--- a/README	Fri Mar 24 18:37:03 2017 +0100
+++ b/README	Fri Mar 24 18:21:48 2017 +0100
@@ -125,6 +125,21 @@
   Using the extension will enable evolution, use 'experimental.evolution=!'
   to disable obsmarkers echange.  The old '__temporary__.advertiseobsolete'
   option is no longer supported.
+
+- a new prototype of obsmarker discovery is available. The prototype is still
+  at early stage and not recommended for production.
+  Examples of current limitations:
+
+  - write access to the repo is highly recommanded for all operation,
+  - large memory footprint,
+  - initial caching is slow,
+  - unusable on large repo (because of various issue pointed earlier),
+  - likely to constains various bugs.
+
+  It can be tested by setting `experimental.obshashrange=1` on both client and
+  server. It is recommanded to get in touch with the evolve maintainer if you
+  decide to test it.
+
 - the 'debugrecordpruneparents' have been moved into the 'evolve.legacy'
   separate extension. enable that extentions if you need to convert/update
   markers in an old repository.