Setu

A post-blockchain settlement prototype: Byzantine fault-tolerant payments without consensus, blocks, mining, or fees — finality in one network round trip. Based on the FastPay/pod/ABC line of research; see SPEC.md for the design and the evidence behind every choice.

Live network

Four authorities run on Fly.io in London, Frankfurt, Washington DC and Singapore (setu-auth-1..4.fly.dev; committee in committee-prod.json, public keys only — private keys are Fly secrets). Payments from a laptop settle in ~200 ms:

$env:SETU_COMMITTEE = "$PWD\committee-prod.json"   # PowerShell
node src/wallet.ts new me
node src/wallet.ts fund me 1000        # devnet-style genesis; endpoint is demo-only
node src/wallet.ts pay me <to> 100
node src/wallet.ts balance me          # as seen by each of the 4 authorities

Each authority app runs exactly one machine (an authority is a single logical signer — Fly's default 2-machine HA split one authority's state in two and broke quorum funding; fly scale count 1 is part of the deploy procedure). State is durable: each authority mounts a Fly volume at /data (SETU_STATE_DIR=/data) and writes it crash-safely (atomic temp+rename with a .bak generation), so state survives process and machine restarts — verified. Redeploy: flyctl deploy . -c deploy/auth-N/fly.toml --dockerfile Dockerfile --remote-only. First-time volume setup: flyctl volumes create setu_data --app setu-auth-N --region <r> --size 1.

Related MCP server: remit.md MCP Server

Use it from an AI agent (MCP)

Setu ships an MCP server so any MCP-speaking agent (Claude Desktop, Claude Code, …) can hold a wallet, pay other agents, and charge for its own services — no Setu-specific code. See packages/setu-mcp. One line of client config:

{ "mcpServers": { "setu": { "command": "node", "args": ["<path>/packages/setu-mcp/server.ts"] } } }

Run locally

Requires Node ≥ 23.6 (native TypeScript). Zero dependencies.

node src/devnet.ts      # persistent local devnet (state in ./state), then use wallet.ts
node src/bench.ts       # throughput benchmark: 423 TPS, p50 223 ms under full load (one laptop)
node src/chain-bench.ts # chained-spend benchmark: can Bob immediately spend money he just
                        # received? 280/280 chained spends first-try, no extra sync delay,
                        # survives an authority failure (localhost)
node src/chain-bench-wan.ts # same, against the LIVE 4-region network: 48/48 chained spends
                        # first-try, ~183 ms/hop, no extra delay over a fresh payment

node src/demo.ts        # v0:   Plane 1 in-process, simulated latency
node src/demo-live.ts   # v0.2: Plane 1, 4 authorities as real OS processes over localhost HTTP
node src/demo-trust.ts  # v0.3: Plane 2, committee-less P2P trust layer (BFT hash-DAG CRDT)
node src/demo-allowance.ts # server-enforced delegated budgets: authorities track cumulative
                        # spend, per-payment cap, and revocation — a signed credential alone
                        # cannot be over-spent or double-presented across merchants
node src/demo-issuer.ts # what a unit IS: a closed-loop Credit issued from a fixed-supply
                        # Treasury (every unit traces to the issuer; supply conserved). See CREDITS.md

Plane 1 demos prove: one-round-trip finality (~4ms over real sockets), liveness with an authority process killed mid-flight, double-spend impossibility, safety against a Byzantine authority, and fee-less anti-spam via per-account rate limits.

The Plane 2 demo proves: P2P convergence with no committee or server, offline-first catch-up, forged/tampered ops rejected by every honest peer, equivocation unable to split the network, and attester-only revocation.

Layout

• src/crypto.ts — ed25519 + canonical serialization; the post-quantum swap seam

• src/types.ts — orders, signatures, certificates

• src/network.ts — network abstraction (v0: in-process with simulated latency)

• src/authority.ts — the protocol core: first-seen locking, quorum settlement, rate limiting; plus an equivocating authority for adversarial demos

• src/client.ts — wallet: broadcast order → collect quorum → certificate = finality

• src/keygen.ts, src/authority-server.ts, src/httpNetwork.ts — v0.2 multi-process deployment

• src/trust/op.ts, src/trust/peer.ts — Plane 2: signed content-addressed ops in a hash-DAG; local-first peers that gossip and converge

• src/demo.ts, src/demo-live.ts, src/demo-trust.ts — the adversarial scenario suites