# ECU credits and billing

{% 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)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.layerlens.ai/11.-admin/ecu-credits-billing.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.