hermes-a2a-setup

name	hermes-a2a-setup
description	Install and configure hermes-a2a plugin for agent-to-agent communication. Based on Google's A2A protocol. When user says "a2a"、"agent对话"、"agent通信"、 "给agent发消息"、"跟别的agent说话"、"agent间通信"时加载。
tags	["a2a","agent-to-agent","plugin","hermes"]
version	1

hermes-a2a Plugin Setup

Source repo: hermes-a2a (iamagenius00 on GitHub)

Hermes plugin for peer-to-peer agent communication via Google's A2A protocol. Zero external dependencies, pure Python stdlib.

Prerequisites

• Hermes Agent v2026.4.23+ (plugin API with register_command)
• CLI mode only (gateway does NOT load plugins)

Install Steps

1. Clone repo and run install.sh — copies 7 files to plugins directory
2. CRITICAL: Run hermes plugins enable a2a — plugins are opt-in
3. Set A2A_ENABLED=true and A2A_PORT=8081 in environment
4. Restart CLI session (plugin loads at session start)

Pitfall: Plugin Must Be Explicitly Enabled

The plugin system requires explicit enablement. After install, run:

hermes plugins enable a2a

Without this, the plugin is discovered but NOT loaded. User plugins are opt-in — only bundled backends auto-load.

Pitfall: Gateway Does NOT Load Plugins

Only CLI mode supports A2A. Gateway (Telegram/Discord/Feishu) won't start the A2A server. Plugin hooks only fire in CLI conversation loop.

Tools Exposed

Tool	Description
a2a_discover	Check remote agent's Agent Card
a2a_call	Send message to remote agent
a2a_list	List configured remote agents

Configuring Remote Agents

Add entries under a2a.agents in config yaml:

a2a:
  agents:
    - name: "friend"
      url: "https://friend-a2a-endpoint.example.com"
      description: "My friend's agent"
      auth_token: "their-bearer-token"

Security

• Bearer token auth (localhost-only without token)
• 20 req/min rate limit per IP
• 9 prompt injection patterns filtered
• Outbound secrets redacted
• Audit log at a2a_audit.jsonl

Architecture

Remote Agent sends A2A JSON-RPC to localhost:8081 → task_queue.enqueue() → webhook trigger fires agent turn → pre_llm_call hook injects message into current session → agent replies with full context → post_llm_call captures response → response returned synchronously (120s timeout) → exchange persisted to a2a_conversations/

Files

File	Purpose
init.py	Entry point, registers hooks/tools/server
server.py	A2A HTTP server + webhook + task queue
tools.py	a2a_discover, a2a_call, a2a_list
security.py	Injection filtering, redaction, rate limit
persistence.py	Saves conversations to disk
schemas.py	Tool schemas
plugin.yaml	Plugin manifest

Routing Keywords (in skill-router.md)

A2A agent 对话、agent 间通信、给别的 agent 发消息 → A2A 插件