diff --git a/portfolio.py b/portfolio.py
index ce79538..8eeef10 100644
--- a/portfolio.py
+++ b/portfolio.py
@@ -49,7 +49,10 @@ class Portfolio:
         if not self._path.exists():
             return
         try:
-            data = json.loads(self._path.read_text())
+            content = self._path.read_text().strip()
+            if not content:
+                return
+            data = json.loads(content)
             self.positions = {pair: Position(**fields) for pair, fields in data.items()}
             log.info("Loaded %d position(s) from %s", len(self.positions), self._path)
         except Exception as exc:
diff --git a/scanner.py b/scanner.py
index 54586cd..eefb205 100644
--- a/scanner.py
+++ b/scanner.py
@@ -120,7 +120,7 @@ class Scanner:
         )
         for opp in opportunities:
             log.info(
-                "  %-12s  change=%+.2f%%  volume=$%,.0f",
+                "  %-12s  change=%+.2f%%  volume=$%.0f",
                 opp.pair, opp.change_pct, opp.volume_usd,
             )
 
diff --git a/update.sh b/update.sh
new file mode 100644
index 0000000..9af9bd3
--- /dev/null
+++ b/update.sh
@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+# Copies updated source files to /opt/crypto-trader after a git pull.
+# Usage: sudo bash update.sh
+set -euo pipefail
+
+INSTALL_DIR="/opt/crypto-trader"
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+if [ "$(id -u)" -ne 0 ]; then
+  echo "ERROR: Run with sudo: sudo bash update.sh"
+  exit 1
+fi
+
+for item in *.py *.txt systemd; do
+  [ -e "$SCRIPT_DIR/$item" ] && cp -r "$SCRIPT_DIR/$item" "$INSTALL_DIR/"
+done
+
+chown -R crypto-trader:crypto-trader "$INSTALL_DIR"
+echo "Updated. Run a test: sudo -u crypto-trader $INSTALL_DIR/venv/bin/python $INSTALL_DIR/bot.py"