fix(lab): keep FeatureFusion running when env is not Development

README.md

@@ -243,6 +243,8 @@ Requires .NET 8 / 9 / 10. HTTP default: `MapBuildingBlocksMcp()` → `/mcp`. Cur
 
 After you add or rename tools, **restart the API and reload the MCP server in Cursor** (Aspire restart alone does not refresh Cursor’s cached `tools/list`).
 
+![Cursor Configure featurefusion: MCP tools from the running lab API (products.list, orders.*, demo.echo, lab.ping, customers.*, catalog.products.list).](docs/medium/images/mcp-cursor-featurefusion-tools.png)
+
 #### Quick start
 
 ```csharp

docs/building-blocks/mcp.md

@@ -208,7 +208,7 @@ Development only (`http://localhost:5141/mcp`):
 | `products.list` | Scan + `ISender` (query) | products query |
 | `lab.ping` | `[McpTool]` + `.WithMcp(app)` on `LabPing` | `GET /api/v1/lab-ping` |
 
-Lab Compose sets `ASPNETCORE_ENVIRONMENT=Development` so MCP is registered (map at `/mcp`). A Production-environment host does not register or map MCP.
+Lab Compose and AppHost set `ASPNETCORE_ENVIRONMENT=Development` so HTTP MCP is mapped at `/mcp`. A Production-environment host still registers MCP services (so `.WithMcp` does not crash startup) but does not map `/mcp`.
 
 Workspace root for this Cursor window is `src/`. Put this in `src/.cursor/mcp.json` (gitignored; copy locally):
 

src/BuildingBlocks/Mcp/Hosting/McpEndpointRouteBuilderExtensions.cs

@@ -101,7 +101,10 @@ private static void Register(
 		}
 
 		var descriptor = McpMethodTool.FromMethod(method, attr, InferKindFromHttp(endpointBuilder));
-		services.GetRequiredService<McpEndpointToolRegistry>().Add(descriptor);
+		var registry = services.GetService<McpEndpointToolRegistry>();
+		if (registry is null)
+			return;
+		registry.Add(descriptor);
 	}
 
 	private static McpToolKind InferKindFromHttp(EndpointBuilder endpointBuilder)

src/Lab/FeatureFusion.AppHost/Program.cs

@@ -1,5 +1,12 @@
 using FeatureFusion.AppHost;
 
+if (string.IsNullOrWhiteSpace(Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT"))
+	&& string.IsNullOrWhiteSpace(Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT")))
+{
+	Environment.SetEnvironmentVariable("ASPNETCORE_ENVIRONMENT", "Development");
+	Environment.SetEnvironmentVariable("DOTNET_ENVIRONMENT", "Development");
+}
+
 // Force Docker when DCP autodetection flakes on Windows + Docker Desktop.
 var builder = DistributedApplication.CreateBuilder(DockerRuntime.Configure(args));
 
@@ -14,6 +21,7 @@
 	.WithHttpEndpoint(port: 5141, name: "http")
 	.WithEndpoint(7762, targetPort: 5002, scheme: "https", name: "featurefusion-https")
 	.WithUrl("/swagger/index.html?urls.primaryName=v1", "Swagger v1")
+	.WithEnvironment("ASPNETCORE_ENVIRONMENT", "Development")
 	.WithInfrastructure(infra)
 	.WithSigNozOtlpExporter(signoz);
 

src/Lab/FeatureFusion/Program.cs

@@ -29,6 +29,13 @@
 using System.Reflection;
 using static RedisSettings;
 
+if (string.IsNullOrWhiteSpace(Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT"))
+	&& string.IsNullOrWhiteSpace(Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT")))
+{
+	Environment.SetEnvironmentVariable("ASPNETCORE_ENVIRONMENT", "Development");
+	Environment.SetEnvironmentVariable("DOTNET_ENVIRONMENT", "Development");
+}
+
 var builder = WebApplication.CreateBuilder(args);
 
 builder.Configuration
@@ -77,38 +84,35 @@
 	cfg.ValidateOnStartup = true;
 });
 
-if (builder.Environment.IsDevelopment())
+builder.Services.AddBuildingBlocksMcp(o =>
 {
-	builder.Services.AddBuildingBlocksMcp(o =>
