diff --git a/.githooks/post-merge b/.githooks/post-merge
index 846b677..88bac9f 100755
--- a/.githooks/post-merge
+++ b/.githooks/post-merge
@@ -11,6 +11,13 @@ fi
 
 SYSTEMD_CHANGED=$(echo "$CHANGED" | grep -c "^system/" || true)
 SCRIPT_CHANGED=$(echo "$CHANGED" | grep -c "^scripts/" || true)
+SKETCH_CHANGED=$(echo "$CHANGED" | grep -c "^sketch/" || true)
+
+# Reflash MCU if sketch changed
+if [ "$SKETCH_CHANGED" -gt 0 ]; then
+    echo "[githook:post-merge] MCU sketch changed — reflashing..."
+    cd "$REPO" && arduino-cli compile --upload --fqbn arduino:zephyr:unoq sketch/ 2>&1
+fi
 
 # Reinstall systemd units if any changed
 if [ "$SYSTEMD_CHANGED" -gt 0 ]; then