AMB - Agent Message Bus

Part of Agent OS - Kernel-level governance for AI agents

Broker-agnostic message transport for decoupled agent communication.

Why AMB?

In multi-agent systems, tight coupling between agents creates dependency graphs that scale exponentially with system size. When Agent A must know about Agent B, C, and D to communicate, the system becomes rigid and unmaintainable.

We built amb because direct agent coupling creates spaghetti code. The solution: Scale by Subtraction.

By removing the requirement for agents to know about each other, we eliminate O(n²) dependencies and replace them with O(1) broadcast semantics. Agents emit signals ("I am thinking", "I need verification") without knowing who listens. The bus stays dumb and fast—it just transports the envelope.

Installation

pip install agentmesh-message-bus

For production deployments with Redis, RabbitMQ, or Kafka:

pip install agentmesh-message-bus[redis]      # Redis support
pip install agentmesh-message-bus[rabbitmq]   # RabbitMQ support
pip install agentmesh-message-bus[kafka]      # Kafka support
pip install agentmesh-message-bus[all]        # All adapters

Quick Start

import asyncio
from amb_core import MessageBus, Message

async def main():
    async with MessageBus() as bus:
        async def handler(msg: Message): print(msg.payload)
        await bus.subscribe("agent.events", handler)
        await bus.publish("agent.events", {"status": "ready"})
        await asyncio.sleep(0.1)

asyncio.run(main())

Features

🚦 Priority Lanes

Tag messages as CRITICAL (Security/Governance) vs BACKGROUND (Memory consolidation). Critical messages jump the queue.

# Critical security alert - jumps ahead
await bus.publish(
    "agent.alerts", 
    {"alert": "Security anomaly detected"},
    priority=MessagePriority.CRITICAL
)

# Background task - processed when system is idle
await bus.publish(
    "agent.tasks",
    {"task": "Memory consolidation"},
    priority=MessagePriority.BACKGROUND
)

Priority Levels: CRITICAL > URGENT > HIGH > NORMAL > LOW > BACKGROUND

🌊 Backpressure Protocols

Implements Reactive Streams-style flow control. If a consumer is slow, the producer automatically slows down.

# Configure backpressure parameters
broker = InMemoryBroker(
    max_queue_size=1000,           # Max messages per topic
    backpressure_threshold=0.8,    # Activate at 80% capacity
    backpressure_delay=0.01        # 10ms delay when active
)

bus = MessageBus(adapter=broker)

# If 100 agents spam the bus, backpressure prevents crashes
for agent_id in range(100):
    await bus.publish("agent.events", {"agent": agent_id})
# Producer automatically throttles when consumer is overwhelmed

Scale by Subtraction: No external load balancer needed. The bus handles flow control automatically.

🔍 OpenTelemetry Tracing (The "X-Ray")

Built-in distributed tracing for debugging multi-agent workflows. When an SDLC agent fails, trace the flow: Thought → Message → Tool Call → Error across all agents.

from amb_core import MessageBus, get_tracer, initialize_tracing

# Initialize tracing (usually done once at startup)
initialize_tracing("my-agent-system")

# Get a tracer for creating spans
tracer = get_tracer("agent-workflow")

async with MessageBus() as bus:
    # Messages published within a span automatically get the trace_id
    with tracer.start_as_current_span("agent-thinking"):
        await bus.publish("agent.thoughts", {"thought": "Processing data"})
    
    # Or explicitly set trace_id for cross-system tracing
    await bus.publish(
        "agent.action",
        {"action": "execute"},
        trace_id="custom-trace-id-from-upstream"
    )

Key Features:

• Automatic Injection: trace_id automatically injected from active OpenTelemetry span
• Cross-Agent Tracing: Same trace_id flows through request-response patterns
• Explicit Control: Can manually set trace_id for integration with external systems
• Zero Config: Works out of the box with InMemoryBroker, scales to production backends

See examples/tracing_demo.py for a complete multi-agent tracing example.

Architecture

amb sits in Layer 2 (Infrastructure) of the Agent OS stack. It transports message envelopes without inspecting content or enforcing policy.

┌──────────────────────────────────────┐
│  Layer 3: Framework                  │  agent-control-plane, scak
│  (Orchestration & Self-Correction)   │
└────────────────┬─────────────────────┘
                 │
┌────────────────▼─────────────────────┐
│  Layer 2: Infrastructure    ← AMB    │  iatp (Trust), atr (Registry)
│  (Transport & Discovery)             │
└────────────────┬─────────────────────┘
                 │
┌────────────────▼─────────────────────┐
│  Layer 1: Primitives                 │  caas (Context), cmvk (Verification),
│  (State & Identity)                  │  emk (Memory)
└──────────────────────────────────────┘

Design Principles:

• No Business Logic: The bus never decides routing based on message content.
• Broker Agnostic: Swap Redis for RabbitMQ without changing application code.
• Local-First: Works on a laptop with InMemoryBroker—no Docker required.
• Separation of Concerns: The bus transports. The receiver validates trust (via iatp), not the bus.

The Agent OS Ecosystem

amb is one component of a modular Agent Operating System. Each layer solves a specific problem.

Layer 1: Primitives (State & Identity)

• caas - Context as a Service: Manages agent context and state
• cmvk - Context Verification Kit: Cryptographic verification of context
• emk - Episodic Memory Kit: Persistent memory for agents

Layer 2: Infrastructure (Transport & Discovery)

• iatp - Inter-Agent Trust Protocol: Trust verification for agent messages
• amb - Agent Message Bus: Broker-agnostic transport (you are here)
• atr - Agent Tool Registry: Decentralized tool discovery

Layer 3: Framework (Orchestration & Self-Correction)

• agent-control-plane - The orchestration core
• scak - Self-Correction & Alignment Kit: Runtime safety and alignment

Citation

If you use AMB in research, please cite:

@software{amb2026,
  author = {Siddique, Imran},
  title = {AMB: Agent Message Bus for Decoupled Multi-Agent Systems},
  year = {2026},
  url = {https://github.com/microsoft/agent-governance-toolkit},
  version = {0.1.0}
}

---

License: MIT | Contributing: CONTRIBUTING.md | Changelog: CHANGELOG.md