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AI setup · Both apps

Where to paste your API key & which model to choose

AI is an optional enhancement in both apps: everything core works without it. With a key you unlock code explanations, error analysis and multi-level structure trees for long sentences.

5 min read AI · API key · setup Keys stay on your device

First: what works without AI

  • KuaiJiZi C++ Tutor — block building, live C++ code generation, block search, local g++ compile & run, project library and automatic practice checking all work normally. AI only adds explanations and error analysis.
  • Kuaijizi 3D English Blocks — the built-in offline static engine analyses the five sentence patterns, tenses, passive voice, questions, there-be sentences and comparatives. Block building, word cards, word lists and project learning are unaffected. AI is for long or deeply nested sentences.
In other words, AI is an “extra teacher”, not an on/off switch. Get value from the offline features first and add a key when you actually hit a limit.

Step 1 — get an API key

AI analysis uses your own model-provider key. Usage is billed by the provider, not by KuaiJiZi. Recommended:

  • In China: DeepSeek platform (directly accessible, pay-as-you-go)
  • International: OpenRouter (one key, many model providers)

Step-by-step screenshots for sign-up, top-up and key creation are in the API Key Guide. Note that the key is shown only once — copy it immediately.

Step 2 — paste it into the app

KuaiJiZi C++ Tutor

  1. Open the app and go to Settings (gear icon).
  2. Find the AI knowledge section and paste your API key.
  3. Choose the provider and model (for example the DeepSeek deepseek-chat family).
  4. Save and return to the knowledge/code explanation screen. If no key is set, the app shows: “No AI API key configured — set it in ⚙ Settings → AI knowledge”.

Kuaijizi 3D English Blocks

  1. Open the app and go to Settings.
  2. Paste the API key in the AI analysis settings and pick a provider (DeepSeek or any OpenAI-compatible endpoint).
  3. In the sentence view click AI analysis to get sentence-type labels and a multi-level structure tree.
  4. For everyday sentences, prefer the offline engine: it is instant and costs nothing.

Privacy and data

  • The key is stored on your device only; it is never uploaded to KuaiJiZi servers.
  • Only when you actively run AI analysis is the sentence or code sent to the provider you configured.
  • Projects, word cards and analysis results live in your local main folder (location configurable) and can be backed up at any time.
  • With AI switched off, both apps run fully offline.

Troubleshooting

Error 401 / invalid key

Usually an incomplete paste or stray spaces. Copy the key again and re-paste, and confirm the key has not been deleted on the provider side.

Insufficient balance

Top up on the provider platform as needed; pricing and rules follow that platform. You can also keep using the offline features meanwhile.

Do I need to re-enter the key on a new PC?

Yes. Keys are stored locally, so a new machine or reinstall needs the key again; the same key keeps working.

The key leaked — now what?

Delete it on the provider platform, create a new one, and replace it in the app settings. A deleted key stops working immediately.

Are analysis results cached?

Yes. In the English tool, AI analysis results are archived per project and reopen instantly without a new request.

No key yet?

The API Key Guide walks through DeepSeek and OpenRouter registration, key creation and copying.

Get an API key Back to knowledge base