RFC: External Integration Architecture — Agentic Ingress, MCP Gateway, A2A Protocol

[lanycrost]

Overview

This RFC proposes the external integration architecture for BubuStack — how the platform accepts inbound connections, hosts agent tools, and enables agent-to-agent collaboration.

Three capabilities, one architecture:

1. Agentic Ingress Layer

A persistent, always-on component that accepts inbound connections and routes them into running streaming pipelines.

Protocols: SIP (telephony/Twilio), WebRTC (realtime), MQTT (IoT), HTTP SSE

Why: The current model is outbound-only — Engrams connect to external endpoints. Inbound scenarios (incoming calls, IoT sensor streams, external-initiated WebSocket connections) have no entry point today.

What it solves:

• Telephony integration (SIP trunks, Twilio)
• IoT device ingestion (MQTT)
• Browser-initiated realtime sessions (WebRTC)
• External webhook-to-streaming bridging (HTTP SSE)

2. MCP Gateway

Production MCP server hosting with session-aware routing, circuit breakers, health monitoring, and tool aggregation from multiple Engrams.

Builds on: Existing mcp-adapter-engram with hardened timeouts, cancellation propagation, and pod recycling for long-lived sessions.

What it solves:

• Long-lived MCP sessions with health monitoring
• Tool discovery and aggregation across Engrams
• Session-aware routing for stateful tool interactions

3. Native A2A Protocol Support

Agent-to-agent negotiation as first-class CRDs. AgentCard makes Engrams discoverable as A2A agents with skills, input/output schemas, and interaction modes.

Relationship:

• MCP handles tool integration (agent → tool)
• A2A handles agent collaboration (agent → agent)
• Ingress handles external protocol adaptation (world → pipeline)

Tasks route to Stories via Extended Hooks.

Dependencies

• Extended Story Hooks (Implement extended story hooks for mid-execution event injection #40)
• CloudEvents adoption (Standardize impulse and hook events as CloudEvents #43)

Questions for discussion

1. Should the Ingress Layer be a separate component or part of bobravoz-grpc?
2. Should MCP Gateway be a standalone service or an enhanced Engram?
3. How should AgentCard discovery work across namespaces/clusters?
4. Priority ordering — which capability is most valuable first?
5. Protocol driver plugin architecture — how to enable community-contributed adapters?

References

• Roadmap: https://bubustack.io/docs/community/roadmap
• A2A Protocol: https://a2a-protocol.org/
• MCP: https://modelcontextprotocol.io/