Add capi.disableWebSocketResponses and provider.transport session options

dotnet/src/Client.cs

@@ -963,6 +963,7 @@ public async Task<CopilotSession> CreateSessionAsync(SessionConfig config, Cance
                 toolFilter.AvailableTools,
                 toolFilter.ExcludedTools,
                 config.Provider,
+                config.Capi,
                 config.EnableSessionTelemetry,
                 config.OnPermissionRequest != null ? true : null,
                 config.OnUserInputRequest != null ? true : null,
@@ -1159,6 +1160,7 @@ public async Task<CopilotSession> ResumeSessionAsync(string sessionId, ResumeSes
                 toolFilter.AvailableTools,
                 toolFilter.ExcludedTools,
                 config.Provider,
+                config.Capi,
                 config.EnableSessionTelemetry,
                 config.OnPermissionRequest != null ? true : null,
                 config.OnUserInputRequest != null ? true : null,
@@ -2355,6 +2357,7 @@ internal record CreateSessionRequest(
         IList<string>? AvailableTools,
         IList<string>? ExcludedTools,
         ProviderConfig? Provider,
+        CapiSessionOptions? Capi,
         bool? EnableSessionTelemetry,
         bool? RequestPermission,
         bool? RequestUserInput,
@@ -2445,6 +2448,7 @@ internal record ResumeSessionRequest(
         IList<string>? AvailableTools,
         IList<string>? ExcludedTools,
         ProviderConfig? Provider,
+        CapiSessionOptions? Capi,
         bool? EnableSessionTelemetry,
         bool? RequestPermission,
         bool? RequestUserInput,
@@ -2569,6 +2573,7 @@ internal record HooksInvokeResponse(
     [JsonSerializable(typeof(EmbeddingCacheStorageMode))]
     [JsonSerializable(typeof(ModelCapabilitiesOverride))]
     [JsonSerializable(typeof(ProviderConfig))]
+    [JsonSerializable(typeof(CapiSessionOptions))]
     [JsonSerializable(typeof(ResumeSessionRequest))]
     [JsonSerializable(typeof(ResumeSessionResponse))]
     [JsonSerializable(typeof(SessionCapabilities))]

dotnet/src/Types.cs

@@ -2058,6 +2058,26 @@ public sealed class ProviderConfig
     public int? MaxOutputTokens { get; set; }
 }
 
+/// <summary>
+/// Provider-scoped options for the CAPI (Copilot API) provider.
+/// </summary>
+public sealed class CapiSessionOptions
+{
+    /// <summary>
+    /// When <see langword="true"/>, opts out of the WebSocket transport for the CAPI Responses API
+    /// and uses the HTTP Responses transport instead.
+    /// </summary>
+    /// <remarks>
+    /// WebSocket transport is the default for CAPI Responses API requests when the model advertises
+    /// the <c>ws:/responses</c> endpoint. Set this option for users behind proxies where WebSockets
+    /// fail. This is equivalent to setting the <c>COPILOT_CLI_DISABLE_WEBSOCKET_RESPONSES</c>
+    /// environment variable. The option is scoped under the <c>capi</c> namespace because a single
+    /// session can host multiple providers, such as CAPI and BYOK, so transport choice is provider-level.
+    /// </remarks>
+    [JsonPropertyName("disableWebSocketResponses")]
+    public bool? DisableWebSocketResponses { get; set; }
+}
+
 /// <summary>
 /// Azure OpenAI-specific provider options.
 /// </summary>
@@ -2494,6 +2514,7 @@ protected SessionConfigBase(SessionConfigBase? other)
         OnPermissionRequest = other.OnPermissionRequest;
         OnUserInputRequest = other.OnUserInputRequest;
         Provider = other.Provider;
+        Capi = other.Capi;
         EnableSessionTelemetry = other.EnableSessionTelemetry;
         SkipCustomInstructions = other.SkipCustomInstructions;
         CustomAgentsLocalOnly = other.CustomAgentsLocalOnly;
@@ -2649,6 +2670,11 @@ protected SessionConfigBase(SessionConfigBase? other)
     /// <summary>Custom model provider configuration for the session.</summary>
     public ProviderConfig? Provider { get; set; }
 
