fix: JSON-RPC ID round-trip preservation for numeric IDs

src/A2A.AspNetCore/A2AJsonRpcProcessor.cs

@@ -40,7 +40,7 @@ internal static async Task<IResult> ProcessRequestAsync(ITaskManager taskManager
         {
             rpcRequest = (JsonRpcRequest?)await JsonSerializer.DeserializeAsync(request.Body, A2AJsonUtilities.DefaultOptions.GetTypeInfo(typeof(JsonRpcRequest)), cancellationToken).ConfigureAwait(false);
 
-            activity?.AddTag("request.id", rpcRequest!.Id);
+            activity?.AddTag("request.id", rpcRequest!.Id.ToString());
             activity?.AddTag("request.method", rpcRequest!.Method);
 
             // Dispatch based on return type
@@ -51,15 +51,17 @@ internal static async Task<IResult> ProcessRequestAsync(ITaskManager taskManager
 
             return await SingleResponseAsync(taskManager, rpcRequest.Id, rpcRequest.Method, rpcRequest.Params, cancellationToken).ConfigureAwait(false);
         }
-        catch (A2AException ex)
-        {
-            activity?.SetStatus(ActivityStatusCode.Error, ex.Message);
-            return new JsonRpcResponseResult(JsonRpcResponse.CreateJsonRpcErrorResponse(rpcRequest?.Id ?? ex.GetRequestId(), ex));
-        }
-        catch (Exception ex)
-        {
-            activity?.SetStatus(ActivityStatusCode.Error, ex.Message);
-            return new JsonRpcResponseResult(JsonRpcResponse.InternalErrorResponse(rpcRequest?.Id, ex.Message));
+        catch (A2AException ex)
+        {
+            activity?.SetStatus(ActivityStatusCode.Error, ex.Message);
+            var errorId = rpcRequest?.Id ?? new JsonRpcId(ex.GetRequestId());
+            return new JsonRpcResponseResult(JsonRpcResponse.CreateJsonRpcErrorResponse(errorId, ex));
+        }
+        catch (Exception ex)
+        {
+            activity?.SetStatus(ActivityStatusCode.Error, ex.Message);
+            var errorId = rpcRequest?.Id ?? new JsonRpcId((string?)null);
+            return new JsonRpcResponseResult(JsonRpcResponse.InternalErrorResponse(errorId, ex.Message));
         }
     }
 
@@ -76,10 +78,10 @@ internal static async Task<IResult> ProcessRequestAsync(ITaskManager taskManager
     /// <param name="parameters">The JSON parameters for the method call.</param>
     /// <param name="cancellationToken">A cancellation token that can be used to cancel the operation.</param>
     /// <returns>A JSON-RPC response result containing the operation result or error.</returns>
-    internal static async Task<JsonRpcResponseResult> SingleResponseAsync(ITaskManager taskManager, string? requestId, string method, JsonElement? parameters, CancellationToken cancellationToken)
+    internal static async Task<JsonRpcResponseResult> SingleResponseAsync(ITaskManager taskManager, JsonRpcId requestId, string method, JsonElement? parameters, CancellationToken cancellationToken)
     {
-        using var activity = ActivitySource.StartActivity($"SingleResponse/{method}", ActivityKind.Server);
-        activity?.SetTag("request.id", requestId);
+        using var activity = ActivitySource.StartActivity($"SingleResponse/{method}", ActivityKind.Server);
+        activity?.SetTag("request.id", requestId.ToString());
         activity?.SetTag("request.method", method);
 