-	{
-		o.ScanAssembly(Assembly.GetExecutingAssembly());
-		o.UseTelemetry(t => t.IncludeExceptionDetails = true);
-		o.UseMemoryIdempotency(TimeSpan.FromHours(1));
-	}).UseDispatcher(async (sp, msg, ct) =>
+	o.ScanAssembly(Assembly.GetExecutingAssembly());
+	o.UseTelemetry(t => t.IncludeExceptionDetails = true);
+	o.UseMemoryIdempotency(TimeSpan.FromHours(1));
+}).UseDispatcher(async (sp, msg, ct) =>
+{
+	await using var scope = sp.CreateAsyncScope();
+	var services = scope.ServiceProvider;
+	if (msg is FeatureFusion.Features.Orders.Commands.CreateOrderCommand createOrder)
 	{
-		await using var scope = sp.CreateAsyncScope();
-		var services = scope.ServiceProvider;
-		if (msg is FeatureFusion.Features.Orders.Commands.CreateOrderCommand createOrder)
+		var admission = services.GetRequiredService<FeatureFusion.Features.Admission.ICapabilityAdmission>();
+		var mcpContext = services.GetService<BuildingBlocks.Mcp.IMcpInvokeContextAccessor>();
+		var decision = await FeatureFusion.Features.Admission.OrderCreateAdmissionGate.AdmitCreateOrderAsync(
+			admission,
+			createOrder,
+			FeatureFusion.Features.Admission.OrderCreateAdmissionGate.ResolveMcpRequestKey(mcpContext),
+			ct);
+		switch (decision)
 		{
-			var admission = services.GetRequiredService<FeatureFusion.Features.Admission.ICapabilityAdmission>();
-			var mcpContext = services.GetService<BuildingBlocks.Mcp.IMcpInvokeContextAccessor>();
-			var decision = await FeatureFusion.Features.Admission.OrderCreateAdmissionGate.AdmitCreateOrderAsync(
-				admission,
-				createOrder,
-				FeatureFusion.Features.Admission.OrderCreateAdmissionGate.ResolveMcpRequestKey(mcpContext),
-				ct);
-			switch (decision)
-			{
-				case FeatureFusion.Features.Admission.AdmissionDecision.Defer defer:
-					return Result<FeatureFusion.Features.Admission.AdmissionPendingResponse>.Success(defer.Pending);
-				case FeatureFusion.Features.Admission.AdmissionDecision.Deny deny:
-					return Result<FeatureFusion.Features.Admission.AdmissionPendingResponse>.Failure(deny.Error, deny.StatusCode);
-			}
+			case FeatureFusion.Features.Admission.AdmissionDecision.Defer defer:
+				return Result<FeatureFusion.Features.Admission.AdmissionPendingResponse>.Success(defer.Pending);
+			case FeatureFusion.Features.Admission.AdmissionDecision.Deny deny:
+				return Result<FeatureFusion.Features.Admission.AdmissionPendingResponse>.Failure(deny.Error, deny.StatusCode);
 		}
+	}
 
-		return await services.GetRequiredService<ISender>().Send(msg, ct);
-	});
-}
+	return await services.GetRequiredService<ISender>().Send(msg, ct);
+});
 
 
 builder.Services.AddApiVersioningWithReader();

tests/BuildingBlocks/Mcp.Tests/CatalogAndInvokerTests.cs

@@ -4,6 +4,7 @@
 using BuildingBlocks.Mcp.Hosting;
 using BuildingBlocks.Mcp.Invocation;
 using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.DependencyInjection;
 using Xunit;
@@ -132,6 +133,17 @@ public async Task WithMcp_And_Scan_Dedupe_Same_Name()
 		Assert.Equal("pong:Ada", result.Value);
 	}
 
+	[Fact]
+	public async Task WithMcp_Without_AddBuildingBlocksMcp_Does_Not_Fail_Host_Start()
+	{
+		var builder = WebApplication.CreateSlimBuilder();
+		builder.WebHost.UseUrls("http://127.0.0.1:0");
+		await using var app = builder.Build();
+		app.MapGet("/named-ping", WithMcpNamedPing).WithMcp(app, "tests.withmcp-no-add", "Named ping");
+		await app.StartAsync();
+		await app.StopAsync();
+	}
+
 	[Fact]
 	public async Task WithMcp_Named_Infers_Query_From_Get()
 	{