# Schema Drift Detection Alert

## Description

The Schema Drift Detection alert fires when data flowing through a monitored pipeline edge deviates from the learned schema, specifically when a record introduces a new field that was not present during learning, or when a field carries a type that was not previously observed.

This alert is **system-managed**: Monad creates and associates a Schema Drift Detection alert rule automatically for your organization. You do not need to create or configure it manually.

See the [Schema Detection guide](/docs/guides/schema-detection) for how to enable schema detection on a pipeline edge and how the learning and detecting modes work. When this alert fires, see [Handling drift alerts](/docs/guides/schema-detection#handling-drift-alerts) for how to triage and respond to each drift event.

## When it fires

A Schema Drift Detection alert fires once per drift event on a given edge. Drift events are:

| Event type | Description |
|---|---|
| `new_field` | A field appeared in a record that was not part of the learned schema |
| `type_change` | A field carried a type not observed during learning |

An edge can fire multiple alerts in a single flush if several fields drifted in the same batch of records.

## Alert severity

| Event type | Severity |
|---|---|
| `new_field` | `low` |
| `type_change` | `medium` |

When a single batch contains both new fields and type changes, the alert takes the highest severity (`medium`).

## Viewing alerts in the UI

Fired alerts appear in the **Alert Stream** on the Alerts page. Each schema drift event shows:

- The affected pipeline and edge
- Severity badge
- A diff table of every changed field, with before and after types
- Links to view the edge in the pipeline and to open the schema viewer

Clicking **View edge** navigates directly to the pipeline with the affected edge selected.

## Routing schema drift alerts

Like all Monad alerts, schema drift events can be routed to any destination through a pipeline using the [Monad Alerts input](/docs/components/inputs/monad/monad-alerts). This lets you send drift notifications to Slack, PagerDuty, a SIEM, or any other output your organization uses.

## Resetting after intentional schema changes

If you intentionally changed the schema of your source data (for example, added a new field to an upstream service), and want to reset the edge schema to make the new shape the new baseline, see [Resetting the schema](/docs/guides/schema-detection#resetting-the-schema) in the Schema Detection guide.