Jan

Jan is an open-source desktop client designed to run models locally. It also supports remote OpenAI-compatible providers, which lets you keep private work on-device and route everything else through CAPI.

Prerequisites

• Jan installed.
• A CAPI API key.

Add CAPI

1. Open Settings → Model Providers.
2. Choose OpenAI (or add a custom provider if your build supports it).
3. Set:

1. Add model IDs manually, for example gpt-5.6, claude-opus-5, gemini-3.1-pro.

Jan lists remote and local models in the same picker, so switching between them is a dropdown change.

Choosing where a prompt runs

A practical split:

• Local (privacy) — anything containing customer data, credentials, or internal documents.
• CAPI (capability) — long-context analysis, multimodal input, and tasks where a frontier model clearly wins.
• CAPI (cost) — high-volume simple turns where a small hosted model is cheaper than the electricity for a local one.

Because both appear in one picker, the decision stays a per-conversation choice rather than a configuration change.

Model selection

Offline fallback

Jan works without a network when pointed at local models only. If you travel or lose connectivity, the remote provider simply errors while local models keep working — no reconfiguration needed.

Assistant templates

Jan's assistants bundle a model with a system prompt. Attach a CAPI model to an assistant when you want consistent remote behaviour, and leave the default local model for ad-hoc chat.

Troubleshooting

Provider shows no models. Jan requires explicit model IDs for remote providers; it does not fetch a list.

Requests time out. Local model threads may be saturating the machine. Reduce local concurrency, or switch the conversation to a remote model.

Key rejected after working previously. The key may have been rotated. Update it in the provider settings.

Next steps

• LLM API quickstart