Steps to reproduce:

Have hundreds of tabs open (no idea how to get exact number, it's not displayed anywhere in Fenix and there is no option to select all).
Starting page is set to open last card.
Open Fenix for the first time (or swipe it away from Recents and then open again).

Pixel 4a, Android 13
Firefox version
120.1.1 (Build #2015990546), 287644eb76+
GV: 120.0.2-20231208211905
AS: 120.0.2

Actual results:

It's take 5-10 seconds before page is loaded.
The GUI itself is opening fast but then there is delay before loading page.
Going to other pages works fast after this first slow load.

Expected results:

No delay when cold starting Fenix.

Troubleshooting information

Forgot to mention: most cards are in the "Inactive tabs" section.

The severity field is not set for this bug.
:amejia, could you have a look please?

For more information, please visit BugBot documentation.

OK, debug drawer appeared in stable Firefox on Android and I can report that I have 631 inactive tabs and one active. Time to first load page is still very long.

Firefox is also killing other apps after some browsing (looks like there are memory leaks with this much inactive tabs?) and slow down my whole phone until I kill Firefox. No such problems on another phone with max only 20 tabs open.

The Performance Impact Calculator has determined this bug's performance impact to be medium. If you'd like to request re-triage, you can reset the Performance Impact flag to "?" or needinfo the triage sheriff.

Platforms: Android
Impact on browser: Causes noticeable startup delay
Impact on site: Causes noticeable jank
Page load impact: Some