Lesson 5 of 8 · Build AI Apps with Real APIs
In this lesson. Assemble messages, memory, and errors into a usable thread.
What you will learn
- Message lists and history caps
- What to persist between sessions
- Error copy users can act on
Walkthrough
A chat feature is a list of messages, a system prompt, and honest errors. You will design the thread, cap history, and decide what is stored. Then you will handle empty replies, moderation blocks, and timeouts with copy a person can understand. The result is a vertical slice you could demo.
Work through the ideas in order. After each point, pause and connect it to a task you already do — a document, a workflow, or a feature you own. The goal of Build AI Apps with Real APIs is usable skill, not a pile of notes.
If something is unclear, rewrite it in your own words before you continue. Teaching the step back to yourself is the fastest way to see gaps.
Practice
Write the message flow for one chat use case including the empty and timeout states.
Keep the first attempt small. A finished example you can reuse beats a perfect plan you never run.
Check your understanding
- Can you explain the goal of this lesson in one sentence to a teammate?
- Where would you apply “Message lists and history caps” in your own work this week?
- What would you change on a second pass of the practice?
Next. Continue to the following lesson when the practice has a real artifact, even a rough one.