Expose session feature flag overrides across SDKs

dotnet/src/Client.cs

@@ -1251,6 +1251,7 @@ public async Task<CopilotSession> CreateSessionAsync(SessionConfig config, Cance
                 Providers: config.Providers,
                 Models: config.Models,
                 ToolFilterPrecedence: toolFilter.ToolFilterPrecedence,
+                FeatureFlags: config.FeatureFlags,
                 ExpAssignments: config.ExpAssignments,
                 EnableManagedSettings: config.EnableManagedSettings,
                 GitHubMcpToolConfig: config.GitHubMcpToolConfig,
@@ -1491,6 +1492,7 @@ public async Task<CopilotSession> ResumeSessionAsync(string sessionId, ResumeSes
                 Providers: config.Providers,
                 Models: config.Models,
                 ToolFilterPrecedence: toolFilter.ToolFilterPrecedence,
+                FeatureFlags: config.FeatureFlags,
                 ExpAssignments: config.ExpAssignments,
                 EnableManagedSettings: config.EnableManagedSettings,
                 GitHubMcpToolConfig: config.GitHubMcpToolConfig,
@@ -2930,6 +2932,7 @@ internal record CreateSessionRequest(
         IList<NamedProviderConfig>? Providers = null,
         IList<ProviderModelConfig>? Models = null,
         OptionsUpdateToolFilterPrecedence? ToolFilterPrecedence = null,
+        [property: JsonPropertyName("featureFlags")] IDictionary<string, bool>? FeatureFlags = null,
         [property: JsonPropertyName("expAssignments")] CopilotExpAssignmentResponse? ExpAssignments = null,
         [property: JsonPropertyName("enableManagedSettings")] bool? EnableManagedSettings = null,
         [property: JsonPropertyName("managedSettings")] ManagedSettings? ManagedSettings = null,
@@ -3047,6 +3050,7 @@ internal record ResumeSessionRequest(
         IList<NamedProviderConfig>? Providers = null,
         IList<ProviderModelConfig>? Models = null,
         OptionsUpdateToolFilterPrecedence? ToolFilterPrecedence = null,
+        [property: JsonPropertyName("featureFlags")] IDictionary<string, bool>? FeatureFlags = null,
         [property: JsonPropertyName("expAssignments")] CopilotExpAssignmentResponse? ExpAssignments = null,
         [property: JsonPropertyName("enableManagedSettings")] bool? EnableManagedSettings = null,
         [property: JsonPropertyName("managedSettings")] ManagedSettings? ManagedSettings = null,

dotnet/src/Types.cs

@@ -3209,6 +3209,9 @@ protected SessionConfigBase(SessionConfigBase? other)
         GitHubToken = other.GitHubToken;
         GitHubTokenProvider = other.GitHubTokenProvider;
         RemoteSession = other.RemoteSession;
+        FeatureFlags = other.FeatureFlags is not null
+            ? new Dictionary<string, bool>(other.FeatureFlags)
+            : null;
         ExpAssignments = other.ExpAssignments;
         EnableManagedSettings = other.EnableManagedSettings;
         ManagedSettings = other.ManagedSettings;
@@ -3696,6 +3699,12 @@ protected SessionConfigBase(SessionConfigBase? other)
     [EditorBrowsable(EditorBrowsableState.Never)]
     public CopilotExpAssignmentResponse? ExpAssignments { get; set; }
 
+    /// <summary>
+    /// Feature-flag values resolved by the host for this session.
+    /// Re-supply them when resuming after a runtime restart.
+    /// </summary>
+    public IDictionary<string, bool>? FeatureFlags { get; set; }
+
     /// <summary>
     /// Opt-in: when <c>true</c>, the runtime self-fetches enterprise managed
     /// settings (bypass-permissions policy) at session bootstrap using the

dotnet/test/Unit/SerializationTests.cs

@@ -630,6 +630,46 @@ public void ResumeSessionConfigClone_PreservesExpAssignments()
         Assert.Equal("exp-resume", clone.ExpAssignments!.Configs[0].Id);
     }
 
