Refactor MCP server config types across all SDK languages

Introduce an abstract McpServerConfig base class in C# with a private
protected constructor and sealed derived types McpStdioServerConfig and
McpHttpServerConfig. Shared properties (Tools, Type, Timeout) are
deduplicated into the base class. The Type property uses the
JsonPolymorphic discriminator pattern consistent with SessionEvent.

All Dictionary<string, object> McpServers properties are now strongly
typed as Dictionary<string, McpServerConfig>.

Rename Local/Remote to Stdio/Http across all four SDK languages to
match MCP protocol terminology:
- C#: McpStdioServerConfig / McpHttpServerConfig
- TypeScript: MCPStdioServerConfig / MCPHttpServerConfig
- Go: MCPStdioServerConfig / MCPHTTPServerConfig
- Python: MCPStdioServerConfig / MCPHttpServerConfig

Update documentation examples accordingly.

Fixes #245

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: stephentoub

docs/features/mcp.md

@@ -143,11 +143,10 @@ await using var client = new CopilotClient();
 await using var session = await client.CreateSessionAsync(new SessionConfig
 {
     Model = "gpt-5",
-    McpServers = new Dictionary<string, object>
+    McpServers = new Dictionary<string, McpServerConfig>
     {
-        ["my-local-server"] = new McpLocalServerConfig
+        ["my-local-server"] = new McpStdioServerConfig
         {
-            Type = "local",
             Command = "node",
             Args = new List<string> { "./mcp-server.js" },
             Tools = new List<string> { "*" },

docs/troubleshooting/mcp-debugging.md

@@ -250,19 +250,17 @@ public static class McpDotnetConfigExample
 {
     public static void Main()
     {
-        var servers = new Dictionary<string, McpLocalServerConfig>
+        var servers = new Dictionary<string, McpServerConfig>
         {
-            ["my-dotnet-server"] = new McpLocalServerConfig
+            ["my-dotnet-server"] = new McpStdioServerConfig
             {
-                Type = "local",
                 Command = @"C:\Tools\MyServer\MyServer.exe",
                 Args = new List<string>(),
                 Cwd = @"C:\Tools\MyServer",
                 Tools = new List<string> { "*" },
             },
-            ["my-dotnet-tool"] = new McpLocalServerConfig
+            ["my-dotnet-tool"] = new McpStdioServerConfig
             {
-                Type = "local",
                 Command = "dotnet",
                 Args = new List<string> { @"C:\Tools\MyTool\MyTool.dll" },
                 Cwd = @"C:\Tools\MyTool",
@@ -275,19 +273,17 @@ public static class McpDotnetConfigExample
 <!-- /docs-validate: hidden -->
 ```csharp
 // Correct configuration for .NET exe
-["my-dotnet-server"] = new McpLocalServerConfig
+["my-dotnet-server"] = new McpStdioServerConfig
 {
-    Type = "local",
     Command = @"C:\Tools\MyServer\MyServer.exe",  // Full path with .exe
     Args = new List<string>(),
     Cwd = @"C:\Tools\MyServer",  // Set working directory
     Tools = new List<string> { "*" },
 }
 
 // For dotnet tool (DLL)
-["my-dotnet-tool"] = new McpLocalServerConfig
+["my-dotnet-tool"] = new McpStdioServerConfig
 {
-    Type = "local", 
     Command = "dotnet",
     Args = new List<string> { @"C:\Tools\MyTool\MyTool.dll" },
     Cwd = @"C:\Tools\MyTool",
@@ -305,11 +301,10 @@ public static class McpNpxConfigExample
 {
     public static void Main()
     {
-        var servers = new Dictionary<string, McpLocalServerConfig>
+        var servers = new Dictionary<string, McpServerConfig>
         {
-            ["filesystem"] = new McpLocalServerConfig
+            ["filesystem"] = new McpStdioServerConfig
             {
-                Type = "local",
                 Command = "cmd",
                 Args = new List<string> { "/c", "npx", "-y", "@modelcontextprotocol/server-filesystem", "C:\\allowed\\path" },
                 Tools = new List<string> { "*" },
@@ -321,9 +316,8 @@ public static class McpNpxConfigExample
 <!-- /docs-validate: hidden -->
 ```csharp
 // Windows needs cmd /c for npx
-["filesystem"] = new McpLocalServerConfig
+["filesystem"] = new McpStdioServerConfig
 {
-    Type = "local",
     Command = "cmd",
     Args = new List<string> { "/c", "npx", "-y", "@modelcontextprotocol/server-filesystem", "C:\\allowed\\path" },
     Tools = new List<string> { "*" },
@@ -357,9 +351,9 @@ xattr -d com.apple.quarantine /path/to/mcp-server
 
