diff --git a/flake.nix b/flake.nix
index 1c0f0038..4f7a6e43 100644
--- a/flake.nix
+++ b/flake.nix
@@ -18,6 +18,9 @@
         {
           default = pkgs.mkShell {
             packages = [
+              # PDK management — ciel: install/switch open PDK revisions (e.g. sky130, gf180)
+              pkgs.ciel
+
               # EDA / verification tools
               pkgs.klayout
               pkgs.magic-vlsi