+    [Fact]
+    public void SessionRequests_CanSerializeFeatureFlags_WithSdkOptions()
+    {
+        var options = GetSerializerOptions();
+        var flags = new Dictionary<string, bool>
+        {
+            ["ENABLED_TEST_FLAG"] = true,
+            ["DISABLED_TEST_FLAG"] = false,
+        };
+
+        foreach (var requestName in new[] { "CreateSessionRequest", "ResumeSessionRequest" })
+        {
+            var requestType = GetNestedType(typeof(CopilotClient), requestName);
+            var request = CreateInternalRequest(
+                requestType,
+                ("SessionId", "session-id"),
+                ("FeatureFlags", flags));
+            using var document = JsonDocument.Parse(
+                JsonSerializer.Serialize(request, requestType, options));
+            var serializedFlags = document.RootElement.GetProperty("featureFlags");
+            Assert.True(serializedFlags.GetProperty("ENABLED_TEST_FLAG").GetBoolean());
+            Assert.False(serializedFlags.GetProperty("DISABLED_TEST_FLAG").GetBoolean());
+        }
+    }
+
+    [Fact]
+    public void SessionConfigClone_CopiesFeatureFlags()
+    {
+        var config = new SessionConfig
+        {
+            FeatureFlags = new Dictionary<string, bool> { ["TEST_FLAG"] = true },
+        };
+
+        var clone = config.Clone();
+        clone.FeatureFlags!["TEST_FLAG"] = false;
+
+        Assert.True(config.FeatureFlags["TEST_FLAG"]);
+        Assert.False(clone.FeatureFlags["TEST_FLAG"]);
+    }
+
     [Fact]
     public void CreateSessionRequest_CanSerializeEnableSessionTelemetry_WithSdkOptions()
     {

go/client.go

@@ -883,6 +883,9 @@ func (c *Client) CreateSession(ctx context.Context, config *SessionConfig) (*Ses
 	req.ExtensionSDKPath = config.ExtensionSDKPath
 	req.ExtensionInfo = config.ExtensionInfo
 	req.ExpAssignments = config.ExpAssignments
+	if config.FeatureFlags != nil {
+		req.FeatureFlags = &config.FeatureFlags
+	}
 	req.EnableManagedSettings = config.EnableManagedSettings
 	req.ManagedSettings = config.ManagedSettings
 
@@ -1289,6 +1292,9 @@ func (c *Client) ResumeSessionWithOptions(ctx context.Context, sessionID string,
 	req.ExtensionSDKPath = config.ExtensionSDKPath
 	req.ExtensionInfo = config.ExtensionInfo
 	req.ExpAssignments = config.ExpAssignments
+	if config.FeatureFlags != nil {
+		req.FeatureFlags = &config.FeatureFlags
+	}
 	req.EnableManagedSettings = config.EnableManagedSettings
 	req.ManagedSettings = config.ManagedSettings
 	if config.OnPermissionRequest != nil {

go/client_test.go

@@ -3904,6 +3904,62 @@ func TestResumeSessionRequest_ExpAssignments(t *testing.T) {
 	})
 }
 
+func TestSessionRequests_FeatureFlags(t *testing.T) {
+	featureFlags := map[string]bool{
+		"ENABLED_TEST_FLAG":  true,
+		"DISABLED_TEST_FLAG": false,
+	}
+
+	for _, tc := range []struct {
+		name string
+		req  any
+	}{
+		{"create", createSessionRequest{FeatureFlags: &featureFlags}},
+		{"resume", resumeSessionRequest{SessionID: "s1", FeatureFlags: &featureFlags}},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			data, err := json.Marshal(tc.req)
+			if err != nil {
+				t.Fatalf("Failed to marshal: %v", err)
+			}
+			var payload map[string]any
+			if err := json.Unmarshal(data, &payload); err != nil {
+				t.Fatalf("Failed to unmarshal: %v", err)
+			}
+			got := payload["featureFlags"].(map[string]any)
+			if got["ENABLED_TEST_FLAG"] != true || got["DISABLED_TEST_FLAG"] != false {
+				t.Errorf("Unexpected featureFlags: %v", got)
+			}
+		})
+	}
+
+	emptyFlags := map[string]bool{}
+	for _, tc := range []struct {
+		name string
+		req  any
+	}{
+		{"create empty", createSessionRequest{FeatureFlags: &emptyFlags}},
+		{"resume empty", resumeSessionRequest{SessionID: "s1", FeatureFlags: &emptyFlags}},
+		{"create unset", createSessionRequest{}},
+		{"resume unset", resumeSessionRequest{SessionID: "s1"}},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			data, err := json.Marshal(tc.req)
+			if err != nil {
+				t.Fatalf("Failed to marshal: %v", err)
+			}
+			var payload map[string]any
+			if err := json.Unmarshal(data, &payload); err != nil {
+				t.Fatalf("Failed to unmarshal: %v", err)
+			}
+			_, present := payload["featureFlags"]
+			if strings.Contains(tc.name, "empty") != present {
+				t.Errorf("featureFlags presence = %v for %s", present, tc.name)
+			}
+		})
+	}
+}
+
 func TestIsTerminal(t *testing.T) {
 	t.Run("IsTerminal is serialized in tool definition", func(t *testing.T) {
 		tool := Tool{

