CopytoClipboardButton does not work when streaming

[nenb]

Bug description

When I try to copy a response to the clipboard when streaming, at most 1 letter seems to be selected.

It appears to work correctly when using the demo assistants (where there is no streaming).

How to reproduce the bug?

Select an assistant that involves streaming and try to copy the response with the button.

Versions and dependencies used

No response

Anything else?

The logic is contained in central_view.py. A ReactiveHTML component is created for CopyToClipboardButton. I think that when we are streaming, we are not passing the full value to this component.

[pmeier]

I don't think we have ever selected a correct behavior here. I think there are two options:

1. Copy whatever message fragment is already there
2. Disable the copy button until streaming is done and afterwards copy the whole message

Of those two I would prefer 2. But we should look around how others, i.e. OpenAI / Anthropic / ..., handle this. No need to diverge here if there is an established behavior.

[nenb]

@pmeier OpenAI follow 2. I would also prefer 2 for performance reasons with panel.

I can open a short PR later if 2 is okay.