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Use platform services from the SDK

Your app reaches the platform through the Product SDK (@parity/product-sdk). This guide covers the services most apps need first: chain access, signing, cloud storage, contract calls, and a user's identity and personhood status. Packages & tools has the install line.

Paseo Next v2

This page covers the PCF Products Devnet (devnet preset). For Paseo Next v2 (paseo preset), see Product SDK or Build.

Before you start

The SDK is a TypeScript umbrella package. You import from its subpath entry points directly: ./chain, ./cloud-storage, ./contracts, ./identity, ./individuality, ./nfts, ./host, ./wallet, ./local-storage, ./crypto, ./address, ./renderer, ./core, ./react, and ./testing.

./react (ProductSDKProvider, useChain, useWallet, useLocalStorage, useProductSDK) declares react ^18 || ^19 as a peer dependency. In a project without React installed, only that subpath fails, with a module-not-found error.

Your app has to run inside a host

Every chain call and every storage call goes through the host container: the Polkadot app (mobile or desktop) or the web gateway at dev-dot.li. Outside a container, createApp() itself throws before you reach any service:

HostUnavailableError: createApp requires a host product context

A chain call made outside a container throws Host provider unavailable for chain <genesisHash>. To run your app in CI, use the test host.

Check results instead of catching errors

Most operations that can fail return a Result instead of throwing. Result<T, E> is { ok: true; value: T } | { ok: false; error: E }, so check res.ok before you read res.value. ok, err and isErrorOf are exported from the package root. createApp, getChainAPI and the app.wallet helpers do throw, so wrap those in try/catch.

Connect to the chains

The chain client gives you typed PAPI access to the three platform chains: Asset Hub, the Bulletin chain, and the Individuality (People) chain. You can connect in two ways.

The simplest is the preset. Call getChainAPI(env) and the SDK loads the right descriptors for you:

import { getChainAPI } from "@parity/product-sdk/chain";

const client = await getChainAPI("devnet");

const account = await client.assetHub.query.System.Account.getValue(address);
const fee = await client.bulletin.query.TransactionStorage.ByteFee.getValue();
client.individuality; // People-chain access
client.raw; // lower-level PAPI handles, keyed by chain name
client.destroy(); // tear the connections down when you are finished

Environment has five values: polkadot, kusama, paseo, previewnet and devnet. polkadot and kusama throw before connecting, because their Bulletin and Individuality chains are not live yet. Connections are cached by each chain's genesis-hash fingerprint.

For a specific or pre-release chain, pass descriptors yourself. They live in @parity/product-sdk-descriptors. To import from it, add it as a direct dependency, as shown in Current Devnet chain metadata:

import { createChainClient } from "@parity/product-sdk/chain";
import { devnet_asset_hub } from "@parity/product-sdk-descriptors/devnet-asset-hub";
import { devnet_bulletin } from "@parity/product-sdk-descriptors/devnet-bulletin";

const client = await createChainClient({
  chains: { assetHub: devnet_asset_hub, bulletin: devnet_bulletin },
});

createChainClient is async. If you leave out the await, the failure only shows up on the next line you write, as a Property 'assetHub' does not exist on type 'Promise<ChainClient<…>>' error.

The descriptor chooses the chain

The descriptor you pass to createChainClient is your network selection. Passing paseo_asset_hub here connects your app to Paseo Next, not this Devnet, whatever --env you deployed with. Nothing fails at build time: the app builds and loads, then throws ChainNotSupportedError at runtime. Match the descriptor prefix to your target network.

Sign transactions

Signing goes through the host wallet, so you never manage keys yourself. Connecting returns a Result with the available accounts. getSigner() returns the selected account's PAPI 3 transaction signer, but only once an account is selected:

import { SignerManager } from "@parity/product-sdk/wallet";

const manager = new SignerManager();
const connected = await manager.connect(); // or connect("dev") for Alice/Bob
if (!connected.ok) throw connected.error;

const [account] = connected.value;
if (!account) throw new Error("Host wallet returned no accounts");

manager.selectAccount(account.address);
const signer = manager.getSigner(); // CommonSignerTxCreator | null

connect() reports failure in its result and does not throw. If you skip the check, you end up with a null signer and no error to explain it.

Store and retrieve data (Cloud Storage)

Cloud Storage is content-addressed storage backed by the Polkadot Bulletin chain, and it is how an app is meant to persist data. You store bytes, get back a root CID, and read the bytes back by CID. Uploads need a connected wallet with a selected account, and a storage authorization on that account. Storage & data explains the model behind it.

import { createApp } from "@parity/product-sdk";

const app = await createApp({
  cloudStorage: { environment: "devnet" },
});

const cloud = app.cloudStorage;
if (!cloud) throw new Error("Cloud Storage is disabled");

const uploaded = await cloud.upload(bytes);
if (!uploaded.ok) throw uploaded.error;

const fetched = await cloud.fetch(uploaded.value);
if (fetched.ok) {
  render(fetched.value); // Uint8Array
}

cloudStorage.environment defaults to paseo

Omit the option and the SDK targets Bulletin on Paseo, which a Devnet host does not serve, so createApp() fails. Pass environment: "devnet". The values are paseo, previewnet and devnet. Passing cloudStorage: false turns the service off, which is why app.cloudStorage can be null.

cloud.computeCid(data) computes the CID of raw bytes without uploading them (calculateCid from the package root does the same without an App). This is not the CID that upload() returns, which is the CID of the stored manifest. Reads only work inside a container. There is no IPFS-gateway fallback.

