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

# OpenAI Provider

> OpenAI GPT-4o, GPT-5, o1, o3, and reasoning models

The OpenAI provider supports all OpenAI chat models including GPT-4o, GPT-5, o1, o3, o4, and reasoning models.

## Configuration

<ParamField path="provider" type="string" required>
  Set to `"openai"`
</ParamField>

<ParamField path="api_key" type="string" required>
  OpenAI API key. Get yours at [platform.openai.com/api-keys](https://platform.openai.com/api-keys)
</ParamField>

<ParamField path="base_url" type="string">
  Custom base URL for proxies (defaults to `https://api.openai.com/v1/chat/completions`)
</ParamField>

<ParamField path="model" type="string" required>
  Model name: `gpt-4o`, `gpt-5`, `o1`, `o3-mini`, etc.
</ParamField>

<ParamField path="temperature" type="number">
  Sampling temperature (0.0-2.0). Defaults to `0.7`. Omitted for reasoning models unless `reasoning_effort: "none"`.
</ParamField>

<ParamField path="max_tokens" type="number">
  Maximum output tokens. For reasoning models (o1, o3, gpt-5), uses `max_completion_tokens` field.
</ParamField>

<ParamField path="reasoning_effort" type="string">
  Reasoning effort for o1/o3/gpt-5 models: `"low"`, `"medium"`, `"high"`, or `"none"` to enable temperature.
</ParamField>

## Example Configuration

```json theme={null}
{
  "provider": "openai",
  "model": "gpt-4o",
  "api_key": "sk-proj-...",
  "temperature": 0.7
}
```

## Reasoning Models

For o1, o3, o4, and gpt-5 models:

```json theme={null}
{
  "provider": "openai",
  "model": "o3-mini",
  "api_key": "sk-proj-...",
  "max_tokens": 100,
  "reasoning_effort": "medium"
}
```

**Key Differences:**

* Temperature is automatically omitted (unless `reasoning_effort: "none"`)
* Uses `max_completion_tokens` instead of `max_tokens` in API request
* Supports `reasoning_effort` parameter (`low`, `medium`, `high`)

## Supported Models

* **GPT-4o**: `gpt-4o`, `gpt-4o-mini`, `gpt-4o-2024-05-13`
* **GPT-5**: `gpt-5`, `gpt-5.1`, `gpt-5.2-turbo`
* **o-series (reasoning)**: `o1`, `o1-mini`, `o1-preview`, `o3`, `o3-mini`, `o4-mini`
* **Codex**: `codex-mini`, `codex-mini-latest`
* **Legacy**: `gpt-4`, `gpt-4-turbo`, `gpt-3.5-turbo`

## Capabilities

| Feature          | Support      |
| ---------------- | ------------ |
| Streaming        | Yes          |
| Function Calling | Yes          |
| Vision (images)  | Yes (gpt-4o) |
| System Messages  | Yes          |
| Tool Calls       | Yes          |

## Authentication

The OpenAI provider uses Bearer token authentication:

```
Authorization: Bearer sk-proj-...
```

API keys are read from:

1. `api_key` field in config
2. `OPENAI_API_KEY` environment variable

## Custom Base URL

For proxies or custom endpoints:

```json theme={null}
{
  "provider": "openai",
  "model": "gpt-4o",
  "api_key": "sk-proj-...",
  "base_url": "https://proxy.example.com/v1/chat/completions"
}
```

## Code Example

From `src/providers/openai.zig`:

```zig theme={null}
pub const OpenAiProvider = struct {
    api_key: ?[]const u8,
    allocator: std.mem.Allocator,

    const BASE_URL = "https://api.openai.com/v1/chat/completions";

    pub fn init(allocator: std.mem.Allocator, api_key: ?[]const u8) OpenAiProvider {
        return .{
            .api_key = api_key,
            .allocator = allocator,
        };
    }

    pub fn provider(self: *OpenAiProvider) Provider {
        return .{
            .ptr = @ptrCast(self),
            .vtable = &vtable,
        };
    }
};
```

## Error Handling

The provider classifies common OpenAI API errors:

* `error.RateLimited` — 429 rate limit exceeded
* `error.ContextLengthExceeded` — Context window too large
* `error.InvalidApiKey` — Authentication failed
* `error.ApiError` — Generic API error
* `error.NoResponseContent` — Empty response

## Related

* [Providers Overview](/providers/overview)
* [Anthropic Provider](/providers/anthropic)
* [OpenRouter Provider](/providers/openrouter)