeExposePaths(nil, overrides) {
 		rules = append(rules, AccessRule{Path: item.Source, Mode: item.Mode})
 	}
 	return rules
 }
 
+func validateWindowsExposePaths(items []config.ExposePath) error {
+	if len(items) == 0 {
+		return nil
+	}
+	return fmt.Errorf("windows isolation does not yet support expose_paths filesystem rules")
+}
+
 // IsSupported reports whether the current platform has an implemented isolation
 // backend.
 func IsSupported() bool {
@@ -334,6 +348,9 @@ func Preflight() error {
 		}
 	}
 	if runtime.GOOS == "windows" {
+		if err := validateWindowsExposePaths(isolation.ExposePaths); err != nil {
+			return err
+		}
 		for _, rule := range BuildWindowsAccessRules(root, isolation.ExposePaths) {
 			if rule.Path == "" {
 				return fmt.Errorf("invalid windows access rule")

pkg/isolation/runtime_test.go

@@ -114,7 +114,6 @@ func TestBuildLinuxMountPlan(t *testing.T) {
 }
 
 func TestBuildWindowsAccessRules(t *testing.T) {
-	t.Setenv("USERPROFILE", `C:\Users\tester`)
 	rules := BuildWindowsAccessRules(
 		`C:\picoclaw`,
 		[]config.ExposePath{{Source: `D:\data`, Target: `C:\mapped`, Mode: "ro"}},
@@ -140,6 +139,37 @@ func TestBuildWindowsAccessRules(t *testing.T) {
 	}
 }
 
+func TestValidateWindowsExposePaths(t *testing.T) {
+	if err := validateWindowsExposePaths(nil); err != nil {
+		t.Fatalf("validateWindowsExposePaths(nil) error = %v", err)
+	}
+	err := validateWindowsExposePaths([]config.ExposePath{{Source: `D:\data`, Target: `D:\data`, Mode: "ro"}})
+	if err == nil {
+		t.Fatal("validateWindowsExposePaths() expected error for expose_paths")
+	}
+}
+
+func TestDefaultLinuxSystemExposePaths(t *testing.T) {
+	paths := defaultLinuxSystemExposePaths()
+	needed := map[string]bool{
+		"/etc/hosts":          false,
+		"/etc/nsswitch.conf":  false,
+		"/etc/ssl":            false,
+		"/usr/share/zoneinfo": false,
+		"/etc/localtime":      false,
+	}
+	for _, item := range paths {
+		if _, ok := needed[item.Source]; ok {
+			needed[item.Source] = true
+		}
+	}
+	for path, found := range needed {
+		if !found {
+			t.Fatalf("defaultLinuxSystemExposePaths missing %s", path)
+		}
+	}
+}
+
 func TestPrepareCommand_AppliesUserEnv(t *testing.T) {
 	t.Setenv(config.EnvHome, filepath.Join(t.TempDir(), "home"))
 	if runtime.GOOS == "linux" {

