Learn VeriCoding (Z3): from zero to expert, then sell it

No AI background needed. Five levels, each with something to actually do, at your own pace. Tick items as you go (your ticks stay in this browser).

Evidence, proof and selling tools for VeriCoding (Z3)

Level 1 Beginner: understand it

Testing checks some inputs. A proof covers all of them. VeriCoding takes a small Python function and a written contract ("the result is never negative", "the balance never goes below zero") and asks Z3, a well-known mathematical solver from Microsoft Research, to check it. The answer is either PROVED (for every input) or a concrete counterexample: the exact input that breaks the contract.

Results are signed and re-checkable offline. It handles a small subset of Python today: whole numbers and simple logic, no loops or lists.

Think of it like this: Testing is tasting a few spoonfuls of soup. Proof is the recipe calculation that shows the salt can never exceed the limit, whatever the pot size.

Read the full plain-English explanation: VeriCoding (Z3), explained.

I read the explanation above.
I can say what it does in one sentence, without notes.

Level 2 User: see it work

Run it live: open the live demo. Before each result, guess what will happen. These are checks it must pass:

Sample: A discount that can make the price negative: Z3 proves the contract or returns a concrete counterexample.
Sample: max3 returns c instead of the true maximum: Z3 proves the contract or returns a concrete counterexample.
Sample: A clamp that returns lo + 1 for low inputs: Z3 proves the contract or returns a concrete counterexample.
Sample: An absolute value that returns x - 1 for non-negative x: Z3 proves the contract or returns a concrete counterexample.
Sample: A correct clamp (Z3 proves the contract already holds): Z3 proves the contract or returns a concrete counterexample.
Your function: division that can divide by zero: Undefined behaviour is never PROVED (the 2026-11-02 fuzzer found this case).

I ran the live demo.
I can explain what one of these checks shows.

Level 3 Verifier: prove it yourself

This is the skill that sets you apart: you don't have to believe us, and neither do your customers.

Install Python 3 if you don't have it (python.org/downloads).
Download the kit and unzip it.
Open a terminal in that folder. On Windows, click the folder's address bar, type cmd and press Enter. On a Mac, right-click the folder and choose New Terminal at Folder.
Run python3 verify.py (on Windows, python verify.py). It checks the seal without the internet.
Run python3 verify.py --live. It repeats every check from your own computer.
Try to cheat it: open transcript.json in a text editor, change one character, save, and run python3 verify.py again. It must now say FAIL. Unzip a fresh copy afterward.

I ran the kit's check on my own computer.
I changed a file and saw it fail.

Level 4 Expert: know the edges

An expert knows what a product does not do, and says it first. That is what makes a buyer trust you.

Read its limits page in full: what VeriCoding (Z3) does not do.

You can say

PROVED covers every input within the supported subset.
Failures come with a concrete counterexample.
"Could not decide" is never reported as a pass.

Never say

"Proves your software is correct": it proves one small function against the contract written.
"Works on any Python": small subset only.
"Independently reviewed": not yet.

Read the questions real buyers send, with honest answers: answers to buyer questions.

Test yourself (click a question to see the answer)

Testing vs proof?

Testing checks some inputs; proof covers all.

What if Z3 times out?

"Could not decide", never a pass.

Can it handle loops and lists?

Not yet.

In the live check "Sample: A discount that can make the price negative", what answer must come back, and why?

false. Z3 proves the contract or returns a concrete counterexample.

In the live check "Sample: max3 returns c instead of the true maximum", what answer must come back, and why?

false. Z3 proves the contract or returns a concrete counterexample.

In the live check "Sample: A clamp that returns lo + 1 for low inputs", what answer must come back, and why?

false. Z3 proves the contract or returns a concrete counterexample.

Does a passing kit prove the product is safe for every possible input?

No. It proves what the live product answered to the inputs listed in the kit, and lets anyone check that again.

Has an independent party audited or certified this product?

No. No third-party audit is complete and no certification is held. Say so if asked.

I got every quiz question right without looking.
I can name one thing it does not do.
I explained it to a friend, and they understood it.

Want a formal study path? The CAIN Academy has courses and exams. Finishing this page is your own practice; it is not a qualification or certification.

Level 5 Seller: put it in front of a customer

Copy, paste, send: the shortest route, no technical skill needed.
Who buys it and where to find them.
The sales conversation, then the offer and the close.
The rules: read these before your first message.
Selling tools with this product's evidence built in: pitch, emails, call script, objection answers, one-pager.

I read the rules.
I sent my first personal message.

About money: your share is agreed in writing with FIRME AI CORPORATION before your first message (email vincent@firmeai.com). Nothing here promises income. Most messages get no reply; that is normal.