Steward

The governance layer for autonomous AI agents.

Encrypted wallets · Credential vault · API proxy · Policy enforcement · Spend tracking

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The Problem

AI agents need API keys, wallet keys, database credentials. Today these sit as plaintext environment variables — one prompt injection away from exfiltration. No spending controls, no audit trail, no kill switch.

The Solution

Steward sits between agents and everything they access. Three pillars:

1. Wallet Vault — AES-256-GCM encrypted keys. Policy-enforced signing. 7 EVM chains + Solana.
2. Secret Vault — Encrypted credential storage. Agents never see real API keys.
3. API Proxy — Every external API call flows through Steward. Credentials injected at the proxy, not in the container. Costs tracked. Everything audited.

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Architecture

Agent Container          Steward                    External APIs
┌─────────────┐    ┌──────────────────┐    ┌──────────────────┐
│ STEWARD_URL │───>│ Auth (JWT)       │    │ OpenAI           │
│ STEWARD_JWT │    │ Policy Engine    │───>│ Anthropic        │
│             │    │ Secret Vault     │    │ DEXs / Chains    │
│ No API keys │    │ Wallet Vault     │    │ Any API          │
│ No priv keys│    │ Audit Log        │    └──────────────────┘
└─────────────┘    └──────────────────┘

The vault encrypts each agent's private key with AES-256-GCM using a key derived from the master password + agent ID. Keys never exist in plaintext outside of a signing operation. All signing happens in-process; the raw key is never sent over the wire.

Policy evaluation is stateless and synchronous. The engine receives the transaction request plus pre-fetched spend/rate context, evaluates all enabled rules, and returns per-policy pass/fail details.

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Quick Start

# Clone & install
git clone https://github.com/Steward-Fi/steward.git
cd steward && bun install

# Configure
cp .env.example .env
# Edit .env: set STEWARD_MASTER_PASSWORD, DATABASE_URL

# Start
bun run packages/api/src/index.ts    # API on :3200
bun run packages/proxy/src/index.ts  # Proxy on :8080

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SDK Usage

npm install @stwd/sdk
# or: bun add @stwd/sdk

import { StewardClient } from "@stwd/sdk";

const client = new StewardClient({
  baseUrl: "http://localhost:3200",
  apiKey: "your-tenant-key",
});

// Create an agent with a wallet
const agent = await client.createWallet("my-agent", "My Trading Agent");
// → { id, walletAddress, walletAddresses: { evm, solana } }

// Sign a transaction (policy-enforced)
const result = await client.signTransaction("my-agent", {
  to: "0xDEX_ROUTER",
  value: "100000000000000000", // 0.1 ETH
  chainId: 8453, // Base
});

// Or route API calls through the proxy
const openai = new OpenAI({
  baseURL: "http://steward-proxy:8080/openai/v1",
  apiKey: "steward", // dummy, replaced by proxy
});

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Policy Types

Type	What it does
spending-limit	Per-tx, daily, weekly caps
approved-addresses	Whitelist or blocklist destination addresses
rate-limit	Max transactions per hour / per day
time-window	Only allow transactions during defined UTC hours/days
auto-approve-threshold	Auto-approve small transactions, queue large ones for human review
api-access	Control which APIs agents can call through the proxy
spend-limit	Per-agent inference and API budgets

Policies are composable — mix and match. Hard policies reject immediately on failure. The auto-approve threshold is the only soft gate; failure queues instead of rejects.

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Packages

Bun monorepo managed with Turborepo.

Package	Description	Status
@stwd/api	REST API (30+ endpoints)	✅ Production
@stwd/proxy	API proxy gateway	✅ Built
@stwd/vault	Wallet + secret encryption	✅ Production
@stwd/policy-engine	Composable policy evaluation	✅ Production
@stwd/sdk	TypeScript SDK (zero deps)	✅ Published
@stwd/redis	Rate limiting + spend tracking	✅ Built
@stwd/eliza-plugin	ElizaOS integration	✅ Published
@stwd/db	Schema + migrations	✅ Production
@stwd/webhooks	Event notifications	✅ Production
@stwd/shared	Types + constants	✅ Production
web	Dashboard + landing	✅ Deployed

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Supported Chains

Ethereum · Base · BSC · Polygon · Arbitrum · Base Sepolia · BSC Testnet · Solana

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Webhook Events

Configure a webhook URL on your tenant and Steward will POST on every state change:

Event	When
approval_required	Transaction queued for manual review
tx_signed	Transaction signed and broadcast
tx_rejected	Transaction rejected by a hard policy
tx_failed	Transaction failed on-chain

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Links

• Website: steward.fi
• Docs: docs.steward.fi
• API: api.steward.fi
• npm: @stwd/sdk
• ElizaOS Plugin: @stwd/eliza-plugin

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License

MIT