  A core-collapse supernova occurs when exothermic fusion ceases in the core of
a massive star, typically due to exhaustion of nuclear fuel. Theory predicts
that fusion could be interrupted earlier, by merging of the star with a compact
binary companion. We report a luminous radio transient, VT J121001+495647,
found in the Very Large Array Sky Survey. The radio emission is consistent with
supernova ejecta colliding with a dense shell of material, potentially ejected
by binary interaction in the centuries prior to explosion. We associate the
supernova with an archival X-ray transient, which implies a relativistic jet
was launched during the explosion. The combination of an early relativistic jet
and late-time dense interaction is consistent with expectations for a
merger-driven explosion.
