[Meta] Deprecate/Remove the Amsterdam Theme

[JasonStoltz]

Target: Tue, Oct 07 2025 is the last planned release of 8.x series.

With the move to the Borealis theme, we no longer need the Amsterdam theme.

However, The Kibana 8.x series still uses Amsterdam. In order to keep Kibana 8.x up to date with EUI bug fixes, and support backward compatibility for 9.x to 8.x backports in Kibana, we are currently maintaining Amsterdam as an available option in EUI.

At this point, we consider Amsterdam to be in "Maintenance" mode. We will no longer invest in new improvements to this theme.

During this period, we will:

• Add compatible tokens added to the Borealis theme to the Amsterdam theme for backward compatibility.
• Fix bugs specific to the Amsterdam that occur in 8.x
• Feature flag large changes when possible, to contain them to Borealis and avoid impacting current Amsterdam implementations (like Kibana 8.x)

This Meta issue serves as both a task to track the removal of Amsterdam as well as a place to tracks known feature flags or switches that can be removed when we remove Amsterdam from EUI.

When will we remove Amsterdam?

When the last planned minor of Kibana 8.x is released, Amsterdam can be removed from EUI.

Is documentation for Amsterdam still available?

Amsterdam documentation is no longer maintained on https://eui.elastic.co/, but the historical versions of EUI are still available, which contain Amsterdam documentation.

Code that can be removed

• [ ] remove packages/eui/src/themes/amsterdam
• [ ] remove flags from EuiThemeShape and implementations (code) & cleanup usages of available flags
  • hasGlobalFocusColor
  • hasVisColorAdjustment
  • buttonVariant
  • formVariant
• [ ] remove provider override that enables flags triggering recomputation (code)
• [ ] remove packages/eui/src/services/theme/theme_variant.ts and cleanup usages of isEuiThemeRefreshVariant and useEuiThemeRefreshVariant (code)