CosmoBLENDER (Cosmological Biases to LENsing and Delensing Due to Extragalactic Radiation) computes foreground-induced biases to temperature-based CMB lensing reconstructions caused by extragalactic radiation. It evaluates the impact of foregrounds on CMB lensing auto-correlations, cross-correlations of CMB lensing with galaxy samples, and internal B-mode delensing. CosmoBLENDER provides Jupyter notebooks that demonstrate bias calculations for auto-correlations, cross-correlations, and delensing while varying cosmological, astrophysical, and experimental parameters.