Elapse
You only pay what elapsed.
Per-second subscriptions on Monad: protocol, merchant SDK, docs, and signed webhooks. Cancel at 83 seconds, pay 83 seconds. Your server finds out via webhook — not a cron job.
Track 2 · Monad Metropolis · Consumer Products & Payments. Submission 13 October 2026.
Hosted
Both modes run real streams on Monad testnet and escrow testnet AUSD (ADR 2026-09-13); nothing is minted, and a wallet short of the cap sees Add funds in the Elapse window, which in test mode offers 15 test AUSD from Elapse's faucet (ADR 2026-10-02). Live mode (sk_live_) moves to mainnet AUSD when a chain-143 record lands, with no integration change.
Surfaces
| Piece | Path | Job |
|---|
| Protocol | contracts/ | Accrue AUSD per second; cancel; settle elapsed only |
| API | api/ | Products, checkout sessions, webhook endpoints, events; src/worker/ delivers webhooks as a second process |
| Web | web/ | Landing, /authorize (the page @elapse/react opens in a window for every signature), subscriber /account, merchant dashboard |
| SDK | sdk/ts | @elapse/sdk — server: products, sessions, start, pause, resume, cancel, webhooks |
| React SDK | sdk/react | @elapse/react — <Authorize> and <Meter> in the merchant's own page; the wallet stays on Elapse's origin |
| CLI | cli/ | elapse listen --forward |
| Indexer | indexer/ | Envio HyperIndex → platform ingest |
| Docs | docs/ | Start here: docs/README.md — product doc, architecture, glossary, specs, onboarding |
| Docs site | docs-site/ | Mintlify site in docs-site/site/: Quickstart, guides, generated API reference. pnpm --filter docs-site dev; snippets synced from code by pnpm --filter docs-site sync-snippets |
| Example | examples/saas/ | Merchant in the demo video: authorise and meter in Acme's own page |
| Example | examples/lambda/ | Per-second serverless compute on real AWS Lambda; the meter runs until you end it, and Northwind pauses it on request |
| Example hosting | examples/deploy/ | Both examples at examples.elapse.finance/saas/ and /lambda/: one nginx server block, two systemd units, the page linking them |
System architecture
One Next.js app, one Bun API with a second worker process, one Postgres, two contracts on Monad, an Envio indexer that reports chain events back to the API, and a relayer wallet that pays gas so subscribers never hold MON. Merchants talk to the API with @elapse/sdk and receive signed webhooks; subscribers never leave the merchant's own page, and the one Elapse surface they see is the window that takes the signature (ADR 2026-09-17, ADR 2026-09-20).
flowchart LR
sub(["Subscriber<br/>phone · Face ID"])
dev(["Merchant developer"])
server["Merchant server<br/>@elapse/sdk"]
cli["elapse listen --forward"]
web["web/ · Next.js on Vercel<br/>/ landing · /authorize · /account · /dashboard"]
api["api/ · Bun + Hono on EC2<br/>REST /v1 · dashboard · /internal/ingest"]
worker["worker process<br/>deliveries · keeper · reconcile · notices"]
pg[("Postgres")]
chain["Monad testnet 10143<br/>StreamFactory → AccrualStream per subscription<br/>AUSD, both modes"]
envio["indexer/ · Envio HyperIndex"]
privy["Privy"]
resend["Resend"]
relayer["Relayer wallet<br/>MON for gas only"]
dev --> web
dev -- "integrates" --> server
server -- "sk_ key" --> api
server -- "session id" --> sub
sub -- "@elapse/react · /authorize window" --> web
web -- "cookie · checkout pass" --> api
web <-- "sign in · permit" --> privy
api --- pg
worker --- pg
worker -- "signed POST · 8 tries" --> server
worker -- "SSE" --> cli --> server
api -- "create(permit)" --> chain
worker -- "settle() hourly" --> chain
relayer -. "signs" .-> chain
chain -- "logs" --> envio
envio -- "INGEST_TOKEN" --> api
api --> resend
worker --> resend
Numbers are the order of one subscription's life: create, run, stop at 83 seconds, pay 83 seconds.
sequenceDiagram
autonumber
participant M as Merchant server
participant A as API
participant W as Worker
participant S as Subscriber (merchant's page)
participant C as Monad (StreamFactory · AccrualStream)
participant E as Envio
M->>A: products.create · checkout.sessions.create (sk_ key)
A-->>M: session id
M->>S: <Authorize session> in the merchant's own page
S->>A: sign in (Privy) · sign permit (Face ID) in the Elapse window
A->>C: create(permit) via relayer
C-->>E: StreamStarted
E->>A: ingest (txHash + logIndex, idempotent)
A->>W: Event subscription.created queued
W->>M: POST signed event · X-Elapse-Signature
Note over S: ticker = rate × (now − started_at), no tx per second
S->>A: stop at 83 s
A->>C: cancel → settle 83 s · refund the rest
C-->>E: Settled · StreamCanceled
E->>A: ingest → Invoice · Ledger · Events
W->>M: invoice.settled · subscription.canceled
Note over W,C: the keeper calls settle() hourly on running streams and ends capped ones
The core loop, start to webhook. The page ticks rate × (now − started_at) locally; nothing touches the chain per second. Money moves only at create, settle, and cancel, and every merchant-facing fact comes back through the indexer, so the API never trusts its own transaction receipt.
