The short answer
Your account, chats, projects, and uploaded files are stored in Germany, in Hetzner Online GmbH data centers in Nuremberg and Falkenstein. Backups also stay in Germany. CALC is not tied to a single language model. Its modular multi-model architecture uses different models depending on the task. For this, CALC works with contracted AI providers. In the chat, CALC currently mainly uses Google Gemini. If Gemini is unavailable, CALC switches to the fallback providers OpenAI or Anthropic. CALC also uses TypeSafe to classify requests (as of October 2026). Each request is handled by one provider. The models do not communicate with each other. We send the provider only the content needed for an answer. When choosing providers, we consider where data is processed, how long it is kept, contractual safeguards, and training terms. Which providers we use may change depending on the current situation. AI processing may also take place outside Europe, in particular in the United States.