Bug: Prompts containing the word "browser" silently fail

Brave Browser Leo AI
1

Hello, everyone !

Leo AI doesn’t seem to like the word “browser”: prompts containing the word finish silently with “Finished” label and no actual response generated; no console errors, no network request, tested in Helium 154 and Chrome 154. Having uBlock origin enabled/disabled makes no difference. No APIs, no fancy or sensitive prompts. Issue can be bypassed when the word is obfuscated.

Steps to reproduce:

  • Navigate to search.brave.com/ask

  • Enter any prompt with the word “browser”. Expected: actual generated answer. Result: no output, only “Finished” prompt.

  • Repeat with obfuscating the word as “b.r.o.w.s.e.r” or “b-r-o-w-s-e-r”. Result: the answer will be generated.

    Sample result:

Screenshot 2026-10-08 091545
Screenshot 2026-10-08 091545940×766 49.3 KB

Planned to join later than this, when I’m more confident, but I guess opportunity presented itself.

2

Not gonna lie, this is a very weird and specific issue – not sure I’ve ever seen a specific word used in a prompt that causes the output to break in that way, especially when all other inputs work as expected.

I went to test this and to my surprise, this issue does not occur in Brave, Chrome, Edge, or Safari, but it does occur when using Ask Brave in Firefox (shown below).

image
image1230×863 69.6 KB

Definitely something weird going on here. I’ve shared this information with our devs to review – will let you know when I have more info on this.

3

Hi, Mattches

Just touching base on this one. Where are we at with this one ? Anything else I could contribute ?

4

I am able to reproduce this on Brave Browser 1.98.63. Leo truly does not like “browser” being thrown around.

It was an interesting find.