Browser Architecture

System design, security model, and component interaction for autonomous agent operations.

High-Level Architecture

┌─────────────────────────────────────────────────────────────┐
│ USER LAYER                                                  │
├─────────────────────────────────────────────────────────────┤
│                                                             │
│  [User Device] ←→ [MPC Key Share 1] (Secure Enclave)       │
│                                                             │
└──────────────────────┬──────────────────────────────────────┘
                       │
┌──────────────────────▼──────────────────────────────────────┐
│ BROWSER LAYER                                               │
├─────────────────────────────────────────────────────────────┤
│                                                             │
│  ┌────────────────┐  ┌─────────────────┐  ┌──────────────┐ │
│  │ Agent Runtime  │  │ Spending Policy │  │ x402 Handler │ │
│  │ (Sandboxed)    │  │ Engine          │  │              │ │
│  └────────┬───────┘  └────────┬────────┘  └──────┬───────┘ │
│           │                   │                  │         │
│  ┌────────▼───────────────────▼──────────────────▼───────┐ │
│  │ MPC Signing Service (Key Share 2)                     │ │
│  │ • Threshold signature generation                      │ │
│  │ • Policy enforcement                                  │ │
│  │ • Transaction batching                                │ │
│  └────────────────────┬──────────────────────────────────┘ │
│                       │                                     │
└───────────────────────┼─────────────────────────────────────┘
                        │
┌───────────────────────▼─────────────────────────────────────┐
│ BLOCKCHAIN LAYER                                            │
├─────────────────────────────────────────────────────────────┤
│                                                             │
│  [Solana RPC] ←→ [SPL Token Program] ←→ [>< Token Mint]   │
│                                                             │
│  [Payment Channels] ←→ [State Channel Contract]            │
│                                                             │
└─────────────────────────────────────────────────────────────┘

Agentic Browser Component Diagram

Key Components

1. Agent Runtime

Sandboxed execution environment for autonomous agents. Features:

  • V8 isolate with restricted syscalls
  • No direct filesystem or network access
  • Communication via message passing only
  • Resource limits (CPU, memory, execution time)

2. Spending Policy Engine

Enforces user-defined spending rules before signature generation. Implements capability-based security model with time-windowed thresholds.

3. MPC Signing Service

Coordinates threshold signature generation across user device and browser. Implements GG20 protocol for 2-of-3 TSS.

4. x402 Handler

Intercepts HTTP 402 responses, parses payment headers, constructs transactions, and retries requests with payment proofs.

Security Model

  • Principle of Least Privilege - Agents receive minimum necessary permissions
  • Defense in Depth - Multiple layers of sandboxing and validation
  • Cryptographic Enforcement - Spending limits enforced by TSS, not software

Next Steps