Designing & building the thread project

This is where you stop practicing and start shipping. Across nine lessons you build one real product — a small social app where people sign in, keep a profile, write posts, follow each other, read a feed, comment, and like. The first lesson writes down what you're building; the eight after it build it, one feature at a time. Each feature ends with something you can see in a browser and a saved version you can go back to.

Your coding agent writes every line of code and installs anything the project needs. You decide what gets built, look at the running app, try the things that should be refused, and say when to save. Every ask in this module is written once and works in either app you might have picked in Module 0.

What this module builds

By the end you have a live social app at a public address. Someone signs in with an email address and a password, sets a name and a bio and a photo, writes posts, follows other people, reads one feed of the newest posts from the people they follow plus their own, opens a post and comments on it, and likes it.

Done looks like this: you open the live link in two different browsers, sign in as two different people, and watch the two accounts behave correctly toward each other — one follows the other and shows up in the right list, each feed carries the right posts, each person can edit only their own words, and a signed-out visitor can read the public parts without being able to change anything.

• Lesson 0 — The plan: write down with your agent what your app is, who it's for, and the eight features in build order, and give it the house rules it follows for the rest of the module.
• Lesson 1 — Put your app online: an empty app at a public address, checked from your phone.
• Lesson 2 — Sign in: an email address and a password; stays signed in across a reload; sign out.
• Lesson 3 — The profile page: name, bio, photo — anyone can look, only the owner can change.
• Lesson 4 — Writing posts: write, edit, and delete your own posts, with an optional picture; signed-out visitors can read them.
• Lesson 5 — Follow and followers: follow, unfollow, two lists — and following someone never makes them follow you back.
• Lesson 6 — The feed: the newest posts from the people you follow plus your own.
• Lesson 7 — Comments: a page for every post; signed-in people comment; only a comment's author can edit or delete it.
• Lesson 8 — Likes, then live: a like count that moves the instant you click, then the whole app checked at its public address with two accounts in two browsers.

How this module works

Your agent owns the code — how the data is shaped, the rules about who may see and change what, which files to touch, every error, and every tool that has to be installed. None of that is taught here, and you are never asked to write, read, or repair it.

You own four things:

1. Saying what you want. "Signed-out visitors should be able to read the posts on my profile but not write one." What, not how. Every ask starts from the plan you write in Lesson 0.
2. Looking at the running app. Open it, click things, sign out and look again, sign in as a second person in a second browser. Almost everything that goes wrong is visible from the outside. The running app is the copy your agent starts on your own computer — when nothing is open, say "Start the app on my computer and open it in my browser." The live link is the other copy, rebuilt from each save that goes up. Both copies use the same database.
3. Running each lesson's checks. Short lists of things to try in the running app, and one question to ask before anything you can't take back. The two shapes are below.
4. Saying when to save. The moment a feature works: "Save this as a working version." Then ask for all three parts of the answer — saved on this computer, the copy went up, and the live copy rebuilt successfully — because each can fail while the others hold. The saved version on this computer is your way back the moment your agent confirms it. When your agent has been heading the wrong way for several turns, start a fresh conversation with the same folder selected and restart the chunk from that saved version.

Nothing needs installing by you. Assume this computer has none of the tools a web app needs. One of the house rules you give your agent in Lesson 0 is that whenever a step needs a tool that isn't here, it installs it, tells you what it's for, asks you only for the approvals only you can give, and checks it works before going on. If an install fails, it stops and tells you what it tried and what you can do next. You never type a command.

What your checks look like

Two moves, and neither asks you to look at anything your agent wrote.

Try the thing that should be refused. In the running app, do what should NOT be allowed and confirm the app stops you. From Lesson 2 onward every chunk has at least one.

TRY THIS: open a private browser window that has never signed in, read what should be public, then try to change something.

EXPECT: reading works, and every way of changing anything is missing, switched off, or bounces you to the sign-in page.

IF IT WORKS: hand it back in one sentence — "While signed out I could delete a post. A signed-out visitor should only be able to read. Fix that."

Ask before anything you can't take back. Ahead of anything you paste into a dashboard, and ahead of anything that changes information already in your project:

BEFORE YOU PASTE: "Does this remove or overwrite anything that is already in my database? List exactly what changes for data that exists today."

THEN: if the dashboard's own warning matches the answer you got, continue. If the warning names something the answer didn't predict — or you never asked — press nothing, and hand the warning's words back to your agent.

And one thing your agent does. Every ask in this module ends with the short list of checks your agent must run and show you before it may say "done". If "done" arrives without that report, say "Run the checks we agreed on and show me the results first." If it says it could not run one of the checks, that check is yours to run or ask about — never to count as passed.

Before you start

You need Module 0's build (Lesson 6), Module 2 Lesson 3, and Module 3 finished. Module 1 is the shape of a web product — read it if you like, or read each lesson the first time a chunk points at it.