Spark (Lightspark)

Spark is an open-source L2 by Lightspark (David Marcus, ex-PayPal / ex-Facebook) launched April 2025. Builds on statechain concepts with FROST threshold signing and a leaf-based structure for partial transfers.

Architecture

Core components:

• Spark Operators (SOs): collective threshold signers, FROST k-of-n.
• Leaves: terminal off-chain UTXOs owned by users; each has a relative-timelock exit transaction.
• Trees: hierarchical structure supporting partial-balance transfers.

Leaves

Each Spark leaf is:

• An off-chain UTXO with FROST-aggregated multisig.
• A relative-timelock unilateral exit tx that anyone can broadcast after CSV expiry to extract the leaf on chain.
• Transferable off-chain via SO-coordinated protocol.

Security model

1-of-n trust on Spark Operator collective:

• As long as one operator behaves honestly, user funds remain secure.
• FROST threshold signing means no single SO controls the keys.
• The user is a required signer on every transfer: the SO set alone cannot move a leaf at any threshold.
• Exit guarantee: even if all SOs collude/disappear, user can always exit via timelocked path.

Mainnet beta runs three founding operators -- Lightspark, Flashnet and Breez (docs.spark.money FAQ, as of September 2026). The SDK's mainnet wallet config signs at a FROST threshold of 2 over those three, i.e. 2-of-3. Spark states additional SOs will join as the network scales; no target set size or jurisdictional split has been published.

Lightning compatibility

Spark integrates with Lightning:

• Spark balance can be used to pay Lightning invoices.
• Lightning balance can flow into Spark.
• Bridges via Lightspark's Lightning infrastructure.

API

Lightspark provides SDKs:

• TypeScript / JavaScript.
• Go.
• Python.
• iOS / Android (Swift / Kotlin).

const wallet = new SparkWallet({ apiKey });
await wallet.deposit({ amount: 10000 });
await wallet.send({ to: "user@spark.money", amount: 5000 });
await wallet.payLightningInvoice("lnbc100u...");

Compared to Ark

Use cases

• Stablecoin / token payments on Bitcoin (multi-asset).
• Mobile-first wallets with no channel-management UX.
• Enterprise: integrated with Lightspark's existing LN infrastructure.

Status (as of September 2026)

• Mainnet beta active with 3 operators (Lightspark, Flashnet, Breez). Spark's own FAQ still calls it "highly experimental".
• USDB -- a USD stablecoin issued by Brale, backed 1:1 by US Treasury bills and cash equivalents -- went live on Spark 21 January 2026.
• Spark's public ecosystem directory lists dozens of wallets, infrastructure providers and investors, among them Polymarket and Wallet of Satoshi (spark.money/ecosystem, September 2026).
• History: a Q2 2026 roadmap listed an expanded operator set, more jurisdictions, deeper Lightning integration and asset support. Treat it as superseded -- the dated items above are the current record, and the operator and asset milestones both predate that roadmap: Breez was announced as a Spark Service Provider on 22 May 2025 and USDB shipped 21 January 2026. Spark has published no date for the BTKN token standard.
• UMA (Universal Money Address) integration alongside Spark for cross-currency payments came from that same roadmap and is still undocumented as of September 2026: the Spark docs reference UMA only as an LNURL/UMA invoice description-hash field. The cross-currency path that is documented is Lightspark Grid (announced 16 October 2025): the Spark docs carry a Grid integration page for fiat on/off-ramp, and Grid lists Spark among its supported networks.

Limitations

• 1-of-n honesty: after a transfer, at least one SO must delete its old key share. The FROST k-of-n threshold is a separate liveness parameter, not the honesty assumption.
• Lightning bridging: requires LSP-like layer; integration costs apply.
• Newer: less battle-tested than Lightning.

See also

• statechains/SKILL.md
• ark/SKILL.md
• ../../cryptography/frost/SKILL.md
• ../../lightning/uma/SKILL.md