A provider is the service that runs the model. Desktop stores the provider choice separately from your workspaces and sessions, so changing projects does not require entering the same credential again.
Hosted providers
OpenRouter, OpenAI, and Anthropic require an API key. Paste the key into Desktop settings, enter the exact model ID you want to use, and save the provider. Desktop does not write the key into project files, prompts, or transcripts.
Local providers
Ollama and LM Studio expose models from your computer through a local OpenAI-compatible endpoint. Start the provider first, load the model you want, and then enter that model's exact ID in Desktop. A key is normally unnecessary.
Verify the connection
Create a short test session and ask for a one-sentence response. If Local Core is healthy but the request fails, check the provider status, endpoint, credential, and model name before restarting Desktop.