How can we help?

A Windows 10 or 11 computer (64 bit), or a Mac with macOS 13 Ventura or later. The Mac version is in testing. KohAI does not run on phones or tablets.

About 420 MB of free disk space. The download is about 170 MB.

For Build and Practice: one AI coding tool, installed and signed in on the same computer: Claude Code, Codex or Gemini CLI. The Learn lessons work without any AI tool, and offline.

A free KohAI account. While KohAI is in testing, creating one needs an invite code.

Use the one you already pay for. KohAI starts that tool on your computer and never handles your login, so your usage counts against your own plan with that company.

• Claude Code (Anthropic) needs a paid Claude plan. The free Claude plan does not include Claude Code.
• Codex (OpenAI) needs a ChatGPT account. A free account can try it; most use comes with a paid plan.
• Gemini CLI (Google) works with a free Gemini API key, with a small daily limit. It needs Node.js first.

No plan yet? Gemini CLI is the cheapest way to try. If you live in the European Union or the United Kingdom, use a paid Gemini API key: on Google's free tier, Google may read and use what you send, including your code.

1. Download the installer from the download page. Only download KohAI from trykohai.com.
2. Open the file you downloaded.
3. Windows shows a blue window called Windows protected your PC. Press More info, then Run anyway. This happens once, see the next question.
4. KohAI installs in under a minute and opens by itself. It updates itself from then on.

1. Download the Mac version from the download page. Pick Apple silicon or Intel: in the Apple menu, About This Mac, a chip named Apple M means Apple silicon.
2. Open the file and drag KohAI onto Applications.
3. In Applications, right click KohAI and choose Open, then Open again.
4. If the Mac only offers Done: open System Settings, then Privacy and Security, scroll down and press Open Anyway.

Windows and macOS warn about apps that are not signed with a paid developer certificate. KohAI is in testing and not signed yet, so you see the warning the first time you open it. After that it opens normally.

The warning does not mean something is wrong with the file, but it is a good reason to download KohAI only from trykohai.com. The download page also shows the file's SHA-256 checksum if you want to check it.

1. Open a terminal. In KohAI, press Open a terminal for me: it opens one in an empty folder called kohai-setup. Or open it yourself: on Windows press the Windows key, type PowerShell and press Enter; on a Mac press Cmd and Space, type Terminal and press Enter.
2. Paste the install line for your computer and press Enter. It downloads Claude Code from Anthropic and installs it, in a minute or two. Wait until you can type in the terminal again.
3. Close the terminal and open a new one, so it finds the program you just installed. Type claude and press Enter.
4. Claude Code asks you to sign in and opens your browser. Use the Claude account with your paid plan. If it does not ask, type /login and press Enter. Once you are signed in you can close it with /exit.
5. Back in KohAI, the step ticks itself. Press Connect.

irm https://claude.ai/install.ps1 | iex

curl -fsSL https://claude.ai/install.sh | bash

Stuck? Common causes

• It says irm is not recognised: you are in Command Prompt, not PowerShell. Open PowerShell and paste the line again.
• It says claude is not recognised (or command not found): close the terminal, open a new one and type it again.
• The browser did not open: the terminal shows a web address. Copy it into your browser.
• It says your account has no access: the free Claude plan does not include Claude Code. The plans are on claude.com/pricing.
• An error about the connection or a download: check that you are online, then paste the line again.

1. Open a terminal, as described for Claude Code above, or press Open a terminal for me in KohAI.
2. Paste the install line for your computer and press Enter. It downloads Codex from OpenAI. Wait until you can type again.
3. Close the terminal, open a new one, type codex and press Enter.
4. Codex asks how to sign in. Choose Sign in with ChatGPT; your browser opens and you sign in with your ChatGPT account.
5. Back in KohAI, the step ticks itself. Press Connect.

powershell -ExecutionPolicy ByPass -c "irm https://chatgpt.com/codex/install.ps1 | iex"

curl -fsSL https://chatgpt.com/codex/install.sh | sh

Stuck? Common causes

• It says codex is not recognised (or command not found): close the terminal, open a new one and type it again.
• The browser did not open: the terminal shows a web address. Copy it into your browser.
• It says you reached a usage limit: a free ChatGPT account comes with little Codex use. The plans are on the Codex pricing page.
• It says irm is not recognised: you are in Command Prompt, not PowerShell. Open PowerShell and paste the line again.

