HTML Side-by-side Stops Working After Dismissing a Pop Up on a URL Assignment

[mkdir-washington-edu]

Copying from this private issue: https://github.com/hypothesis/support/issues/202

Bug report form

Steps to reproduce

1. Go to Incognito mode. This ensures the pop up to show up in Step 3.
2. Access a URL assignment that uses the URL https://www.edutopia.org/article/scaffolding-complex-topics-middle-school-social-studies.
   Sample assignment: https://hypothesis.instructure.com/courses/676/assignments/9133
3. Scroll in the page with the sidebar open until the pop-up shows up.
4. With the sidebar open, dismiss the sidebar by pressing the ESC key.

Notes:

• If you close the sidebar, close the popup, and open the sidebar, we keep the HTML page pushed over so the Sidebar fits.
• If you dismiss the popup with the Sidebar open (via the escape key) the HTML page underneath expands under the Sidebar.

Expected behaviour

Side-by-side display will be maintained. Sidebar will not overlap with the webpage.

Actual behaviour

Side-by-side display is no longer observed. Sidebar overlaps with the webpage.

Sample video:

edu1.webm

Browser/system information

Chrome 138
Mac OS 15.5

Additional details

Slack thread: https://hypothes-is.slack.com/archives/C2BLQDKHA/p1751988112662259