[EuiTooltip] a11y - fix missing tooltip content announcement

[alexwizp]

Summary

This PR fixes an accessibility issue in EuiTooltip where tooltip content wasn’t consistently announced by screen readers. The root cause was delayed tooltip content rendering while aria-describedby already referenced the tooltip id, leaving assistive tech with nothing to read at the time of focus/hover.

To address this, the JS-based timeout/delay was removed in favor of CSS-driven styles for the visual delay/transition. This ensures the described element exists when aria-describedby points to it, while keeping the same UX behavior.

Key changes

• Removed the JS timeout that delayed tooltip content mounting/rendering.
• Implemented the delay/visibility behavior using CSS styles instead of JS timers.
• Ensured the tooltip content is present in the DOM when referenced by aria-describedby, so screen readers can announce it reliably.
• Removed _isMounted. I’m not entirely sure why we need this field, since it exists outside the standard component lifecycle methods.

Key changes

• Fixes missing/late announcements caused by aria-describedby referencing an element that was not yet rendered.

Why are we making this change?

Screen readers cannot announce a description that doesn’t exist yet. By removing JS-driven delayed rendering and relying on CSS for presentation, we keep the element available for assistive technologies while still achieving the intended visual timing for sighted users.

Screenshots #

Screen.Recording.2026-02-20.at.18.41.53.mov

Impact to users

Previous behavior retained

QA

Remove or strikethrough items that do not apply to your PR.

General checklist

• Browser QA
  • Checked in both light and dark modes
  • Checked in both MacOS and Windows high contrast modes
    • (emulate forced colors if you do not have access to a Windows machine.)
  • Checked in mobile
  • Checked in Chrome, Safari, Edge, and Firefox
  • Checked for accessibility including keyboard-only and screenreader modes
• Docs site QA
  • Added documentation
  • Props have proper autodocs (using @default if default values are missing) and playground toggles
  • Checked Code Sandbox works for any docs examples
• Code quality checklist
  • Added or updated jest and cypress tests
  • Updated visual regression tests
• Release checklist
  • A changelog entry exists and is marked appropriately
  • If applicable, added the breaking change issue label (and filled out the breaking change checklist)
  • If the changes unblock an issue in a different repo, smoke tested carefully (see Testing EUI features in Kibana ahead of time)
• Designer checklist
  • If applicable, file an issue to update EUI's Figma library with any corresponding UI changes. (This is an internal repo, if you are external to Elastic, ask a maintainer to submit this request)

[elasticmachine]

💚 Build Succeeded

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• Commit: 4415270
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History

• 💚 Build #2777 succeeded e9cd12a
• 💔 Build #2774 failed 6fb9fd0
• 💚 Build #2766 succeeded 6546e71
• 💔 Build #2764 failed 5b71724
• 💔 Build #2763 failed 3695a62

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💔 Build Failed

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• Commit: 4415270

Failed CI Steps

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History

• 💔 Build #5882 failed e9cd12a
• 💔 Build #5873 failed 6546e71