[cbasdev]

The createRoot and hydrateRoot reference pages say that onCaughtError receives an errorInfo object containing only the componentStack. React also passes errorInfo.errorBoundary: the instance of the Error Boundary that caught the error.

This field has been passed since onCaughtError was introduced in react/react#28641 (React 19). See ReactFiberErrorLogger.js:

onCaughtError(error, {
  componentStack: errorInfo.stack,
  errorBoundary:
    boundary.tag === ClassComponent
      ? boundary.stateNode // This should always be the case as long as we only have class boundaries
      : null,
});

Without this, readers of the reference have no way to know that onCaughtError can tell which Error Boundary handled the error, for example to tag error reports by boundary.

This PR mentions errorBoundary in the onCaughtError option description and in the "Error logging in production" section of both pages. The code example, code blocks, and <CodeStep> highlighting are unchanged.

Test plan

Ran against published react@19.3.1 and react-dom@19.3.1 on Node 26.13.0 (jsdom), rendering a class Error Boundary around a component that throws, with an onCaughtError callback passed to createRoot:

react-dom version: 19.3.1
error.message: boom
errorInfo keys: [ 'componentStack', 'errorBoundary' ]
typeof componentStack: string
errorBoundary instanceof Boundary: true
errorBoundary === rendered instance (after commit): true

yarn lint, yarn tsc, yarn lint-heading-ids, yarn deadlinks and git diff --check pass.

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[github-actions]

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