+    /// <summary>
+    /// CAPI (Copilot API) provider-scoped configuration for the session.
+    /// </summary>
+    public CapiSessionOptions? Capi { get; set; }
+
     /// <summary>
     /// Enables or disables internal session telemetry for this session.
     /// When <c>false</c>, disables session telemetry. When <c>null</c> (the default) or <c>true</c>,
@@ -3554,6 +3580,7 @@ public sealed class SystemMessageTransformRpcResponse
 [JsonSerializable(typeof(PingRequest))]
 [JsonSerializable(typeof(PingResponse))]
 [JsonSerializable(typeof(ProviderConfig))]
+[JsonSerializable(typeof(CapiSessionOptions))]
 [JsonSerializable(typeof(SessionContext))]
 [JsonSerializable(typeof(SessionLifecycleEvent))]
 [JsonSerializable(typeof(SessionLifecycleEventMetadata))]

dotnet/test/Unit/CloneTests.cs

@@ -82,6 +82,7 @@ public void SessionConfig_Clone_CopiesAllProperties()
             McpOAuthTokenStorage = McpOAuthTokenStorageMode.Persistent,
             CustomAgents = [new CustomAgentConfig { Name = "agent1", Model = "claude-haiku-4.5" }],
             Agent = "agent1",
+            Capi = new CapiSessionOptions { DisableWebSocketResponses = true },
             Cloud = new CloudSessionOptions
             {
                 Repository = new CloudSessionRepository
@@ -123,6 +124,7 @@ public void SessionConfig_Clone_CopiesAllProperties()
         Assert.Equal(original.CustomAgents.Count, clone.CustomAgents!.Count);
         Assert.Equal(original.CustomAgents[0].Model, clone.CustomAgents[0].Model);
         Assert.Equal(original.Agent, clone.Agent);
+        Assert.Same(original.Capi, clone.Capi);
         Assert.Same(original.Cloud, clone.Cloud);
         Assert.Equal(original.DefaultAgent!.ExcludedTools, clone.DefaultAgent!.ExcludedTools);
         Assert.Equal(original.SkillDirectories, clone.SkillDirectories);
@@ -515,4 +517,30 @@ public void ResumeSessionConfig_Clone_CopiesMcpOAuthTokenStorage()
 
         Assert.Equal(McpOAuthTokenStorageMode.Persistent, clone.McpOAuthTokenStorage);
     }
+
+    [Fact]
+    public void SessionConfig_Clone_CopiesCapiOptions()
+    {
+        var original = new SessionConfig
+        {
+            Capi = new CapiSessionOptions { DisableWebSocketResponses = true },
+        };
+
+        var clone = original.Clone();
+
+        Assert.Same(original.Capi, clone.Capi);
+    }
+
+    [Fact]
+    public void ResumeSessionConfig_Clone_CopiesCapiOptions()
+    {
+        var original = new ResumeSessionConfig
+        {
+            Capi = new CapiSessionOptions { DisableWebSocketResponses = true },
+        };
+
+        var clone = original.Clone();
+
+        Assert.Same(original.Capi, clone.Capi);
+    }
 }

dotnet/test/Unit/SerializationTests.cs

@@ -50,6 +50,25 @@ public void ProviderConfig_CanSerializeHeaders_WithSdkOptions()
         Assert.Equal(4096, deserialized.MaxOutputTokens);
     }
 
+    [Fact]
+    public void CapiSessionOptions_CanSerializeDisableWebSocketResponses_WithSdkOptions()
+    {
+        var options = GetSerializerOptions();
+        var original = new CapiSessionOptions
+        {
+            DisableWebSocketResponses = true
+        };
+
+        var json = JsonSerializer.Serialize(original, options);
+        using var document = JsonDocument.Parse(json);
+        var root = document.RootElement;
+        Assert.True(root.GetProperty("disableWebSocketResponses").GetBoolean());
+
+        var deserialized = JsonSerializer.Deserialize<CapiSessionOptions>(json, options);
+        Assert.NotNull(deserialized);
+        Assert.True(deserialized.DisableWebSocketResponses);
+    }
+
     [Fact]
     public void ModelBilling_CanSerializeTokenPrices_WithSdkOptions()
     {
@@ -221,6 +240,57 @@ public void ResumeSessionRequest_CanSerializeInstructionDirectories_WithSdkOptio
         Assert.Equal("C:\\resume-instructions", root.GetProperty("instructionDirectories")[0].GetString());
     }
 
