sdk: Expose disabled MCP servers across languages

docs/features/mcp.md

@@ -154,6 +154,35 @@ await using var session = await client.CreateSessionAsync(new SessionConfig
 });
 ```
 
+## Disabling configured servers per session
+
+Set `disabledMcpServers` to exact MCP server names that must not run in a session.
+The setting is scoped to the individual create or resume request; it does not
+modify global MCP settings or the server configuration.
+
+```typescript
+const session = await client.createSession({
+    mcpServers: {
+        filesystem: { type: "local", command: "npx", args: ["-y", "@modelcontextprotocol/server-filesystem", "."] },
+        github: { type: "http", url: "https://api.githubcopilot.com/mcp/" },
+    },
+    disabledMcpServers: ["github"],
+});
+```
+
+| SDK | Configuration property |
+| --- | --- |
+| Node.js | `disabledMcpServers` |
+| Python | `disabled_mcp_servers` |
+| Go | `DisabledMCPServers` |
+| .NET | `DisabledMcpServers` |
+| Java | `setDisabledMcpServers(...)` |
+| Rust | `with_disabled_mcp_servers(...)` |
+
+On session creation and a **cold** resume, disabled servers are not started and
+the runtime does not initiate their authentication. A resident resume cannot
+undo a server that the runtime has already spawned. Names are matched exactly.
+
 ## Tool configuration
 
 You can control which tools are available to an MCP server using the `tools` field.

dotnet/src/Client.cs

@@ -1186,6 +1186,7 @@ public async Task<CopilotSession> CreateSessionAsync(SessionConfig config, Cance
                 Cloud: config.Cloud,
                 InstructionDirectories: config.InstructionDirectories,
                 PluginDirectories: config.PluginDirectories,
+                DisabledMcpServers: config.DisabledMcpServers,
                 LargeOutput: config.LargeOutput,
                 ToolSearch: config.ToolSearch,
                 Memory: config.Memory,
@@ -1401,6 +1402,7 @@ public async Task<CopilotSession> ResumeSessionAsync(string sessionId, ResumeSes
                 ContinuePendingWork: config.ContinuePendingWork,
                 InstructionDirectories: config.InstructionDirectories,
                 PluginDirectories: config.PluginDirectories,
+                DisabledMcpServers: config.DisabledMcpServers,
                 LargeOutput: config.LargeOutput,
                 ToolSearch: config.ToolSearch,
                 Memory: config.Memory,
@@ -2755,6 +2757,7 @@ internal record CreateSessionRequest(
         CloudSessionOptions? Cloud = null,
         IList<string>? InstructionDirectories = null,
         IList<string>? PluginDirectories = null,
+        [property: JsonPropertyName("disabledMcpServers")] IList<string>? DisabledMcpServers = null,
         LargeToolOutputConfig? LargeOutput = null,
         ToolSearchConfig? ToolSearch = null,
         MemoryConfiguration? Memory = null,
@@ -2862,6 +2865,7 @@ internal record ResumeSessionRequest(
         bool? ContinuePendingWork = null,
         IList<string>? InstructionDirectories = null,
         IList<string>? PluginDirectories = null,
+        [property: JsonPropertyName("disabledMcpServers")] IList<string>? DisabledMcpServers = null,
         LargeToolOutputConfig? LargeOutput = null,
         ToolSearchConfig? ToolSearch = null,
         MemoryConfiguration? Memory = null,

dotnet/src/Types.cs

@@ -3016,6 +3016,7 @@ protected SessionConfigBase(SessionConfigBase? other)
         DefaultAgent = other.DefaultAgent;
         Agent = other.Agent;
         DisabledSkills = other.DisabledSkills is not null ? [.. other.DisabledSkills] : null;
+        DisabledMcpServers = other.DisabledMcpServers is not null ? [.. other.DisabledMcpServers] : null;
         EnableCitations = other.EnableCitations;
         EnableConfigDiscovery = other.EnableConfigDiscovery;
         SkipEmbeddingRetrieval = other.SkipEmbeddingRetrieval;
@@ -3429,6 +3430,13 @@ protected SessionConfigBase(SessionConfigBase? other)
     /// <summary>List of skill names to disable.</summary>
     public IList<string>? DisabledSkills { get; set; }
 
+    /// <summary>
+    /// Exact MCP server names to disable for this session. Disabled servers are not
+    /// started or authenticated on create or cold resume; a resident resume cannot
+    /// stop servers that are already running.
