name: bitcoin-l2-spark
description: |
Spark by Lightspark: statechain-derived L2 with FROST threshold
signatures, leaf architecture, Lightning compatibility. Beta
launched April 2025; managed by Spark Operators (SOs).
USE WHEN: integrating with Spark, evaluating Spark vs Ark vs
Lightning, designing leaf-based UTXO trees.
allowed-tools: Read, Grep, Glob
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
| Aspect | Spark | Ark |
|---|
| Operator | k-of-n FROST | 1 ASP per round |
| Architecture | Leaf trees | VTXO trees |
| Round-based | Continuous | Periodic rounds |
| Status | Live beta | ARKADE live beta |
| Lightning integration | Native | Optional / future |
| Stablecoins / tokens | Yes (USDB live Jan 2026) | Yes (Arkade Assets) |
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