Salesforce passes styling values into your embedded app as CSS custom properties, so the app can match host colors, spacing, and other design values.
Where: This change applies to Lightning Experience, Experience Cloud LWR and Aura sites, and the Salesforce mobile app in Enterprise, Performance, Unlimited, Developer, and Partner Developer editions hosted on Hyperforce where English is the default language.
When: This feature is available starting September 14, 2026.
Who: This change is for developers who build embedded apps and who can create Lightning web components.
Why: Make the embedded app feel like part of Salesforce instead of a separate, differently styled surface.
How: The host provides a set of CSS custom properties, or styling tokens, to the embedded app. Your app consumes those properties in its own styles to align with the Salesforce theme. Theming is limited to CSS custom properties and doesn't automatically restyle your app's components.