We have an extinct chaintip with a single stale block something like once per month. But if I remember right, we haven’t had a multiblock reorg (two competing chaintips with at least two blocks depth) in at least five years. When actually was the last multiblock reorg?

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I ran getchaintips on my well-connected node that has been running continuously mostly since early 2019.

It has seen two header chains that are not part of the currently active chain, with branches longer than 1 header:

  • height 788687, 07 May 2023, hash 0000000000000000000070ec61b72a3cab40a0f5cea33e4266a08044fd48ee27
  • height 656478, 11 Nov 2020, hash 00000000000000000005f8f74e57aa4584aacfed509b8a6feb20bc22e7d60a34

Note that these are just headers chains, so by the time these were announced to my node, it already knew of a better header chain, and it never downloaded the corresponding blocks.

And, of course, this is just what one node observed. The shorter the time between the production time of blocks is, the less far their information will propagate across the network.

  • So would it then be possible that those header chains may have been proposed to your node after the best chain was already longer?
    – Murch
    Commented Oct 20, 2023 at 18:56
  • It's likely that my node already had the full blocks of what would become the main chain up to the same height already by the time these headers were announced to me. Commented Oct 20, 2023 at 19:03

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