Headings tool not detecting headings in the shadow DOM with slotted content

[ben-basten]

Describe the bug

The ad hoc "Headings" scanner tool is not detecting heading tags that are in the shadow DOM and contain slotted content.

To Reproduce
Steps to reproduce the behavior:

1. Navigate to: https://shadow-sandbox.netlify.app/
2. In Acessibility Insights for Web, go to "Ad hoc tools > Headings" and toggle it on
3. Observe that the h1 with slotted content is not detected by the scanner

CodePen repro example

• Demo: https://shadow-sandbox.netlify.app/
• Source: https://github.com/ben-basten/shadow-sandbox

Expected behavior

All headings are detected.

Screenshots

Context (please complete the following information)

• OS Name & Version: MacOS Sequoia 15.4
• AI-Web Version & Environment: 2.46.0
• Browser Version: 135.0.7049.85 (Official Build) (arm64)
• Target Page: https://shadow-sandbox.netlify.app/

Are you willing to submit a PR?

No

Did you search for similar existing issues?

Yes

Additional context

N/A