+    /// </summary>
+    public IList<string>? DisabledMcpServers { get; set; }
+
     /// <summary>
     /// Infinite session configuration for persistent workspaces and automatic compaction.
     /// When enabled (default), sessions automatically manage context limits and persist state.

dotnet/test/Unit/CloneTests.cs

@@ -98,6 +98,7 @@ public void SessionConfig_Clone_CopiesAllProperties()
             SkillDirectories = ["/skills"],
             InstructionDirectories = ["/instructions"],
             DisabledSkills = ["skill1"],
+            DisabledMcpServers = ["server1"],
             PluginDirectories = ["/plugins"],
             LargeOutput = new LargeToolOutputConfig { Enabled = true, MaxSizeBytes = 2048, OutputDirectory = "/tmp/out" },
             Memory = new MemoryConfiguration { Enabled = true },
@@ -136,6 +137,7 @@ public void SessionConfig_Clone_CopiesAllProperties()
         Assert.Equal(original.SkillDirectories, clone.SkillDirectories);
         Assert.Equal(original.InstructionDirectories, clone.InstructionDirectories);
         Assert.Equal(original.DisabledSkills, clone.DisabledSkills);
+        Assert.Equal(original.DisabledMcpServers, clone.DisabledMcpServers);
         Assert.Equal(original.PluginDirectories, clone.PluginDirectories);
         Assert.Same(original.LargeOutput, clone.LargeOutput);
         Assert.Same(original.Memory, clone.Memory);
@@ -157,6 +159,7 @@ public void SessionConfig_Clone_CollectionsAreIndependent()
             SkillDirectories = ["/skills"],
             InstructionDirectories = ["/instructions"],
             DisabledSkills = ["skill1"],
+            DisabledMcpServers = ["server1"],
         };
 
         var clone = original.Clone();
@@ -170,6 +173,7 @@ public void SessionConfig_Clone_CollectionsAreIndependent()
         clone.SkillDirectories!.Add("/more");
         clone.InstructionDirectories!.Add("/more-instructions");
         clone.DisabledSkills!.Add("skill99");
+        clone.DisabledMcpServers!.Add("server99");
 
         // Original is unaffected
         Assert.Single(original.AvailableTools!);
@@ -180,6 +184,7 @@ public void SessionConfig_Clone_CollectionsAreIndependent()
         Assert.Single(original.SkillDirectories!);
         Assert.Single(original.InstructionDirectories!);
         Assert.Single(original.DisabledSkills!);
+        Assert.Single(original.DisabledMcpServers!);
     }
 
     [Fact]
@@ -206,6 +211,7 @@ public void ResumeSessionConfig_Clone_CollectionsAreIndependent()
             SkillDirectories = ["/skills"],
             InstructionDirectories = ["/instructions"],
             DisabledSkills = ["skill1"],
+            DisabledMcpServers = ["server1"],
         };
 
         var clone = original.Clone();
@@ -219,6 +225,7 @@ public void ResumeSessionConfig_Clone_CollectionsAreIndependent()
         clone.SkillDirectories!.Add("/more");
         clone.InstructionDirectories!.Add("/more-instructions");
         clone.DisabledSkills!.Add("skill99");
+        clone.DisabledMcpServers!.Add("server99");
 
         // Original is unaffected
         Assert.Single(original.AvailableTools!);
@@ -229,6 +236,7 @@ public void ResumeSessionConfig_Clone_CollectionsAreIndependent()
         Assert.Single(original.SkillDirectories!);
         Assert.Single(original.InstructionDirectories!);
         Assert.Single(original.DisabledSkills!);
+        Assert.Single(original.DisabledMcpServers!);
     }
 
     [Fact]
@@ -289,6 +297,7 @@ public void Clone_WithNullCollections_ReturnsNullCollections()
         Assert.Null(clone.SkillDirectories);
         Assert.Null(clone.InstructionDirectories);
         Assert.Null(clone.DisabledSkills);
+        Assert.Null(clone.DisabledMcpServers);
         Assert.Null(clone.Tools);
