What did you do?

• open Alerts Page
• filter for a alert name, wait a few ms and try to delete or type more characters

What did you expect to see?

a responsive filter

What did you see instead? Under which circumstances?

The webpage gets very unresponsive, it cannot be used after all. I tried to capture some metrics using edge development tools:

We have around 530 rules in our instance grouped by 4 (1 large, 1 medium and 2 small sized groups).
We are in the process of switching from Prometheus2.55.1 to 3.X (3.4.2). We are facing a huge delay as soon as you type something in the search filter of alerts page compared to Prometheus2. Even characters got lost during typing.

Browser: Edge 137.0.3296.93
Computer: various tested, VMs and Desktop PCs
OS: WIndows 10

System information

Linux 4.18.0-553.56.1.el8_10.x86_64 x86_64

Prometheus version

prometheus, version 3.4.2 (branch: HEAD, revision: b392caf256d7ed36980992496c8a6274e5557d36)
  build user:       root@f841ca3a6e68
  build date:       20250626-20:51:48
  go version:       go1.24.4
  platform:         linux/amd64
  tags:             netgo,builtinassets,stringlabels

Prometheus configuration file

Alertmanager version

Alertmanager configuration file

Logs