Nucleotide-binding, leucine-rich repeat (NLR) receptors are widespread intracellular immune sensors across kingdoms. Plant G10-type coiled-coil (CCG10)-NLRs constitute a distinct phylogenetic clade that remains poorly characterized. Here, we identified a gain-of-function mutant of wheat autoimmunity 3 (WAI3GOF), which encodes a constitutively active CCG10-NLR resulting from a residue substitution in the leucine-rich repeat (LRR) domain. Cryo-electron microscopy (cryo-EM) analysis reveals that activated WAI3 assembles into a distinctive octameric resistosome. Arabidopsis RPS2, another CCG10-NLR, also forms an octamer, indicating a conserved structural property across monocot and dicot plants. The WAI3 resistosome induces a prolonged and sustained increase in cytosolic calcium, likely facilitated by a unique channel architecture arising from its divergent coiled-coil (CC) domain configuration. Notably, this domain arrangement may be shared by plant NLRs that lack the conserved EDVID (Glu-Asp-Val-Ile-Asp) motif in their CC domains. Together, our findings uncover a conserved yet previously uncharacterized NLR resistosome structure and provide insights into the plant immune receptor plasticity.