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

# Simulate, then activate a monitor

> Prove the monitor on history before it touches live traffic.

# Simulate, then activate a monitor

A monitor goes through three states: **draft → simulated → active**. You never
skip straight to active.

## Step 1 — Simulate

On the monitor page, click **Simulate**, set the window, and click **Run
simulation**. EvalGate runs the scorer against
historical traces that match the filter and shows you the would-be alert rate,
score distribution, and any samples that would have fired.

![A screenshot of the simulation results showing the would-be alert rate.](https://mintcdn.com/evalgate/c7l4ztAi8W3wgmvV/help/images/activate-monitor-simulate.png?fit=max\&auto=format\&n=c7l4ztAi8W3wgmvV\&q=85\&s=23f8d6f53c5b8d6966a62d96e1ac0625)

## Step 2 — Adjust if needed

If the simulation fires too often or never, adjust the threshold or scorer, save
a new version, and simulate again. A monitor that never fires is as useless as
one that always fires.

## Step 3 — Activate

When the simulation looks right, click **Activate v1** (the draft's version
number) and confirm with **Activate version**. The monitor now samples
live traffic, scores it, and can fire alerts.

![A screenshot of the Activate button on a simulated monitor.](https://mintcdn.com/evalgate/c7l4ztAi8W3wgmvV/help/images/activate-monitor-activate.png?fit=max\&auto=format\&n=c7l4ztAi8W3wgmvV\&q=85\&s=dfe606945127848d40829fbc7c6199d7)

## Step 4 — Pause or resume

You can click **Pause** on an active monitor at any time (for example, during
an incident) and **Resume** it later. Pausing keeps the version; it only stops sampling.

## Backfill

If you need to score older traffic under the current monitor, use **Run bounded backfill**
with a bounded time window. Backfill is explicit and bounded — it does not
silently re-score everything.

## Up next

When the monitor fires, [read the alert](https://evalgate.com/docs/help/continuous-eval/read-alert.md).


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