         JsonRpcResponse? response = null;
@@ -165,10 +167,10 @@ private static T DeserializeAndValidate<T>(JsonElement jsonParamValue) where T :
     /// <param name="parameters">The JSON parameters for the streaming method call.</param>
     /// <param name="cancellationToken">A cancellation token that can be used to cancel the operation.</param>
     /// <returns>An HTTP result that streams JSON-RPC responses as Server-Sent Events or an error response.</returns>
-    internal static IResult StreamResponse(ITaskManager taskManager, string? requestId, string method, JsonElement? parameters, CancellationToken cancellationToken)
+    internal static IResult StreamResponse(ITaskManager taskManager, JsonRpcId requestId, string method, JsonElement? parameters, CancellationToken cancellationToken)
     {
-        using var activity = ActivitySource.StartActivity("StreamResponse", ActivityKind.Server);
-        activity?.SetTag("request.id", requestId);
+        using var activity = ActivitySource.StartActivity("StreamResponse", ActivityKind.Server);
+        activity?.SetTag("request.id", requestId.ToString());
 
         if (parameters == null)
         {

src/A2A.AspNetCore/JsonRpcStreamedResult.cs

@@ -15,14 +15,14 @@ namespace A2A.AspNetCore;
 public class JsonRpcStreamedResult : IResult
 {
     private readonly IAsyncEnumerable<A2AEvent> _events;
-    private readonly string? requestId;
+    private readonly JsonRpcId requestId;
 
     /// <summary>
     /// Initializes a new instance of the JsonRpcStreamedResult class.
     /// </summary>
     /// <param name="events">The async enumerable stream of A2A events to send as Server-Sent Events.</param>
     /// <param name="requestId">The JSON-RPC request ID used for correlating responses with the original request.</param>
-    public JsonRpcStreamedResult(IAsyncEnumerable<A2AEvent> events, string? requestId)
+    public JsonRpcStreamedResult(IAsyncEnumerable<A2AEvent> events, JsonRpcId requestId)
     {
         ArgumentNullException.ThrowIfNull(events);
 

src/A2A/A2A.csproj

@@ -20,6 +20,7 @@
   <!-- Dependencies only needed by netstandard2.0 -->
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
     <PackageReference Include="System.Text.Json" />
+        <PackageReference Include="System.Threading.Channels" />
   </ItemGroup>
 
   <!-- Dependencies needed by all -->
@@ -36,7 +37,6 @@
           <PrivateAssets>all</PrivateAssets>
           <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       </PackageReference>
-      <PackageReference Include="System.Threading.Channels" />
   </ItemGroup>
 
 	<ItemGroup>

src/A2A/A2AExceptionExtensions.cs

@@ -30,12 +30,35 @@ public static A2AException WithRequestId(this A2AException exception, string? re
             return exception;
         }
 
+        /// <summary>
+        /// Associates a request ID with the specified <see cref="A2AException"/>.
+        /// </summary>
+        /// <param name="exception">The <see cref="A2AException"/> to associate the request ID with.</param>
+        /// <param name="requestId">The request ID to associate with the exception.</param>
+        /// <returns>The same <see cref="A2AException"/> instance with the request ID stored in its Data collection.</returns>
+        /// <remarks>
+        /// This method stores the request ID in the exception's Data collection using the key "RequestId".
+        /// The request ID can be later retrieved using the <see cref="GetRequestId"/> method.
+        /// This is useful for correlating exceptions with specific HTTP requests in logging and debugging scenarios.
+        /// </remarks>
+        public static A2AException WithRequestId(this A2AException exception, JsonRpcId requestId)
+        {
+            if (exception is null)
+            {
+                throw new ArgumentNullException(nameof(exception));
+            }
+
+            exception.Data[RequestIdKey] = requestId.ToString();
+
+            return exception;
+        }
+
         /// <summary>
         /// Retrieves the request ID associated with the specified <see cref="A2AException"/>.
         /// </summary>
         /// <param name="exception">The <see cref="A2AException"/> to retrieve the request ID from.</param>
         /// <returns>
-        /// The request ID associated with the exception if one was previously set using <see cref="WithRequestId"/>,
+        /// The request ID associated with the exception if one was previously set using <see cref="WithRequestId(A2AException, string?)"/>,
         /// or null if no request ID was set or if the stored value is not a string.
         /// </returns>
         /// <remarks>

