# Fast Mode

Fast mode requests a higher-priority capacity tier upstream, which means shorter queuing and faster responses. You can force it on directly at the API key level, with no client-side changes.

For clients without a built-in Fast toggle (such as Codex Desktop), setting the key policy to force Fast on applies automatically.

::: warning Costs are subject to model display
Fast mode uses the upstream priority pricing tier. Specific charges are subject to the current display on the [Models](https://tryflux.net/models) page; you can also query `fast_*` pricing for each model via the public API [https://tryflux.net/api/v1/marketplace/models](https://tryflux.net/api/v1/marketplace/models). Make sure it aligns with your business expectations before enabling it.
:::

## How to Set It

1. Open the [API keys page](https://tryflux.net/keys).
2. Create a new key, or click `Edit` on an existing one.
3. Find `Fast mode policy` and pick an option.
4. Save.

<div style="text-align: center;">
  <img src="https://docs.tryflux.net/images/fast-mode/policy-select.png" alt="Fast mode policy dropdown in the Flux key form, with follow request, force Fast on, and force Fast off options" />
</div>

## Policy Options

| Option                     | Behavior                                                             |
| -------------------------- | -------------------------------------------------------------------- |
| `Follow request` (default) | Passes through whatever the client sent, adding and removing nothing |
| `Force Fast on`            | Sends requests as Fast whether or not the client asked for it        |
| `Force Fast off`           | Strips any Fast flag the client included                             |

`Force Fast off` removes only the Fast flag. It leaves other priority settings such as `flex`, `auto`, `default`, and `scale` untouched.

## Scope

The setting applies to all requests made with this key, including regular chat completions, Responses, and Anthropic format.

Changes take effect **immediately**. Even on long-lived WebSocket connections, the new policy is picked up on the next turn - no reconnect or client restart needed.

## When Force On Does Not Apply

`Force Fast on` has prerequisites. When they are not met it is **silently skipped**: no error, and the request goes out in regular mode.

- The key is not currently routed to an OpenAI or Anthropic account
- The Anthropic account uses Bedrock, Vertex, or OAuth credentials (only API key credentials are supported)
- The current model does not support the priority tier
- A platform administrator has configured a global Fast filter or block policy (platform policy takes precedence over per-key settings and cannot be bypassed)

## Related Links

- [Create API Key](https://docs.tryflux.net/en/docs/flux/create-apikey.md) - how keys are created
- [Codex Guide](https://docs.tryflux.net/en/docs/agents/codex.md) - Codex integration setup
- [Billing](https://docs.tryflux.net/en/docs/flux/billing.md) - billing unit and group multipliers