The Stacks testnet network stalled at BTC block 107099 and STX block 3631980 at approximately 6:08PM ET Oct 29th 2025, affecting all services and APIs across the ecosystem which relied on the testnet network. The network was restored at roughly 8:22PM ET Oct 29th 2025 starting at BTC block 106884 and STX block 3630559, initiating a regtest Bitcoin and testnet Stacks network chain split. Remaining impacted Hiro services and APIs were gradually restored by 12:04PM ET Oct 30th 2025.
The network stall impacted all users and services which use the Stacks testnet network. This includes Hiro's testnet infrastructure and services, such as the Stacks Blockchain API, Stacks Core RPC pools, Stacks testnet Seeds, Token Metadata API, Signer Metrics API, Chainhooks, Archival services for the Stacks Blockchain API, Stacks miner, regtest Bitcoin seed, regtest Bitcoin miner, regtest Bitcoin Explorer, and other internal services.
The testnet stall occurred due to signers not be able to issue stack-extend contract function calls for their associated Stacks addresses. The addresses they used did not have enough unlocked STX to complete the contract function call, and thus were not eligible for stacking in the upcoming cycle 119. A requirement for a signer to actively sign newly proposed blocks is they must be stacking STX.
Once the Bitcoin block boundary was passed to enter cycle 119, the network did not have enough signing power to continue since the signers were no longer stacked, at which point the network entered an unrecoverable state.
Action was immediately taken to communicate, diagnosis, and rectify the network stall through restoration to an earlier point before the chain stall. The testnet network was restored at roughly 8:22PM ET Oct 29th 2025 using disk snapshots taken earlier that same day at BTC block 106884 and STX block 3630559.
The order in which services were restored were as follows:
In addition to Hiro, anyone running a Testnet Stacks Core node, Regtest Bitcoin node, Stacks signer, sBTC signer, or other API service on testnet will have to restore to a point at or before BTC block 106884 and STX block 3630559.
Further action will be taken to prevent testnet network stalls as a result of stacking problems, and improvements will be made to ensure network restores are quicker and easier if needed again.
Below are some items Hiro will complete to prevent another testnet network stall under similar conditions, and to improve the speed at which the network is recovered: