SDK

caplane-sdk is the TypeScript client mcp.caplane.xyz is built on. It wraps viem and adds nothing that changes chain state — every export here is a read. registry.caplane.xyz decodes the same reads by hand instead of importing this package, to avoid shipping viem to a page that never signs anything — but it verifies that hand-rolled decode against this package in its own test suite, field for field, against the live chain (see the Lien reference).

npm install caplane-sdk

Every function below takes a CaplaneClient, created once per caller with createCaplaneClient.

Reference

createCaplaneClient

function createCaplaneClient(options?: {
  rpcUrls?: readonly string[]
  registry?: `0x${string}`
  quorum?: boolean
}): CaplaneClient

Builds a reader over one or more RPC endpoints. With no arguments it points at the two default Arc Testnet endpoints and compares their answers (quorum: true whenever more than one endpoint is configured) — a caller running their own node should pass it and set quorum: false, since a lone endpoint has nothing to agree with.

import { createCaplaneClient } from 'caplane-sdk'

const client = createCaplaneClient()
const code = await client.registryCode()

Used in production by the MCP server's registry_identity tool (services/mcp/src/tools.ts), and by the claims page (web/app/[mode]/claims/claims.tsx) to read a wallet's own submission history.

CaplaneClient

type CaplaneClient = {
  endpoints: readonly string[]
  registry: `0x${string}`
  read: PublicClient
  agree: <T>(ask: (client: PublicClient) => Promise<T>) => Promise<T>
  registryCode: () => Promise<`0x${string}`>
  workflowName: () => Promise<`0x${string}`>
}

What createCaplaneClient returns. agree is what every other read in this package calls instead of read directly — it asks every configured endpoint and throws if they disagree, so a single hostile endpoint cannot answer a question alone. registryCode and workflowName are an identity check: an address alone does not prove which contract is deployed there.

arcTestnet

const arcTestnet: Chain // viem Chain, id 5042002

The viem chain definition Caplane runs on — native currency is USDC at six decimals, not ether at eighteen. Pass it to any viem client that needs to talk to Arc directly; createCaplaneClient already uses it internally.

deployments

const deployments: {
  registry: `0x${string}`
  inbox: `0x${string}`
  pool: `0x${string}`
  escrow: `0x${string}`
  forwarder: `0x${string}`
  chainSelector: bigint
  workflowOwner: `0x${string}`
  workflowName: `0x${string}`
  blockNumber: bigint
}

The address book for the current deployment, read from the package's vendored copy rather than retyped by each caller. chainSelector is a bigint because it exceeds Number.MAX_SAFE_INTEGER. Consumed directly by the MCP server (services/mcp/src/rpc.ts and tools.ts) to build ABI calls without hardcoding an address.

Deployments

type Deployments = {
  registry: `0x${string}`
  inbox: `0x${string}`
  pool: `0x${string}`
  escrow: `0x${string}`
  forwarder: `0x${string}`
  chainSelector: bigint
  workflowOwner: `0x${string}`
  workflowName: `0x${string}`
  blockNumber: bigint
}

The type of deployments, exported so a caller can type their own function parameters against it without retyping the shape.