NIRISS 1D slitless spectrum of HCM 6A. The spectrum combines extractions from the NIRISS GR150C and GR150R grisms crossed with the F090WN, F115WN, F150WN, and F200WN filters. The spectrum shows a clear detection of the Lyα emission line at λ_obs ≈ 9200 Å, consistent with z ≈ 6.6 (solid vertical line). Dashed vertical lines indicate the expected positions of selected undetected emission lines.