nextjs - 💡(How to fix) Fix Instrumentation.onRequestError error parameter type does not match the docs [2 pull requests]

Link to the code that reproduces this issue

https://github.com/sculli-net/instrumentation-types-reproduction

To Reproduce

1. Clone repo
2. Install packages pnpm i
3. Open instrumentation.ts

Current vs. Expected behavior

The code within instrumentation.ts is an exact copy of the sample within the next.js docs. Despite the docs saying the following:

Types:

export function onRequestError(
  error: { digest: string } & Error,
  request: {
    path: string // resource path, e.g. /blog?name=foo
    method: string // request method. e.g. GET, POST, etc
    headers: { [key: string]: string | string[] }
  },
  context: {
    routerKind: 'Pages Router' | 'App Router' // the router type
    routePath: string // the route file path, e.g. /app/blog/[dynamic]
    routeType: 'render' | 'route' | 'action' | 'proxy' // the context in which the error occurred
    renderSource:
      | 'react-server-components'
      | 'react-server-components-payload'
      | 'server-rendering'
    revalidateReason: 'on-demand' | 'stale' | undefined // undefined is a normal request without revalidation
    renderType: 'dynamic' | 'dynamic-resume' // 'dynamic-resume' for PPR
  }
): void | Promise<void>

• error: The caught error itself (type is always Error), and a digest property which is the unique ID of the error.
• 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')).

Type of err shows up as unknown, despite the docs describing it as error: { digest: string } & Error. This requires either a cast or a type check to enable this code to pass typescript build checks. <img width="616" height="429" alt="Image" src="https://github.com/user-attachments/assets/f37f6b68-8f44-4df7-9151-212dae30aa42" />

The docs do specify the following:

The error instance might not be the original error instance thrown, as it may be processed by React if encountered during Server Components rendering. If this happens, you can use digest property on an error to identify the actual error type.

Though if a type check is expected then the sample should show something like message: err instanceof Error ? err.message : String(err), otherwise we should modify the Type with the source code to match the expected { digest: string } & Error type.

Provide environment information

Operating System:
  Platform: darwin
  Arch: x64
  Version: Darwin Kernel Version 23.6.0: Mon Jan 19 22:02:22 PST 2026; root:xnu-10063.141.1.710.3~1/RELEASE_X86_64
  Available memory (MB): 32768
  Available CPU cores: 16
Binaries:
  Node: 22.18.0
  npm: 10.9.3
  Yarn: 1.22.22
  pnpm: 11.5.0
Relevant Packages:
  next: 16.3.0-canary.42 // Latest available version is detected (16.3.0-canary.42).
  eslint-config-next: N/A
  react: 19.2.7
  react-dom: 19.2.7
  typescript: 5.9.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Instrumentation

Which stage(s) are affected? (Select all that apply)

next build (local)

Additional context

I am using the project/workspace version of typescript.