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name: bitcoin-l2-strata description: | Strata by Alpen Labs: ZK rollup on Bitcoin, glock (garbled lock) bridge, EVM-compatible execution. Emerging Bitcoin L2 in 2025-2026. USE WHEN: evaluating Strata for deployment, comparing with Citrea. allowed-tools: Read, Grep, Glob

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The BitVM2 Take/Assert/Disprove flow is therefore superseded for Strata; Alpen's own 2024 bridge post now carries a historical-note banner saying so.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.

See also

• citrea/SKILL.md
• bsquared/SKILL.md
• bitvm/SKILL.md
• bitlayer/SKILL.md