Introduction

fullstackhero is an opinionated, production-first .NET 10 starter for building multi-tenant SaaS and enterprise APIs. You get the full source — BuildingBlocks, Modules, and a composition-root Host — wired through Minimal APIs, Mediator, and EF Core. No black-box NuGet packages: you own and can modify everything.

It’s aimed at teams that want to ship features on day one without spending a sprint wiring identity, tenancy, auditing, caching, jobs, storage, observability, and API docs.

Highlights

• Modular monolith, vertical slices. Each module is a bounded context with its own DbContext, contracts, and feature folders. Communication across modules goes through *.Contracts projects only — runtime projects never reference each other.
• Multi-tenant from day one. Finbuckle-powered tenancy across Identity and module DbContexts. Tenant resolution via claim, header, or query string. Per-tenant migrations and seeding on startup.
• Identity + permission-based auth. ASP.NET Identity with JWT issue/refresh, roles, granular permissions enforced via .RequirePermission() on endpoints.
• Eventing built in. Domain events on aggregates + integration events through Mediator. Outbox-friendly entity model.
• Webhooks with HMAC signing. Tenant-scoped subscriptions, retries, and delivery logs.
• Realtime + SSE. SignalR for hubs, Server-Sent Events for one-way streaming.
• Idempotency. Idempotency-Key header with cache-backed replay.
• Feature flags with tenant overrides. Microsoft.FeatureManagement, scoped per tenant.
• Quotas. Per-tenant request and resource limits.
• Observability baked in. OpenTelemetry traces, metrics, and logs (OTLP); Serilog structured logging; health checks; security/exception auditing.
• API docs. OpenAPI + Scalar UI. Versioned routes via Asp.Versioning (/api/v{version}/{module}).
• Cloud-ready. .NET Aspire AppHost brings up Postgres, Valkey (a Redis-compatible, BSD-licensed Redis fork), and the API host locally with one command. Production deploy via Docker Compose included.
• Two frontends. React + Vite admin console and dashboard, both in clients/.
• CLI + template. Scaffold new projects with fsh new or dotnet new fsh, or clone the repo directly.

High-level architecture

dotnet-starter-kit/
├── src/
│   ├── BuildingBlocks/        Shared framework libraries
│   │   ├── Core                  DDD primitives, exceptions, abstractions
│   │   ├── Persistence           EF Core base contexts, specifications, soft delete
│   │   ├── Web                   Host wiring: auth, OpenAPI, rate limit, CORS, errors
│   │   ├── Caching               HybridCache + Valkey
│   │   ├── Eventing              Domain + integration events
│   │   ├── Eventing.Abstractions Contracts for cross-module events
│   │   ├── Jobs                  Hangfire
│   │   ├── Mailing               MailKit / SendGrid
│   │   ├── Storage               Local + S3-compatible
│   │   ├── Quota                 Per-tenant limits
│   │   └── Shared                Permission constants, common contracts
│   │
│   ├── Modules/               Bounded contexts (each = runtime + contracts pair)
│   │   ├── Identity              ASP.NET Identity, JWT, roles, permissions
│   │   ├── Multitenancy          Tenant CRUD, migrations, upgrades
│   │   ├── Auditing              Activity / security / exception audit trail
│   │   ├── Webhooks              HMAC-signed delivery, retries, logs
│   │   ├── Files                 Upload URLs, storage abstraction
│   │   ├── Notifications         In-app notifications
│   │   └── Billing · Catalog · Chat · Tickets   Sample modules
│   │
│   ├── Host/
│   │   ├── FSH.Starter.Api               Composition root (Program.cs)
│   │   ├── FSH.Starter.AppHost           .NET Aspire orchestrator
│   │   ├── FSH.Starter.DbMigrator        Migrations + seed-demo CLI
│   │   └── FSH.Starter.Migrations.PostgreSQL
│   │
│   ├── Tools/CLI              The `fsh` CLI (Spectre.Console)
│   └── Tests/                 Architecture tests + per-module test projects
│
├── clients/
│   ├── admin                  React + Vite admin console
│   └── dashboard              React + Vite dashboard
│
└── deploy/                    Docker Compose, Dokploy, Terraform

Module boundaries are enforced by NetArchTest rules in src/Tests/Architecture.Tests.

Feature slice layout

Each feature is a vertical slice. For Modules.Identity registering a user:

Modules.Identity.Contracts/v1/Users/RegisterUser/
  RegisterUserCommand.cs
  RegisterUserResponse.cs

Modules.Identity/Features/v1/Users/RegisterUser/
  RegisterUserEndpoint.cs          ← Minimal API
  RegisterUserCommandHandler.cs    ← Mediator handler
  RegisterUserCommandValidator.cs  ← FluentValidation

Handlers are public sealed, return ValueTask<T>, and use .ConfigureAwait(false). Endpoints are static extensions on IEndpointRouteBuilder.

Composition root

src/Host/FSH.Starter.Api/Program.cs wires the platform in three calls:

builder.Services.AddMediator(o => { o.Assemblies = [/* command + handler markers */]; });

builder.AddHeroPlatform(o =>
{
    o.EnableCaching = true;
    o.EnableMailing = true;
    o.EnableJobs = true;
    o.EnableQuotas = true;
    o.EnableSse = true;
    o.EnableRealtime = true;
});

builder.AddModules(moduleAssemblies);

var app = builder.Build();
app.UseHeroMultiTenantDatabases();
app.UseHeroPlatform(p => { p.MapModules = true; /* ... */ });

The API never mutates data on startup. Demo data (acme/globex tenants, sample catalog/tickets/chat) is provisioned by FSH.Starter.DbMigrator seed-demo.

Stack

Runtime

Frontends

Testing

Distribution

Where to go next

• Prerequisites — what you need installed.
• Quick Start — run a project in 60 seconds.
• Architecture — modular monolith, VSA, module boundaries.
• Modules — Identity, Multitenancy, Auditing, Webhooks.
• Guides — task-oriented walkthroughs.