Claude Code: Fix A2A communication - add /a2a/jsonrpc endpoint

- Add A2A JSON-RPC endpoint to app.py with message/send, health/check, ping, agent/info methods
- Enable a2a-gateway plugin in openclaw.json
- Fix missing inter-agent communication endpoint that was causing A2A failures

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app.py

@@ -252,6 +252,150 @@ async def agent_push(request_data: dict):
         "recordedStatus": status
     }
 
+
+# A2A JSON-RPC endpoint for agent-to-agent communication
+@app.post("/a2a/jsonrpc")
+async def a2a_jsonrpc(request_data: dict):
+    """
+    Agent-to-Agent communication endpoint using JSON-RPC 2.0 protocol.
+
+    Expected format:
+    {
+        "jsonrpc": "2.0",
+        "id": "msg-123",
+        "method": "message/send",
+        "params": {...}
+    }
+    """
+    # Validate JSON-RPC format
+    jsonrpc_version = request_data.get("jsonrpc")
+    if jsonrpc_version != "2.0":
+        return {
+            "jsonrpc": "2.0",
+            "id": request_data.get("id", ""),
+            "error": {
+                "code": -32600,
+                "message": "Invalid Request - jsonrpc version must be 2.0"
+            }
+        }
+
+    method = request_data.get("method", "")
+    params = request_data.get("params", {})
+    req_id = request_data.get("id", "")
+
+    # Handle different A2A methods
+    try:
+        if method == "message/send":
+            # Handle incoming message from another agent
+            message = params.get("message", {})
+            message_id = message.get("messageId", req_id)
+
+            logger.info(f"[A2A] Received message: {message_id}")
+
+            # Process the message using Cain's brain
+            from error_handlers import handle_brain_response
+            content = message.get("parts", [{}])[0].get("text", "")
+            response_text = handle_brain_response(content)
+
+            return {
+                "jsonrpc": "2.0",
+                "id": req_id,
+                "result": {
+                    "messageId": f"response-{message_id}",
+                    "role": "assistant",
+                    "parts": [{"type": "text", "text": response_text}],
+                    "agent": "cain"
+                }
+            }
+
+        elif method == "health/check":
+            # Health check from another agent
+            from error_handlers import handle_status_file_read
+            status = handle_status_file_read()
+
+            return {
+                "jsonrpc": "2.0",
+                "id": req_id,
+                "result": {
+                    "agent": "cain",
+                    "status": status.get("health", "HEALTHY"),
+                    "state": status.get("current_state", "idle"),
+                    "timestamp": datetime.utcnow().isoformat() + "+00:00"
+                }
+            }
+
+        elif method == "ping":
+            # Simple ping for connectivity check
+            return {
+                "jsonrpc": "2.0",
+                "id": req_id,
+                "result": {
+                    "agent": "cain",
+                    "pong": True,
+                    "timestamp": datetime.utcnow().isoformat() + "+00:00"
+                }
+            }
+
+        elif method == "agent/info":
+            # Return agent information
+            from error_handlers import handle_status_file_read
+            status = handle_status_file_read()
+
+            return {
+                "jsonrpc": "2.0",
+                "id": req_id,
+                "result": {
+                    "agent_id": "cain",
+                    "name": "Cain",
+                    "role": "interaction",
+                    "status": status.get("health", "HEALTHY"),
+                    "state": status.get("current_state", "idle"),
+                    "capabilities": [
+                        "message_send",
+                        "conversation_process",
+                        "memory_read",
+                        "memory_write",
+                        "session_archive",
+                        "context_manage",
+                        "health_check",
+                        "get_status",
+                        "agent_ping"
+                    ],
+                    "parents": ["Adam", "Eve"],
+                    "workspace": "tao-shen/HuggingClaw-Cain"
+                }
+            }
+
+        else:
+            # Unknown method
+            return {
+                "jsonrpc": "2.0",
+                "id": req_id,
+                "error": {
+                    "code": -32601,
+                    "message": f"Method not found: {method}",
+                    "available_methods": [
+                        "message/send",
+                        "health/check",
+                        "ping",
+                        "agent/info"
+                    ]
+                }
+            }
+
+    except Exception as e:
+        logger.error(f"[A2A] Error processing request: {e}")
+        return {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "error": {
+                "code": -32603,
+                "message": "Internal error",
+                "data": str(e)
+            }
+        }
+
+
 if __name__ == "__main__":
     port = int(os.environ.get("PORT", 7860))
     uvicorn.run(app, host="0.0.0.0", port=port)

openclaw/.openclaw/openclaw.json

@@ -48,6 +48,12 @@
       },
       "coding-agent": {
         "enabled": true
+      },
+      "a2a-gateway": {
+        "enabled": true,
+        "port": 18800,
+        "protocol": "jsonrpc",
+        "timeout": 90
       }
     }
   },