+    [Fact]
+    public void SessionRequests_CanSerializeCapiOptions_WithSdkOptions()
+    {
+        var options = GetSerializerOptions();
+        var capi = new CapiSessionOptions { DisableWebSocketResponses = true };
+
+        var createRequestType = GetNestedType(typeof(CopilotClient), "CreateSessionRequest");
+        var createRequest = CreateInternalRequest(
+            createRequestType,
+            ("SessionId", "session-id"),
+            ("Capi", capi));
+
+        var createJson = JsonSerializer.Serialize(createRequest, createRequestType, options);
+        using var createDocument = JsonDocument.Parse(createJson);
+        Assert.True(createDocument.RootElement.GetProperty("capi").GetProperty("disableWebSocketResponses").GetBoolean());
+
+        var resumeRequestType = GetNestedType(typeof(CopilotClient), "ResumeSessionRequest");
+        var resumeRequest = CreateInternalRequest(
+            resumeRequestType,
+            ("SessionId", "session-id"),
+            ("Capi", capi));
+
+        var resumeJson = JsonSerializer.Serialize(resumeRequest, resumeRequestType, options);
+        using var resumeDocument = JsonDocument.Parse(resumeJson);
+        Assert.True(resumeDocument.RootElement.GetProperty("capi").GetProperty("disableWebSocketResponses").GetBoolean());
+    }
+
+    [Fact]
+    public void SessionRequests_OmitCapiOptions_WhenUnset()
+    {
+        var options = GetSerializerOptions();
+
+        var createRequestType = GetNestedType(typeof(CopilotClient), "CreateSessionRequest");
+        var createRequest = CreateInternalRequest(
+            createRequestType,
+            ("SessionId", "session-id"));
+
+        var createJson = JsonSerializer.Serialize(createRequest, createRequestType, options);
+        using var createDocument = JsonDocument.Parse(createJson);
+        Assert.False(createDocument.RootElement.TryGetProperty("capi", out _));
+
+        var resumeRequestType = GetNestedType(typeof(CopilotClient), "ResumeSessionRequest");
+        var resumeRequest = CreateInternalRequest(
+            resumeRequestType,
+            ("SessionId", "session-id"));
+
+        var resumeJson = JsonSerializer.Serialize(resumeRequest, resumeRequestType, options);
+        using var resumeDocument = JsonDocument.Parse(resumeJson);
+        Assert.False(resumeDocument.RootElement.TryGetProperty("capi", out _));
+    }
+
     [Fact]
     public void SessionRequests_CanSerializeReasoningSummary_WithSdkOptions()
     {

go/client.go

@@ -681,6 +681,7 @@ func (c *Client) CreateSession(ctx context.Context, config *SessionConfig) (*Ses
 	req.ExcludedTools = excludedTools
 	req.ToolFilterPrecedence = precedence
 	req.Provider = config.Provider
+	req.Capi = config.Capi
 	req.EnableSessionTelemetry = config.EnableSessionTelemetry
 	req.SkipCustomInstructions = config.SkipCustomInstructions
 	req.CustomAgentsLocalOnly = config.CustomAgentsLocalOnly
@@ -976,6 +977,7 @@ func (c *Client) ResumeSessionWithOptions(ctx context.Context, sessionID string,
 	req.SystemMessage = wireSystemMessage
 	req.Tools = config.Tools
 	req.Provider = config.Provider
+	req.Capi = config.Capi
 	req.EnableSessionTelemetry = config.EnableSessionTelemetry
 	req.SkipCustomInstructions = config.SkipCustomInstructions
 	req.CustomAgentsLocalOnly = config.CustomAgentsLocalOnly

go/client_test.go

@@ -209,6 +209,76 @@ func newRuntimeShutdownRpcPair(t *testing.T) (*jsonrpc2.Client, *jsonrpc2.Client
 	return rpcClient, server, shutdownCalled
 }
 
