MSTR Cat

Blockchain/Level X · Full circle/10.3 Living on bitcoin/Lesson 1

Spending: Lightning in practice

Keys, channels, and the trade-off between sovereignty and convenience

MaterialsA smartphone with a non-custodial Lightning wallet installed (Phoenix, Breez, or Zeus)Access to a public channel graph explorer such as mempool.space or 1ML.comThe documentation page of one Lightning service provider detailing fee schedules

Wonder

  1. What is held in a custodial wallet if not bitcoin?
  2. How does a non-custodial mobile node secure inbound liquidity without waiting for a counterparty to open a channel first?
  3. Why do most holders keep savings on-chain while spending from Lightning?

Explore

  1. Lightning wallets divide into two categories by key custody. Custodial wallets hold user funds; the provider keeps keys, runs nodes, manages channels, and issues IOUs to users. Users trade sovereignty for simplicity: no setup, instant receiving, but total reliance on provider solvency and compliance posture. Non-custodial wallets keep keys on the user’s device; the user controls funds directly but must manage or procure channel liquidity.
  2. Phoenix, developed by ACINQ in France, is a prominent non-custodial mobile node built on Lightning-KMP, a Kotlin implementation optimized for smartphones. When users first receive funds, Phoenix automatically opens a channel with ACINQ’s node, supplying inbound capacity without user intervention. Other non-custodial wallets take different routes: Breez buys channels from Lightning service providers, and ZEUS began as a remote control for a node the user runs at home and now also embeds a node of its own.
  3. Lightning service providers function as infrastructure partners rather than custodians. They open channels toward users’ nodes, ensuring immediate receiving capability. This solves the onboarding bottleneck where new users possess only outbound capacity from self-funded channel openings. Providers charge for this service, typically a fee when opening a channel or adding liquidity.
  4. Exchanges and payment applications increasingly integrate Lightning deposits and withdrawals, letting users move funds quickly between exchange accounts and their own wallets. The exchange holds custody until withdrawal. Users often keep small spending balances on Lightning while holding savings in cold storage (lessons 4.3.1–4.3.3), balancing liquidity for payments with security for long-term holdings.
  5. Self-custodial wallets require occasional online presence to maintain channels and respond to network events. Users must monitor channel states, rebalance liquidity as needed, and ensure their nodes remain synchronized with the Bitcoin blockchain. Custodial wallets handle these tasks internally; users simply send and receive without managing underlying infrastructure.
  6. Open a public network graph viewer such as mempool.space Lightning or 1ML. Identify a node with high inbound capacity and note its connected peers. Then check mobile wallet documentation to see which service providers it partners with for initial channel funding. Compare fee schedules: some providers charge flat opening costs, others take percentages of swaps.

Key facts

  • Custodial Lightning wallets hold user funds; non-custodial wallets keep keys on the user’s device.
  • Phoenix by ACINQ automatically opens a channel with ACINQ’s node when users first receive funds.
  • Lightning service providers open channels toward users’ nodes to supply instant receiving capacity for a fee.
  • Non-custodial wallets such as Breez and ZEUS can buy inbound liquidity from Lightning service providers while the user keeps the keys.
  • Exchanges integrate Lightning deposits and withdrawals to connect fiat accounts with the second layer.
  • Most holders keep small spending balances on Lightning while holding savings in cold storage.

Exercise nine, six, three, one

9CollectList 9 Lightning wallet implementations. Note whether each is custodial or non-custodial, which node software it runs (if any), and how it sources inbound liquidity for new users.
6ClusterGroup the 9 into 6 by their key-custody model and liquidity procurement method: fully custodial, LSP-backed self-custody, user-managed channels, exchange-integrated, custodial with a Lightning address, or other hybrid.
3DistillReduce the 6 groups to 3 core trade-offs between sovereignty, convenience, and counterparty risk.
1CrystallizeWrite 1 sentence on what a Lightning service provider actually does for a non-custodial user that the user cannot easily do alone at onboarding time.

Fact check

Dates, figures and claims checked against the published sources listed below.

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