How to start live input.harbor stream so the first few seconds aren't cut off?

[kmnx]

I have a simple setup with a fallback of a stream playing archived shows, and a live input.harbor.

When a DJ connects I'd like to fade out the archive stream, play a jingle, and start the input.harbor from the first second.

But I can't get it to work, as any operations done in the transition cause the live-stream to start several seconds in, and not from the first second. It only works if it's a hard fallback without any transitions (or add/sequence with 0 fade time).

As soon as I try to use something like sequence([fade.out(duration=3.,a),b]) source b starts 3 seconds into the stream.

Is there a way to do this?
Ideally it should fade out the fallback stream, play a jingle, and start the live show from second 0 without fade in.

I've messed around with different combinations of sequences, adds, buffers, transition times in the fallback, and can't get it to work.

Here's the most minimal version i could think of:

set("log.level", 4)
settings.harbor.bind_addrs.set(["0.0.0.0"])
replaystream = "https://ourlittleradio.org/stream"
restream = mksafe(id="restream",buffer(input.http(id="replaystream",replaystream,max_buffer=10.)))
live = input.harbor("stream",port=42600,password="hackme",buffer=10.,max=20.)

def seq(a,b)
  sequence(merge=true,
    [fade.out(duration=3.,a),
     sequence([b])
    ])
end


def torestream(a,b)
  add(normalize=false,[
    sequence([
      fade.in(duration=1.7,type="sin",b)
    ])
  ])
end


livestream = fallback(track_sensitive=false,transitions=[seq,torestream],
                 [live,restream])

So my idea was that this would fade out the restream over 3 seconds, then start the live stream from second 0. Instead, it starts 3 seconds in.

I there a way to do this so the live stream is audible from second 1 after the fades are done?
In my mind it should be possible since the live input can have 10-20 seconds buffer. So when the dj connects the 3-6 seconds of fade.out and jingle could happen while the live source "waits" until it's supposed to play the first second of its buffer.