Foundry wins six-block race after dual mining of 941,881

On March 24, 2026, Antpool and Foundry USA each produced different valid versions of Bitcoin block 941,881 within 12 seconds, creating two competing versions of the blockchain until one branch prevailed.

Antpool broadcast a candidate for block 941,881 at 15:49:35 UTC. Foundry USA broadcast a different valid block at the same height 12 seconds later. Miners diverged: ViaBTC extended Antpool’s block with 941,882 while Foundry built on its own tip. Foundry then mined blocks 941,883 through 941,886 in succession. When Foundry’s branch accumulated more proof-of-work, nodes reorganized to that chain and the Antpool and ViaBTC blocks were dropped as orphaned. The miners on those blocks lost the immediate block rewards and transaction fees; transactions in the orphaned blocks returned to the mempool and were confirmed again shortly afterward.

Simultaneous valid blocks occur because block data must travel across a global network of nodes and that propagation takes time. If a second miner finds a valid block before the first block has reached them, both blocks can exist briefly at the same height. Bitcoin’s protocol resolves such ties by accepting the chain that accumulates the most proof-of-work; the competing block or blocks that do not end up on the longest chain are excluded from the recognized ledger.

On-chain timestamps for the three days before the reorganization (block heights 941,452 to 941,887) show 40 of 435 consecutive-block intervals, about 9.2%, occurred within 60 seconds of each other, including one pair five seconds apart. Most of these close intervals resolve after a single follow-on block and receive little attention. A two-block-deep race, where the tie survives an entire additional round of mining, is less common.

An on-chain analyst, b10c, described the incident as “a rare-ish two block fork/reorg between Foundry and AntPool+ViaBTC.” A Bitcoin developer tracking the event reported Foundry’s chain became “the heaviest by a wide margin,” prompting the network-wide reorganization.

Several large mining pools use compact block relay and low-latency relay networks such as FIBRE to reduce propagation delays. Pools that control a larger share of network hashrate have higher statistical odds of winning mining races and of mining consecutive follow-on blocks that resolve ties in their favor.