The low densities and strong electric fields typical during tokamak startup provide exactly the right environment for runaway electrons to be produced. Runaway electrons are however undesired during tokamak startup as they reduce the Ohmic heating efficiency, which could lead to failed burn-through, a limited plasma temperature, and the generation of a large relativistic current. To study the generation of runaway electrons during tokamak startup, a self-consistent approach which accounts for the evolution of plasma and runaway current, temperature, ionization, etc. is necessary. In this contribution we present the new startup runaway code STREAM, derived from the disruption simulation tool DREAM [^1], which features a conventional 0D burn-through model such as in DYON[^2], but with a relativistic current component. In simulations using STREAM we find that runaway electrons only accumulate after closed flux surfaces have been formed, but at which point they may carry a significant, or even dominant, fraction of the plasma current, due to the strong Dreicer generation, and prevent further heating. Injecting additional deuterium shortly after successful burn-through is one possible method to prevent the build-up of a large runaway seed and thus to prevent the formation of startup runaways. Further studies using STREAM will benefit from the wealth of physics already implemented in DREAM which includes kinetic effects of the runaways, such as the formation of superthermal electrons and the collisional heating of the bulk plasma by runaway electrons. [^1]: Hoppe, Embreus and Fülöp, *Comp. Phys. Commun.* **268** 108098 (2021) [doi:10.1016/j.cpc.2021.108098](https://doi.org/10.1016/j.cpc.2021.108098). [^2]: Kim, Fundamenski, Sips and EFDA-JET Contributors, *Nucl. Fusion* **52** 103016 (2012) [doi:10.1088/0029-5515/52/10/103016](https://doi.org/10.1088/0029-5515/52/10/103016)