diff --git a/default.nix b/default.nix
index c625c4ac3ff0d4105ba40c096c5344bc081e5ef3..ff011207e568062417a90d54ba77171df74b3f19 100644
--- a/default.nix
+++ b/default.nix
@@ -1,6 +1,6 @@
 { kapack ? import
-    (fetchTarball "https://github.com/oar-team/nur-kapack/archive/f5aab9b631b549e68ddc4e6878f5a4cf6ba8a58d.tar.gz")
-    # commit 27/04/23 "lib: add helper function for c++ dev/ci packages"
+    (fetchTarball "https://github.com/oar-team/nur-kapack/archive/901a5b656f695f2c82d17c091a55db2318ed3f39.tar.gz")
+    # commit 02/08/23 "batsim: 4.2.0"
   {}
 , doCheck ? false
 , doCoverage ? true
@@ -12,16 +12,6 @@
 with kapack.pkgs;
 
 let self = rec {
-  batsim_latest = kapack.batsim.overrideAttrs (attr: rec{
-    name = "batsim";
-    version = "e3dbc246c5e3acd117a84909d351b94bfb6e4a59"; # commit "code: prevent temporary memleak for zmq msgs"
-    src = fetchgit rec {
-      url = "https://framagit.org/batsim/batsim.git";
-      rev = version;
-      sha256 = "sha256-+SGdNrPjRTGInrEQyFMCWcPIESD5yS+Enc1WRDCdKbQ=";
-    };
-  });
-
   batmen = kapack.batsched.overrideAttrs (attr: rec {
     name = "batmen";
     version = "refs/tags/replay_feedback2023";
@@ -35,12 +25,13 @@ let self = rec {
   swf2userSessions = pythonPackages.buildPythonPackage rec {
     pname = "swf2userSessions";
     format = "pyproject";
-    version = "612382de6965bce418a34acb1cc764c5c2b622c9"; # commit 26/05/23 "align with batmen-tools: changed validity condition for jobs"
+    version = "refs/tags/replay_feedback2023";
     buildInputs = with pythonPackages; [flit];
     propagatedBuildInputs = [ pythonPackages.networkx ];
-    src = builtins.fetchGit {
+    src = fetchgit {
       url = "https://gitlab.irit.fr/sepia-pub/mael/swf2userSessions.git";
       rev = version;
+      sha256 = "sha256-Ot+NNpBARn87nqoAOtaD7+zaa+qLvz6RTTSKx6oSP9Q=";
     };
   };
 
@@ -61,13 +52,14 @@ let self = rec {
 
   exp_env = mkShell rec {
     buildInputs = with pythonPackages; [
-      batsim_latest
+      kapack.batsim-420
       batmen
       swf2userSessions
       batmenTools
       batexpe
       kapack.evalys       # for data visualization
-      ipykernel pandas numpy matplotlib jinja2 pip
+      ipykernel jupyter   # for jupyter notebood
+      pandas numpy matplotlib jinja2 pip  # for data analysis
       
       # wget
     ];