An AI coding agent can scaffold a signup flow in about ninety seconds. Route, form, validation, a call to Resend, a token in the database. Then it stops.
It stops because the next step is open the inbox and click the link, and the agent has no inbox. So it does one of three things: mocks the email provider and declares victory, writes a test that asserts sendEmail was called, or asks you to check your Gmail and paste the code back. All three break the loop. The agent can no longer verify its own work.
This is a tooling gap, not a model limitation. The agent can drive a browser and read a database. It just can't receive mail.
The shape of the fix
Give the agent three capabilities and the loop closes:
