diff --git a/cmd/containerd-shim-nerdbox-v1/main.go b/cmd/containerd-shim-nerdbox-v1/main.go
index 50c469a..2cf5d97 100644
--- a/cmd/containerd-shim-nerdbox-v1/main.go
+++ b/cmd/containerd-shim-nerdbox-v1/main.go
@@ -21,7 +21,7 @@ import (
 
 	"github.com/containerd/containerd/v2/pkg/shim"
 
-	"github.com/containerd/nerdbox/internal/shim/manager"
+	"github.com/containerd/nerdbox/pkg/shim/manager"
 
 	_ "github.com/containerd/nerdbox/plugins/shim/sandbox"
 	_ "github.com/containerd/nerdbox/plugins/shim/streaming"
@@ -31,5 +31,5 @@ import (
 )
 
 func main() {
-	shim.RunShim(context.Background(), manager.NewShimManager("io.containerd.nerdbox.v1"))
+	shim.RunShim(context.Background(), manager.New("io.containerd.nerdbox.v1"))
 }
diff --git a/internal/shim/manager/manager.go b/pkg/shim/manager/manager.go
similarity index 88%
rename from internal/shim/manager/manager.go
rename to pkg/shim/manager/manager.go
index c04cadf..6003566 100644
--- a/internal/shim/manager/manager.go
+++ b/pkg/shim/manager/manager.go
@@ -26,9 +26,11 @@ import (
 	"github.com/containerd/containerd/v2/pkg/shim"
 )
 
-// NewShimManager returns an implementation of the shim manager
-// using run_vminitd
-func NewShimManager(name string) shim.Shim {
+// New returns a shim manager implementation that launches the nerdbox shim
+// process. The name is the runtime identifier reported to containerd (for
+// example "io.containerd.nerdbox.v1"). External callers building variants
+// of the nerdbox shim use this to assemble their own main package.
+func New(name string) shim.Shim {
 	return &manager{
 		name: name,
 	}
diff --git a/pkg/shim/manager/manager_test.go b/pkg/shim/manager/manager_test.go
new file mode 100644
index 0000000..0985e53
--- /dev/null
+++ b/pkg/shim/manager/manager_test.go
@@ -0,0 +1,93 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package manager
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestNewName(t *testing.T) {
+	const name = "io.containerd.nerdbox.v1"
+	s := New(name)
+	if got := s.Name(); got != name {
+		t.Errorf("Name() = %q, want %q", got, name)
+	}
+}
+
+func TestInfo(t *testing.T) {
+	const name = "io.containerd.nerdbox.v1"
+	s := New(name)
+	info, err := s.Info(context.Background(), strings.NewReader(""))
+	if err != nil {
+		t.Fatalf("Info() error: %v", err)
+	}
+	if info.Name != name {
+		t.Errorf("Info().Name = %q, want %q", info.Name, name)
+	}
+	if got := info.Annotations["containerd.io/runtime-allow-mounts"]; got == "" {
+		t.Errorf("Info().Annotations missing runtime-allow-mounts: %v", info.Annotations)
+	}
+}
+
+func TestReadSpec(t *testing.T) {
+	dir := t.TempDir()
+	configPath := filepath.Join(dir, "config.json")
+	const body = `{"annotations":{"io.kubernetes.cri.sandbox-id":"abc123","other":"value"}}`
+	if err := os.WriteFile(configPath, []byte(body), 0o600); err != nil {
+		t.Fatal(err)
+	}
+
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { os.Chdir(cwd) })
+	if err := os.Chdir(dir); err != nil {
+		t.Fatal(err)
+	}
+
+	spec, err := readSpec()
+	if err != nil {
+		t.Fatalf("readSpec() error: %v", err)
+	}
+	if got := spec.Annotations["io.kubernetes.cri.sandbox-id"]; got != "abc123" {
+		t.Errorf("annotation sandbox-id = %q, want %q", got, "abc123")
+	}
+	if got := spec.Annotations["other"]; got != "value" {
+		t.Errorf("annotation other = %q, want %q", got, "value")
+	}
+}
+
+func TestReadSpecMissing(t *testing.T) {
+	dir := t.TempDir()
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { os.Chdir(cwd) })
+	if err := os.Chdir(dir); err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := readSpec(); !os.IsNotExist(err) {
+		t.Errorf("readSpec() error = %v, want os.IsNotExist", err)
+	}
+}
diff --git a/internal/shim/manager/manager_unix.go b/pkg/shim/manager/manager_unix.go
similarity index 100%
rename from internal/shim/manager/manager_unix.go
rename to pkg/shim/manager/manager_unix.go
diff --git a/internal/shim/manager/manager_windows.go b/pkg/shim/manager/manager_windows.go
similarity index 100%
rename from internal/shim/manager/manager_windows.go
rename to pkg/shim/manager/manager_windows.go
diff --git a/internal/shim/manager/mount_linux.go b/pkg/shim/manager/mount_linux.go
similarity index 100%
rename from internal/shim/manager/mount_linux.go
rename to pkg/shim/manager/mount_linux.go
diff --git a/internal/shim/manager/mount_other.go b/pkg/shim/manager/mount_other.go
similarity index 100%
rename from internal/shim/manager/mount_other.go
rename to pkg/shim/manager/mount_other.go