Follow up conversation citations going to the wrong source

[MadhaviSeelam]

Description

Found while testing #45152. Citation sources are incorrect for follow up conversations. However, correct sources are shown for a new conversation.

Steps to reproduce

1. Install 1.79.99
2. launched Brave
3. open full-page chat via Leo toolbar button
4. query Leo and get some citations
5. query with another question as a follow up
6. click on the citation link

Actual result

Navigated to a web source from previous conversation

2025-05-05_14h24_57.mp4

Expected result

Should be navigated to correct sources.

Reproduces how often

Easily reproduced

Brave version (brave://version info)

Brave	1.79.99 Chromium: 136.0.7103.60 (Official Build) beta (64-bit)
Revision	7d26f4dfbf0420b00c2d679483c7b6c0b88d8284
OS	Windows 11 Version 24H2 (Build 26100.3775)

Channel information

• release (stable)
• beta
• nightly

Reproducibility

• with Brave Shields disabled
• with Brave Rewards disabled
• in the latest version of Chrome

Miscellaneous information

@bbondy
cc: @mattmcalister @rebron @srirambv