Managing runtime qubit allocation for executing quantum services is disclosed. In one example, a processor device of a quantum computing system implements a quantum backoff service (QBS) that enables safe runtime qubit allocation for executing quantum services. The QBS receives a request from a quantum service scheduler for allocation of one or more qubits for an executing quantum service. Upon receiving the request for allocation, the QBS determines whether the one or more qubits are unavailable for execution. If the QBS determines that the one or more qubits are unavailable for allocation, the QBS places the executing quantum service into a sleep state. The QBS in some examples may subsequently receive an indication that the one or more qubits have become available for allocation. The QBS then restores the executing quantum service into an executing state and allocates the one or more qubits for the executing quantum service.