is a widely consumed edible mushroom and the only species currently cultivated on an industrial scale. Despite its economic importance, its trophic strategy and genomic adaptations remain elusive. Here, we presented high-quality, chromosome-level genome assemblies for two sexually compatible monokaryons (PP78 and PP85) of . Comparative genomic analysis revealed a genome size difference of 1.17 Mb (30.87 vs. 32.04 Mb), primarily attributed to transposable element (TE) expansion in strain PP85. Genome structural variations were largely driven by TEs, particularly LTR retrotransposons. DNA transposons were also involved in structural rearrangement of secondary metabolite biosynthetic gene clusters, impacting their organization and transcriptional profiles. Functional annotation identified 187 PP78-specific and 236 PP85-specific genes, with the latter enriched in TE-related and putative virulence factors. displays genomic signatures of both ECM symbiosis (reduced lignocellulose-degrading enzymes) and saprotroph (expanded glycoside hydrolase 31 and sugar transporters), supporting a facultative ECM lifestyle. The expansion of non-ribosomal peptide synthetase and polyketide synthase pathways, alongside contraction of terpenoid clusters typical of ECM fungi, further indicated its adaptation to saprotroph. These findings highlight the role of TEs in driving genome plasticity, metabolic diversity, and nuclear divergence in , providing valuable genomic resources for this species.