Part 2 was about the scaffold breaking in four different ways before it worked. This one is about the day the app actually started talking back and about three more bugs, quieter than the ones before. Postgres, and a client that shouldn’t be reborn every request Wiring up Postgres was the easy part: a table for exchanges (prompt, response, timestamp) and a DatabaseClient wrapping a SQLAlchemy connection. The first version created a new client and a new connection on every single request. It worked, but it’s the wrong shape: a real app should open one connection when it starts and reuse it, not pay connection overhead on every prompt. ...

Part 3 ended with the backend able to talk to Claude Code, but no way for a person to talk to any of it. This one covers the rest of the distance to v1: a UI, a Docker Compose stack that actually works end to end, a way to see and delete conversation history, and lastly, a test suite, built specifically so the next change doesn’t need a live browser to verify. ...