"... GitLab Duo is finding an answer" never go away in Classic Duo Chat

Issue

I'm using GitLab Duo Chat (non Agentic mode) in the web UI and it's answered my question, but the ... GitLab Duo is finding an answer is still there (and the stop button is still present). This has happened the last few interactions with it. ITK?

https://gitlab.slack.com/archives/CETG54GQ0/p1763127855166229

Hey @ai-duo-chat-engs we have an issue with classic chat right now. When prompting it seems to be responding fine, but it never ends searching for an answer. Even a simple “hi” will provide a response identifying itself as Duo Chat, but then get hung up processing and “searching an answer” with the stop button enabled. Can you try and see if you can reproduce the problem? Thoughts on what might be going on?

https://gitlab.slack.com/archives/C06LWENL58F/p1763499947373699

hi team , trying to understand a couple of similar failures we're seeing in #e2e-run-master: on .com, seeing the same behaviour as #is-this-known in https://gitlab.slack.com/archives/CETG54GQ0/p1763127855166229. we quarantined this test a couple days ago. think this expects the feedback UI at the bottom and fails on self-managed, we're seeing similar behaviour with "mock" being returned, but again the test expects the feedback UI at the bottom and fails

https://gitlab.slack.com/archives/C06D5C70MD2/p1763138084496859

Root cause

c38ec653 removed state.loading = false; which is for dismissing loading state when the assistant message (a.k.a. final answer) is received. We need to set false to isWaitingOnPrompt when it happens.