diff --git a/home-manager/progs/zen/default.nix b/home-manager/progs/zen/default.nix
index 186ab20..e1c2e5a 100644
--- a/home-manager/progs/zen/default.nix
+++ b/home-manager/progs/zen/default.nix
@@ -84,6 +84,11 @@ in
         "identity.sync.tokenserver.uri" = "https://firefox-sync.sigkill.computer/1.0/sync/1.5";
         # auto-enable extensions on install
         "extensions.autoDisableScopes" = 0;
+        # don't sync prefs/addons — we manage them declaratively via nix
+        # syncing fights with the declarative config and can cause data loss
+        # https://github.com/nix-community/home-manager/issues/6083
+        "services.sync.engine.prefs" = false;
+        "services.sync.engine.addons" = false;
       };
     };
   };