BTCNutServer primary sources — 2026-05-02

Project status in this pass

• No canonical standalone BTCNutServer whitepaper or litepaper surfaced.
• The clearest current sources of truth were the official GitHub README, the BTCPay plugin listing, and the official Cashu projects directory.
• The materials consistently frame BTCNutServer as merchant acceptance and settlement infrastructure for Cashu inside BTCPay Server rather than as a simple experimental plugin.

Primary-source snapshots

1) Official repository README

• URL: https://raw.githubusercontent.com/cashubtc/BTCNutServer/main/README.md
• Key excerpt:
  • The README says BTCNutServer is a BTCPay Server plugin that lets merchants accept Bitcoin payments via Cashu ecash tokens.
  • It says received proofs are stored in a per-store wallet and that the plugin handles double-spend protection, fee validation, and payment recovery automatically.
  • This immediately makes the project look like merchant operations infrastructure, not just a one-screen checkout patch.

2) Settlement-mode design

• URL: https://raw.githubusercontent.com/cashubtc/BTCNutServer/main/README.md
• Key excerpt:
  • The README defines three payment modes: Trusted Mints Only, Hold When Trusted, and Auto Convert.
  • It says merchants can either hold proofs from trusted mints, melt untrusted proofs directly to Lightning, or melt everything immediately regardless of mint.
  • That policy surface is the strongest clue that BTCNutServer is packaging a settlement control plane around ecash acceptance.

3) Checkout and wallet flows

• URL: https://raw.githubusercontent.com/cashubtc/BTCNutServer/main/README.md
• Key excerpt:
  • The checkout section says BTCPay invoice pages display a NUT-18 payment request as a cashu://... QR code and also support direct paste of serialized Cashu v4 tokens.
  • The wallet section says each store has an embedded wallet, can generate or restore a mnemonic, and can export balances as Cashu tokens grouped by mint and unit.
  • This shows the project is bundling customer payment intake and merchant wallet operations together.

4) Cashu-backed Lightning client

• URL: https://raw.githubusercontent.com/cashubtc/BTCNutServer/main/README.md
• Key excerpt:
  • The README says the plugin registers a custom ILightningClient that uses a Cashu mint as a Lightning backend.
  • It says the client creates NUT-04 mint quotes, tracks payment confirmation over NUT-17 WebSockets, and pays outbound Lightning invoices by melting stored proofs via NUT-05.
  • This is strong evidence that BTCNutServer reaches beyond checkout into reusable payment-rail orchestration inside BTCPay.

5) Recovery and management APIs

• URL: https://raw.githubusercontent.com/cashubtc/BTCNutServer/main/README.md
• Key excerpt:
  • The README says failed swap or melt operations are retried automatically every 2 minutes with exponential backoff for up to 20 attempts.
  • It also documents REST endpoints for configuration, wallet creation and restore, balance inspection, failed-transaction listing, and manual retry.
  • That operational surface makes BTCNutServer look like merchant settlement middleware rather than a thin UI add-on.

6) BTCPay plugin listing

• URL: https://plugin-builder.btcpayserver.org/public/plugins/btcnutserver
• Key excerpt:
  • The official plugin listing describes BTCNutServer as enabling Cashu ecash payments in BTCPay Server.
  • It also explicitly warns that the plugin is early beta and should be used carefully.
  • That warning matters because it distinguishes a meaningful live integration from a polished-but-empty marketing page.

7) Cashu ecosystem directory

• URL: https://docs.cashu.space/projects
• Key excerpt:
  • The official Cashu projects page highlights BTCNutServer as a project that enables BTCPay Server to accept Bitcoin payments via Cashu tokens.
  • Its inclusion alongside other first-party-recognized Cashu applications supports treating BTCNutServer as a legitimate ecosystem merchant-infrastructure project.

Working conclusion

BTCNutServer is best cataloged as a Cashu merchant-payments and settlement control plane inside BTCPay Server. The deciding evidence in this pass was the combination of NUT-18 checkout support, embedded per-store wallets, configurable mint-trust and Lightning-melt policies, a custom Cashu-backed Lightning client, automatic payment-recovery jobs, and a management API surface.