> For the complete documentation index, see [llms.txt](https://docs.layerlens.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.layerlens.ai/11.-admin/ecu-credits-billing.md).

# ECU credits and billing

ECU credits, consumption, and billing in Stratix Premium.

{% hint style="info" %}
**Available in Stratix Premium.** This surface is part of the logged-in workspace at [stratix.layerlens.ai](https://stratix.layerlens.ai). Stratix Public users can browse the catalog but cannot use this feature.
{% endhint %}

Stratix Premium bills compute-intensive operations against an **ECU** (Evaluation Compute Unit) balance. This page covers how it works, how to top up, and how to track consumption.

## What ECU bills

* **Model inference** — token-based, by model
* **Judge runs** — per-run, by judging model (judges are LLMs)
* **GEPA optimization** — per-iteration
* **Trace evaluation runs** — per-trace × per-judge

ECU does NOT bill:

* Browsing the catalog (Public or Premium)
* Saving spaces, creating scorers, configuring evaluations
* Tokens consumed by your own provider key (BYOK custom models bill against your provider, not ECU)

## Buying ECU

In the header, click **Buy Now** or open **Settings → Billing → Buy ECU**.

Options:

* **Free starter pack** — included with every Free account
* **One-time top-up** — pay-as-you-go in fixed increments
* **Auto-top-up** — automatic top-up when balance drops below a threshold
* **Volume / annual** — Enterprise tier; talk to sales

## Tracking consumption

**Settings → Billing → Consumption** shows:

* Current balance
* Daily / monthly consumption
* Top consumers (by user, by model, by job type)
* Forecast (when balance is expected to run out at current rate)

## Cost preview before runs

Before any compute-intensive operation, Stratix shows a worst-case ECU estimate. You approve before it runs. The actual consumption may be lower if a job short-circuits.

## Low-balance warnings

In-app and email notifications fire when balance drops below configurable thresholds. The default warns at 20% remaining and again at 5%.

## What happens at zero ECU

New compute-intensive operations are blocked until you top up. Existing runs in progress complete. Catalog browsing, saving, and other no-ECU operations continue to work.

## Where to next

* [Concept: ECU credits](/11.-admin/concepts-ecu-credits.md)
* [Pricing](/11.-admin/11-admin.md)
* [Settings](/11.-admin/settings.md)