Support new `splitViewId` in `tabs.Tab` (Firefox >= 149)

[ariasuni]

Feature Request

https://blog.mozilla.org/addons/2026/04/23/webextensions-api-changes-firefox-149-152/

Firefox 149 introduces a new read-only splitViewId property on the tabs.Tab object to expose Firefox’s new split view feature (where two tabs are displayed side-by-side in one window).

I’ve read quickly but I don’t think the other changes require a change in WXT.

Is your feature request related to a bug?

N/A

What are the alternatives?

N/A

Additional context

N/A

[aklinker1]

Yeah, I doubt the @types/chrome package will be adding a type for a Firefox feature... My policy for WXT has been to just use those types.

But this isn't the first issue, and won't be the last, that asks for better type support for Firefox... Maybe it's time we break away from relying on Chrome's types... But that would be a lot of work to maintain... I wish chrome and Firefox would just come together and settle on a standard :/

[ariasuni]

I wish chrome and Firefox would just come together and settle on a standard

Well there is kind of a standard, but a few APIs and types will inevitably be different since they reflect different browser features, hummmm…

[aklinker1]

Or just agree on a type interface with all their types in it.