 <!-- docs-validate: hidden -->
 ```typescript
-import { MCPLocalServerConfig } from "@github/copilot-sdk";
+import { MCPStdioServerConfig } from "@github/copilot-sdk";
 
-const mcpServers: Record<string, MCPLocalServerConfig> = {
+const mcpServers: Record<string, MCPStdioServerConfig> = {
   "my-server": {
     command: "/opt/homebrew/bin/node",
     args: ["/path/to/server.js"],

dotnet/src/Client.cs

@@ -1637,7 +1637,7 @@ internal record CreateSessionRequest(
         bool? Hooks,
         string? WorkingDirectory,
         bool? Streaming,
-        Dictionary<string, object>? McpServers,
+        Dictionary<string, McpServerConfig>? McpServers,
         string? EnvValueMode,
         List<CustomAgentConfig>? CustomAgents,
         string? Agent,
@@ -1692,7 +1692,7 @@ internal record ResumeSessionRequest(
         bool? EnableConfigDiscovery,
         bool? DisableResume,
         bool? Streaming,
-        Dictionary<string, object>? McpServers,
+        Dictionary<string, McpServerConfig>? McpServers,
         string? EnvValueMode,
         List<CustomAgentConfig>? CustomAgents,
         string? Agent,

dotnet/src/Types.cs

@@ -1413,27 +1413,44 @@ public class AzureOptions
 // ============================================================================
 
 /// <summary>
-/// Configuration for a local/stdio MCP server.
+/// Abstract base class for MCP server configurations.
 /// </summary>
-public class McpLocalServerConfig
+[JsonPolymorphic(
+    TypeDiscriminatorPropertyName = "type",
+    IgnoreUnrecognizedTypeDiscriminators = true)]
+[JsonDerivedType(typeof(McpStdioServerConfig), "stdio")]
+[JsonDerivedType(typeof(McpHttpServerConfig), "http")]
+public abstract class McpServerConfig
 {
+    private protected McpServerConfig() { }
+
     /// <summary>
     /// List of tools to include from this server. Empty list means none. Use "*" for all.
     /// </summary>
     [JsonPropertyName("tools")]
     public List<string> Tools { get; set; } = [];
 
     /// <summary>
-    /// Server type. Defaults to "local".
+    /// The server type discriminator.
     /// </summary>
-    [JsonPropertyName("type")]
-    public string? Type { get; set; }
+    [JsonIgnore]
+    public virtual string Type => "unknown";
 
     /// <summary>
     /// Optional timeout in milliseconds for tool calls to this server.
     /// </summary>
     [JsonPropertyName("timeout")]
     public int? Timeout { get; set; }
+}
+
+/// <summary>
+/// Configuration for a local/stdio MCP server.
+/// </summary>
+public sealed class McpStdioServerConfig : McpServerConfig
+{
+    /// <inheritdoc />
+    [JsonIgnore]
+    public override string Type => "stdio";
 
     /// <summary>
     /// Command to run the MCP server.
@@ -1463,25 +1480,11 @@ public class McpLocalServerConfig
 /// <summary>
 /// Configuration for a remote MCP server (HTTP or SSE).
 /// </summary>
-public class McpRemoteServerConfig
+public sealed class McpHttpServerConfig : McpServerConfig
 {
-    /// <summary>
-    /// List of tools to include from this server. Empty list means none. Use "*" for all.
-    /// </summary>
-    [JsonPropertyName("tools")]
-    public List<string> Tools { get; set; } = [];
-
-    /// <summary>
-    /// Server type. Must be "http" or "sse".
-    /// </summary>
-    [JsonPropertyName("type")]
-    public string Type { get; set; } = "http";
-
-    /// <summary>
-    /// Optional timeout in milliseconds for tool calls to this server.
-    /// </summary>
-    [JsonPropertyName("timeout")]
-    public int? Timeout { get; set; }
