diff --git a/scripts/prepare-test-ledger.sh b/scripts/prepare-test-ledger.sh
new file mode 100755
index 00000000000..839b19a8ab2
--- /dev/null
+++ b/scripts/prepare-test-ledger.sh
@@ -0,0 +1,86 @@
+#!/usr/bin/env bash
+
+# Usage: ./scripts/prepare-test-ledger.sh <BP key 1> <BP key 2> ... <BP key n>
+
+# Number of keys in ledger that won't be re-delegated
+NUM_GHOST_KEYS=${NUM_GHOST_KEYS:-0}
+KEY_BALANCE=100000
+
+echo "Script assumes mainnet's start was at epoch 0 on 17th March 2021, if it's not the case, update the script please" >&2
+
+if [[ $# -eq 0 ]]; then
+  echo "Usage: ./scripts/prepare-test-ledger.sh <BP key 1> <BP key 2> ... <BP key n>" >&2
+  exit 1
+fi
+
+num_keys=$#
+num_keys_and_ghost=$((num_keys + NUM_GHOST_KEYS))
+
+now=$(date +%s)
+mainnet_start=$(date --date='2021-03-17 00:00:00' -u +%s)
+epoch_now=$(( (now-mainnet_start)/7140/180 ))
+
+ledger_file="$epoch_now.json"
+
+echo "Current epoch: $epoch_now" >&2
+
+if [[ ! -f "$ledger_file" ]]; then
+  ledgers_url="https://storage.googleapis.com/storage/v1/b/mina-staking-ledgers/o?maxResults=1&prefix=staking-$epoch_now"
+  ledger_url=$(curl "$ledgers_url" | jq -r .items[0].mediaLink)
+
+  wget -O $ledger_file "$ledger_url"
+fi
+
+keys_=""
+for key in "$@"; do
+  keys_="\"$key\",$keys_"
+done
+keys_="${keys_:0:-1}"
+
+# jq filter to exclude block PKs from the ledger
+pre_filter="[.[] | select(.pk | IN($keys_) | not)]"
+
+##########################################################
+# Calculate and print approximate new balances
+##########################################################
+
+num_accounts=$(<$ledger_file jq "$pre_filter | length")
+total_balance=$(<$ledger_file jq "$pre_filter | [.[].balance | tonumber] | add | round")
+new_total_balance=$((total_balance+num_keys*KEY_BALANCE))
+echo "Total accounts: $num_accounts, balance: $total_balance, new balance: $new_total_balance" >&2
+
+function make_balance_expr(){
+  i=$1
+  key=$2
+  echo "$key: (((([.[range($i; $num_accounts; $num_keys_and_ghost)].balance | tonumber] | add) + $KEY_BALANCE)/$new_total_balance*10000|round/100 | tostring) + \"%\")"
+}
+
+balance_expr=$({ i=0; while [[ $i -lt $num_keys ]]; do
+  j=$((i+1))
+  make_balance_expr $i "${!j}"
+  i=$j
+done } | tr "\n" "," | head -c -1)
+
+echo "Balance map:" >&2
+jq <$ledger_file "$pre_filter | {$balance_expr}" 1>&2
+
+##########################################################
+# Build new ledger
+##########################################################
+
+function make_expr(){
+  i=$1
+  key=$2
+
+  # Substitute delegate of some ledger keys with the BP key
+  echo ".[range($i; $num_accounts; $num_keys_and_ghost)].delegate = \"$key\""
+  echo ".[$((i+num_accounts))] = {pk:\"$key\", balance:\"$KEY_BALANCE\"}"
+}
+
+expr=$({ i=0; while [[ $i -lt $num_keys ]]; do
+  j=$((i+1))
+  make_expr $i "${!j}"
+  i=$j
+done } | tr "\n" "|" | head -c -1)
+
+jq <$ledger_file "$pre_filter | $expr"
diff --git a/src/mina_stdlib.opam b/src/mina_stdlib.opam
new file mode 100644
index 00000000000..e69de29bb2d