feat: add A2A (Agent-to-Agent) protocol integration

a2a_adapter/__init__.py

@@ -0,0 +1,5 @@
+"""A2A (Agent-to-Agent) protocol server adapter for hermes-agent.
+
+Exposes Hermes as an A2A-discoverable agent that can receive tasks from
+any A2A-compliant client or agent, regardless of framework.
+"""

a2a_adapter/__main__.py

@@ -0,0 +1,6 @@
+"""Allow running with ``python -m a2a_adapter``."""
+
+from a2a_adapter.entry import main
+
+if __name__ == "__main__":
+    main()

a2a_adapter/entry.py

@@ -0,0 +1,121 @@
+#!/usr/bin/env python3
+"""Entry point for the Hermes A2A server.
+
+Starts Hermes as an A2A-discoverable agent on HTTP, serving:
+  - /.well-known/agent.json  — Agent Card (discovery)
+  - /                        — JSON-RPC endpoint (task execution)
+
+Usage:
+    hermes-a2a                              # default port 9990
+    hermes-a2a --port 8080                  # custom port
+    hermes-a2a --host 127.0.0.1 --port 8080  # bind to localhost only
+    hermes-a2a --name "My Agent"            # custom agent name
+"""
+
+import argparse
+import logging
+import os
+import sys
+
+
+def _setup_logging():
+    """Configure logging to stderr so stdout stays clean for HTTP."""
+    handler = logging.StreamHandler(sys.stderr)
+    handler.setFormatter(
+        logging.Formatter("%(asctime)s [%(name)s] %(levelname)s: %(message)s")
+    )
+    root = logging.getLogger()
+    root.addHandler(handler)
+    root.setLevel(logging.INFO)
+
+
+def _load_env():
+    """Load environment from ~/.hermes/.env if available."""
+    try:
+        from hermes_cli.env_loader import load_dotenv
+        load_dotenv()
+    except ImportError:
+        pass
+
+
+def main():
+    """Start the Hermes A2A server."""
+    parser = argparse.ArgumentParser(
+        description="Run Hermes as an A2A-discoverable agent server"
+    )
+    parser.add_argument(
+        "--host", default="127.0.0.1",
+        help="Host to bind to (default: 127.0.0.1). Use 0.0.0.0 for remote access (requires --bearer-token)."
+    )
+    parser.add_argument(
+        "--port", type=int, default=9990,
+        help="Port to listen on (default: 9990)"
+    )
+    parser.add_argument(
+        "--name", default="Hermes Agent",
+        help="Agent name in the Agent Card (default: 'Hermes Agent')"
+    )
+    parser.add_argument(
+        "--bearer-token",
+        default=os.environ.get("HERMES_A2A_BEARER_TOKEN"),
+        help="Require this bearer token for all requests (env: HERMES_A2A_BEARER_TOKEN). "
+             "Strongly recommended when binding to 0.0.0.0.",
+    )
+    parser.add_argument(
+        "--toolset", default="hermes-cli",
+        help="Toolset for agent sessions (default: hermes-cli). Use 'hermes-acp' for restricted access.",
+    )
+    args = parser.parse_args()
+
+    _setup_logging()
+    _load_env()
+
+    logger = logging.getLogger(__name__)
+
+    # Security: warn loudly if binding to all interfaces without auth
+    if args.host == "0.0.0.0" and not args.bearer_token:
+        logger.warning(
+            "WARNING: Binding to 0.0.0.0 WITHOUT --bearer-token. "
+            "This exposes full agent access (terminal, files, code execution) "
+            "to anyone who can reach this port. Set --bearer-token or use "
+            "HERMES_A2A_BEARER_TOKEN env var to require authentication."
+        )
+
+    try:
+        from a2a_adapter.server import build_application, is_server_available
+    except ImportError:
+        logger.error(
+            "A2A server dependencies not installed. "
+            "Install with: pip install 'hermes-agent[a2a]' or pip install 'a2a-sdk[http-server]'"
+        )
+        sys.exit(1)
+
+    if not is_server_available():
+        logger.error(
+            "A2A SDK server components not available. "
+            "Install with: pip install 'a2a-sdk[http-server]'"
+        )
+        sys.exit(1)
+
+    try:
+        import uvicorn
+    except ImportError:
+        logger.error(
+            "uvicorn not installed. Install with: pip install uvicorn[standard]"
+        )
+        sys.exit(1)
+
+    logger.info("Starting Hermes A2A server on %s:%d", args.host, args.port)
+    if args.bearer_token:
+        logger.info("Bearer token authentication ENABLED")
+    logger.info("Agent Card: http://%s:%d/.well-known/agent.json", args.host, args.port)
+
+    app = build_application(
+        host=args.host, port=args.port, name=args.name,
+        bearer_token=args.bearer_token, toolset=args.toolset,
+    )
+    uvicorn.run(app.build(), host=args.host, port=args.port)
+
+
+if __name__ == "__main__":
+    main()