> ## Documentation Index
> Fetch the complete documentation index at: https://docs.docwriter.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Connect a provider

> Choose a provider, authenticate it, and select a model.

DocWriter supports Claude, OpenAI, Codex, Cursor, and Pi. The provider and model controls are in the page header.

## Choose a provider

Click the provider pill in the header and choose one provider. Click the model pill beside it to search the available models or add a custom model identifier.

Changing providers starts a fresh provider conversation. Your workspace files, rules, references, hooks, and comments remain in place.

When you switch to an earlier session through **Settings**, then **Sessions**, DocWriter restores the saved provider and model when the provider session is still valid. Read [Sessions and history](/agent/sessions-and-history) when an old provider session cannot resume.

## Add credentials

Open **Settings**, then **API keys**. The panel shows whether each provider is using a saved key, an existing login, or no credential.

Saved keys live in `~/.docwriter/keys.env`. A process environment variable or project `.env` value takes precedence over that file.

### Claude

Use an Anthropic key or an existing Claude login:

```sh theme={null}
export ANTHROPIC_API_KEY=sk-ant-...
# or
claude login
```

### OpenAI and Codex

OpenAI uses `OPENAI_API_KEY`. Codex can use an existing Codex login. Choose a model that is available to the account.

### Cursor

Cursor uses the signed in Cursor environment. Session recovery differs from provider to provider, so start a new session when a saved provider session can no longer resume.

### Pi

Pi can use provider keys such as `TOGETHER_API_KEY`, `GEMINI_API_KEY`, `OPENAI_API_KEY`, or `ANTHROPIC_API_KEY`, depending on the selected model.

## Tools and skills

Claude uses the Agent SDK tool set. Other providers use DocWriter's normalized tool handlers. Skills can use a provider's native skill support or be included in the provider prompt. Read [Providers and tools](/contribute/providers-and-tools) for implementation details.

## Test the connection

Open a small text file, click **Chat** in the agent dock, and send:

```text theme={null}
Read the open file and summarize the main point. Do not edit the file.
```

If the request fails, open [Provider errors](/help/provider-errors).