@agent-shield/custody-crossmint

Crossmint TEE custody adapter for AgentShield — hardware-enclave signing for AI agents. The private key never leaves the Trusted Execution Environment.

@agent-shield/custody-crossmint wraps Crossmint's Intel TDX-backed wallets into a standard WalletLike interface that works with shield() and the rest of the AgentShield ecosystem. Your agent gets a signing interface; the private key stays in hardware.

Installation

npm install @agent-shield/custody-crossmint @solana/web3.js

Optional peer dependency: @agent-shield/solana (for shield() integration)

Quick Start

import { shield } from "@agent-shield/solana";
import { crossmint } from "@agent-shield/custody-crossmint";

// Create a TEE-backed wallet and wrap it with spending controls
const wallet = shield(
  await crossmint({ apiKey: "sk_production_..." }),
  { maxSpend: "500 USDC/day" }
);

// Use like any other wallet — signing happens in hardware
await wallet.signTransaction(tx);

Zero-Config from Environment

import { shield } from "@agent-shield/solana";
import { crossmintFromEnv } from "@agent-shield/custody-crossmint";

// Reads CROSSMINT_API_KEY from environment
const wallet = shield(await crossmintFromEnv(), { maxSpend: "500 USDC/day" });

API Reference

crossmint(config, client?): Promise<CrossmintWallet>

Create a CrossmintWallet from explicit configuration. If no locator is provided, a new wallet is created via the Crossmint API.

const wallet = await crossmint({ apiKey: "sk_production_..." });
console.log(wallet.publicKey.toBase58()); // Solana address

crossmintFromEnv(client?): Promise<CrossmintWallet>

Create a CrossmintWallet from environment variables. Throws if CROSSMINT_API_KEY is not set.

CrossmintWallet

Implements WalletLike — compatible with shield(), Solana Agent Kit, and any code expecting a standard wallet interface.

| Property/Method | Description | |-----------------|-------------| | publicKey | Solana PublicKey of the TEE-backed wallet | | locator | Crossmint wallet locator string | | provider | Always "crossmint" | | signTransaction(tx) | Sign via TEE — serializes tx, sends to Crossmint, returns signed tx | | signAllTransactions(txs) | Sign multiple transactions sequentially via TEE | | CrossmintWallet.create(config, client?) | Static factory method |

CrossmintRESTClient

Default SDK client that calls Crossmint's REST API directly. Used automatically when no custom client is provided.

| Method | Description | |--------|-------------| | createWallet(params) | Create a new wallet via Crossmint API | | getWallet(locator) | Get an existing wallet's address by locator | | signTransaction(locator, transaction, encoding) | Sign a serialized transaction |

Configuration Utilities

| Export | Description | |--------|-------------| | configFromEnv() | Parse CrossmintWalletConfig from environment variables | | validateConfig(config) | Validate config, throw on missing/invalid fields | | CROSSMINT_ENV_KEYS | Environment variable key constants |

Configuration

CrossmintWalletConfig

interface CrossmintWalletConfig {
  apiKey: string;              // Required — Crossmint server-side API key
  locator?: string;            // Existing wallet locator (creates new if omitted)
  chain?: string;              // Default: "solana"
  signerType?: "api-key" | "evm-keypair";  // Default: "api-key"
  baseUrl?: string;            // Default: "https://www.crossmint.com"
  linkedUser?: string;         // User identifier for wallet association
}

Environment Variables

| Variable | Required | Default | Description | |----------|----------|---------|-------------| | CROSSMINT_API_KEY | Yes | — | Server-side API key (needs wallets.create + wallets:transactions.sign scopes) | | CROSSMINT_WALLET_LOCATOR | No | — | Existing wallet locator (creates new wallet if omitted) | | CROSSMINT_SIGNER_TYPE | No | api-key | "api-key" (custodial) or "evm-keypair" | | CROSSMINT_BASE_URL | No | https://www.crossmint.com | API base URL override | | CROSSMINT_LINKED_USER | No | — | Linked user for wallet association |

Integration with shield()

import { shield, ShieldDeniedError } from "@agent-shield/solana";
import { crossmint } from "@agent-shield/custody-crossmint";

const teeWallet = await crossmint({ apiKey: "sk_..." });
const protectedWallet = shield(teeWallet, {
  maxSpend: ["500 USDC/day", "10 SOL/day"],
  blockUnknownPrograms: true,
  rateLimit: { maxTransactions: 60, windowMs: 3_600_000 },
});

// Two layers of protection:
// 1. Private key in TEE — agent code never sees it
// 2. shield() enforces spending caps before signing
try {
  await protectedWallet.signTransaction(tx);
} catch (error) {
  if (error instanceof ShieldDeniedError) {
    console.log("Policy blocked:", error.violations[0].suggestion);
  }
}

Related Packages

| Package | Description | |---------|-------------| | @agent-shield/solana | Client-side wallet wrapper (shield()) | | @agent-shield/sdk | On-chain vault SDK (Level 3 enforcement) | | @agent-shield/core | Pure TypeScript policy engine | | @agent-shield/mcp | MCP server for AI tools | | @agent-shield/plugin-elizaos | ElizaOS integration (supports Crossmint custody) |

Support

• X/Twitter: @MightieMags
• Telegram: MightyMags
• Issues: GitHub Issues

License

MIT