Reload MCP servers after session resume

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

Copilot-Session: 812b44f2-ef93-4b32-b051-c7092f612279

Author: stephentoub

dotnet/src/Client.cs

@@ -1480,6 +1480,15 @@ public async Task<CopilotSession> ResumeSessionAsync(string sessionId, ResumeSes
             session.SetCapabilities(response.Capabilities);
             session.SetOpenCanvases(response.OpenCanvases);
 
+            if (config.McpServers is not null)
+            {
+                await InvokeRpcAsync<JsonElement>(
+                    connection.Rpc,
+                    "session.mcp.reloadWithConfig",
+                    [new ReloadMcpServersRequest(sessionId, new ReloadMcpServersConfig(config.McpServers))],
+                    cancellationToken);
+            }
+
             if (config.OnMcpAuthRequest is not null)
             {
                 await session.Rpc.EventLog.RegisterInterestAsync("mcp.oauth_required", cancellationToken);
@@ -2952,6 +2961,13 @@ internal record ResumeSessionResponse(
         IList<OpenCanvasInstance>? OpenCanvases = null);
 #pragma warning restore GHCP001
 
+    internal record ReloadMcpServersRequest(
+        string SessionId,
+        ReloadMcpServersConfig Config);
+
+    internal record ReloadMcpServersConfig(
+        IDictionary<string, McpServerConfig> McpServers);
+
     internal record CommandWireDefinition(
         string Name,
         string Description);
@@ -3028,6 +3044,8 @@ internal record HooksInvokeResponse(
     [JsonSerializable(typeof(CapiSessionOptions))]
     [JsonSerializable(typeof(NamedProviderConfig))]
     [JsonSerializable(typeof(ProviderModelConfig))]
+    [JsonSerializable(typeof(ReloadMcpServersConfig))]
+    [JsonSerializable(typeof(ReloadMcpServersRequest))]
     [JsonSerializable(typeof(SessionLimitsConfig))]
     [JsonSerializable(typeof(ResumeSessionRequest))]
     [JsonSerializable(typeof(ResumeSessionResponse))]

dotnet/test/E2E/SessionMcpAndAgentConfigE2ETests.cs

@@ -58,7 +58,6 @@ public async Task Should_Accept_MCP_Server_Configuration_On_Session_Resume()
         // Create a session first
         var session1 = await CreateSessionAsync();
         var sessionId = session1.SessionId;
-        await session1.SendAndWaitAsync(new MessageOptions { Prompt = "What is 1+1?" });
         await session1.DisposeAsync();
 
         // Resume with MCP servers

go/client.go

@@ -1356,6 +1356,19 @@ func (c *Client) ResumeSessionWithOptions(ctx context.Context, sessionID string,
 		return nil, fmt.Errorf("failed to unmarshal response: %w", err)
 	}
 
+	if config.MCPServers != nil {
+		internalSessionRPC := rpc.NewInternalSessionRPC(c.client, sessionID)
+		_, err := internalSessionRPC.MCP.ReloadWithConfig(ctx, &rpc.MCPReloadWithConfigRequest{
+			Config: map[string]any{"mcpServers": config.MCPServers},
+		})
+		if err != nil {
+			c.sessionsMux.Lock()
+			delete(c.sessions, sessionID)
+			c.sessionsMux.Unlock()
+			return nil, fmt.Errorf("failed to reload MCP servers after resume: %w", err)
+		}
+	}
+
 	if config.OnMCPAuthRequest != nil {
 		if _, err := c.client.Request(ctx, "session.eventLog.registerInterest", map[string]any{
 			"sessionId": sessionID,

go/internal/e2e/mcp_and_agents_e2e_test.go

@@ -88,11 +88,6 @@ func TestMCPServersE2E(t *testing.T) {
 		}
 		sessionID := session1.SessionID
 
-		_, err = session1.SendAndWait(t.Context(), copilot.MessageOptions{Prompt: "What is 1+1?"})
-		if err != nil {
-			t.Fatalf("Failed to send message: %v", err)
-		}
-
 		// Resume with MCP servers
 		mcpServers := testMCPServers(t, "test-server")
 

