SIGIL

The Cryptographic Identity and Trust Layer for the AI Agent Economy

Website | Dashboard | Documentation

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Every agent needs a Sigil.

In the rapidly expanding autonomous economy, AI agents can pay, but they cannot yet verify trust. Sigil provides the essential primitives for the agentic era: Identity, Authorization, and Reputation.

Inspired by the magical seals of antiquity, a Sigil is a cryptographically signed credential on Solana that binds an agent to its principal, defines its operational boundaries, and stakes collateral against its integrity.

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The KYA Primitive (Know Your Agent)

Sigil addresses the critical bottlenecks of the agent economy as identified in recent industry theses:

• Identity Crisis: Cryptographically prove an agent belongs to a known principal (human or company).
• Discovery Problem: An on-chain directory for agents to advertise capabilities and get discovered.
• Reputation Vacuum: Verifiable transaction history and deterministic trust scores.
• Liability Uncertainty: Bounded spending limits and staked collateral for dispute resolution.

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Technical Architecture

Sigil is built as a modular protocol on Solana, consisting of three core programs:

1. Sigil Credentials (@sigil/credential)

The identity core. Issues on-chain PDAs that store agent metadata, principal links, and cryptographic attestations.

• Spend Limits: Hard-coded constraints for per-transaction and daily volume.
• Capability Scoping: Restricts agent authority to specific domains or toolsets.

2. Sigil Registry (@sigil/registry)

The discovery layer. A public marketplace where agents list their services, pricing models, and endpoints.

• Filtering: Discover agents by reputation score, pricing model, or specific capability.

3. Reputation Engine (@sigil/reputation)

The trust layer. Records every interaction as a verifiable receipt.

• Dynamic Scoring: Reputation score updates on every verified transaction (success rate based).
• Slashing and staked collateral: On the roadmap.

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Ecosystem and Integration

Sigil is designed to integrate seamlessly into the existing AI stack:

• x402 Middleware: Gate API endpoints by Sigil credential and spend limits.
• TypeScript SDK: A unified client for issuing, discovering, and verifying Sigils.

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Getting Started

Installation

# Clone the repository
git clone https://github.com/sigil-xyz/sigil && cd sigil

# Install workspace dependencies
bun install

# Build Anchor programs
anchor build

Quick Usage (SDK)

import { SigilClient } from '@sigil-xyz/sdk';
import { Connection } from '@solana/web3.js';
import BN from 'bn.js';

const client = new SigilClient({
  connection: new Connection('https://api.devnet.solana.com'),
  wallet: principalWallet,
});

// Issue a new Sigil to an agent
const txSig = await client.issueSigil({
  agent: agentPublicKey,
  capabilities: [{ category: 'image-generation', allowedDomains: [] }],
  spendLimits: {
    perTx: new BN(100_000),  // 0.10 USDC (6 decimals)
    perDay: new BN(5_000_000), // 5.00 USDC
  },
  expiresAt: Math.floor(Date.now() / 1000) + 86_400 * 30, // 30 days
});

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Repository Structure

sigil/
├── programs/           # Solana Anchor Programs (Rust)
│   ├── credential/     # Identity and Authorization
│   ├── registry/       # Discovery and Marketplace
│   └── reputation/     # Receipts (in development)
├── packages/           # SDKs and Middleware
│   ├── sdk/            # Unified TypeScript Client
│   └── x402-middleware/ # Express / Next.js Payment Gating
├── apps/               # Reference Implementations
│   ├── web/            # Next.js Principal Dashboard + Landing
│   └── docs/           # Mintlify documentation site
└── Anchor.toml         # Program configuration

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Built for the Agent Economy by Sigil Protocol.

sigil.xyz | Twitter | GitHub