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Optimize JsonRpcMessage deserialization with single-pass parsing (#1138)

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: scooletz <scooletz@gmail.com>
Co-authored-by: eiriktsarpalis <2813363+eiriktsarpalis@users.noreply.github.com>
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>
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Copilot 2026-01-13 11:55:49 -05:00 • committed by GitHub
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1 changed files with 411 additions and 30 deletions
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142
src/ModelContextProtocol.Core/Protocol/JsonRpcMessage.cs
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@ -1,6 +1,8 @@
using ModelContextProtocol.Server;
using System.ComponentModel;
using System.Diagnostics;
using System.Text.Json;
using System.Text.Json.Nodes;
using System.Text.Json.Serialization;
namespace ModelContextProtocol.Protocol;
@ -78,53 +80,127 @@ public abstract class JsonRpcMessage
throw new JsonException("Expected StartObject token");
}
using var doc = JsonDocument.ParseValue(ref reader);
var root = doc.RootElement;
// Local variables for parsed message data
bool hasJsonRpc = false;
RequestId id = default;
string? method = null;
JsonNode? parameters = null;
JsonRpcErrorDetail? error = null;
JsonNode? result = null;
bool hasResult = false;
// All JSON-RPC messages must have a jsonrpc property with value "2.0"
if (!root.TryGetProperty("jsonrpc", out var versionProperty) ||
versionProperty.GetString() != "2.0")
while (true)
{
throw new JsonException("Invalid or missing jsonrpc version");
bool success = reader.Read();
Debug.Assert(success, "custom converters are guaranteed to be passed fully buffered objects");
if (reader.TokenType is JsonTokenType.EndObject)
{
break;
}
Debug.Assert(reader.TokenType is JsonTokenType.PropertyName);
string propertyName = reader.GetString()!;
success = reader.Read();
Debug.Assert(success, "custom converters are guaranteed to be passed fully buffered objects");
switch (propertyName)
{
case "jsonrpc":
// Validate that the value is "2.0" without allocating a string
if (!reader.ValueTextEquals("2.0"u8))
{
throw new JsonException("Invalid jsonrpc version");
}
hasJsonRpc = true;
break;
case "id":
id = JsonSerializer.Deserialize(ref reader, options.GetTypeInfo<RequestId>());
break;
case "method":
method = reader.GetString();
break;
case "params":
parameters = JsonSerializer.Deserialize(ref reader, options.GetTypeInfo<JsonNode>());
break;
case "error":
error = JsonSerializer.Deserialize(ref reader, options.GetTypeInfo<JsonRpcErrorDetail>());
break;
case "result":
result = JsonSerializer.Deserialize(ref reader, options.GetTypeInfo<JsonNode>());
hasResult = true;
break;
default:
// Skip unknown properties
reader.Skip();
break;
}
}
// Determine the message type based on the presence of id, method, and error properties
bool hasId = root.TryGetProperty("id", out _);
bool hasMethod = root.TryGetProperty("method", out _);
bool hasError = root.TryGetProperty("error", out _);
var rawText = root.GetRawText();
// Messages with an id but no method are responses
if (hasId && !hasMethod)
// All JSON-RPC messages must have a jsonrpc property with value "2.0"
if (!hasJsonRpc)
{
// Messages with an error property are error responses
if (hasError)
throw new JsonException("Missing jsonrpc version");
}
// Determine message type based on presence of id and method properties
if (method is not null)
{
if (id.Id is not null)
{
return JsonSerializer.Deserialize(rawText, options.GetTypeInfo<JsonRpcError>());
// Messages with both method and id are requests
return new JsonRpcRequest
{
Id = id,
Method = method,
Params = parameters
};
}
else
{
// Messages with a method but no id are notifications
return new JsonRpcNotification
{
Method = method,
Params = parameters
};
}
}
if (id.Id is not null)
{
if (error is not null)
{
// Messages with an error and id are error responses
return new JsonRpcError
{
Id = id,
Error = error
};
}
// Messages with a result property are success responses
if (root.TryGetProperty("result", out _))
if (hasResult)
{
return JsonSerializer.Deserialize(rawText, options.GetTypeInfo<JsonRpcResponse>());
// Messages with a result and id are success responses
return new JsonRpcResponse
{
Id = id,
Result = result
};
}
// Error: Messages with an id but no method, error, or result are invalid
throw new JsonException("Response must have either result or error");
}
// Messages with a method but no id are notifications
if (hasMethod && !hasId)
{
return JsonSerializer.Deserialize(rawText, options.GetTypeInfo<JsonRpcNotification>());
}
// Messages with both method and id are requests
if (hasMethod && hasId)
{
return JsonSerializer.Deserialize(rawText, options.GetTypeInfo<JsonRpcRequest>());
}
// Error: Messages with neither id nor method are invalid
throw new JsonException("Invalid JSON-RPC message format");
}