go/types.go

@@ -1559,6 +1559,9 @@ type SessionConfig struct {
 	// intended for trusted out-of-process integrators, and is not intended for
 	// general external use.
 	ExpAssignments *CopilotExpAssignmentResponse
+	// FeatureFlags contains feature-flag values resolved by the host for this session.
+	// Re-supply them when resuming after a runtime restart.
+	FeatureFlags map[string]bool
 	// EnableManagedSettings, when set to true, opts the runtime into
 	// self-fetching enterprise managed settings (bypass-permissions policy) at
 	// session bootstrap using the session's GitHubToken. Requires GitHubToken to
@@ -2085,6 +2088,9 @@ type ResumeSessionConfig struct {
 	// intended for trusted out-of-process integrators, and is not intended for
 	// general external use.
 	ExpAssignments *CopilotExpAssignmentResponse
+	// FeatureFlags contains host-resolved feature-flag values to apply on resume.
+	// See SessionConfig.FeatureFlags.
+	FeatureFlags map[string]bool
 	// EnableManagedSettings injects the same opt-in flag on resume. See
 	// SessionConfig.EnableManagedSettings. Re-supply on resume so the runtime
 	// re-applies the managed-settings self-fetch after a CLI process restart.
@@ -2557,6 +2563,7 @@ type createSessionRequest struct {
 	ExtensionInfo                      *ExtensionInfo                         `json:"extensionInfo,omitempty"`
 	CanvasProvider                     *CanvasProviderIdentity                `json:"canvasProvider,omitempty"`
 	ExpAssignments                     *CopilotExpAssignmentResponse          `json:"expAssignments,omitempty"`
+	FeatureFlags                       *map[string]bool                       `json:"featureFlags,omitempty"`
 	EnableManagedSettings              *bool                                  `json:"enableManagedSettings,omitempty"`
 	ManagedSettings                    *ManagedSettings                       `json:"managedSettings,omitempty"`
 	Traceparent                        string                                 `json:"traceparent,omitempty"`
@@ -2656,6 +2663,7 @@ type resumeSessionRequest struct {
 	ExtensionInfo                      *ExtensionInfo                         `json:"extensionInfo,omitempty"`
 	CanvasProvider                     *CanvasProviderIdentity                `json:"canvasProvider,omitempty"`
 	ExpAssignments                     *CopilotExpAssignmentResponse          `json:"expAssignments,omitempty"`
+	FeatureFlags                       *map[string]bool                       `json:"featureFlags,omitempty"`
 	EnableManagedSettings              *bool                                  `json:"enableManagedSettings,omitempty"`
 	ManagedSettings                    *ManagedSettings                       `json:"managedSettings,omitempty"`
 	Traceparent                        string                                 `json:"traceparent,omitempty"`

