Four packages. One signed-inference stack.
MIT-licensed npm packages for building agents that sign their own requests, paying per call in USDC, verifying any receipt, and serving signed inference from your own API.
Pick the one that matches your role.
Use one, use four — they compose without forcing a stack on you. Each is independently published and versioned.
@vdm-nexus/sdk
Generate a fresh Ed25519 keypair (or load an existing one), sign requests, and call any signed-inference endpoint. The agent's public key IS their identity — no API keys, no rotating secrets.
Use it when Building an agent that calls Nexus or any SIR-compatible endpoint.
@vdm-nexus/x402
x402-native client for paying per inference call in USDC (Solana or Base) and verifying any returned receipt end-to-end. Five-check verifier: hashes, operator signature, on-chain settlement, payer match, and recipient anchor.
Use it when Building an agent that pays per call, OR verifying receipts you got from somewhere else.
@vdm-nexus/paywall
Drop-in middleware for Express, Hono, or Next.js. Wrap any handler; every paid call returns a signed Ed25519 receipt of what your handler produced. You become an SIR endpoint without writing the protocol layer.
Use it when Monetizing your own AI API with per-call USDC + cryptographic receipts.
@vdm-nexus/mcp
Model Context Protocol server that exposes signed inference as a tool. Drop it into your Claude Desktop, Cursor, or any MCP-aware client config — your agent immediately gets paid calls with verifiable receipts. Zero code change.
Use it when Plugging Nexus into a Claude Desktop / Cursor workflow without writing a custom agent.
One protocol, four entry points.
Agent (you) Nexus / any SIR endpoint
─────────── ───────────────────────────
@vdm-nexus/sdk @vdm-nexus/paywall
│ │
│ signed request │ signed receipt
└──────────────►────────┘
│
▼
@vdm-nexus/x402.verifyReceipt
│
(verify 5 checks: hashes,
signature, on-chain tx,
payer match, recipient)
Or skip the custom agent and use MCP:
Claude Desktop / Cursor
│
│ config: @vdm-nexus/mcp
└──────────────► NexusThree things we will not change.
MIT, open source
Every package is MIT-licensed and developed in the open at github.com/vdmnexus/vdmnexus. Fork it, embed it, ship it.
Tiny dependency surface
@vdm-nexus/sdk has two runtime deps. The whole chain is auditable in an afternoon. No mystery transitive load.
Spec is public
Receipts follow the SIR v2 spec. Any package — ours or someone else's — can produce or verify them. The protocol matters, not the library.
Every package above runs a real call in the playground.