Don't scroll page to top when opening or closing a side modal

[david-crespo]

Closes #3321

Because side modals get their own routes, and the scroll height cache is keyed (in part) by route, opening a side modal counts as a new page with no saved scroll height, so it scrolls the document to top. The fix is to handle the modal scenario specially by opting out of resetting scroll when we switch to a new location that has the same underlying page path as the previous one.

2026-08-18-scroll-height-fix.mp4

Example flows

Each of these scenarios is covered by e2e tests.

The underlying "page path" for a location is the path of the last non-titleOnly crumb, i.e., where the nav breadcrumbs point: a regular page's own path, or for a side modal, the path of the page under it. When a nav starts, we save the current scroll under the outgoing location's key. When it completes, if the page path changed we scroll to the new location's cached position (0 if none); if it didn't (side modal open/close), we leave the scroll alone and just record it under the new key so back/forward still works.

Normal page → page nav (…/disks → …/snapshots, then back)

Step	Location	Page path	Cache	Scroll
Scroll the disks page	…/disks (k1)	…/disks		143
Click Snapshots: nav starts	…/disks (k1)	…/disks	k1: 143	143
Nav completes: page changed → scroll to cached (none)	…/snapshots (k2)	…/snapshots	k1: 143	0
Back: nav starts	…/snapshots (k2)	…/snapshots	k1: 143, k2: 0	0
Nav completes: page changed → scroll to cached	…/disks (k1)	…/disks	k1: 143, k2: 0	143

Page → modal → page (open the New disk form, then dismiss it)

Step	Location	Page path	Cache	Scroll
Scroll the disks page	…/disks (k1)	…/disks		143
Click New disk: nav starts	…/disks (k1)	…/disks	k1: 143	143
Nav completes: same page → leave scroll, record under new key	…/disks-new (k2)	…/disks	k1: 143, k2: 143	143
Dismiss: nav starts	…/disks-new (k2)	…/disks	k1: 143, k2: 143	143
Nav completes: same page → leave scroll, record under new key	…/disks (k3)	…/disks	k1: 143, k2: 143, k3: 143	143

Modal submit → new page (create a VPC, land on VPC detail page)

Step	Location	Page path	Cache	Scroll
Modal open over scrolled VPCs page	…/vpcs-new (k2)	…/vpcs	k1: 143, k2: 143	143
Submit: nav starts	…/vpcs-new (k2)	…/vpcs	k1: 143, k2: 143	143
Nav completes: page changed → scroll to cached (none)	…/vpcs/my-vpc (k3)	…/vpcs/my-vpc	k1: 143, k2: 143	0

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Project	Deployment	Actions	Updated (UTC)
console	Ready	Preview	Aug 19, 2026 12:52am