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

@@ -200,6 +200,7 @@ static CreateSessionRequest buildCreateRequest(SessionConfig config, String sess
         request.setGitHubToken(config.getGitHubToken());
         request.setRemoteSession(config.getRemoteSession());
         request.setCloud(config.getCloud());
+        request.setFeatureFlags(config.getFeatureFlags());
         request.setExpAssignments(config.getExpAssignments());
         config.getEnableManagedSettings().ifPresent(request::setEnableManagedSettings);
         request.setManagedSettings(config.getManagedSettings());
@@ -338,6 +339,7 @@ static ResumeSessionRequest buildResumeRequest(String sessionId, ResumeSessionCo
         }
         request.setGitHubToken(config.getGitHubToken());
         request.setRemoteSession(config.getRemoteSession());
+        request.setFeatureFlags(config.getFeatureFlags());
         request.setExpAssignments(config.getExpAssignments());
         config.getEnableManagedSettings().ifPresent(request::setEnableManagedSettings);
         request.setManagedSettings(config.getManagedSettings());

java/sdk/src/main/java/com/github/copilot/rpc/CreateSessionRequest.java

@@ -236,6 +236,9 @@ public final class CreateSessionRequest {
     @JsonProperty("expAssignments")
     private CopilotExpAssignmentResponse expAssignments;
 
+    @JsonProperty("featureFlags")
+    private Map<String, Boolean> featureFlags;
+
     @JsonProperty("enableManagedSettings")
     @JsonInclude(JsonInclude.Include.NON_NULL)
     private Boolean enableManagedSettings;
@@ -1113,6 +1116,16 @@ public void setExpAssignments(CopilotExpAssignmentResponse expAssignments) {
         this.expAssignments = expAssignments;
     }
 
+    /** Gets host-resolved feature flags. @return the feature flags */
+    public Map<String, Boolean> getFeatureFlags() {
+        return featureFlags;
+    }
+
+    /** Sets host-resolved feature flags. @param featureFlags the feature flags */
+    public void setFeatureFlags(Map<String, Boolean> featureFlags) {
+        this.featureFlags = featureFlags;
+    }
+
     /**
      * Gets the self-fetch managed settings flag. @return the flag, or {@code null}
      * if not set

java/sdk/src/main/java/com/github/copilot/rpc/ResumeSessionConfig.java

@@ -111,6 +111,7 @@ public class ResumeSessionConfig {
     private String remoteSession;
     private CopilotExpAssignmentResponse expAssignments;
     private Boolean enableManagedSettings;
+    private Map<String, Boolean> featureFlags;
     private ManagedSettings managedSettings;
 
     /**
@@ -1969,6 +1970,23 @@ public ResumeSessionConfig setExpAssignments(CopilotExpAssignmentResponse expAss
         return this;
     }
 
+    /** Gets host-resolved feature-flag values. @return the feature flags */
+    public Map<String, Boolean> getFeatureFlags() {
+        return featureFlags;
+    }
+
+    /**
+     * Sets feature-flag values resolved by the host to apply on resume.
+     *
+     * @param featureFlags
+     *            the feature flags
+     * @return this config for method chaining
+     */
+    public ResumeSessionConfig setFeatureFlags(Map<String, Boolean> featureFlags) {
+        this.featureFlags = featureFlags;
+        return this;
+    }
+
     /**
      * Gets whether the runtime self-fetches enterprise managed settings at session
      * bootstrap on resume.
@@ -2102,6 +2120,7 @@ public ResumeSessionConfig clone() {
         copy.gitHubToken = this.gitHubToken;
         copy.gitHubTokenProvider = this.gitHubTokenProvider;
         copy.remoteSession = this.remoteSession;
+        copy.featureFlags = this.featureFlags != null ? new java.util.HashMap<>(this.featureFlags) : null;
         copy.expAssignments = this.expAssignments;
         copy.enableManagedSettings = this.enableManagedSettings;
         copy.managedSettings = this.managedSettings;

java/sdk/src/main/java/com/github/copilot/rpc/ResumeSessionRequest.java

@@ -238,6 +238,9 @@ public final class ResumeSessionRequest {
     @JsonProperty("expAssignments")
     private CopilotExpAssignmentResponse expAssignments;
 
+    @JsonProperty("featureFlags")
+    private Map<String, Boolean> featureFlags;
+
     @JsonProperty("enableManagedSettings")
     @JsonInclude(JsonInclude.Include.NON_NULL)
     private Boolean enableManagedSettings;
@@ -1128,6 +1131,16 @@ public void setExpAssignments(CopilotExpAssignmentResponse expAssignments) {
         this.expAssignments = expAssignments;
     }
 
