[Feature]: Openfort wallet provider entrypoint (@polymarket/client/openfort)

[joalavedra]

What would you like the SDK to support?

A new @polymarket/client/openfort entrypoint that lets server-side applications sign and trade with Openfort backend wallets, mirroring the existing Privy integration (packages/client/src/privy.ts).

Concretely:

• packages/client/src/openfort.ts exporting signerFrom(config: OpenfortWalletConfig): Signer, implementing the same Signer contract (getAddress, signTypedData, signMessage, sendTransaction) used by createSecureClient.
• Same structure and guarantees as the Privy entrypoint: Node-only runtime guards, the same error mapping (SigningError, CancelledSigningError, TimeoutError, TransactionFailedError), and a direct transaction handle that waits for receipts via viem.
• @openfort/openfort-node added as an optional peer dependency, exactly like @privy-io/node is today.
• A new ./openfort entry in exports / typesVersions of packages/client/package.json.
• An integration test tests/integration/openfort.test.ts mirroring privy.test.ts (authenticates a secure client, places and cancels a limit order), gated on OPENFORT_TEST_* env vars and skipping when they are unset — same pattern as the Privy suite.

Why do you need this?

Openfort provides TEE-backed server wallets with a criteria-based policy engine (allowed contracts, value limits, per-operation rules), which is a common setup for trading agents and backend services that operate on Polymarket programmatically.

Today, teams on Openfort who want to use @polymarket/client have to either export raw private keys into a viem account (defeating the purpose of custodied server wallets) or hand-roll the Signer interface themselves. A first-class entrypoint — like the SDK already ships for Privy — removes that friction and keeps key material inside the wallet infrastructure.

Disclosure: I'm a founder at Openfort. We're happy to author the PR, maintain the integration going forward, and provide Polymarket-side test credentials (a funded test backend wallet) for the integration suite if useful.

Example API or additional context

import { createSecureClient } from '@polymarket/client';
import { type OpenfortWalletConfig, signerFrom } from '@polymarket/client/openfort';
import Openfort from '@openfort/openfort-node';

const wallet: OpenfortWalletConfig = {
  openfort: new Openfort(process.env.OPENFORT_SECRET_KEY, {
    walletSecret: process.env.OPENFORT_WALLET_SECRET,
  }),
  accountId: 'acc_...', // Openfort EVM backend wallet
};

const secureClient = await createSecureClient({
  signer: signerFrom(wallet),
});

await secureClient.placeLimitOrder({ /* ... */ });

Signer method mapping (all available in @openfort/openfort-node today):

Signer method	Openfort backend wallet API
getAddress	accounts.evm.backend.get({ id })
signTypedData	EIP-712 typed-data signing on the backend wallet
signMessage	Message signing on the backend wallet
sendTransaction	Gasless/sponsored or direct transaction submission on Polygon

Per CONTRIBUTING.md we're not starting the PR until this is discussed and agreed — happy to adjust scope, naming, or test strategy to whatever fits the SDK's direction during the beta.

[cesarenaldi]

Thank you @joalavedra for putting this together. The scope and naming seems clear to me. Once we open to external contribution this is a good first issue to work on.