src/A2A/A2AJsonUtilities.cs

@@ -35,6 +35,7 @@ public static partial class A2AJsonUtilities
 
     // JSON-RPC
     [JsonSerializable(typeof(JsonRpcError))]
+    [JsonSerializable(typeof(JsonRpcId))]
     [JsonSerializable(typeof(JsonRpcRequest))]
     [JsonSerializable(typeof(JsonRpcResponse))]
     [JsonSerializable(typeof(Dictionary<string, JsonElement>))]

src/A2A/Client/A2AClient.cs

@@ -135,7 +135,7 @@ private async IAsyncEnumerable<SseItem<TOutput>> SendRpcSseRequestAsync<TInput,
             "text/event-stream",
             cancellationToken).ConfigureAwait(false);
 
-        var sseParser = SseParser.Create(responseStream, (eventType, data) =>
+        var sseParser = SseParser.Create(responseStream, (_, data) =>
         {
             var reader = new Utf8JsonReader(data);
 
@@ -146,7 +146,12 @@ private async IAsyncEnumerable<SseItem<TOutput>> SendRpcSseRequestAsync<TInput,
                 throw new A2AException(error.Message, (A2AErrorCode)error.Code);
             }
 
-            return JsonSerializer.Deserialize(responseObject?.Result, outputTypeInfo) ??
+            if (responseObject?.Result is null)
+            {
+                throw new InvalidOperationException("Failed to deserialize the event: Result is null.");
+            }
+
+            return responseObject.Result.Deserialize(outputTypeInfo) ??
                 throw new InvalidOperationException("Failed to deserialize the event.");
         });
 