On chain (Monad testnet 10143). From contracts/deployments/10143.json, copied into api/deployments/ by pnpm --filter @elapse/api sync-deployments.
| Contract | Address |
|---|
| StreamFactory | 0x9Df0003Bd18733a730Db709B55e0ff08824b8052 |
| AccrualStream implementation | 0x373fc259A328aEC212435eA0D5B3936d31086A45 |
| AUSD (live mode) | 0xa9012a055bd4e0eDfF8Ce09f960291C09D5322dC |
The chain picks the token (ADR 2026-09-13): AUSD, in both modes — six decimals, ERC-2612 permit, never minted by us. A short wallet sees Add funds and must be sent AUSD. After the hackathon, live mode moves to mainnet AUSD (0x00000000eFE302BEAA2b3e6e1b18d08D69a9012a on chain 143). MockUSD survives only as a Foundry test fixture.
Platform fee 2 % of each settlement to treasury (ADR 2026-09-08).
Trust boundaries. Secret keys and webhook secrets are hashed or encrypted at rest and shown once. The indexer holds no merchant secret; it only knows the ingest token. Subscribers never see a private key, an address, or a transaction outside judge mode. The relayer key signs transactions and holds no AUSD.
SDK (target)
import { Elapse } from "@elapse/sdk";
const elapse = new Elapse({ secretKey: process.env.ELAPSE_SECRET_KEY });
const product = await elapse.products.create({
name: "GPU · 4090",
rateUsdPerSecond: "0.004",
});
const session = await elapse.checkout.sessions.create({
product: product.id,
successUrl: "https://merchant.example/ok",
cancelUrl: "https://merchant.example/cancel",
});
// Node types a header as `string | string[] | undefined`, so narrow it first.
const sent = req.headers["x-elapse-signature"];
const signature = Array.isArray(sent) ? sent[0] : sent;
const event = elapse.webhooks.constructEvent(
rawBody,
signature,
process.env.ELAPSE_WEBHOOK_SECRET
);
No per-second webhooks. Accrue onchain; notify on subscription.created, subscription.canceled, invoice.settled, invoice.payment_failed.
In the browser, @elapse/react takes the session id and nothing else secret:
import { Authorize, ElapseProvider, Meter } from "@elapse/react";
import "@elapse/react/styles.css";
<ElapseProvider publishableKey={process.env.NEXT_PUBLIC_ELAPSE_KEY!}>
{started ? <Meter session={id} dock="bottom-right" /> : <Authorize session={id} onStarted={() => setStarted(true)} />}
</ElapseProvider>
Face ID happens in a window on Elapse's origin, one window per signature (ADR 2026-09-20),
so the merchant's code never touches the subscriber's wallet. dock floats the meter as a capsule, proof drops the
start and end transactions in, and controls={false} hides Stop for a meter only the merchant
stops. Full options in sdk/react/README.md.
Week 1 kill
Start → cancel mid-stream → settle elapsed seconds on Monad testnet. If that does not work, the rest of the platform is theatre.
Run it locally
Prerequisites: pnpm 9, Bun 1.2+, Postgres 16, Foundry for the contracts. Copy each .env.example to .env and fill it; every secret stays out of git.
pnpm install
pnpm --filter @elapse/api migrate && pnpm --filter @elapse/api dev # API on :4000
pnpm --filter @elapse/api worker # deliveries, keeper, notices
NEXT_PUBLIC_DASHBOARD_MOCK=1 pnpm --filter web dev # app on :3000 against the seeded mock
pnpm --filter docs-site dev # docs on :3333
Point web/.env at the local API instead of the mock to run the real thing end to end; examples/saas is a complete merchant that receives webhooks through the CLI.
Tests
Every feature is test-driven and named after its FR id in docs/specs/. CI blocks merge on any failure.
cd contracts && forge test # start, cancel, settle, refund, fuzzed elapsed math
pnpm --filter @elapse/api test # routes, worker, ingest, keeper (needs Postgres)
pnpm --filter web test # components, meter math, checkout, dashboard
pnpm --filter @elapse/sdk test # HMAC construct and verify, expired, tampered
pnpm --filter @elapse/cli test
pnpm --filter docs-site test # every page, every snippet
Stack
Foundry · viem · Next.js · Privy · Envio · AUSD · pnpm
License
MIT