1. Install Node.js first, a free program that many developer tools need. Open nodejs.org, download the installer (the LTS version) and run it. The default choices are fine.
2. Open a new terminal and paste the install line for your computer. npm, which came with Node.js, downloads Gemini CLI from Google. Yellow lines that start with npm warn are normal.
3. Close the terminal, open a new one, type gemini and press Enter.
4. Gemini CLI asks how to sign in. Choose Use Gemini API key. Make a key at aistudio.google.com/app/apikey: sign in with your Google account, click Create API key and copy it. Paste it into Gemini CLI and press Enter.
5. When Gemini CLI shows a box where you can type a message, it works. Type /quit to close it, then press Gemini CLI works in KohAI.

npm.cmd install -g @google/gemini-cli

npm install -g @google/gemini-cli

The key stays inside Gemini CLI. KohAI never sees it, keeps it or sends it anywhere. In the European Union or the United Kingdom, use a paid Gemini API key: on Google's free tier, Google may read and use what you send, including your code.

Stuck? Common causes

• The terminal says npm is not recognised: close it and open a new one. A terminal only knows programs that were installed before it opened.
• PowerShell says running scripts is disabled and names npm.ps1 or gemini.ps1: use the line with npm.cmd above, and start Gemini CLI with gemini.cmd.
• Sign in with Google is refused: a personal Google account no longer works in Gemini CLI since 18 June 2026. Choose Use Gemini API key.
• It says EACCES or permission denied on a Mac: npm may not write to that system folder. If you use Homebrew, brew install gemini-cli installs it too.
• It says quota exceeded or 429: the free key has a small daily limit for each model. Wait until tomorrow, or pick another model in KohAI.

KohAI checks every few seconds. Press Check now on the Connect screen. If nothing changes, close KohAI and open it again: a program installed while KohAI was open is sometimes only found after a restart.

Still nothing? Press Copy what I see on the Connect screen. It copies a short status (the tool, the step and what KohAI found, never folders, names or keys) that you can paste into a message to us.

Open a project folder, or start a new one, and tell your AI what to build. Every file it changes appears as a card with what changed, in plain language. The walkthrough on the right takes you through the important lines: you predict what a line does first, then read the explanation, and short checks follow.

You decide how much your AI may do on its own with the mode next to the message box: Ask me (it asks before every change and command), Accept edits, Let it run and Plan first. Shift and Tab in the message box moves to the next mode.

Short lessons of two to four minutes in JavaScript, Python, and HTML and CSS, plus git, the command line, security and finding bugs. Each lesson introduces one idea with an example, then asks you to use it: choose the answer, fill the gap, order the lines or find the broken line. Lessons work offline and need no AI tool.

What you get wrong comes back later in your review, because that is what you learn the most from.

Pick a task, or let your AI propose one from your own project, and write the code in the editor. Ask for a hint whenever you want one. When you hand it in, your own AI reviews it: what works, what to fix and on which line. You can hand it in as often as you like, then save it into your project.

Every lesson, check and practice task earns experience points (XP). Your player level runs from 1 to 1000 and never goes down. Your streak counts the days in a row with at least one lesson, check or task.

Your skill level is separate: it decides how deep the explanations go. The placement test sets your starting point, and you can retake it at any time without losing anything.

Every 100 XP earns a chest, and level milestones bring extra ones. A chest holds gems and now and then a rare item. Chests are only earned: they are never sold, and nothing random is ever sold for money.

You spend gems in the shop on looks for Brackets, color themes, pets, streak freezes and boosts. Gems you earn are always spent before gems you bought.

Brackets is the KohAI avatar. You can dress it in items from the shop or from chests, pick a color theme for the app and choose a pet that sits next to Brackets while you work. Looks change nothing about how KohAI works.

In Settings you choose one of four steps: Gentle, Standard, Challenging and Expert. They change how plain the explanations are, whether a hint is already open, and how hard Find the bug is. Easier steps are always open. A harder step opens once you have shown you are ready, and then stays open. By default your level picks the step.

The app, the lessons and this website come in English, Dutch, German, French, Japanese and Simplified Chinese. Change it in Settings, Language. Your AI explains in the same language. Code, file names and commands stay as they are.

Yes, a free one, to use the app. It holds your name, email and plan, never your code. KohAI is for people aged 18 and over; you confirm that when you create the account.

While KohAI is in testing, creating an account needs an invite code. Open the link from your invitation: it shows the code and lets you create your account with the code filled in. You can also type the code in the Invite code field on the account page, or in the app under Create account.

A code that is used up, expired or switched off gets a clear message. Ask the person who invited you for a new one.

We sometimes pause new accounts for a short while, for example to fix something. Sign in keeps working. Join the wait list on the account page and we will email you when you can create your account.

1. On the account page, choose Sign in, then Forgot your password?
2. Enter your email and complete the human check. If the email has an account, a link arrives within a few minutes. Look in your spam folder too.
3. Open the link within 30 minutes and choose a new password. Every device is signed out, so sign in again in the app.

Sign in on the account page and open Change password. Enter your current password and a new one of at least 10 characters. Every other device is signed out; the one you use stays signed in.

In the app: Settings, Account, Sign out. On the website: the Sign out button on the account page. Changing your password signs out every other device at once.

