Synthetic JWST transmission atmospheric spectra of GJ 806 b. Left panel: fiducial models with solar abundance and clear atmosphere (solid red line) or haze (solid blue line), and simulated spectral measurements after one transit observation with JWST NIRISS-SOSS, NIRSpec-G395M, and MIRI-LRS configurations. Middle panel: analogous models with metallicity enhanced by a factor of 100. Right panel: fiducial model for a secondary atmosphere made of water, and simulated spectral measurements after combining four transits for each observing mode.