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

# tier_opt_in_required

> HTTP 400 — Model requires explicit tier opt-in.

## HTTP status

`400 invalid_request_error`

## Typical cause

The requested model is available under a premium pricing tier (e.g., Anthropic fast mode at 6x cost). To prevent accidental cost escalation, these offerings require explicit opt-in.

Note: Auriko's "priority" tier refers to Anthropic Fast Mode (2.5x speed), not Anthropic's separate Priority Tier (committed capacity SLA).

## Resolution

Set `gateway.routing.tier` to `"priority"` in your request to opt in to premium-tier routing.