The current version of a reference design for a liquid-metal-cooled tandem mirror fusion breeder (fusion-fission hybrid reactor) is summarized. The design update incorporates the results of several recent studies that have attempted to resolve key technical issues that were associated with an earlier reference design completed in 1982. The issues addressed relate to the following areas of design and performance: nuclear performance, magnetohydrodynamic (MHD) pressure loading, beryllium multiplier lifetime, structural efficiency and lifetime, reactor safety, corrosion/mass transfer, and fusion breeder capital cost. The updated blanket design provides increased performance and reduced technological risk in comparison with earlier fission-suppressed hybrid blanket designs. Specifically, the blanket is expected to achieve a net fissile breeding ratio (per fusion) of 0.84, with a tritium breeding ratio of 1.06, and an average blanket energy multiplication of 2.44. It would operate at a relatively low neutron wall loading (1.7 MW/m2) with a low lithium coolant outlet temperature (425° C). These features provide for a very low beryllium swelling (∼0.3% ΔV/V) over the operating cycle. Similarly, the irradiation lifetime of the ferritic steel blanket structure is expected to exceed 10 calendar-yr (180 dpa). Despite the increased blanket energy multiplication and reduced lithium coolant outlet temperature, an acceptable first-wall MHD pressure of 1.7 MPa is estimated for the reference flow conditions. The updated design provides for a mobile, pebble-shaped, beryllium/thorium fuel element that can be loaded and discharged to a dump tank without removal of the blanket. The dump tank can be passively cooled to provide attractive reactor safety features. In addition to the blanket design revisions, a plant concept, cost, and fuel cycle economics assessment has been completed. Assuming that the fusion breeder uses the same 2600-MW(fusion) fusion plant design as was developed for the 1983 Mirror Advanced Reactor Study, the total plant cost and net-electrical production are expected to be $6.3 billion and 1990 MW(electric), respectively. In comparison with the MARS fusion-electric plant estimates, these are both ∼1.7 times higher. However, the fusion breeder also would produce 6660 kg/yr of 233U fuel for consumption in fission burner reactors. Specifically, the 6660 kg/yr would be sufficient to provide makeup for ∼25 light water reactors (LWRs) operating on a denatured thorium fuel cycle. Economics studies that reflect this high level of market leverage indicate that the reference fusion breeder would be economical if the price of mined uranium were to increase to only about $200/kg ($90/lb). In summary, an updated liquid-metal-cooled blanket design for a tandem mirror fusion breeder has been completed. Several prior feasibility issues have been addressed, and the design continues to promise attractive levels of performance as an economical producer of fissile fuel for many client LWRs.