         Assert.Null(clone.DefaultAgent);
         Assert.True(clone.IncludeSubAgentStreamingEvents);

dotnet/test/Unit/SerializationTests.cs

@@ -411,12 +411,14 @@ public void SessionRequests_CanSerializePluginDirectoriesAndLargeOutput_WithSdkO
             createRequestType,
             ("SessionId", "session-id"),
             ("PluginDirectories", pluginDirs),
+            ("DisabledMcpServers", new List<string> { "local-files", "remote-github" }),
             ("LargeOutput", largeOutput));
 
         var createJson = JsonSerializer.Serialize(createRequest, createRequestType, options);
         using var createDocument = JsonDocument.Parse(createJson);
         var createRoot = createDocument.RootElement;
         Assert.Equal("/tmp/plugins/a", createRoot.GetProperty("pluginDirectories")[0].GetString());
+        Assert.Equal("local-files", createRoot.GetProperty("disabledMcpServers")[0].GetString());
         Assert.Equal("/tmp/plugins/b", createRoot.GetProperty("pluginDirectories")[1].GetString());
         var createLargeOutput = createRoot.GetProperty("largeOutput");
         Assert.True(createLargeOutput.GetProperty("enabled").GetBoolean());
@@ -428,12 +430,14 @@ public void SessionRequests_CanSerializePluginDirectoriesAndLargeOutput_WithSdkO
             resumeRequestType,
             ("SessionId", "session-id"),
             ("PluginDirectories", pluginDirs),
+            ("DisabledMcpServers", new List<string> { "local-files", "remote-github" }),
             ("LargeOutput", largeOutput));
 
         var resumeJson = JsonSerializer.Serialize(resumeRequest, resumeRequestType, options);
         using var resumeDocument = JsonDocument.Parse(resumeJson);
         var resumeRoot = resumeDocument.RootElement;
         Assert.Equal("/tmp/plugins/a", resumeRoot.GetProperty("pluginDirectories")[0].GetString());
+        Assert.Equal("local-files", resumeRoot.GetProperty("disabledMcpServers")[0].GetString());
         var resumeLargeOutput = resumeRoot.GetProperty("largeOutput");
         Assert.True(resumeLargeOutput.GetProperty("enabled").GetBoolean());
         Assert.Equal(1024, resumeLargeOutput.GetProperty("maxSizeBytes").GetInt64());

go/client.go

@@ -812,6 +812,9 @@ func (c *Client) CreateSession(ctx context.Context, config *SessionConfig) (*Ses
 	req.PluginDirectories = config.PluginDirectories
 	req.InstructionDirectories = config.InstructionDirectories
 	req.DisabledSkills = config.DisabledSkills
+	if config.DisabledMCPServers != nil {
+		req.DisabledMCPServers = &config.DisabledMCPServers
+	}
 	req.InfiniteSessions = config.InfiniteSessions
 	req.LargeOutput = config.LargeOutput
 	req.ToolSearch = config.ToolSearch
@@ -1187,6 +1190,9 @@ func (c *Client) ResumeSessionWithOptions(ctx context.Context, sessionID string,
 	req.PluginDirectories = config.PluginDirectories
 	req.InstructionDirectories = config.InstructionDirectories
 	req.DisabledSkills = config.DisabledSkills
+	if config.DisabledMCPServers != nil {
+		req.DisabledMCPServers = &config.DisabledMCPServers
+	}
 	req.InfiniteSessions = config.InfiniteSessions
 	req.LargeOutput = config.LargeOutput
 	req.ToolSearch = config.ToolSearch

go/client_test.go

@@ -1049,9 +1049,11 @@ func TestSessionRequests_PluginDirectoriesAndLargeOutput(t *testing.T) {
 		"outputDir":    "/tmp/large-output",
 	}
 	expectedPluginDirs := []any{"/tmp/plugins/a", "/tmp/plugins/b"}
+	expectedDisabledMCPServers := []any{"local-files", "remote-github"}
+	disabledMCPServers := []string{"local-files", "remote-github"}
 
 	t.Run("create includes pluginDirectories and largeOutput in JSON when set", func(t *testing.T) {
-		req := createSessionRequest{PluginDirectories: pluginDirs, LargeOutput: largeOutput}
