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icyJoseph merged 2 commits into from
Jun 8, 2026
+18 −4
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docs: fix onRequestError error type example #94518

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49efd16
docs: fix onRequestError error type example
danyalahmed1995 Jun 6, 2026
e2264c8
docs: show digest narrowing for onRequestError
danyalahmed1995 Jun 8, 2026
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22 changes: 18 additions & 4 deletions docs/01-app/03-api-reference/03-file-conventions/instrumentation.mdx
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Original file line number Diff line number Diff line change
Expand Up @@ -48,10 +48,17 @@ export const onRequestError: Instrumentation.onRequestError = async (
request,
context
) => {
const message = err instanceof Error ? err.message : String(err)
const digest =
typeof err === 'object' && err !== null && 'digest' in err
? String(err.digest)
: undefined

await fetch('https://.../report-error', {
method: 'POST',
body: JSON.stringify({
message: err.message,
message,
digest,
request,
context,
}),
Expand All @@ -64,10 +71,17 @@ export const onRequestError: Instrumentation.onRequestError = async (

```js filename="instrumentation.js" switcher
export async function onRequestError(err, request, context) {
const message = err instanceof Error ? err.message : String(err)
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const digest =
typeof err === 'object' && err !== null && 'digest' in err
? String(err.digest)
: undefined

await fetch('https://.../report-error', {
method: 'POST',
body: JSON.stringify({
message: err.message,
message,
digest,
request,
context,
}),
Expand All @@ -84,7 +98,7 @@ The function accepts three parameters: `error`, `request`, and `context`.

```ts filename="Types"
export function onRequestError(
error: { digest: string } & Error,
error: unknown,
request: {
path: string // resource path, e.g. /blog?name=foo
method: string // request method. e.g. GET, POST, etc
Expand All @@ -104,7 +118,7 @@ export function onRequestError(
): void | Promise<void>
```

- `error`: The caught error itself (type is always `Error`), and a `digest` property which is the unique ID of the error.
- `error`: The caught value is typed as `unknown`. Narrow it before reading properties like `message` or `digest`.
- `request`: Read-only request information associated with the error.
- `context`: The context in which the error occurred. This can be the type of router (App or Pages Router), and/or (Server Components (`'render'`), Route Handlers (`'route'`), Server Actions (`'action'`), or Proxy (`'proxy'`)).

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