diff --git a/scripts/setup/native_mariadb_port_takeover.sh b/scripts/setup/native_mariadb_port_takeover.sh
index 5496d00..6102773 100755
--- a/scripts/setup/native_mariadb_port_takeover.sh
+++ b/scripts/setup/native_mariadb_port_takeover.sh
@@ -107,6 +107,133 @@ preflight_new_port_free() {
   log "Port docelowy $NEW_NATIVE_PORT jest wolny."
 }
 
+DID_SET_MYSQL_INST_NO=0
+CONFIG_BACKUPS=()
+
+disable_custombuild_mysql_management() {
+  if [ "$NATIVE_CURRENT_MYSQL_INST" = "no" ]; then
+    log "mysql_inst jest już ustawione na 'no' - pomijam."
+    return 0
+  fi
+  "$DA_CLI_BIN" build set mysql_inst no >>"$LOG_FILE" 2>&1 \
+    || die "Nie udało się ustawić mysql_inst=no przez '$DA_CLI_BIN build set mysql_inst no'."
+  DID_SET_MYSQL_INST_NO=1
+  log "Ustawiono mysql_inst=no przez CustomBuild."
+}
+
+restore_custombuild_mysql_management() {
+  [ "$DID_SET_MYSQL_INST_NO" -eq 1 ] || return 0
+  "$DA_CLI_BIN" build set mysql_inst "$NATIVE_CURRENT_MYSQL_INST" >>"$LOG_FILE" 2>&1 \
+    || log "OSTRZEŻENIE: nie udało się przywrócić mysql_inst=$NATIVE_CURRENT_MYSQL_INST."
+  log "Przywrócono mysql_inst=$NATIVE_CURRENT_MYSQL_INST."
+}
+
+backup_config_file() {
+  local file="$1"
+  local backup
+  backup="${file}.bak.$(date +%Y%m%d%H%M%S)"
+  cp -a "$file" "$backup"
+  CONFIG_BACKUPS+=("$file:$backup")
+  log "Utworzono kopię zapasową $file jako $backup."
+}
+
+rewrite_port_in_file() {
+  local file="$1" new_port="$2"
+  local tmp changed=0
+
+  [ -r "$file" ] || return 1
+  tmp="$(mktemp)"
+
+  awk -v new_port="$new_port" '
+    BEGIN { in_section = 0; changed = 0 }
+    /^[[:space:]]*\[[^]]+\][[:space:]]*$/ {
+      section = tolower($0)
+      gsub(/^[[:space:]]*\[[[:space:]]*/, "", section)
+      gsub(/[[:space:]]*\][[:space:]]*$/, "", section)
+      in_section = (section == "mysqld" || section == "mariadb" || section == "server")
+      print
+      next
+    }
+    in_section && /^[[:space:]]*port[[:space:]]*=/ {
+      print "port=" new_port
+      changed = 1
+      next
+    }
+    { print }
+    END { if (changed) exit 0; else exit 1 }
+  ' "$file" > "$tmp"
+  local awk_status=$?
+
+  if [ "$awk_status" -eq 0 ]; then
+    cp "$tmp" "$file"
+    changed=1
+  fi
+  rm -f "$tmp"
+  [ "$changed" -eq 1 ]
+}
+
+find_and_rewrite_native_port_configs() {
+  local any_changed=0
+  local f
+
+  for f in "$NATIVE_MY_CNF" "$NATIVE_MY_CNF_D"/*.cnf; do
+    [ -f "$f" ] || continue
+    if grep -Eq '^[[:space:]]*port[[:space:]]*=[[:space:]]*3306[[:space:]]*$' "$f"; then
+      backup_config_file "$f"
+      if rewrite_port_in_file "$f" "$NEW_NATIVE_PORT"; then
+        any_changed=1
+        log "Zaktualizowano port w $f."
