A customer is charged twice
A slow payment gets sent again.
Fix: a unique key on every payment, so a retry can’t charge twice (an idempotency key).
35 short modules you read in your browser. Each shows how AI-built apps break with real users, and the prompt that fixes it in Claude Code, Codex or Antigravity.
Bad data gets saved
The AI changes how it answers. Your app saves it anyway.
Fix: check every answer before saving it (a validation gate).
An agent runs for hours
A step keeps failing, the agent keeps trying, and you get the bill.
A crash leaves bad data behind
One step of a job fails, and the steps after it keep going anyway.
Fix: save points that stop the run and go back to the last good state (checkpoints).
Can a second customer open the first customer’s page?
Sign up twice, in a normal window and a private one, and try to open one account’s page from the other.
Is your database locked?
See whether the lock that keeps strangers out of your data is switched on, in the tool you built with.
Is a secret key in your page?
Search your app’s page for secret keys that anyone could copy, and tell them apart from the keys that are meant to be public.
Start the free check
Fail a check and you get one prompt to paste into your AI. Free with an account.
Step 01
Understand the failure
A short story of one failure. Choose what to build and see what each option leads to.
Step 02
Write the spec
A spec is a plan for your own app that your AI builds from. The module helps you write it, then gives you the prompt to hand it to Claude Code, Codex or Antigravity.
Step 03
Pass the quiz
A short quiz. Pass it and the next module opens.
The failure
A payment step timed out and the app kept retrying. 38 customers were charged four times in 90 seconds.
Your call
A refund request times out after the charge went through. Retry straight away, or give every refund a unique key first? You choose, then see where each path ends.
The fix
A unique key on every payment, and a check on every answer before it is saved. Also known as an idempotency key and a validation gate.
Your spec
You write the rules for your own payment step, with a template and a checklist. It downloads as a text file you keep in your project.
Hand it to your AI
The module gives you the prompt and a checklist to check what your AI built.
Read docs/specs/validation-gates.md before you write any code. … Show me the test output before you say it’s done.
- Send the same request twice with the same key: one row in the database.
- Send a malformed payload: nothing is saved.
Every module has the same parts: a short quiz at the end opens the next one.Start the free check
Stop double charges and bad data.
Systems Foundations
Jobs that recover after a crash.
Graph Engineering
Catch bad data early.
Contract Engineering
Stop retries that run up your bill.
Loop Engineering
Put it all together in one app.
Integrated Systems
Keep your AI agent under control.
Agent Engineering
Protect keys, accounts and data.
Security Engineering
See all 35 modules
Systems Foundations
Graph Engineering
Contract Engineering
Loop Engineering
Integrated Systems
Agent Engineering
How to stop users from seeing other users’ data
Make sure each customer only sees their own things.
What to do when your API key leaks
Switch the key off first, then keep keys out of your code.
How to stop retries from charging customers twice
Make a payment safe to retry, so nobody pays twice.
How to protect your AI feature from prompt injection
Stop text from strangers taking control of your AI feature.
How to stop an AI agent loop from running up your bill
Give your AI agent a spending limit and a rule to stop.
How to check a package your AI suggests is safe to install
Check a package is real before your AI installs it.
Your AI coding agent
Builds what you describe, fast. It adds the safeguards you ask for, and only those.
ArcLab shows you what to ask for, and gives you the spec and the prompt to hand over.
Documentation
Explains one tool at a time.
ArcLab starts from the failure and shows the fix across your whole app.
Tutorials and videos
Walk you through someone else’s demo project.
Every ArcLab module ends with a spec for your own app.
Trial and error
You find out from your users, or from the bill.
ArcLab shows you the failure first, in a scenario you can safely get wrong.
- 35 modules in 7 tracks, each ending in a final module that puts the track together
- A ready-to-use spec in every module: a plan for your own app that your AI builds from
- The prompt for Claude Code, Codex or Antigravity, plus a checklist to check the result
- Bonus: the Build & Ship track, 9 modules on taking an AI product from idea to launch
- Lifetime access, including modules added later
- The free check: one complete module, “Is your app safe to share?”
- 10 free guides
- A workspace preview: the track maps and a short diagnostic
- Everything free, plus
- All 35 modules and the Build & Ship bonus track
- A plan for your app, a prompt and a checklist in every module
“I spent a year watching AI-built apps break in production. This is the system I needed.”
$29 one-time
Goes up to $49 after the first 100 members
14-day refund, as long as you haven’t completed more than one module.
What is ArcLab?
35 written modules you read online. Each one covers one way AI-built apps break with real users and ends with a ready-to-use spec, so your AI builds the fix in your own app.
Can’t I ask my AI to fix this?
Only for the problems you know about. Your AI builds what you ask for and leaves out what you don’t mention, like a check that stops a double charge. ArcLab shows you what to ask for, gives you the engineering term, and provides the spec.
I don’t know the engineering terms. Is that a problem?
No. ArcLab’s public pages explain every term in plain language, and the free check shows the approach on your own app before you buy. Inside, the modules use the engineering terms on purpose, because they are the terms you will give your AI, and each spec tells you exactly what to ask for.
Do I need to know how to code?
No. Your AI writes the code. You should have built at least one app with an AI tool and be comfortable reading short code examples. ArcLab is not for someone who has never built anything.
Is this a tool or something I read?
Something you read and work through. There is nothing to install. You read a module, choose what to build in a scenario, write a spec for your own app with the module’s guidance, and hand it to your AI. Each module ends with a short quiz.
What do I get for $29?
All 35 modules in 7 tracks, plus the 9-module Build & Ship bonus track. Every module ends with a spec for your own app, the prompt to hand it to your AI, and a checklist to check the result. One payment, lifetime access, including modules added later.
Does ArcLab change my code?
No. ArcLab never touches your project. It shows you what to build and gives you the spec and the prompt. Your AI does the building, and you check the result against the module’s checklist.
Which AI tools does it work with?
Claude Code, Codex and Antigravity, and any AI coding tool that can read a file in your project. ArcLab does not plug into them. Each spec is a text file: add it to your project, use the prompt provided, and check the result against the checklist.
How long does it take?
Reading a module takes about 5 to 10 minutes. The scenario, the quiz and your spec take longer, depending on your app. There are no deadlines, and access does not expire.
Can I try it before I buy?
Yes. Create a free account and run the free check, “Is your app safe to share?”: one complete module with three checks on your own app. If you buy and it is not for you, there is a 14-day refund, as long as you haven’t completed more than one module.
What if it isn’t for me?
14-day refund, as long as you haven’t completed more than one module. Email hello@arclab.systems and we refund the full price.
Are there limits I should know about?
Modules open in order: finish Systems Foundations to open the other tracks, and pass each module’s quiz to open the next. Specs are text files you download; there is no plugin. The modules use short code examples in JavaScript, TypeScript and Python.
What happens after I pay?
Your workspace opens, usually within a minute. Sign in with the same account and start with Systems Foundations, Module 01.