+    /** Gets host-resolved feature flags. @return the feature flags */
+    public Map<String, Boolean> getFeatureFlags() {
+        return featureFlags;
+    }
+
+    /** Sets host-resolved feature flags. @param featureFlags the feature flags */
+    public void setFeatureFlags(Map<String, Boolean> featureFlags) {
+        this.featureFlags = featureFlags;
+    }
+
     /**
      * Gets the self-fetch managed settings flag. @return the flag, or {@code null}
      * if not set

java/sdk/src/main/java/com/github/copilot/rpc/SessionConfig.java

@@ -112,6 +112,7 @@ public class SessionConfig {
     private CloudSessionOptions cloud;
     private CopilotExpAssignmentResponse expAssignments;
     private Boolean enableManagedSettings;
+    private Map<String, Boolean> featureFlags;
     private ManagedSettings managedSettings;
 
     /**
@@ -2097,6 +2098,23 @@ public SessionConfig setExpAssignments(CopilotExpAssignmentResponse expAssignmen
         return this;
     }
 
+    /** Gets host-resolved feature-flag values. @return the feature flags */
+    public Map<String, Boolean> getFeatureFlags() {
+        return featureFlags;
+    }
+
+    /**
+     * Sets feature-flag values resolved by the host for this session.
+     *
+     * @param featureFlags
+     *            the feature flags
+     * @return this config instance for method chaining
+     */
+    public SessionConfig setFeatureFlags(Map<String, Boolean> featureFlags) {
+        this.featureFlags = featureFlags;
+        return this;
+    }
+
     /**
      * Gets whether the runtime self-fetches enterprise managed settings at session
      * bootstrap.
@@ -2243,6 +2261,7 @@ public SessionConfig clone() {
         copy.gitHubTokenProvider = this.gitHubTokenProvider;
         copy.remoteSession = this.remoteSession;
         copy.cloud = this.cloud;
+        copy.featureFlags = this.featureFlags != null ? new java.util.HashMap<>(this.featureFlags) : null;
         copy.expAssignments = this.expAssignments;
         copy.enableManagedSettings = this.enableManagedSettings;
         copy.managedSettings = this.managedSettings;

java/sdk/src/test/java/com/github/copilot/SessionRequestBuilderTest.java

@@ -1055,6 +1055,26 @@ void testBuildRequestsOmitExpAssignmentsWhenUnset() throws Exception {
         assertFalse(resumeJson.contains("\"expAssignments\""), "expAssignments should be omitted when null");
     }
 
+    @Test
+    void testBuildRequestsPropagateAndSerializeFeatureFlags() throws Exception {
+        var mapper = JsonRpcClient.getObjectMapper();
+        var flags = Map.of("ENABLED_TEST_FLAG", true, "DISABLED_TEST_FLAG", false);
+
+        var createConfig = new SessionConfig().setFeatureFlags(flags);
+        CreateSessionRequest createRequest = SessionRequestBuilder.buildCreateRequest(createConfig, "session-1");
+        assertEquals(flags, createRequest.getFeatureFlags());
+        var createJson = mapper.readTree(mapper.writeValueAsString(createRequest));
+        assertTrue(createJson.path("featureFlags").path("ENABLED_TEST_FLAG").asBoolean());
+        assertFalse(createJson.path("featureFlags").path("DISABLED_TEST_FLAG").asBoolean());
+
+        var resumeConfig = new ResumeSessionConfig().setFeatureFlags(flags);
+        ResumeSessionRequest resumeRequest = SessionRequestBuilder.buildResumeRequest("session-1", resumeConfig);
+        assertEquals(flags, resumeRequest.getFeatureFlags());
+        var resumeJson = mapper.readTree(mapper.writeValueAsString(resumeRequest));
+        assertTrue(resumeJson.path("featureFlags").path("ENABLED_TEST_FLAG").asBoolean());
+        assertFalse(resumeJson.path("featureFlags").path("DISABLED_TEST_FLAG").asBoolean());
+    }
+
     @Test
     void testClonePreservesAndForwardsExpAssignments() throws Exception {
         var mapper = JsonRpcClient.getObjectMapper();