Operability of an autothermal fixed-bed catalytic reactor within a Heat-Exchanger Network (HEN) is investigated. A retrofit HEN is designed by considering the critical temperature deviations that cause run-away behavior for the reactor. The flexible retrofit design is of minimum cost (area) and keeps both the hot-spot temperature (maximum temperature rise) in the reactor within a strict safety margin and the overall conversion within a strict feasibility margin against a set of possible disturbance directions. The flexible retrofit HEN enables creation of favorable disturbance-propagation paths via optimal manipulation of bypass-stream flow rates, and thus, increases the operability and controllability of the autothermal reactor within the HEN.