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

@@ -40,6 +40,8 @@
 import com.github.copilot.generated.rpc.GitHubTelemetryNotification;
 import com.github.copilot.generated.rpc.ServerRpc;
 import com.github.copilot.generated.rpc.SessionEventLogRegisterInterestParams;
+import com.github.copilot.generated.rpc.SessionMcpReloadWithConfigParams;
+import com.github.copilot.generated.rpc.SessionMcpReloadWithConfigResult;
 import com.github.copilot.rpc.DeleteSessionResponse;
 import com.github.copilot.rpc.GetAuthStatusResponse;
 import com.github.copilot.rpc.GetLastSessionIdResponse;
@@ -1146,11 +1148,17 @@ public CompletableFuture<CopilotSession> resumeSession(String sessionId, ResumeS
                                 rpcNanos);
                         String returnedId = response.sessionId();
                         String interestSessionId = returnedId != null ? returnedId : sessionId;
+                        CompletableFuture<?> reload = config.getMcpServers() != null
+                                ? connection.rpc.invoke("session.mcp.reloadWithConfig",
+                                        new SessionMcpReloadWithConfigParams(interestSessionId,
+                                                Map.of("mcpServers", config.getMcpServers())),
+                                        SessionMcpReloadWithConfigResult.class)
+                                : CompletableFuture.completedFuture(null);
                         CompletableFuture<?> interest = config.getOnMcpAuthRequest() != null
                                 ? session.getRpc().eventLog.registerInterest(new SessionEventLogRegisterInterestParams(
                                         interestSessionId, "mcp.oauth_required"))
                                 : CompletableFuture.completedFuture(null);
-                        return interest.thenApply(interestResult -> {
+                        return reload.thenCompose(ignored -> interest).thenApply(interestResult -> {
                             logMcpAuthInterestRegistration(interestResult);
                             return response;
                         });

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

@@ -131,7 +131,6 @@ void testShouldAcceptMcpServerConfigurationOnSessionResume() throws Exception {
             CopilotSession session1 = client
                     .createSession(new SessionConfig().setOnPermissionRequest(PermissionHandler.APPROVE_ALL)).get();
             String sessionId = session1.getSessionId();
-            session1.sendAndWait(new MessageOptions().setPrompt("What is 1+1?")).get(60, TimeUnit.SECONDS);
 
             // Resume with MCP servers
             var mcpServers = createTestMcpServers("test-server");

python/copilot/client.py

@@ -3423,6 +3423,14 @@ async def resume_session(
                 session._set_open_canvases(
                     [OpenCanvasInstance.from_dict(inst) for inst in open_canvases_raw]
                 )
+            if mcp_servers is not None:
+                await self._client.request(
+                    "session.mcp.reloadWithConfig",
+                    {
+                        "sessionId": session_id,
+                        "config": {"mcpServers": _mcp_servers_to_wire(mcp_servers)},
+                    },
+                )
             if on_mcp_auth_request is not None:
                 await self._client.request(
                     "session.eventLog.registerInterest",

python/e2e/test_mcp_and_agents_e2e.py

@@ -99,7 +99,6 @@ async def test_should_accept_mcp_server_configuration_on_session_resume(
             on_permission_request=PermissionHandler.approve_all
         )
         session_id = session1.session_id
-        await session1.send_and_wait("What is 1+1?")
 
         # Resume with MCP servers
         mcp_servers = _test_mcp_servers("test-server")

rust/src/session.rs

@@ -1293,6 +1293,20 @@ impl Client {
             })
             .into());
         }
+        if let Some(mcp_servers) = wire.mcp_servers.as_ref()
+            && let Err(error) = self
+                .call(
+                    "session.mcp.reloadWithConfig",
+                    Some(serde_json::json!({
+                        "sessionId": session_id,
+                        "config": { "mcpServers": mcp_servers },
+                    })),
+                )
+                .await
+        {
+            registration.cleanup(event_loop).await;
+            return Err(error);
+        }
         if has_mcp_auth_handler {
             register_mcp_auth_interest(self, &session_id).await?;
         }