Which assistant to build with
You build a lernapps.net app together with an AI coding assistant. Any assistant works if it can use skills and change files in a folder. That is true of every common harness and model. Two setups we have used a lot ourselves.
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Claude Code with Sonnet 5.5
Our everyday setup
We build the tooling and our own apps with Claude Code on the web, and most of our evals run on it. With Sonnet 5.5 we do not worry: in our evals it passed the check in every run, on every kind of app.
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OpenCode with DeepSeek V4.1 Flash
Our lowest budget
The cheapest setup we test, through OpenCode Go. A whole app cost about 20 US cents and took 24 to 33 minutes. It still built apps that are technically sound and teach well: see the three below.
Three apps from the budget setup
DeepSeek V4.1 Flash built these in our evals, one of each kind of app. A simulated teacher answered its questions; no person changed anything. The apps are not listed on lernapps.net and no teacher has checked their content.
- Bruchrechnung A quiz: 45 questions on comparing, adding and subtracting fractions, for year 6. In German.
- Der elektrische Stromkreis Explanation pages: 5 chapters with exercises and a glossary, for year 8. In German.
- Zehnfinger-Tipptrainer An interactive app: touch typing on a German keyboard in 9 levels, for year 4. In German.
One run per kind of app is an anecdote, not a measure. The numbers of these runs are on Prompt engineering, next to Haiku 5.5's.
What counts most: you
The assistant follows the process: it asks, plans, builds and checks. What makes an app good for learners comes from you, the creator: what the learners already know, where they go wrong, which examples work in class, and your yes or no at each checkpoint.
A better model saves you time and corrections. It does not replace what you know about teaching your subject.
Start
Build an app on lernapps.net gives you the prompt to start with. How we test that assistants keep to the process: How we evaluate the guidance.