# EVENT_SOURCE_TYPE

> EVENT_SOURCE_TYPE is a lint warning: an explicit source frame has the wrong domain type for its target.

- **Tier:** lint
- **Severity:** warning
- **Origins:** source

## What triggers it

A command sourced from something other than UI/processor, an event from something other than a command, a read model from something other than an event, or UI/processor from something other than a read model.

## How to fix it

Correct the source reference or the authored frame type. Keep the connection when it deliberately documents a domain violation; the diagnostic remains advisory.

## Example

```mermaid
eventmodeling
tf 01 rmo CartItems
tf 02 evt CartChanged ->> 01
```

Run `am verify diagram.mmd --json`, inspect this code, and apply the smallest source or typed mutation that clears it. If it persists after two mechanical attempts, return the warning and ask for human review.

Full page: https://agentic-mermaid.dev/warnings/EVENT_SOURCE_TYPE/