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SINT Protocol includes 12 bridge adapters that translate between the SINT capability token system and external protocols. Each bridge enforces the same security guarantees — capability verification, constraint checking, and evidence logging — regardless of the downstream protocol.

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Bridge Architecture

Every bridge follows the same pattern: 
Agent Request → Capability Token → Policy Gateway → Bridge Adapter → External Protocol
                                                         ↕
                                                   Evidence Ledger
Bridges are not passthrough proxies. They intercept every command, validate the agent’s capability token, enforce physical constraints, and log the decision before forwarding to the target system.

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Available Bridges

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Robotics & Physical AI

ROS2 Bridge

Package: @sint/bridge-ros2Bridges SINT capability tokens to ROS2 (Robot Operating System 2). Wraps cmd_vel, joint commands, and sensor subscriptions with policy enforcement.
  • Control loop latency: P50 < 1ms, P95 < 2ms (benchmarked)
  • Supports geometry_msgs/Twist, sensor_msgs/JointState
  • Topic-level capability scoping

MAVLink Bridge

Package: @sint/bridge-mavlinkConnects SINT to drone and UAV systems via the MAVLink protocol. Enforces geofence constraints, altitude limits, and velocity caps.
  • MAVLink v2 message framing
  • GPS-based geofence enforcement
  • Flight mode restriction via capability tokens

OpenRMF Bridge

Package: @sint/bridge-open-rmfIntegration with Open-RMF (Robotics Middleware Framework) for multi-robot fleet management in facilities like hospitals, warehouses, and airports.
  • Fleet dispatch governance
  • Zone-based access control
  • Task priority enforcement

HAL Engine

Package: @sint/engine-halHardware Abstraction Layer for direct actuator control. Provides a unified interface across motor controllers, servos, and sensor arrays.
  • Vendor-agnostic motor API
  • Real-time constraint enforcement
  • Sensor fusion support

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Industrial Protocols

gRPC Bridge

Package: @sint/bridge-grpcWraps gRPC service calls with capability token authentication. Supports unary, server-streaming, and bidirectional streaming RPCs.
  • 176+ lines of protobuf-driven integration
  • Interceptor-based token injection
  • Streaming policy enforcement

MQTT/Sparkplug Bridge

Package: @sint/bridge-mqtt-sparkplugSparkplug B protocol adapter for SCADA and industrial IoT. Bridges SINT policy enforcement to MQTT-based control systems.
  • Sparkplug B topic namespace compliance
  • Device/node birth/death tracking
  • Metric-level access control

OPC-UA Bridge

Package: @sint/bridge-opcuaOPC Unified Architecture adapter for industrial automation. Connects SINT to PLCs, SCADA systems, and manufacturing execution systems.
  • Node-level capability scoping
  • Subscription-based monitoring with policy gating
  • Historical data access governance

IoT Bridge

Package: @sint/bridge-iotGeneric IoT device bridge for constrained environments. Supports lightweight protocols and device shadow patterns.
  • Device twin management
  • Command-and-control with capability tokens
  • Telemetry ingestion with policy filtering

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AI & Agent Protocols

MCP Bridge

Package: @sint/bridge-mcpModel Context Protocol adapter. Allows MCP-compliant AI agents to interact with SINT-governed resources. Tool calls are intercepted and policy-checked before execution.
  • MCP tool discovery with capability-scoped filtering
  • Context preservation across tool calls
  • Automatic evidence logging per tool invocation

A2A Bridge

Package: @sint/bridge-a2aAgent-to-Agent protocol bridge (Google A2A). Enables secure inter-agent communication with capability token delegation.
  • Agent card registration and discovery
  • Message routing with capability verification
  • Task delegation across agent boundaries

Economy Bridge

Package: @sint/bridge-economyMetered resource management. Tracks agent budgets, computes action costs, and enforces economic constraints.
  • Per-agent balance tracking
  • Cost quoting before execution
  • Budget enforcement with overdraft prevention
  • Event stream for billing integration

Swarm Bridge

Package: @sint/bridge-swarmMulti-agent swarm coordination. Manages consensus, task allocation, and collective decision-making for agent groups.
  • Swarm membership governance
  • Consensus protocol with capability-weighted voting
  • Task allocation with constraint propagation

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Cognitive Engines

In addition to protocol bridges, SINT includes three cognitive engine packages:
EnginePackagePurpose
System 1@sint/engine-system1Fast, reactive subsystem — handles real-time sensor responses and reflexive safety actions (sub-millisecond)
System 2@sint/engine-system2Deliberative planning subsystem — handles complex multi-step reasoning and plan generation
Capsule Sandbox@sint/engine-capsule-sandboxIsolated execution environment for untrusted agent code with syscall-level sandboxing

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Adding a New Bridge

All bridges implement the same interface pattern: 
import { PolicyGateway } from "@sint/gate-policy-gateway";
import { LedgerWriter } from "@sint/gate-evidence-ledger";

export function createBridge(
  gateway: PolicyGateway,
  ledger: LedgerWriter,
  config: BridgeConfig
) {
  return {
    async handleCommand(cmd: ExternalCommand) {
      // 1. Map external command to SINT intercept request
      const request = mapToIntercept(cmd);

      // 2. Policy check (token validation, constraints, tier)
      const decision = gateway.intercept(request);

      // 3. Log to evidence ledger
      ledger.append(decision);

      // 4. If approved, forward to external system
      if (decision.outcome === "approve") {
        return forwardToProtocol(cmd, decision);
      }

      return { denied: true, reason: decision.reason };
    },
  };
}
Every bridge follows this exact pattern: intercept → check → log → forward. There are no “lightweight” or “bypass” modes. The evidence ledger captures every decision.

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Gateway Server Endpoints

The bridge system is exposed through the gateway server’s unified API:
BridgeEndpointMethod
Core intercept/v1/interceptPOST
Batch intercept/v1/intercept/batchPOST
A2A messaging/v1/a2aPOST
A2A agent registry/v1/a2a/agentsGET, POST
Economy balance/v1/economy/balance/:agentIdGET
Economy budget/v1/economy/budget/:agentIdGET
Economy quote/v1/economy/quotePOST
Economy routing/v1/economy/routePOST
Risk stream/v1/risk/streamGET (SSE)
All bridge endpoints inherit the gateway’s authentication, rate limiting, and evidence logging.