BioSimBench evaluates how well language models predict changes in gene expression after drugs, gene knockdowns, and immune signals, scoring predictions against measured laboratory responses. Its five tracks cover held-out drugs and cell contexts, gene knockdowns, drug-response conditions, immune signals, and tool-using research agents. CellType reports prediction-track results separately from the research-agent track and describes its scoring and evaluation setup on the benchmark page. The benchmark is paired with BioSimGym, CellType’s training environments for biological prediction tasks.