Call smart contracts

Contracts on the devnet are PolkaVM bytecode running on Asset Hub through pallet-revive, with Solidity-style ABIs. Build a runtime from a raw PAPI client, then a typed contract handle:

import {
  createContract,
  createContractRuntimeFromClient,
} from "@parity/product-sdk/contracts";

// client and manager as above; address and abi are your contract's.
const runtime = createContractRuntimeFromClient(client.raw.assetHub, devnet_asset_hub);
const contract = createContract(runtime, address, abi, { signerManager: manager });

The argument order is (runtime, address, abi), with the address first. The optional fourth argument supplies the signer: pass { signerManager } for .tx() calls, which look up the selected account when you call them. Read-only .query() calls need no account and fall back to the keyless QUERY_FALLBACK_ORIGIN. ensureContractAccountMapped(runtime, address, signer) maps an account for pallet-revive when a call needs it.

Read identity and personhood

To prove a user controls a .dot identity, sign with the account that owns it. The wallet looks up the username's owner on the People chain and signs with that account:

import { devnet_individuality } from "@parity/product-sdk-descriptors/devnet-individuality";

const proof = await app.wallet.signMessageWithDotNsIdentity({
  peopleChain: devnet_individuality,
  username: "alice", // omit to use the user's primary .dot name
  message: "Sign in to my-app",
});

proof.username; // username used for the lookup
proof.accountId; // owning AccountId32, 0x-prefixed
proof.signature; // Uint8Array

Usernames are matched byte for byte against the chain's records, and the .dot suffix is not handled for you, so pass the exact registered value. If you omit username, the host shows an identity-permission prompt. If your app already connects the People chain with app.chain.connect({ … }), the lookup reuses that connection.

For an app-scoped account, or a per-context alias that cannot be linked back to the user's account, use SignerManager.getProductAccount() and SignerManager.getProductAccountAlias(). Both go through the host. isValidDotNsName(name, suffix) and normalizeDotNsName(name, suffix) validate and canonicalise a name. Pass the TLD suffix, which is ".dot" on this Devnet.

For the raw host session (login state, product accounts, ring proofs), call getAccountsProvider() from @parity/product-sdk/host. It is async and resolves to null outside a host container. Its methods return neverthrow ResultAsync values (.isOk()), not the SDK's own Result.

To read a user's personhood tier on-chain, call the personhood pallet-revive precompile at the fixed address 0x000000000000000000000000000000000A010000 with a contract handle. Its personhoodStatus(account, bytes32 context) returns a status (0 = None, 1 = Lite, 2 = Full) and a per-application contextAlias. Identity & personhood has the full model.

Test without the real host

@parity/truapi-host ships a Playwright test host that runs the real host core with auto-signing dev accounts, so you can drive your app end to end in CI:

npm i -D @parity/truapi-host@0.25.0 @playwright/test esbuild

import { test as base, expect } from "@playwright/test";
import {
  createTestHostFixture,
  type TestHost,
} from "@parity/truapi-host/testing/playwright";

const test = base.extend<{ testHost: TestHost }>(
  createTestHostFixture({
    productUrl: "http://localhost:5173",
    productId: "my-app.dot", // the .dot name your app signs as
    accounts: ["alice"],
    networks: [
      {
        id: "devnet-asset-hub",
        name: "Devnet Asset Hub",
        genesisHash: "0xd6eec26135305a8ad257a20d003357284c8aa03d0bdb2b357ab0a22371e11ef2",
        rpcUrl: "wss://asset-hub-paseo-rpc.n.dwellir.com",
        tokenSymbol: "PAS",
        tokenDecimals: 10,
      },
    ],
  }),
);

test("signs a transfer", async ({ testHost }) => {
  await testHost.waitForConnection();
  await testHost.productFrame().getByRole("button", { name: "Send" }).click();

  const signed = await testHost.getSigningLog();
  expect(signed.length).toBeGreaterThan(0);
});

The fixture embeds your product in an iframe, signs in the dev accounts, auto-signs signing requests, and proxies chain RPC to the chains you list. switchAccount, getSigningLog and the permission, notification and chat logs let tests check what the host did.

Each networks entry's id suffix sets its role (-asset-hub, -people, -bulletin). If your app uses People or Bulletin, add entries for them from Networks & endpoints. productId must be the name your app signs as, because the host refuses a signing request scoped to another product.

Learn more

Last update: November 4, 2026
| Created: July 16, 2026