  GeV-scale dark matter is an increasingly attractive target for direct
detection, indirect detection, and collider searches. Its annihilation into
hadronic final states produces a challenging zoo of light hadronic resonances.
We update Herwig7 to study the photon and positron spectra from annihilation
through a vector mediator. It covers dark matter masses between 250 MeV and 5
GeV and includes an error estimate.
