AntPool and ViaBTC had two blocks orphaned from the Bitcoin network after Foundry USA mined a longer competing chain, triggering a rare blockchain reorganization that lasted several blocks. The incident, while not a network failure or security breach, underscores the concentrated hash power held by dominant mining pools in Bitcoin's consensus mechanism.
The reorganization occurred when Bitcoin's network briefly split into two competing branches. Foundry USA accumulated sufficient computational work to extend its chain faster than the blocks mined by AntPool and ViaBTC, causing the Bitcoin protocol to automatically recognize the chain with the most accumulated proof-of-work as canonical. The orphaned blocks from the two pools were discarded, though any transactions they contained were returned to the network's memory pool for potential inclusion in subsequent blocks.
Such reorganizations are mechanically normal within Bitcoin's consensus design but remain statistically uncommon at this scale. The incident renewed focus on mining centralization, as Foundry USA demonstrated the capacity to mine multiple consecutive blocks—a capability dependent on controlling a substantial portion of the network's total hash rate. This concentration of mining power among a handful of large pools continues to be scrutinized by network participants monitoring risks to Bitcoin's decentralization.