Can a prompt replace Busuu Premium?

Build a writing practice log for a language you are learning, where the value accumulates in the corrections rather than in the exercises.

The loop: pick or write a prompt, write a short piece in the target language, and submit it. Run it through LanguageTool, which is open source and self-hostable, and store every suggestion as a structured record — rule id, category, the span it matched, and whether you accepted it.

The report is the point, and it is built on that accepted/rejected flag. Group your accepted corrections by rule id and show the top ten by frequency, each with three examples from your own writing. After a month this is a precise, personal list of the mistakes you actually make, which no course can give you because no course sees your output.

Add a rejected-corrections view too. Checkers are wrong often, especially about word order and register, and a rule you have rejected five times should be muted rather than argued with every time.

Keep pieces as dated Markdown files with the corrections stored beside them in SQLite, so the writing stays readable without the app.

Do not simulate a native speaker with a model in this build. An LLM will confidently rewrite idiomatic text into textbook text, and if you cannot yet tell the difference you will learn the wrong lesson. If you add a model at all, restrict it to answering "is this natural?" with a yes or no and a one-sentence reason, and label the answer as machine-generated wherever it appears.