You have an undo. Here's what undo doesn't fix¶

Verified: 2026-10-15

In developers' words: What version control does not cover: data, secrets, cost

You're here

You came in with one change that broke everything and no way back. You leave with a commit that worked, tagged so you can return to it; a plan you read before you say yes; a preview your users never see; a rule for when to reset; and your app and its database on your own drive, where no platform can take them.

It was never the prompt, the repository or the skills. It's a few things, and you can learn them. You just learned one.

What undo doesn't fix

Here is what the checks turned up along the way, in the order you met them. Each one is a problem of its own, and each has its own row on the map.

Level 2: your last three changes touched files you didn't ask for. Know what you built.
Level 3: your preview writes to the same database your users are in. The hard three, and Find it before your users do.
Level 4: the retries are the most expensive thing on your bill. Stop the credit burn.
Level 5: the export didn't carry everything. The second way out.

The next wall

Pick the one you found. Whatever it is, it is one move, and it is learned the same way this one was: on your own app, in an hour, once. Nothing you found is a reason to start over, and none of it needs a developer.

The map is at jmlr.dev/stuck. Your row is on it.

THE FRAME
Developers say	In the game	Plain
`the developer`	the player	YouYou give the orders and check the work. The controller never changes hands.
`the agent, the assistant`	the character you give orders to	Your AI tool: Lovable, Bolt, Cursor, Claude CodeFast and tireless, and it guesses what you meant. When it guesses wrong, level 4 is the way out.
`the project`	your world	Your app: the folder of files you are buildingNot the chat and not the editor. It can be saved, copied and moved, and every move in this course keeps it safe.
`the platform defaults, rollback`	autosave	The platform’s own undoIt saves when it wants, in one slot with no name, and writes over it. Fine until the day it isn’t.
`process, developers’ habits`	the strategy guide	The five habits in this courseWhat developers do so that losing work stops happening. One per level.

LEVEL 1 · A SAVE POINT
Developers say	In the game	Plain
`a repository, on GitHub`	your save files	A copy of your app on GitHub, under your own accountIt lives outside the platform, so nothing the platform does can write over it. Every commit goes here.
`a commit`	a save	A snapshot of your app: every file as it is at one moment, with a date and a messageThe tool gives each commit a short id like a1b2c3d. Level 2 keeps each one to a single change.
`a tag`	the save’s name	A name you put on a commit, like v1-worksMany commits say “working”. The tag is the one you ask for by name, and still recognise in three weeks.
`“go back to v1-works”`	load	Go back to a commit, by its tag“Go back to v1-works” puts every file back as it was then. It brings back the app, never the data.
`rollback`	autosave	The platform’s undo buttonIts autosave: one slot, no name, written over. Not a commit, and not yours.

LEVEL 2 · READ THE CHANGE
Developers say	In the game	Plain
`the plan`	the placement ghost	The list of files a change will touch, before anything changesAsk for it, read it, then say go. A file you never asked about is the one to ask “why?” about.
`small commits`	one block per save	One change per commitThen “which change broke it” has one answer, and one commit to take out.
`a diff, in plain words`		What changed since a commit, file by fileAsk for it in plain words, with the commit each file came in with. The file name tells you where to look.
`Login.tsx, SignUp.tsx`	a file in the world folder	One page or part of your app, as a fileUsually named after what it does: Login.tsx is the login. A file name on a plan or a diff is the clue.

LEVEL 3 · TRY IT ON A COPY
Developers say	In the game	Plain
`your users`	the guests	The people who use your appThey use what you built, get stuck, and leave if it is broken. Everything you try, you try in front of them, unless there is a preview.
`publishing, going live, deploying`	opening the gates	Sending a change to the live copyOnce it is published, your users see it. The preview comes first.
`a preview, a staging environment`	practice mode, the gates closed	A second copy of your app at its own address, where nothing countsBuilt from its own line of commits, with its own test database. Every change goes here before it is published.
`production`	the gates open	The live copy of your app, the one your users are inWhatever is published here is real. Nothing here is a test.
`an environment variable`	the copy’s world settings	A setting that says which database, email service or payment provider a copy of the app usesOne line like DATABASE_URL, set per copy. It decides where a form’s data went; the green tick does not.
`the database`	the guest book	Where your app keeps what your users typedTables of rows on the platform’s servers. A commit never holds it, so going back to v1-works never touches it.

LEVEL 4 · STOP AFTER TWO TRIES
Developers say	In the game	Plain
`an attempt`	one death	One fix: your order, and everything the AI changed in answerTwo that fail is the limit. The third is a fix of the fix.
`the error message, the stack trace`	the death message	The line the tool printed when it brokeThe closest thing you have to the cause. Read it before you try again.
`reset to the save point`	load the save	Go back to v1-works after two failed attemptsThe attempts were never committed, so they go. The original problem is still there, on its own, without the two new ones.
`/clear, a new chat`	a fresh run	A new chat that has not seen the two failed attemptsIt remembers nothing, so tell it: the commit you are at, the error message, the two attempts, and “don’t repeat those”.
`the loop`	the death loop	Try, try again, worse each timeEach attempt is built on the last broken one. The way out: stop, reset, new conversation.
`a bug report`	a guest’s complaint	A user’s “it broke”, in their wordsAn error message you did not see yourself. Read it the same way, then the same three moves.