diff --git a/pkg/agent/plugin_test.go b/pkg/agent/plugin_test.go
index 7bbcd3624..c02cf6eaa 100644
--- a/pkg/agent/plugin_test.go
+++ b/pkg/agent/plugin_test.go
@@ -17,6 +17,10 @@ func (p blockingPlugin) Name() string {
 	return "block-outbound"
 }
 
+func (p blockingPlugin) APIVersion() string {
+	return plugin.APIVersion
+}
+
 func (p blockingPlugin) Register(r *hooks.HookRegistry) error {
 	r.OnMessageSending("block-all", 0, func(_ context.Context, e *hooks.MessageSendingEvent) error {
 		e.Cancel = true
diff --git a/pkg/plugin/demoplugin/policy_demo.go b/pkg/plugin/demoplugin/policy_demo.go
index c0b10b932..1b0f56572 100644
--- a/pkg/plugin/demoplugin/policy_demo.go
+++ b/pkg/plugin/demoplugin/policy_demo.go
@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"github.com/sipeed/picoclaw/pkg/hooks"
+	"github.com/sipeed/picoclaw/pkg/plugin"
 )
 
 // PolicyDemoConfig controls the demo plugin behavior.
@@ -108,6 +109,10 @@ func (p *PolicyDemoPlugin) Name() string {
 	return "policy-demo"
 }
 
+func (p *PolicyDemoPlugin) APIVersion() string {
+	return plugin.APIVersion
+}
+
 func (p *PolicyDemoPlugin) Snapshot() PolicyDemoStats {
 	p.mu.Lock()
 	defer p.mu.Unlock()
diff --git a/pkg/plugin/manager.go b/pkg/plugin/manager.go
index 03be959c9..bf671bb20 100644
--- a/pkg/plugin/manager.go
+++ b/pkg/plugin/manager.go
@@ -22,6 +22,7 @@ const APIVersion = "v1alpha1"
 // Plugin is the Phase-1 compile-time contract for PicoClaw extensions.
 type Plugin interface {
 	Name() string
+	APIVersion() string
 	Register(*hooks.HookRegistry) error
 }
 
@@ -62,6 +63,17 @@ func (m *Manager) Register(p Plugin) error {
 	if name == "" {
 		return errors.New("plugin name is required")
 	}
+	if got := strings.TrimSpace(p.APIVersion()); got != APIVersion {
+		if got == "" {
+			got = "<empty>"
+		}
+		return fmt.Errorf(
+			"plugin %q api version mismatch: got %s, want %s",
+			name,
+			got,
+			APIVersion,
+		)
+	}
 
 	m.mu.Lock()
 	defer m.mu.Unlock()
@@ -85,4 +97,3 @@ func (m *Manager) RegisterAll(plugins ...Plugin) error {
 	}
 	return nil
 }
-
diff --git a/pkg/plugin/manager_test.go b/pkg/plugin/manager_test.go
index 8684dbc3a..8b8e431e7 100644
--- a/pkg/plugin/manager_test.go
+++ b/pkg/plugin/manager_test.go
@@ -10,6 +10,7 @@ import (
 
 type testPlugin struct {
 	name       string
+	apiVersion string
 	registerFn func(*hooks.HookRegistry) error
 }
 
@@ -24,6 +25,13 @@ func (p testPlugin) Register(r *hooks.HookRegistry) error {
 	return nil
 }
 
+func (p testPlugin) APIVersion() string {
+	if p.apiVersion == "" {
+		return APIVersion
+	}
+	return p.apiVersion
+}
+
 func TestNewManager(t *testing.T) {
 	m := NewManager()
 	if m == nil {
@@ -110,3 +118,14 @@ func TestRegisterPropagatesPluginError(t *testing.T) {
 	}
 }
 
+func TestRegisterRejectsPluginVersionMismatch(t *testing.T) {
+	m := NewManager()
+	p := testPlugin{
+		name:       "old-plugin",
+		apiVersion: "v0",
+	}
+	err := m.Register(p)
+	if err == nil {
+		t.Fatal("expected version mismatch error")
+	}
+}