yt-dlp live download & Updating m3u8 playlist

[doctorm]

I've been using yt-dlp to occasionally download live streams. Some sources need --live-from-start, other start from the beginning because that's how the playlist is.

Something I've been trying to figure out is that if the stream is still ongoing when I start the download, yt-dlp usually downloads until the time point that I started, but no further.
I'm aware that the .m3u8 file gets update as the stream goes on, but yt-dlp never seems to check for additional frags (at least by default).

If I'm using something like this:

yt-dlp --no-part --restrict-filenames --live-from-start "(streamlink).m3u8" -o "livestream.mp4"

Is there something I can add to get yt-dlp to re-check the m3u8 file when it reaches the last fragment? Would ffmpeg work better?

[doctorm]

So at the moment, what works is using ffmpeg to start downloading from the current time until the end and yt-dlp to download from start to current time with running both simultaneously.

yt-dlp.exe "%stream%" -o "D:\Part1.mp4"

ffmpeg.exe -i "%stream%"  -c copy -bsf:a aac_adtstoasc "D:\Part2.mp4"

Not a great answer. I'm aware ffmpeg has -live_start_index, but I can't get that to work.