Gems can be bought in fixed packs in the KohAI shop, when buying is switched on. Each pack shows the exact number of gems and the full price with tax before you pay, and you confirm that you are 18 or older and agree to the terms. Payment runs through Stripe; we never see your card details.

Gems are a way to unlock things inside KohAI, not money. They cannot be exchanged for money or anything outside KohAI, except through the refund rule below.

For 14 days after you buy a pack, you can get your money back for the part of that pack you have not spent. No reason needed.

• Gems you earned by learning are always spent first.
• Of your bought gems, the oldest are spent first, so a newer pack stays unspent for as long as possible.
• You get back the unspent share of the price. Example: you bought a pack of 1,200 gems and spent 300. 900 of 1,200 are unspent, so you get three quarters of the price back and those 900 gems leave your balance.
• Gems spent on items are used. The items stay yours, and that part is not refunded.

The full text is in the refund policy. Nothing in it takes away your rights under the law where you live.

1. Sign in on the account page and go to Purchases and refunds.
2. Next to the purchase, press Refund unspent gems. KohAI shows the exact amount and the number of gems before anything happens.
3. Press Yes, refund to confirm. The money goes back to the way you paid, usually within a few days and at most within 14. You get a confirmation by email.

No button next to a purchase? The line under it says why: the 14 days have passed, or every gem of that pack is spent.

Gems arrive as soon as Stripe confirms the payment, usually within a minute. Some payment methods take longer. Check Purchases and refunds on the account page: a purchase listed there is on your account.

Charged but nothing is listed after an hour, charged twice or charged the wrong amount: you always get a refund for that. Write to us with the guided form below, with the email of your KohAI account and the date of the payment.

Not yet. KohAI is free during testing. When paid plans come, we tell you well before anything changes, prices are shown with tax, and you can cancel online in your account at any time.

No. KohAI reads your project on your own computer, to show what changed and to build the walkthrough, and never uploads it. Your code and messages go only to the AI tool you connected, exactly as when you use that tool without KohAI.

The app talks to us for your account only: your email and password once when you sign in, then only a sign in token to check your plan, and your gem purchases. No analytics, no tracking and no crash reports.

On your computer, in a folder called .kohai in your home folder: your level, lessons, gems you earned, items, settings and saved chats. Uninstalling KohAI keeps that folder, so your progress is still there if you install again. Delete the folder to remove it all. Turn off saved chats, or clear them, in Settings.

Sign in on the account page and press Download my data. You get a file with everything our server holds about your account: your account details, where you are signed in, and your purchases and refunds.

Sign in on the account page, open Delete my account and enter your password. Your name, email and password are wiped at once and every device is signed out. Records of purchases stay for 7 years because tax law requires it, without your name or email. Bought gems that were not refunded are lost.

Your progress on your computer is not touched. Delete the .kohai folder to remove it too.

Only what is needed: a sign in cookie on the account page, and your cookie choice. If we run ads, we ask before setting a marketing cookie, and a browser that sends Global Privacy Control is treated as a no. Visit counts use Cloudflare Web Analytics, which sets no cookies. Every item is listed in the cookie notice.

Every email we send to the wait list explains how to stop them. You can also write to us with the guided form below from the address you signed up with, and we remove it. Wait list entries are deleted automatically 24 months after our last email to you.

KohAI checks once a day for a new version and updates itself. To check now: Settings, Updates, Check for updates. It asks trykohai.com which version is the newest and sends nothing about you or your code. Each download is checked for its exact size and checksum before it installs.

Speaking instead of typing turns your voice into text on your computer; nothing is sent anywhere.

• Windows: open Settings, then Privacy and security, then Microphone, and turn on Microphone access and Let desktop apps access your microphone.
• Mac: open System Settings, then Privacy and Security, then Microphone, and turn KohAI on.
• Another program is using the microphone: close it and try again.
• Pick the right microphone in KohAI under Settings, Microphone, and press Test it: the bars move when it hears you.

That is on purpose. Let it run lets through changes and commands that stay inside your project folder. A command that leaves the folder, reaches the internet or looks unusual still asks you first.

Keep in mind what KohAI cannot check: a program your AI writes and runs can still do anything a program can do on your computer. Use Accept edits and Let it run only on projects you trust, and keep a backup or use git so you can undo a change.

The free Gemini API key has a small daily limit for each model. Wait until the next day, pick another model in KohAI, or use a paid key. These limits are Google's; see Google's rate limits page.

These messages come from your AI tool's maker, not from KohAI. Busy usually passes within minutes. A usage limit belongs to your plan with that company; it resets after the period your plan states. KohAI keeps your queued messages until you press Send next.

We pause signing in and downloads for a few minutes during an update. The app keeps working on your computer, including your lessons and your connected AI. Try again a little later.