Summary: Fystack is best cataloged as a self-hosted custody-and-payment control plane rather than as a simple wallet API, MPC library, or managed custody vendor. Its first-party materials consistently frame the product as the wallet layer for stablecoin businesses: a stack that combines MPC wallets, high-volume derived wallets, multi-chain deposit detection, automated sweeps, policy and approval controls, audit logging, and private-cloud or on-prem deployment. The key distinction is that Fystack is packaging the operational wallet layer for payment processors, fintechs, and digital-asset platforms that want to run stablecoin flows inside their own compliance boundary instead of outsourcing custody and transaction operations to a third-party black box.
What it does:
Provides self-hosted MPC wallet infrastructure for secure threshold signing and operational treasury wallets
Supports high-volume derived wallets alongside MPC wallets so teams can separate end-user wallet generation from higher-security operational custody
Exposes deposit-address generation, webhook notifications, and multi-chain transaction indexing for payment collection and reconciliation workflows
Automates treasury sweeps based on configurable thresholds and internal-wallet or address-book destinations
Adds approval groups, transaction policies, RBAC, audit trails, and workspace-level controls for operator governance
Ships a self-hosted stack with Apex backend services, MPCIUM signing nodes, indexers, and deployment scripts for Docker-based evaluation
Key claims:
The homepage describes Fystack as “the wallet layer for stablecoin businesses” and says teams can integrate stablecoin rails across multiple blockchains without needing a dedicated web3 team
The homepage says Fystack is live in production with payment processors, fintechs, and digital-asset platforms, with 20+ self-hosted instances launched and running in production
The homepage positions self-hosting as a core differentiator: teams deploy on their own infrastructure, keep keys in their own cloud, and avoid vendor custody or transaction-based revenue sharing
The docs homepage says developers can use the API to create and manage secure MPC wallets, authorize transactions, and integrate features like transaction policies and multi-approval flows without ever touching a private key
The wallet docs say Fystack supports both Hyper wallets for fast high-volume user-wallet generation and MPC wallets for institutional-grade hot-wallet and custody use cases, with automatic sweep-task support built into wallet creation
The self-hosted scripts repository describes Fystack as a self-hosted custody stack for crypto and stablecoin payments with threshold signing, multi-chain deposit detection across 10+ chains, automated sweeps, approval and policy controls, audit trails, RBAC, and a developer-first SDK
The same repository shows the stack includes Apex, MPCIUM nodes, transaction indexing, rescanning, audit logging, and a local portal, which reinforces that Fystack is operating a full custody-and-payments backend rather than publishing a narrow signing primitive
The public GitHub organization also exposes adjacent first-party components such as MPC wallet infrastructure, multichain indexers, and deployment tooling, which strengthens the control-plane categorization
Whitepaper: No canonical standalone Fystack whitepaper or litepaper surfaced in this pass. The clearest current sources of truth were the official homepage, docs portal, wallet API docs, GitHub organization, and self-hosted deployment repository; see ../whitepapers/fystack-primary-sources-2026-05-03.md.