src/A2A/JsonRpc/JsonRpcId.cs

@@ -0,0 +1,170 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace A2A;
+
+/// <summary>
+/// Represents a JSON-RPC ID that can be either a string or a number, preserving the original type.
+/// </summary>
+[JsonConverter(typeof(Converter))]
+public readonly struct JsonRpcId : IEquatable<JsonRpcId>
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="JsonRpcId"/> struct with a string value.
+    /// </summary>
+    /// <param name="value">The string value.</param>
+    public JsonRpcId(string? value) => Value = value;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="JsonRpcId"/> struct with a numeric value.
+    /// </summary>
+    /// <param name="value">The numeric value.</param>
+    public JsonRpcId(long value) => Value = value;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="JsonRpcId"/> struct with a numeric value.
+    /// </summary>
+    /// <param name="value">The numeric value.</param>
+    public JsonRpcId(int value) => Value = (long)value;
+
+    /// <summary>
+    /// Gets a value indicating whether this ID has a value.
+    /// </summary>
+    public bool HasValue => Value is not null;
+
+    /// <summary>
+    /// Gets a value indicating whether this ID is a string.
+    /// </summary>
+    public bool IsString => Value is string;
+
+    /// <summary>
+    /// Gets a value indicating whether this ID is a number.
+    /// </summary>
+    public bool IsNumber => Value is long;
+
+    /// <summary>
+    /// Gets the string value of this ID if it's a string.
+    /// </summary>
+    /// <returns>The string value, or null if not a string.</returns>
+    public string? AsString() => Value as string;
+
+    /// <summary>
+    /// Gets the numeric value of this ID if it's a number.
+    /// </summary>
+    /// <returns>The numeric value, or null if not a number.</returns>
+    public long? AsNumber() => Value as long?;
+
+    /// <summary>
+    /// Gets the raw value as an object.
+    /// </summary>
+    /// <returns>The raw value as an object.</returns>
+    public object? Value { get; }
+
+    /// <summary>
+    /// Returns a string representation of this ID.
+    /// </summary>
+    /// <returns>A string representation of the ID.</returns>
+    public override string? ToString() => Value?.ToString();
+
+    /// <summary>
+    /// Determines whether the specified object is equal to the current ID.
+    /// </summary>
+    /// <param name="obj">The object to compare with the current ID.</param>
+    /// <returns>true if the specified object is equal to the current ID; otherwise, false.</returns>
+    public override bool Equals(object? obj) => obj is JsonRpcId other && Equals(other);
+
+    /// <summary>
+    /// Determines whether the specified ID is equal to the current ID.
+    /// </summary>
+    /// <param name="other">The ID to compare with the current ID.</param>
+    /// <returns>true if the specified ID is equal to the current ID; otherwise, false.</returns>
+    public bool Equals(JsonRpcId other) => Equals(Value, other.Value);
+
+    /// <summary>
+    /// Returns the hash code for this ID.
+    /// </summary>
+    /// <returns>A hash code for the current ID.</returns>
+    public override int GetHashCode() => Value?.GetHashCode() ?? 0;
+
+    /// <summary>
+    /// Determines whether two IDs are equal.
+    /// </summary>
+    /// <param name="left">The first ID to compare.</param>
+    /// <param name="right">The second ID to compare.</param>
+    /// <returns>true if the IDs are equal; otherwise, false.</returns>
+    public static bool operator ==(JsonRpcId left, JsonRpcId right) => left.Equals(right);
+
+    /// <summary>
+    /// Determines whether two IDs are not equal.
+    /// </summary>
+    /// <param name="left">The first ID to compare.</param>
+    /// <param name="right">The second ID to compare.</param>
+    /// <returns>true if the IDs are not equal; otherwise, false.</returns>
+    public static bool operator !=(JsonRpcId left, JsonRpcId right) => !left.Equals(right);
+
+    /// <summary>
+    /// Implicitly converts a string to a JsonRpcId.
+    /// </summary>
+    /// <param name="value">The string value.</param>
+    /// <returns>A JsonRpcId with the string value.</returns>
+    public static implicit operator JsonRpcId(string? value) => new(value);
+
+    /// <summary>
+    /// Implicitly converts a long to a JsonRpcId.
+    /// </summary>
+    /// <param name="value">The numeric value.</param>
+    /// <returns>A JsonRpcId with the numeric value.</returns>
+    public static implicit operator JsonRpcId(long value) => new(value);
+
+    /// <summary>
+    /// Implicitly converts an int to a JsonRpcId.
+    /// </summary>
+    /// <param name="value">The numeric value.</param>
+    /// <returns>A JsonRpcId with the numeric value.</returns>
+    public static implicit operator JsonRpcId(int value) => new(value);
+
+    /// <summary>
+    /// JSON converter for JsonRpcId that preserves the original type during serialization/deserialization.
+    /// </summary>
+    internal sealed class Converter : JsonConverter<JsonRpcId>
+    {
+        public override JsonRpcId Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            switch (reader.TokenType)
+            {
+                case JsonTokenType.String:
+                    return new JsonRpcId(reader.GetString());
+                case JsonTokenType.Number:
+                    if (reader.TryGetInt64(out var longValue))
+                    {
+                        return new JsonRpcId(longValue);
+                    }
+                    throw new JsonException("Invalid numeric value for JSON-RPC ID.");
+                case JsonTokenType.Null:
+                    return new JsonRpcId(null);
+                default:
+                    throw new JsonException("Invalid JSON-RPC ID format. Must be string, number, or null.");
+            }
+        }
+
+        public override void Write(Utf8JsonWriter writer, JsonRpcId value, JsonSerializerOptions options)
+        {
+            if (!value.HasValue)
+            {
+                writer.WriteNullValue();
+            }
+            else if (value.IsString)
+            {
+                writer.WriteStringValue(value.AsString());
+            }
+            else if (value.IsNumber)
+            {
+                writer.WriteNumberValue(value.AsNumber()!.Value);
+            }
+            else
+            {
+                writer.WriteNullValue();
+            }
+        }
+    }
+}

src/A2A/JsonRpc/JsonRpcRequest.cs

@@ -26,7 +26,7 @@ public sealed class JsonRpcRequest
     /// Numbers SHOULD NOT contain fractional parts.
     /// </remarks>
     [JsonPropertyName("id")]
-    public string? Id { get; set; }
+    public JsonRpcId Id { get; set; }
 
     /// <summary>
     /// Gets or sets the string containing the name of the method to be invoked.