Tautomers are different ways to depict the same substance, and their existence in chemistry causes all sorts of wrinkles for us. The Phoenix project is introducing a lot of exciting new ideas to CAS content, some of which you can learn about in other Tech Day talks this year. One of their new ideas about tautomers had some unforeseen consequences for products and our user experience! I'll talk about about how something as seemingly tiny as a change to tautomers can result in changes all the way across CAS from content to product, and I'll talk about what we're trying to do to reap all the benefits and mitigate the downsides.