#4607·mobx

React 19.2x introduced performance tracks cause observables to be accessed outside reaction

Author: ahoislCreated Jan 9, 2026Updated Aug 20, 2026
Labels🐛 bug

Intended outcome:

Use React 19.2.x with mobx in development mode and observableRequiresReaction=true without being spammed by following warnings: [mobx] Observable 'someProp' being read outside a reactive context.

Actual outcome:

With React 19.2.0, new performance tracks were introduced that show changed props for components: https://react.dev/reference/dev-tools/react-performance-tracks#changed-props

If observable objects are passed into components, these performance tracks cause warnings if the observableRequiresReaction is enabled: [mobx] Observable 'someProp' being read outside a reactive context.

How to reproduce the issue:

See the following minimal reproduction sandbox: https://codesandbox.io/p/sandbox/component-performace-tracks-mobx-warnings-c8wkwy

  1. open the sandbox
  2. open the dev tools console
  3. click the "Next item" button -> see warnings logged in the console

Does not happen with same sandbox when using React 19.1.4: https://codesandbox.io/p/sandbox/component-performace-tracks-no-warnings-ttx7gt

Versions

react 19.2.0 and higher mobx 6.15.0 (but most probably every version)