Strata (Alpen Labs)
ZK rollup on Bitcoin developed by Alpen Labs. Aims to be a flexible execution environment with EVM compatibility and a trust-minimized bridge to Bitcoin.
Naming note (as of September 2026): Alpen Labs now splits the stack in two. Alpen is the EVM-compatible execution rollup; Strata is the lightweight orchestration layer that anchors state to Bitcoin and hosts the enshrined Strata bridge. Older material that calls the whole rollup "Strata" predates this split.
Architecture
- Off-chain execution (zkEVM-style, Reth-based).
- Validity proofs committed to Bitcoin via Strata checkpoints.
- Glock (garbled lock) bridge for trust-minimized peg-in/out, 1-of-N honest-operator trust model.
- Sequencer for ordering txs (initially centralized, decentralizing).
Status
- Active development; testnet phases through 2025-2026.
- Testnet III live on Bitcoin signet since 28 July 2026, with 21+ launch partners; Stakely and Chainflow run independent bridge operators alongside Alpen Labs.
- Mainnet: not launched as of September 2026; docs still state mainnet support is "planned for a future release".
- Comparable goals to Citrea but distinct implementation choices.
Bridge design history
- 2024-2025: Alpen built and published a BitVM2-style bridge design (the original "Strata bridge" post, December 2024).
- July-August 2025: Alpen announced Glock (garbled circuit-based script locks) and reoriented to it, citing BitVM2's transaction cost, design complexity and ~5 BTC operator stake as unfixable within that paradigm.
- 7 May 2026: Alpen announces Mosaic - the production fault-proof verifier that realizes Glock (eprint 2026/812, received April 2026, revised July 2026; github.com/alpenlabs/mosaic).
- July 2026: Testnet III ships the glock-based bridge, which Alpen describes as the first publicly usable garbled-circuit verifier for Bitcoin applications.
The BitVM2 Take/Assert/Disprove flow is therefore superseded for Strata; Alpen's own 2024 bridge post now carries a historical-note banner saying so.
Use cases
- DeFi: Solidity contracts on Bitcoin.
- Cross-chain bridges for assets.
- High-throughput payment apps that need EVM-style programmability.
Comparison
| Aspect | Strata | Citrea | BSquared |
|---|---|---|---|
| Status | Testnet III on signet (Jul 2026); no mainnet as of Sep 2026 | Mainnet (Jan 2026) | Mainnet (Apr 2024) |
| ZK system | zkVM | zkEVM type-2 | zk + optimistic hybrid |
| Bridge | Glock / Mosaic garbled locks (2026) | BitVM2 | Federation + zk |
| Backing | Alpen Labs | Citrea team | B² Network |
BSquared status re-checked 16 September 2026 against the B² mainnet
RPC (rpc.bsquared.network): chain ID 223, genesis block timestamp
15 April 2024, still producing blocks.