+		req := createSessionRequest{PluginDirectories: pluginDirs, DisabledMCPServers: &disabledMCPServers, LargeOutput: largeOutput}
 		data, err := json.Marshal(req)
 		if err != nil {
 			t.Fatalf("Failed to marshal: %v", err)
@@ -1063,13 +1065,16 @@ func TestSessionRequests_PluginDirectoriesAndLargeOutput(t *testing.T) {
 		if !reflect.DeepEqual(m["pluginDirectories"], expectedPluginDirs) {
 			t.Errorf("Expected pluginDirectories %v, got %v", expectedPluginDirs, m["pluginDirectories"])
 		}
+		if !reflect.DeepEqual(m["disabledMcpServers"], expectedDisabledMCPServers) {
+			t.Errorf("Expected disabledMcpServers %v, got %v", expectedDisabledMCPServers, m["disabledMcpServers"])
+		}
 		if !reflect.DeepEqual(m["largeOutput"], expectedLargeOutput) {
 			t.Errorf("Expected largeOutput %v, got %v", expectedLargeOutput, m["largeOutput"])
 		}
 	})
 
 	t.Run("resume includes pluginDirectories and largeOutput in JSON when set", func(t *testing.T) {
-		req := resumeSessionRequest{SessionID: "s1", PluginDirectories: pluginDirs, LargeOutput: largeOutput}
+		req := resumeSessionRequest{SessionID: "s1", PluginDirectories: pluginDirs, DisabledMCPServers: &disabledMCPServers, LargeOutput: largeOutput}
 		data, err := json.Marshal(req)
 		if err != nil {
 			t.Fatalf("Failed to marshal: %v", err)
@@ -1081,11 +1086,36 @@ func TestSessionRequests_PluginDirectoriesAndLargeOutput(t *testing.T) {
 		if !reflect.DeepEqual(m["pluginDirectories"], expectedPluginDirs) {
 			t.Errorf("Expected pluginDirectories %v, got %v", expectedPluginDirs, m["pluginDirectories"])
 		}
+		if !reflect.DeepEqual(m["disabledMcpServers"], expectedDisabledMCPServers) {
+			t.Errorf("Expected disabledMcpServers %v, got %v", expectedDisabledMCPServers, m["disabledMcpServers"])
+		}
 		if !reflect.DeepEqual(m["largeOutput"], expectedLargeOutput) {
 			t.Errorf("Expected largeOutput %v, got %v", expectedLargeOutput, m["largeOutput"])
 		}
 	})
 
+	t.Run("create and resume include explicit empty disabledMcpServers", func(t *testing.T) {
+		emptyDisabledMCPServers := []string{}
+		requests := []any{
+			createSessionRequest{DisabledMCPServers: &emptyDisabledMCPServers},
+			resumeSessionRequest{SessionID: "s1", DisabledMCPServers: &emptyDisabledMCPServers},
+		}
+
+		for _, request := range requests {
+			data, err := json.Marshal(request)
+			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)
+			}
+			if value, ok := m["disabledMcpServers"]; !ok || !reflect.DeepEqual(value, []any{}) {
+				t.Errorf("Expected explicit empty disabledMcpServers, got %v", value)
+			}
+		}
+	})
+
 	t.Run("create omits pluginDirectories and largeOutput when nil", func(t *testing.T) {
 		req := createSessionRequest{}
 		data, err := json.Marshal(req)
@@ -1099,10 +1129,28 @@ func TestSessionRequests_PluginDirectoriesAndLargeOutput(t *testing.T) {
 		if _, ok := m["pluginDirectories"]; ok {
 			t.Errorf("Expected pluginDirectories to be omitted")
 		}
+		if _, ok := m["disabledMcpServers"]; ok {
+			t.Error("Expected disabledMcpServers to be omitted")
+		}
 		if _, ok := m["largeOutput"]; ok {
 			t.Errorf("Expected largeOutput to be omitted")
 		}
 	})
+
+	t.Run("resume omits disabledMcpServers when nil", func(t *testing.T) {
+		req := resumeSessionRequest{SessionID: "s1"}
+		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)
+		}
+		if _, ok := m["disabledMcpServers"]; ok {
+			t.Error("Expected disabledMcpServers to be omitted")
+		}
+	})
 }
 
 func TestSessionRequests_Memory(t *testing.T) {

go/types.go

@@ -1328,6 +1328,10 @@ type SessionConfig struct {
 	InstructionDirectories []string
 	// DisabledSkills is a list of skill names to disable
 	DisabledSkills []string
+	// DisabledMCPServers is a list of exact MCP server names to disable for this session.
