works have proposed a variety of different estimation methods for proximal causal inference [Kallus et al., 2021, Ghassami et al., 2021b, Deaner, 2021, Singh, 2020, Miao and Tchetgen, 2018, Mastouri et al., 2021, Cui et al., 2020. The proximal causal inference framework has been also extended to longitudinal **data** analysis [Imbens et al., 2021, Ying et al., 2021, Shi et al., 2021, mediation analysis [Dukes et al., 2021, Ghassami et al., 2021a, and off-policy evaluation and learning [Bennett and Kallus, 2021, Tennenholtz et al., 2020, Qi et al., 2021, Xu et al., 2021.