BIP 50: March 2013 Chain Fork Post-Mortem

The post-mortem of the March 2013 chain split, when a large block was accepted by newer (v0.8) nodes but rejected by older (v0.7) nodes because of an undocumented database limit, briefly forking the network into two chains. It was resolved socially and operationally: major mining pools downgraded to v0.7 so the network reconverged on the chain the widest set of nodes could follow.

It is cited here as a precedent for emergency coordination. The lesson cuts both ways: the network recovered within hours, but only because a handful of large pools could be reached and chose to act — a reminder that coordination, not code, was the binding constraint.