+	// Disabled servers are not started or authenticated on create or cold resume.
+	// A resident resume cannot stop servers that are already running.
+	DisabledMCPServers []string
 	// InfiniteSessions configures infinite sessions for persistent workspaces and automatic compaction.
 	// When enabled (default), sessions automatically manage context limits and persist state.
 	InfiniteSessions *InfiniteSessionConfig
@@ -1800,6 +1804,10 @@ type ResumeSessionConfig struct {
 	InstructionDirectories []string
 	// DisabledSkills is a list of skill names to disable
 	DisabledSkills []string
+	// DisabledMCPServers is a list of exact MCP server names to disable for this session.
+	// Disabled servers are not started or authenticated on create or cold resume.
+	// A resident resume cannot stop servers that are already running.
+	DisabledMCPServers []string
 	// InfiniteSessions configures infinite sessions for persistent workspaces and automatic compaction.
 	InfiniteSessions *InfiniteSessionConfig
 	// LargeOutput configures handling of large tool outputs. When a tool produces
@@ -2333,6 +2341,7 @@ type createSessionRequest struct {
 	PluginDirectories                  []string                               `json:"pluginDirectories,omitempty"`
 	InstructionDirectories             []string                               `json:"instructionDirectories,omitempty"`
 	DisabledSkills                     []string                               `json:"disabledSkills,omitempty"`
+	DisabledMCPServers                 *[]string                              `json:"disabledMcpServers,omitempty"`
 	InfiniteSessions                   *InfiniteSessionConfig                 `json:"infiniteSessions,omitempty"`
 	LargeOutput                        *LargeToolOutputConfig                 `json:"largeOutput,omitempty"`
 	ToolSearch                         *ToolSearchConfig                      `json:"toolSearch,omitempty"`
@@ -2426,6 +2435,7 @@ type resumeSessionRequest struct {
 	PluginDirectories                  []string                               `json:"pluginDirectories,omitempty"`
 	InstructionDirectories             []string                               `json:"instructionDirectories,omitempty"`
 	DisabledSkills                     []string                               `json:"disabledSkills,omitempty"`
+	DisabledMCPServers                 *[]string                              `json:"disabledMcpServers,omitempty"`
 	InfiniteSessions                   *InfiniteSessionConfig                 `json:"infiniteSessions,omitempty"`
 	LargeOutput                        *LargeToolOutputConfig                 `json:"largeOutput,omitempty"`
 	ToolSearch                         *ToolSearchConfig                      `json:"toolSearch,omitempty"`

java/src/main/java/com/github/copilot/SessionRequestBuilder.java

@@ -156,6 +156,7 @@ static CreateSessionRequest buildCreateRequest(SessionConfig config, String sess
         request.setToolSearch(config.getToolSearch());
         request.setMemory(config.getMemory());
         request.setDisabledSkills(config.getDisabledSkills());
+        request.setDisabledMcpServers(config.getDisabledMcpServers());
         request.setConfigDirectory(config.getConfigDirectory());
         config.getEnableConfigDiscovery().ifPresent(request::setEnableConfigDiscovery);
         config.getSkipEmbeddingRetrieval().ifPresent(request::setSkipEmbeddingRetrieval);
@@ -302,6 +303,7 @@ static ResumeSessionRequest buildResumeRequest(String sessionId, ResumeSessionCo
         request.setToolSearch(config.getToolSearch());
         request.setMemory(config.getMemory());
         request.setDisabledSkills(config.getDisabledSkills());
+        request.setDisabledMcpServers(config.getDisabledMcpServers());
         request.setInfiniteSessions(config.getInfiniteSessions());
         request.setModelCapabilities(config.getModelCapabilities());