--- a/hgext3rd/topic/__init__.py	Sat Dec 09 05:05:39 2017 +0100
+++ b/hgext3rd/topic/__init__.py	Sat Dec 09 06:13:28 2017 +0100
@@ -199,6 +199,9 @@
     configitem('_internal', 'keep-topic',
                default=False,
     )
+    configitem('experimental', 'topic-mode.server',
+               default=configitem.dynamicdefault,
+    )
 
     def extsetup(ui):
         # register config that strictly belong to other code (thg, core, etc)
@@ -223,6 +226,7 @@
         return ''
     return self.extra().get(constants.extrakey, '')
 context.basectx.topic = _contexttopic
+
 def _contexttopicidx(self):
     topic = self.topic()
     if not topic:
@@ -421,7 +425,19 @@
                     origvalidator(tr2)
                 tr.validator = validator
 
-            if (repo.ui.configbool('experimental', 'topic.publish-bare-branch')
+            topicmodeserver = repo.ui.config('experimental',
+                                             'topic-mode.server', 'ignore')
+            ispush = (desc.startswith('push') or desc.startswith('serve'))
+            if (topicmodeserver != 'ignore' and ispush):
+                origvalidator = tr.validator
+
+                def validator(tr2):
+                    repo = reporef()
+                    flow.rejectuntopicedchangeset(repo, tr2)
+                    return origvalidator(tr2)
+                tr.validator = validator
+
+            elif (repo.ui.configbool('experimental', 'topic.publish-bare-branch')
                     and (desc.startswith('push')
                          or desc.startswith('serve'))
                     ):