Bitcoin Experiences Rare 2-Block Reorg Amid Mining Concentration

Bitcoin’s blockchain experienced a rare two block reorganization at height 941,881 when Foundry USA produced seven consecutive blocks, orphaning valid blocks mined by AntPool and ViaBTC. The event occurred shortly after a 7.76% drop in mining difficulty, the second-largest adjustment of 2026.

During the reorg, blocks found nearly simultaneously by AntPool and Foundry briefly split the network. Foundry’s chain extended through block 941,886, becoming the longest and rendering competing blocks stale. Orphaned transactions were returned to the mempool for inclusion in future blocks, preserving network integrity.

Hashrate Concentration and Market Implications

The reorg highlights growing hashrate concentration in fewer large mining pools as smaller operators exit due to high production costs, with Bitcoin trading at $70,000 versus an estimated $88,000 mining break-even. Total network hashrate has retreated to approximately 920 EH/s from 1 ZH/s recorded in 2025.

While two block reorganizations do not compromise Bitcoin’s security, concentrated mining increases the likelihood of consecutive block wins by a single pool, raising the probability of temporary chain splits. The network’s consensus rules resolved the event efficiently, favoring the heaviest chain.

Disclaimer

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