Zac, 

That's probably because the question, and my post, are off-topic.  They are not about FlyClient, which is not interesting to me because bitcoin's header chain is tiny.

Instead they touch on two techniques which would improve on most historical implementations of SPV clients by adding protocol support for them.

Sorry for the distraction.

Tom

Tom I can’t seem to grok the question or your explanation of it. Could you spell it out for us in detail?

Thanks, Zac

On Sun, May 3, 2026 at 12:58 PM Tom Harding <tomh@thinlink.com> wrote:

In the linked presentation by Benedict Bünz, it's worth listening to the first audience question/answer.  Questioner is spot on that an SPV client polling the network to gain probabilistic confidence of unspentness could easily subsume the task of gaining input inclusion proofs from the network, with no forking change necessary.

On Wednesday, April 29, 2026 at 2:03:36 PM UTC-7 Zac Mitton wrote:

Hi, Ive been looking into FlyClient first described here. I don't see any BIPs, or previous discussion in this forum about it either.

On bitcoin It could allow a light-client to verify the entire work of the heaviest chain with a single ~100KB proof.

It can theoretically be done as a soft-fork by injecting a single hash into the coinbase tx (similar to how segwit is committed to). 

What do you guy's think?