pkg/mcp/isolated_command_transport.go

@@ -0,0 +1,224 @@
+package mcp
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os/exec"
+	"sync"
+	"syscall"
+	"time"
+
+	"github.com/modelcontextprotocol/go-sdk/jsonrpc"
+	sdkmcp "github.com/modelcontextprotocol/go-sdk/mcp"
+
+	"github.com/sipeed/picoclaw/pkg/isolation"
+)
+
+var isolatedCommandTerminateDuration = 5 * time.Second
+
+// isolatedCommandTransport mirrors the SDK command transport but routes
+// process startup through pkg/isolation so Windows post-start hooks run too.
+type isolatedCommandTransport struct {
+	Command           *exec.Cmd
+	TerminateDuration time.Duration
+}
+
+func (t *isolatedCommandTransport) Connect(ctx context.Context) (sdkmcp.Connection, error) {
+	stdout, err := t.Command.StdoutPipe()
+	if err != nil {
+		return nil, err
+	}
+	stdout = io.NopCloser(stdout)
+	stdin, err := t.Command.StdinPipe()
+	if err != nil {
+		return nil, err
+	}
+	if err := isolation.Start(t.Command); err != nil {
+		return nil, err
+	}
+	td := t.TerminateDuration
+	if td <= 0 {
+		td = isolatedCommandTerminateDuration
+	}
+	return newIsolatedIOConn(&isolatedPipeRWC{cmd: t.Command, stdout: stdout, stdin: stdin, terminateDuration: td}), nil
+}
+
+type isolatedPipeRWC struct {
+	cmd               *exec.Cmd
+	stdout            io.ReadCloser
+	stdin             io.WriteCloser
+	terminateDuration time.Duration
+}
+
+func (s *isolatedPipeRWC) Read(p []byte) (n int, err error) {
+	return s.stdout.Read(p)
+}
+
+func (s *isolatedPipeRWC) Write(p []byte) (n int, err error) {
+	return s.stdin.Write(p)
+}
+
+func (s *isolatedPipeRWC) Close() error {
+	if err := s.stdin.Close(); err != nil {
+		return fmt.Errorf("closing stdin: %v", err)
+	}
+	resChan := make(chan error, 1)
+	go func() {
+		resChan <- s.cmd.Wait()
+	}()
+	wait := func() (error, bool) {
+		select {
+		case err := <-resChan:
+			return err, true
+		case <-time.After(s.terminateDuration):
+		}
+		return nil, false
+	}
+	if err, ok := wait(); ok {
+		return err
+	}
+	if err := s.cmd.Process.Signal(syscall.SIGTERM); err == nil {
+		if err, ok := wait(); ok {
+			return err
+		}
+	}
+	if err := s.cmd.Process.Kill(); err != nil {
+		return err
+	}
+	if err, ok := wait(); ok {
+		return err
+	}
+	return fmt.Errorf("unresponsive subprocess")
+}
+
+type isolatedIOConn struct {
+	writeMu   sync.Mutex
+	rwc       io.ReadWriteCloser
+	incoming  <-chan isolatedMsgOrErr
+	queue     []jsonrpc.Message
+	closeOnce sync.Once
+	closed    chan struct{}
+	closeErr  error
+}
+
+type isolatedMsgOrErr struct {
+	msg json.RawMessage
+	err error
+}
+
+func newIsolatedIOConn(rwc io.ReadWriteCloser) *isolatedIOConn {
+	incoming := make(chan isolatedMsgOrErr)
+	closed := make(chan struct{})
+	go func() {
+		dec := json.NewDecoder(rwc)
+		for {
+			var raw json.RawMessage
+			err := dec.Decode(&raw)
+			if err == nil {
+				var tr [1]byte
+				if n, readErr := dec.Buffered().Read(tr[:]); n > 0 {
+					if tr[0] != '\n' && tr[0] != '\r' {
+						err = fmt.Errorf("invalid trailing data at the end of stream")
+					}
+				} else if readErr != nil && readErr != io.EOF {
+					err = readErr
+				}
+			}
+			select {
+			case incoming <- isolatedMsgOrErr{msg: raw, err: err}:
+			case <-closed:
+				return
+			}
+			if err != nil {
+				return
+			}
+		}
+	}()
+	return &isolatedIOConn{rwc: rwc, incoming: incoming, closed: closed}
+}
+
+func (c *isolatedIOConn) SessionID() string { return "" }
+
+func (c *isolatedIOConn) Read(ctx context.Context) (jsonrpc.Message, error) {
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	default:
+	}
+	if len(c.queue) > 0 {
+		next := c.queue[0]
+		c.queue = c.queue[1:]
+		return next, nil
+	}
+	var raw json.RawMessage
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	case v := <-c.incoming:
+		if v.err != nil {
+			return nil, v.err
+		}
+		raw = v.msg
+	case <-c.closed:
+		return nil, io.EOF
+	}
+	msgs, err := readIsolatedBatch(raw)
+	if err != nil {
+		return nil, err
+	}
+	c.queue = msgs[1:]
+	return msgs[0], nil
+}
+
+func readIsolatedBatch(data []byte) ([]jsonrpc.Message, error) {
+	var rawBatch []json.RawMessage
+	if err := json.Unmarshal(data, &rawBatch); err == nil {
+		if len(rawBatch) == 0 {
+			return nil, fmt.Errorf("empty batch")
+		}
+		msgs := make([]jsonrpc.Message, 0, len(rawBatch))
+		for _, raw := range rawBatch {
+			msg, err := jsonrpc.DecodeMessage(raw)
+			if err != nil {
+				return nil, err
+			}
+			msgs = append(msgs, msg)
+		}
+		return msgs, nil
+	}
+	msg, err := jsonrpc.DecodeMessage(data)
+	if err != nil {
+		return nil, err
+	}
+	return []jsonrpc.Message{msg}, nil
+}
+
+func (c *isolatedIOConn) Write(ctx context.Context, msg jsonrpc.Message) error {
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	default:
+	}
+	c.writeMu.Lock()
+	defer c.writeMu.Unlock()
+	data, err := jsonrpc.EncodeMessage(msg)
+	if err != nil {
+		return fmt.Errorf("marshaling message: %v", err)
+	}
+	data = append(data, '\n')
+	_, err = c.rwc.Write(data)
+	return err
+}
+
+func (c *isolatedIOConn) Close() error {
+	c.closeOnce.Do(func() {
+		c.closeErr = c.rwc.Close()
+		close(c.closed)
+	})
+	return c.closeErr
+}
+
+var _ sdkmcp.Transport = (*isolatedCommandTransport)(nil)
+var _ sdkmcp.Connection = (*isolatedIOConn)(nil)

pkg/mcp/manager.go

@@ -372,7 +372,7 @@ func (m *Manager) ConnectServer(
 			return fmt.Errorf("prepare stdio MCP isolation: %w", err)
 		}
 
-		transport = &mcp.CommandTransport{Command: cmd}
+		transport = &isolatedCommandTransport{Command: cmd}
 	default:
 		return fmt.Errorf(
 			"unsupported transport type: %s (supported: stdio, sse, http)",