You have an email agent that works in a test inbox. It classifies a support request, pulls the relevant context, and drafts a plausible reply. The risky next step is turning it loose on support@yourcompany.com : a new prompt can misunderstand a frustrated customer, a new model can change its format, and a harmless-looking tool change can make the agent write twice. There is a useful stage between “it passed the fixture” and “it can send customer email”: shadow mode . The candidate agent rec...