+      fi
+    fi
+  done
+
+  if [ "$any_changed" -eq 0 ]; then
+    backup_config_file "$NATIVE_MY_CNF"
+    if grep -Eq '^[[:space:]]*\[mysqld\][[:space:]]*$' "$NATIVE_MY_CNF"; then
+      awk -v new_port="$NEW_NATIVE_PORT" '
+        { print }
+        /^[[:space:]]*\[mysqld\][[:space:]]*$/ && !done { print "port=" new_port; done=1 }
+      ' "$NATIVE_MY_CNF" > "${NATIVE_MY_CNF}.tmp" && mv "${NATIVE_MY_CNF}.tmp" "$NATIVE_MY_CNF"
+    else
+      printf '\n[mysqld]\nport=%s\n' "$NEW_NATIVE_PORT" >> "$NATIVE_MY_CNF"
+    fi
+    log "Brak istniejącej dyrektywy port= w sekcji serwera - dodano port=$NEW_NATIVE_PORT do $NATIVE_MY_CNF."
+  fi
+}
+
+update_native_mysql_conf_port() {
+  local target_port="$1"
+  local tmp
+  tmp="$(mktemp)"
+  awk -v new_port="$target_port" '
+    BEGIN { done = 0 }
+    /^[[:space:]]*port[[:space:]]*=/ { print "port=" new_port; done=1; next }
+    { print }
+    END { if (!done) print "port=" new_port }
+  ' "$NATIVE_MYSQL_CONF" > "$tmp"
+  cp "$tmp" "$NATIVE_MYSQL_CONF"
+  rm -f "$tmp"
+}
+
+apply_config_mutations() {
+  backup_config_file "$NATIVE_MYSQL_CONF"
+  find_and_rewrite_native_port_configs
+  update_native_mysql_conf_port "$NEW_NATIVE_PORT"
+  log "Zaktualizowano $NATIVE_MYSQL_CONF na port $NEW_NATIVE_PORT."
+}
+
+rollback_config_changes() {
+  local pair file backup
+  for pair in "${CONFIG_BACKUPS[@]}"; do
+    file="${pair%%:*}"
+    backup="${pair#*:}"
+    if [ -r "$backup" ]; then
+      cp -a "$backup" "$file"
+      log "Przywrócono $file z kopii zapasowej $backup."
+    fi
+  done
+}
+
 [ -r "$COMMON_FILE" ] || die "missing helper: $COMMON_FILE"
 # shellcheck source=./mysql_common.sh
 source "$COMMON_FILE"
diff --git a/tests/native_mariadb_port_takeover_mutation_test.sh b/tests/native_mariadb_port_takeover_mutation_test.sh
new file mode 100644
index 0000000..0327c86
--- /dev/null
+++ b/tests/native_mariadb_port_takeover_mutation_test.sh
@@ -0,0 +1,100 @@
+#!/bin/bash
+set -euo pipefail
+
+PLUGIN_DIR="$(cd "$(dirname "$0")/.." && pwd)"
+SCRIPT="$PLUGIN_DIR/scripts/setup/native_mariadb_port_takeover.sh"
+TMP_DIR="$(mktemp -d)"
+trap 'rm -rf "$TMP_DIR"' EXIT
+
+fail() {
+  echo "FAIL: $*" >&2
+  exit 1
+}
+
+mkdir -p "$TMP_DIR/bin" "$TMP_DIR/my.cnf.d"
+CALL_LOG="$TMP_DIR/calls.log"
+
+cat > "$TMP_DIR/bin/da" <<EOF
+#!/bin/bash
+echo "\$*" >> "$CALL_LOG"
+exit 0
+EOF
+chmod 755 "$TMP_DIR/bin/da"
+
+cat > "$TMP_DIR/my.cnf" <<'EOF'
+[client]
+port=3306
+
+[mysqld]
+datadir=/var/lib/mysql
+port=3306
+socket=/var/lib/mysql/mysql.sock
+EOF
+
+cat > "$TMP_DIR/mysql.conf" <<'EOF'
