diff --git a/update_cached_hashes.sh b/update_cached_hashes.sh
new file mode 100755
index 0000000..f468c5d
--- /dev/null
+++ b/update_cached_hashes.sh
@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+
+# this guy updates the hash of the last
+# successful build of nixpkgs on hydra
+# (so we don't have to rebuild EVERYTHING)
+RELEASE=24.11
+
+new=$(curl -sL "https://monitoring.nixos.org/prometheus/api/v1/query?query=channel_revision" | jq -r ".data.result[] | select(.metric.channel==\"nixos-${RELEASE}\") | .metric.revision")
+old=$(jq -r ".nodes.nixpkgs.locked.rev" flake.lock)
+
+echo "Old hash: ${old}"
+echo "New hash: ${new}"
+
+sed -i s/"${old}"/"${new}"/ flake.nix