+func TestClient_ForwardsCapiOptionsToSessionRequests(t *testing.T) {
+	rpcClient, server, _ := newRuntimeShutdownRpcPair(t)
+	t.Cleanup(server.Stop)
+	client := &Client{
+		client:   rpcClient,
+		RPC:      rpc.NewServerRPC(rpcClient),
+		sessions: make(map[string]*Session),
+	}
+
+	createParams := make(chan json.RawMessage, 1)
+	server.SetRequestHandler("session.create", func(params json.RawMessage) (json.RawMessage, *jsonrpc2.Error) {
+		createParams <- append(json.RawMessage(nil), params...)
+		sessionID := sessionIDFromParams(t, params)
+		return []byte(`{"sessionId":"` + sessionID + `","workspacePath":"/workspace"}`), nil
+	})
+
+	_, err := client.CreateSession(t.Context(), &SessionConfig{
+		Capi: &CapiSessionOptions{DisableWebSocketResponses: Bool(true)},
+	})
+	if err != nil {
+		t.Fatalf("CreateSession failed: %v", err)
+	}
+	assertCapiDisableWebSocketResponses(t, <-createParams)
+
+	resumeParams := make(chan json.RawMessage, 1)
+	server.SetRequestHandler("session.resume", func(params json.RawMessage) (json.RawMessage, *jsonrpc2.Error) {
+		resumeParams <- append(json.RawMessage(nil), params...)
+		return []byte(`{"sessionId":"resumed-capi","workspacePath":"/workspace"}`), nil
+	})
+
+	_, err = client.ResumeSessionWithOptions(t.Context(), "resumed-capi", &ResumeSessionConfig{
+		Capi: &CapiSessionOptions{DisableWebSocketResponses: Bool(true)},
+	})
+	if err != nil {
+		t.Fatalf("ResumeSessionWithOptions failed: %v", err)
+	}
+	assertCapiDisableWebSocketResponses(t, <-resumeParams)
+}
+
+func assertCapiDisableWebSocketResponses(t *testing.T, params json.RawMessage) {
+	t.Helper()
+
+	var decoded map[string]any
+	if err := json.Unmarshal(params, &decoded); err != nil {
+		t.Fatalf("failed to unmarshal request params: %v", err)
+	}
+	capi, ok := decoded["capi"].(map[string]any)
+	if !ok {
+		t.Fatalf("expected capi object in request params, got %T", decoded["capi"])
+	}
+	if capi["disableWebSocketResponses"] != true {
+		t.Fatalf("expected capi.disableWebSocketResponses=true, got %v", capi["disableWebSocketResponses"])
+	}
+}
+
+func sessionIDFromParams(t *testing.T, params json.RawMessage) string {
+	t.Helper()
+
+	var decoded struct {
+		SessionID string `json:"sessionId"`
+	}
+	if err := json.Unmarshal(params, &decoded); err != nil {
+		t.Fatalf("failed to unmarshal request params: %v", err)
+	}
+	if decoded.SessionID == "" {
+		t.Fatal("expected generated sessionId in request params")
+	}
+	return decoded.SessionID
+}
+
 func assertRuntimeShutdownNotCalled(t *testing.T, shutdownCalled <-chan struct{}) {
 	t.Helper()
 	select {
@@ -1339,6 +1409,61 @@ func TestCreateSessionRequest_Cloud(t *testing.T) {
 	})
 }
 
+func TestSessionRequests_Capi(t *testing.T) {
+	t.Run("forwards capi options in session.create RPC", func(t *testing.T) {
+		req := createSessionRequest{
+			Capi: &CapiSessionOptions{DisableWebSocketResponses: Bool(true)},
+		}
+		data, err := json.Marshal(req)
+		if err != nil {
+			t.Fatalf("Failed to marshal: %v", err)
+		}
+		var m map[string]any
+		if err := json.Unmarshal(data, &m); err != nil {
+			t.Fatalf("Failed to unmarshal: %v", err)
+		}
+		capi, ok := m["capi"].(map[string]any)
+		if !ok {
+			t.Fatalf("Expected capi to be an object, got %T", m["capi"])
+		}
+		if capi["disableWebSocketResponses"] != true {
+			t.Errorf("Expected disableWebSocketResponses=true, got %v", capi["disableWebSocketResponses"])
+		}
+	})
+
+	t.Run("forwards capi options in session.resume RPC", func(t *testing.T) {
+		req := resumeSessionRequest{
+			SessionID: "s1",
+			Capi:      &CapiSessionOptions{DisableWebSocketResponses: Bool(true)},
+		}
+		data, err := json.Marshal(req)
+		if err != nil {
+			t.Fatalf("Failed to marshal: %v", err)
+		}
+		var m map[string]any
+		if err := json.Unmarshal(data, &m); err != nil {
+			t.Fatalf("Failed to unmarshal: %v", err)
+		}
+		capi, ok := m["capi"].(map[string]any)
+		if !ok {
+			t.Fatalf("Expected capi to be an object, got %T", m["capi"])
+		}
+		if capi["disableWebSocketResponses"] != true {
+			t.Errorf("Expected disableWebSocketResponses=true, got %v", capi["disableWebSocketResponses"])
+		}
+	})
+
+	t.Run("omits capi from JSON when unset", func(t *testing.T) {
+		req := createSessionRequest{}
+		data, _ := json.Marshal(req)
+		var m map[string]any
+		json.Unmarshal(data, &m)
+		if _, ok := m["capi"]; ok {
+			t.Error("Expected capi to be omitted when unset")
+		}
+	})
+}
+
 func TestResumeSessionRequest_Commands(t *testing.T) {
 	t.Run("forwards commands in session.resume RPC", func(t *testing.T) {
 		req := resumeSessionRequest{