+    /// <inheritdoc />
+    [JsonIgnore]
+    public override string Type => "http";
 
     /// <summary>
     /// URL of the remote server.
@@ -1539,7 +1542,7 @@ public class CustomAgentConfig
     /// MCP servers specific to this agent.
     /// </summary>
     [JsonPropertyName("mcpServers")]
-    public Dictionary<string, object>? McpServers { get; set; }
+    public Dictionary<string, McpServerConfig>? McpServers { get; set; }
 
     /// <summary>
     /// Whether the agent should be available for model inference.
@@ -1608,7 +1611,7 @@ protected SessionConfig(SessionConfig? other)
         Hooks = other.Hooks;
         InfiniteSessions = other.InfiniteSessions;
         McpServers = other.McpServers is not null
-            ? new Dictionary<string, object>(other.McpServers, other.McpServers.Comparer)
+            ? new Dictionary<string, McpServerConfig>(other.McpServers, other.McpServers.Comparer)
             : null;
         Model = other.Model;
         ModelCapabilities = other.ModelCapabilities;
@@ -1740,9 +1743,9 @@ protected SessionConfig(SessionConfig? other)
 
     /// <summary>
     /// MCP server configurations for the session.
-    /// Keys are server names, values are server configurations (McpLocalServerConfig or McpRemoteServerConfig).
+    /// Keys are server names, values are server configurations (<see cref="McpStdioServerConfig"/> or <see cref="McpHttpServerConfig"/>).
     /// </summary>
-    public Dictionary<string, object>? McpServers { get; set; }
+    public Dictionary<string, McpServerConfig>? McpServers { get; set; }
 
     /// <summary>
     /// Custom agent configurations for the session.
@@ -1836,7 +1839,7 @@ protected ResumeSessionConfig(ResumeSessionConfig? other)
         Hooks = other.Hooks;
         InfiniteSessions = other.InfiniteSessions;
         McpServers = other.McpServers is not null
-            ? new Dictionary<string, object>(other.McpServers, other.McpServers.Comparer)
+            ? new Dictionary<string, McpServerConfig>(other.McpServers, other.McpServers.Comparer)
             : null;
         Model = other.Model;
         ModelCapabilities = other.ModelCapabilities;
@@ -1972,9 +1975,9 @@ protected ResumeSessionConfig(ResumeSessionConfig? other)
 
     /// <summary>
     /// MCP server configurations for the session.
-    /// Keys are server names, values are server configurations (McpLocalServerConfig or McpRemoteServerConfig).
+    /// Keys are server names, values are server configurations (<see cref="McpStdioServerConfig"/> or <see cref="McpHttpServerConfig"/>).
     /// </summary>
-    public Dictionary<string, object>? McpServers { get; set; }
+    public Dictionary<string, McpServerConfig>? McpServers { get; set; }
 
     /// <summary>
     /// Custom agent configurations for the session.
@@ -2519,8 +2522,7 @@ public class SystemMessageTransformRpcResponse
 [JsonSerializable(typeof(GetForegroundSessionResponse))]
 [JsonSerializable(typeof(GetModelsResponse))]
 [JsonSerializable(typeof(GetStatusResponse))]
-[JsonSerializable(typeof(McpLocalServerConfig))]
-[JsonSerializable(typeof(McpRemoteServerConfig))]
+[JsonSerializable(typeof(McpServerConfig))]
 [JsonSerializable(typeof(MessageOptions))]
 [JsonSerializable(typeof(ModelBilling))]
 [JsonSerializable(typeof(ModelCapabilities))]

dotnet/test/CloneTests.cs

@@ -86,7 +86,7 @@ public void SessionConfig_Clone_CopiesAllProperties()
             ExcludedTools = ["tool3"],
             WorkingDirectory = "/workspace",
             Streaming = true,
