# Detectors & audits

> The analyzers that turn snapshots into issues.

Where collectors measure, detectors judge. Each detector watches for one class
of problem — a bloated DOM, a growing heap, a duplicated request — and emits a
`VibeIssue` when a threshold trips. Thirteen ship enabled by default.

## The `Detector` interface

A detector is a factory function `create*Detector()` that returns an object
implementing:

```ts
interface Detector {
  readonly name: DetectorName
  start(): void
  stop(): void
  getIssues(): readonly VibeIssue[]
  clear(): void
}
```

The engine calls `start()` on each enabled detector, then reads `getIssues()`
from all of them every snapshot. `clear()` empties a detector's issue buffer.

## Issues carry evidence

Detectors create issues through a shared `createIssue()` helper, so every issue
has the same shape — `id`, `detector`, `severity`, `title`, `description`,
`evidence`, `timestamp`, plus `acknowledged` / `resolved` flags. The `evidence`
object is typed per detector (see `IssueEvidenceMap` in the protocol), so a
`dom-bloat` issue carries `{ nodeCount, maxDepth, selector }` while a
`duplicate-requests` issue carries `{ url, method, count, windowMs }`. That
evidence is what your agent reads to write a targeted fix.

## The thirteen detectors

Ten catch runtime and payload problems; three are audits that emit one issue per
failed check.

| Category | Detectors |
| --- | --- |
| Runtime | `dom-bloat`, `memory-leak`, `layout-thrashing`, `long-task-attribution`, `console-spam`, `duplicate-requests` |
| Payload | `unoptimized-images`, `large-images`, `resource-bloat`, `heavy-library` |
| Audits | `seo` (20 checks), `aeo` (9 checks), `web-essentials` (4 checks) |

See the [Detector & audit reference](/docs/reference/detectors) for every
threshold and check id, each cross-linked to a `/fix` guide.

## Toggling detectors

All thirteen are enabled by default. Turn any of them off through the engine's
`detectors` config:

```ts
import { VibeCheckEngine } from '@wcgw/vibe-check-core'

const engine = new VibeCheckEngine({
  detectors: {
    consoleSpam: false, // quiet a chatty dev build
    seo: false,
  },
})
engine.start()
```

**Ordering is deliberate**

  Some collectors and detectors monkey-patch the same globals (`console`,
  `fetch`). The engine starts collectors before detectors and tears them down in
  reverse, so each patch is unwound top-down and the host's real globals are
  always restored.