This study presents the first James Webb Space Telescope (JWST) transmission spectrum of LTT 9779 b, a hot-Neptune that has retained a significant H/He-dominated atmosphere. The spectrum shows muted spectral features, rejecting a perfectly flat line at >5σ. The analysis explores water and methane-dominated atmosphere scenarios for LTT 9779 b's terminator, and retrieval analyses reveal a continuum of potential combinations of metallicity and cloudiness. Comparisons to previous population synthesis works and interior structure modeling constrain LTT 9779 b's atmosphere metallicity to 20–850× solar. Within this range, retrieval analyses prefer solutions with clouds at mbar pressures, regardless of whether the atmosphere is water- or methane-dominated. Silicate clouds can readily condense in the terminator region of LTT 9779 b. Advection of these clouds onto the day-side could explain the high day-side albedo previously inferred for this planet and be part of a feedback loop aiding the survival of LTT 9779 b's atmosphere in the hot-Neptune desert. The study also finds no evidence for atmospheric escape via the He 1.083 μm metastable triplet. The results suggest that LTT 9779 b's atmosphere is likely cloudy and high-metallicity, with metallicity between 20 and 850× solar. The study concludes that the atmosphere's survival in the hot-Neptune desert may be due to a positive feedback loop involving cloud formation and atmospheric loss.This study presents the first James Webb Space Telescope (JWST) transmission spectrum of LTT 9779 b, a hot-Neptune that has retained a significant H/He-dominated atmosphere. The spectrum shows muted spectral features, rejecting a perfectly flat line at >5σ. The analysis explores water and methane-dominated atmosphere scenarios for LTT 9779 b's terminator, and retrieval analyses reveal a continuum of potential combinations of metallicity and cloudiness. Comparisons to previous population synthesis works and interior structure modeling constrain LTT 9779 b's atmosphere metallicity to 20–850× solar. Within this range, retrieval analyses prefer solutions with clouds at mbar pressures, regardless of whether the atmosphere is water- or methane-dominated. Silicate clouds can readily condense in the terminator region of LTT 9779 b. Advection of these clouds onto the day-side could explain the high day-side albedo previously inferred for this planet and be part of a feedback loop aiding the survival of LTT 9779 b's atmosphere in the hot-Neptune desert. The study also finds no evidence for atmospheric escape via the He 1.083 μm metastable triplet. The results suggest that LTT 9779 b's atmosphere is likely cloudy and high-metallicity, with metallicity between 20 and 850× solar. The study concludes that the atmosphere's survival in the hot-Neptune desert may be due to a positive feedback loop involving cloud formation and atmospheric loss.