-            McpServers = new Dictionary<string, object> { ["server1"] = new object() },
+            McpServers = new Dictionary<string, McpServerConfig> { ["server1"] = new McpStdioServerConfig { Command = "echo" } },
             CustomAgents = [new CustomAgentConfig { Name = "agent1" }],
             Agent = "agent1",
             SkillDirectories = ["/skills"],
@@ -118,7 +118,7 @@ public void SessionConfig_Clone_CollectionsAreIndependent()
         {
             AvailableTools = ["tool1"],
             ExcludedTools = ["tool2"],
-            McpServers = new Dictionary<string, object> { ["s1"] = new object() },
+            McpServers = new Dictionary<string, McpServerConfig> { ["s1"] = new McpStdioServerConfig { Command = "echo" } },
             CustomAgents = [new CustomAgentConfig { Name = "a1" }],
             SkillDirectories = ["/skills"],
             DisabledSkills = ["skill1"],
@@ -129,7 +129,7 @@ public void SessionConfig_Clone_CollectionsAreIndependent()
         // Mutate clone collections
         clone.AvailableTools!.Add("tool99");
         clone.ExcludedTools!.Add("tool99");
-        clone.McpServers!["s2"] = new object();
+        clone.McpServers!["s2"] = new McpStdioServerConfig { Command = "echo" };
         clone.CustomAgents!.Add(new CustomAgentConfig { Name = "a2" });
         clone.SkillDirectories!.Add("/more");
         clone.DisabledSkills!.Add("skill99");
@@ -146,7 +146,7 @@ public void SessionConfig_Clone_CollectionsAreIndependent()
     [Fact]
     public void SessionConfig_Clone_PreservesMcpServersComparer()
     {
-        var servers = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase) { ["server"] = new object() };
+        var servers = new Dictionary<string, McpServerConfig>(StringComparer.OrdinalIgnoreCase) { ["server"] = new McpStdioServerConfig { Command = "echo" } };
         var original = new SessionConfig { McpServers = servers };
 
         var clone = original.Clone();
@@ -161,7 +161,7 @@ public void ResumeSessionConfig_Clone_CollectionsAreIndependent()
         {
             AvailableTools = ["tool1"],
             ExcludedTools = ["tool2"],
-            McpServers = new Dictionary<string, object> { ["s1"] = new object() },
+            McpServers = new Dictionary<string, McpServerConfig> { ["s1"] = new McpStdioServerConfig { Command = "echo" } },
             CustomAgents = [new CustomAgentConfig { Name = "a1" }],
             SkillDirectories = ["/skills"],
             DisabledSkills = ["skill1"],
@@ -172,7 +172,7 @@ public void ResumeSessionConfig_Clone_CollectionsAreIndependent()
         // Mutate clone collections
         clone.AvailableTools!.Add("tool99");
         clone.ExcludedTools!.Add("tool99");
-        clone.McpServers!["s2"] = new object();
+        clone.McpServers!["s2"] = new McpStdioServerConfig { Command = "echo" };
         clone.CustomAgents!.Add(new CustomAgentConfig { Name = "a2" });
         clone.SkillDirectories!.Add("/more");
         clone.DisabledSkills!.Add("skill99");
@@ -189,7 +189,7 @@ public void ResumeSessionConfig_Clone_CollectionsAreIndependent()
     [Fact]
     public void ResumeSessionConfig_Clone_PreservesMcpServersComparer()
     {
-        var servers = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase) { ["server"] = new object() };
+        var servers = new Dictionary<string, McpServerConfig>(StringComparer.OrdinalIgnoreCase) { ["server"] = new McpStdioServerConfig { Command = "echo" } };
         var original = new ResumeSessionConfig { McpServers = servers };
 
         var clone = original.Clone();