diff --git a/internal/tools/exec_workspace.go b/internal/tools/exec_workspace.go
index c996cbe..765f2e1 100644
--- a/internal/tools/exec_workspace.go
+++ b/internal/tools/exec_workspace.go
@@ -386,6 +386,8 @@ func relaxAndRemove(root string) {
 		return nil // 清理尽力而为：失败留给会话目录清理兜底
 	})
 	_ = os.RemoveAll(root)
+	// -ws 根目录在空时顺手移除（每会话一个壳，不清理会随会话累积）。
+	_ = os.Remove(filepath.Dir(root))
 }
 
 func (p *overlayProcess) Kill() error { return p.inner.Kill() }
diff --git a/internal/tools/exec_workspace_test.go b/internal/tools/exec_workspace_test.go
index 26a2f9a..ab9de17 100644
--- a/internal/tools/exec_workspace_test.go
+++ b/internal/tools/exec_workspace_test.go
@@ -231,3 +231,25 @@ func TestSandboxWorkspaceOverlayTimeoutDiscards(t *testing.T) {
 }
 
 func shortTimeout() time.Duration { return 1500 * time.Millisecond }
+
+// -ws 壳目录在空时移除（不随会话累积）。
+func TestOverlayCleansShellDir(t *testing.T) {
+	if _, err := exec.LookPath("bwrap"); err != nil {
+		t.Skip("bwrap not available")
+	}
+	old := workspaceOverlay
+	workspaceOverlay = true
+	defer func() { workspaceOverlay = old }()
+	dir := t.TempDir()
+	spec := ExecSpec{Bin: "/bin/bash", Args: []string{"-c", "echo hi"}, Dir: dir, Env: []string{"PATH=/usr/bin:/bin"}}
+	proc, err := sandboxBackend{}.Start(context.Background(), spec, &strings.Builder{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := proc.Wait(); err != nil {
+		t.Fatal(err)
+	}
+	if _, serr := os.Stat(dir + "-ws"); !os.IsNotExist(serr) {
+		t.Fatalf("-ws shell dir must be removed when empty: %v", serr)
+	}
+}