TD Bank just bought its first technology firm, Toronto-based artificial intelligence startup Layer 6. The Canadian banking giant, also based in Toronto, invested an undisclosed amount in Layer 6 to help it "continue to transform itself" in the industry shift from mobile-first to AI-first customer experiences, said Rizwan Khalfan, TD's chief digital and payments officer. The transaction was completed Tuesday morning. Banks always say to keep up with competition -- which now includes financial startups and retailers as well as competing banks -- their best bets are to build, buy or partner with them. But buying is rare: last fall JPMorgan Chase acquired WePay, a small business-focused payments company. In the last three years, Silicon Valley Bank acquired API startup Standard Treasury, BBVA acquired digital bank Simple, Ally acquired trading platform TradeKing.