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

> ## Agent Instructions
> For Fireworks Nexus, start at https://docs.fireworks.ai/nexus.
> Use https://docs.fireworks.ai/nexus/quickstart for coding harnesses, custom agents, APIs, SDKs, and LLM gateways.
> Use https://docs.fireworks.ai/nexus/firerouter for how model routers work, the supported model list, composition, closed-model credentials, and pricing.
> Prefer canonical short model IDs such as firerouter/opus. In LiteLLM litellm_params.model, use the full path fireworks_ai/accounts/fireworks/routers/firerouter/opus.
> Family names such as opus track the latest evaluated family version; do not describe them as fixed model versions.

# Routing Preferences

> Adjust how strongly a firerouter request favors its primary model or lower-cost models.

Routing preference controls how strongly a `firerouter` request favors its primary model or lower-cost models. Set it per HTTP request with `x-routing-preference`, or configure it for a supported harness with FireConnect.

## Preference levels

Send an integer from **1** (strongest preference for the primary model) to **5** (strongest preference for lower-cost models):

| Value | Name | Behavior |
| - | - | - |
| `1` | `max-intelligence` | Keep the turn on the primary model |
| `2` | `more-intelligence` | Lean toward the primary, compared with balanced |
| `3` | `balanced` | Default when the header is omitted |
| `4` | `more-savings` | Lean toward lower cost, compared with balanced |
| `5` | `max-savings` | Prefer the lower-cost models in the route |

## HTTP header

The HTTP header accepts only the integers `1` to `5`. Names such as `balanced` are FireConnect CLI values, not HTTP header values.

Set the header on an API request:

```bash wrap theme={null}
curl https://api.fireworks.ai/inference/v1/chat/completions \
  -H "Authorization: Bearer $FIREWORKS_API_KEY" \
  -H "x-anthropic-api-key: $ANTHROPIC_API_KEY" \
  -H "x-routing-preference: 4" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "firerouter",
    "messages": [{"role": "user", "content": "Add a docstring to this function."}]
  }'
```

If the header is missing, invalid, or out of range, the router uses balanced behavior. It does not add a literal `x-routing-preference: 3` header.

## FireConnect

When you connect a harness to `firerouter` or a supported `firerouter/...` ID, pass `--routing-preference` with the connect command:

```bash wrap theme={null}
fireconnect claude --model firerouter --routing-preference 4
fireconnect opencode --model firerouter --routing-preference 2
fireconnect pi --model firerouter --routing-preference 5
```

Every harness can use any FireRouter ID. The table shows which IDs accept FireConnect's `--routing-preference` flag:

| Harness | IDs that accept `--routing-preference` |
| - | - |
| Claude Code | Bare `firerouter` only |
| OpenCode, Pi, VS Code | `firerouter` or any ID beginning with `firerouter/` |
| Codex, Cursor IDE, Copilot App, Copilot CLI, DeepSeek Harness | None |

FireConnect accepts values `1` to `5` or the corresponding level names. In Claude Code, `fireconnect claude --model firerouter/opus` works, but adding `--routing-preference` to that ID returns an error: `--routing-preference requires --model firerouter`.

To set a preference where FireConnect does not support it, send the `x-routing-preference` header with [manual setup](/nexus/firerouter/setup#set-up-your-harness), for example in `ANTHROPIC_CUSTOM_HEADERS` for Claude Code or `http_headers` for Codex. Cursor IDE and the Copilot App cannot send extra headers. Cursor CLI is not supported.

## When to adjust

* **High-volume workloads with many simple requests**: try `4` or `5` so summaries, formatting, and straightforward Q\&A are more likely to use a lower-cost model.
* **Tasks where quality is critical** (security review, complex reasoning, nuanced writing): try `1` or `2` so the router favors its primary model.
* **Evaluating routing**: start at `3` (balanced), then move one step at a time and compare cost and output quality.

## Related

* [FireRouter](/nexus/firerouter): `firerouter`, `firerouter/opus`, `firerouter/astra`, and `firerouter/sol`
* [APIs and SDKs](/nexus/apis-and-sdks): HTTP headers and Provider Keys
* [FireConnect](/nexus/fireconnect): enable a router in a coding harness