diff --git a/pkg/api/authentication_test.go b/pkg/api/authentication_test.go
index 3bcf0720..af32aa41 100644
--- a/pkg/api/authentication_test.go
+++ b/pkg/api/authentication_test.go
@@ -19,6 +19,61 @@ func Test_AuthnNoToken(t *testing.T) {
 	})
 }
 
+func Test_AuthnNoTokenNonV3(t *testing.T) {
+	ctx := context.Background()
+	testGRPCAndHTTP(t, ctx, func(t *testing.T, client messageclient.Client, server *Server) {
+		_, err := client.Publish(ctx, &messageV1.PublishRequest{
+			Envelopes: []*messageV1.Envelope{
+				{
+					ContentTopic: "/xmtp/0/m-0x1234/proto",
+					TimestampNs:  0,
+					Message:      []byte{},
+				},
+			},
+		})
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "authorization token is not provided")
+	})
+}
+
+func Test_AuthnNoTokenV3(t *testing.T) {
+	ctx := context.Background()
+	testGRPCAndHTTP(t, ctx, func(t *testing.T, client messageclient.Client, server *Server) {
+		_, err := client.Publish(ctx, &messageV1.PublishRequest{
+			Envelopes: []*messageV1.Envelope{
+				{
+					ContentTopic: "/xmtp/3/m-0x1234/proto",
+					TimestampNs:  0,
+					Message:      []byte{},
+				},
+			},
+		})
+		require.NoError(t, err)
+	})
+}
+
+func Test_AuthnNoTokenMixedV0V3(t *testing.T) {
+	ctx := context.Background()
+	testGRPCAndHTTP(t, ctx, func(t *testing.T, client messageclient.Client, server *Server) {
+		_, err := client.Publish(ctx, &messageV1.PublishRequest{
+			Envelopes: []*messageV1.Envelope{
+				{
+					ContentTopic: "/xmtp/0/m-0x1234/proto",
+					TimestampNs:  0,
+					Message:      []byte{},
+				},
+				{
+					ContentTopic: "/xmtp/3/m-0x1234/proto",
+					TimestampNs:  0,
+					Message:      []byte{},
+				},
+			},
+		})
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "authorization token is not provided")
+	})
+}
+
 // Private key topic queries must be let through without authn
 func Test_AuthnAllowedWithoutAuthn(t *testing.T) {
 	ctx := context.Background()
diff --git a/pkg/api/config.go b/pkg/api/config.go
index 02555534..d20ac9d0 100644
--- a/pkg/api/config.go
+++ b/pkg/api/config.go
@@ -35,6 +35,7 @@ type Config struct {
 // Options bundle command line options associated with the authn package.
 type AuthnOptions struct {
 	Enable              bool     `long:"enable" description:"require client authentication via wallet tokens"`
+	EnableV3            bool     `long:"enable-v3" description:"require client authentication for V3"`
 	Ratelimits          bool     `long:"ratelimits" description:"apply rate limits per wallet"`
 	AllowLists          bool     `long:"allowlists" description:"apply higher limits for allow listed wallets (requires authz and ratelimits)"`
 	PrivilegedAddresses []string `long:"privileged-address" description:"allow this address to publish into other user's topics"`
diff --git a/pkg/api/interceptor.go b/pkg/api/interceptor.go
index f0581ec6..5581ba4b 100644
--- a/pkg/api/interceptor.go
+++ b/pkg/api/interceptor.go
@@ -67,9 +67,23 @@ func (wa *WalletAuthorizer) Stream() grpc.StreamServerInterceptor {
 	}
 }
 
+func (wa *WalletAuthorizer) isProtocolVersion3(request *messagev1.PublishRequest) bool {
+	envelopes := request.Envelopes
+	if envelopes == nil || len(envelopes) == 0 {
+		return false
+	}
+	// If any of the envelopes are not for a v3 topic, then we treat the request as non-v3
+	for _, envelope := range envelopes {
+		if !strings.HasPrefix(envelope.ContentTopic, "/xmtp/3/") {
+			return false
+		}
+	}
+	return true
+}
+
 func (wa *WalletAuthorizer) requiresAuthorization(req interface{}) bool {
-	_, isPublish := req.(*messagev1.PublishRequest)
-	return isPublish
+	publishRequest, isPublish := req.(*messagev1.PublishRequest)
+	return isPublish && (!wa.isProtocolVersion3(publishRequest) || wa.AuthnConfig.EnableV3)
 }
 
 func (wa *WalletAuthorizer) authorize(ctx context.Context, req interface{}) error {