+user=da_admin
+passwd=secret
+port=3306
+socket=/var/lib/mysql/mysql.sock
+host=
+EOF
+
+NATIVE_TAKEOVER_LOG="$TMP_DIR/takeover.log" \
+  source "$SCRIPT"
+
+NATIVE_MY_CNF="$TMP_DIR/my.cnf"
+NATIVE_MY_CNF_D="$TMP_DIR/my.cnf.d"
+NATIVE_MYSQL_CONF="$TMP_DIR/mysql.conf"
+NEW_NATIVE_PORT="3307"
+DA_CLI_BIN="$TMP_DIR/bin/da"
+NATIVE_CURRENT_MYSQL_INST="mariadb"
+
+# --- disable_custombuild_mysql_management ---
+: > "$CALL_LOG"
+disable_custombuild_mysql_management
+grep -Fxq "build set mysql_inst no" "$CALL_LOG" \
+  || fail "expected 'da build set mysql_inst no' to be called, got: $(cat "$CALL_LOG")"
+[ "$DID_SET_MYSQL_INST_NO" -eq 1 ] || fail "expected DID_SET_MYSQL_INST_NO to be set"
+
+# --- idempotency: already "no" must skip calling da ---
+: > "$CALL_LOG"
+DID_SET_MYSQL_INST_NO=0
+NATIVE_CURRENT_MYSQL_INST="no"
+disable_custombuild_mysql_management
+[ ! -s "$CALL_LOG" ] || fail "expected no 'da' call when mysql_inst is already 'no'"
+[ "$DID_SET_MYSQL_INST_NO" -eq 0 ] || fail "DID_SET_MYSQL_INST_NO should stay 0 when already 'no'"
+NATIVE_CURRENT_MYSQL_INST="mariadb"
+
+# --- apply_config_mutations ---
+CONFIG_BACKUPS=()
+apply_config_mutations
+
+grep -Fxq "port=3307" "$TMP_DIR/mysql.conf" \
+  || fail "expected mysql.conf port to be rewritten to 3307, got: $(cat "$TMP_DIR/mysql.conf")"
+grep -Fxq "passwd=secret" "$TMP_DIR/mysql.conf" \
+  || fail "expected mysql.conf passwd to be preserved untouched"
+
+grep -A2 '^\[mysqld\]' "$TMP_DIR/my.cnf" | grep -Fxq "port=3307" \
+  || fail "expected [mysqld] port in my.cnf to be rewritten to 3307"
+grep -A1 '^\[client\]' "$TMP_DIR/my.cnf" | grep -Fxq "port=3306" \
+  || fail "expected [client] port in my.cnf to be left at 3306 (only server sections rewritten)"
+
+[ "${#CONFIG_BACKUPS[@]}" -ge 2 ] \
+  || fail "expected at least 2 backup entries (my.cnf + mysql.conf), got ${#CONFIG_BACKUPS[@]}"
+
+# --- rollback_config_changes ---
+rollback_config_changes
+
+grep -A2 '^\[mysqld\]' "$TMP_DIR/my.cnf" | grep -Fxq "port=3306" \
+  || fail "expected [mysqld] port in my.cnf to be restored to 3306 after rollback"
+grep -Fxq "port=3306" "$TMP_DIR/mysql.conf" \
+  || fail "expected mysql.conf port to be restored to 3306 after rollback"
+
+# --- restore_custombuild_mysql_management ---
+: > "$CALL_LOG"
+DID_SET_MYSQL_INST_NO=1
+restore_custombuild_mysql_management
+grep -Fxq "build set mysql_inst mariadb" "$CALL_LOG" \
+  || fail "expected 'da build set mysql_inst mariadb' to be called on rollback, got: $(cat "$CALL_LOG")"
+
+echo "native_mariadb_port_takeover_mutation_test: OK"