If a user uses the toggle to switch between "Search the web" and "Use company sources" in their initial prompt, that selection applies to every response in the conversation, even if they change their selection in a follow up prompt in the thread. Since the initial selection sticks for the entire thread, why not remove the option from the reply "Ask anything…" box?
For example, if I select only "Search the web" in my initial prompt and then switch to "Use company sources" in my first reply, the response to the reply still uses web sources and web sources only.
As an aside…Now that I type that "Ask anything…" also seems an odd instruction text if it's beyond the first prompt in the thread.