The paper presents the results of a transmission spectrum observation of the sub-Neptune exoplanet TOI-836c using the JWST NIRSpec G395H instrument. The study aims to understand the atmospheric compositions of planets between the sizes of Earth and Neptune, which are common in the Galaxy. TOI-836c, with a radius of 2.587 Earth radii and a mass of 9.6 Earth masses, is an ideal candidate for such a study due to its position on either side of the radius valley, allowing for direct comparisons with its sibling planet, TOI-836b. The observations yield average precisions of ~24 ppm for NRS1 and ~43 ppm for NRS2 per spectral bin, but residual correlated noise is present in the data. The authors correct this noise using the JWST Engineering Database and find a featureless transmission spectrum, ruling out atmospheric metallicities <175× Solar in the absence of aerosols at ≤1 millibar. They also determine that aerosols at such low pressures are physically plausible using microphysical models. This work is part of the COMPASS program, which aims to study the atmospheres of 12 super-Earths/sub-Neptunes to better understand their evolutionary trajectories.The paper presents the results of a transmission spectrum observation of the sub-Neptune exoplanet TOI-836c using the JWST NIRSpec G395H instrument. The study aims to understand the atmospheric compositions of planets between the sizes of Earth and Neptune, which are common in the Galaxy. TOI-836c, with a radius of 2.587 Earth radii and a mass of 9.6 Earth masses, is an ideal candidate for such a study due to its position on either side of the radius valley, allowing for direct comparisons with its sibling planet, TOI-836b. The observations yield average precisions of ~24 ppm for NRS1 and ~43 ppm for NRS2 per spectral bin, but residual correlated noise is present in the data. The authors correct this noise using the JWST Engineering Database and find a featureless transmission spectrum, ruling out atmospheric metallicities <175× Solar in the absence of aerosols at ≤1 millibar. They also determine that aerosols at such low pressures are physically plausible using microphysical models. This work is part of the COMPASS program, which aims to study the atmospheres of 12 super-Earths/sub-Neptunes to better understand their evolutionary trajectories.