fix: update protocol negotiation error code from -32004 to -32022 across all transport versions

Author: anubhav756

packages/toolbox-core/src/toolbox_core/mcp_transport/v20250618/mcp.py

@@ -73,7 +73,7 @@ async def _send_request(
             # Check for JSON-RPC Error
             if "error" in json_resp:
                 err_val = json_resp["error"]
-                if isinstance(err_val, dict) and err_val.get("code") == -32004:
+                if isinstance(err_val, dict) and err_val.get("code") == -32022:
                     server_supported = err_val.get("data", {}).get("supported", [])
                     client_supported = self._supported_protocols
                     mutually_supported = [

packages/toolbox-core/src/toolbox_core/mcp_transport/v20251125/mcp.py

@@ -73,7 +73,7 @@ async def _send_request(
             # Check for JSON-RPC Error
             if "error" in json_resp:
                 err_val = json_resp["error"]
-                if isinstance(err_val, dict) and err_val.get("code") == -32004:
+                if isinstance(err_val, dict) and err_val.get("code") == -32022:
                     server_supported = err_val.get("data", {}).get("supported", [])
                     client_supported = self._supported_protocols
                     mutually_supported = [

packages/toolbox-core/src/toolbox_core/mcp_transport/v20260618/mcp.py

@@ -83,7 +83,7 @@ async def _send_request(
                     json_resp = await response.json()
                     if "error" in json_resp:
                         err_val = json_resp["error"]
-                        if isinstance(err_val, dict) and err_val.get("code") == -32004:
+                        if isinstance(err_val, dict) and err_val.get("code") == -32022:
                             server_supported = err_val.get("data", {}).get(
                                 "supported", []
                             )

packages/toolbox-core/tests/mcp_transport/test_v20260618.py

@@ -239,7 +239,7 @@ async def test_version_negotiation_raises_fallback(self, transport):
             "jsonrpc": "2.0",
             "id": "1",
             "error": {
-                "code": -32004,
+                "code": -32022,
                 "message": "Unsupported protocol version",
                 "data": {"supported": ["DRAFT-2026-v1"]},
             },
@@ -266,7 +266,7 @@ def get_result_model(self):
         assert transport._session.post.call_count == 1
 
     async def test_version_negotiation_raises_fallback_200_ok(self, transport):
-        """Tests that the client raises ProtocolNegotiationError when the server returns 200 OK with -32004."""
+        """Tests that the client raises ProtocolNegotiationError when the server returns 200 OK with -32022."""
         from toolbox_core.exceptions import ProtocolNegotiationError
 
         mock_response_reject = AsyncMock()
@@ -277,7 +277,7 @@ async def test_version_negotiation_raises_fallback_200_ok(self, transport):
             "jsonrpc": "2.0",
             "id": "1",
             "error": {
-                "code": -32004,
+                "code": -32022,
                 "message": "Unsupported protocol version",
                 "data": {"supported": ["DRAFT-2026-v1"]},
             },
@@ -312,7 +312,7 @@ async def test_version_negotiation_empty_intersection(self, transport):
             "jsonrpc": "2.0",
             "id": "1",
             "error": {
-                "code": -32004,
+                "code": -32022,
                 "message": "Unsupported protocol version",
                 "data": {"supported": ["UNSUPPORTED-VERSION"]},
             },