Our study establishes a novel T7 exonuclease‐mediated strand‐conversion strategy combined with CRISPR/Cas14a for the specific detection of the breast cancer‐associated ctDNA PIK3CA H1047R mutation.[26, 32, 50, 51] Unlike conventional approaches, our system utilizes the 5′→3′ double‐stranded DNA (dsDNA) digestion specificity of T7 exonuclease. Here, PIK3CA is linked to breast carcinoma.