Continuity on the Ames network occasionally needs to be broken (though with increasing rarity) in order to correct a networking error. These infrequent events are known as breaches, which cause an individual ship to forget its network message history.
Breaches are always initiated by the user, frequently in response to a connectivity error. The easiest way to do this is with Bridge. There are two types of personal breaches: changing networking keys, and changing the Urbit ID ownership address.
Historically, there were also "network breaches", which happened when a major Arvo revision that could not be implemented via an OTA update occured. Network breaches were effectively breaching every ship on the network at once. The most recent network breach occurred in December 2020, and we expect it to be the final one.