backend-dotnet

name	backend-dotnet
description	Deliver C# and .NET backends with explicit API, validation, auth, async, and operational patterns centered on ASP.NET Core.

Backend .NET

Use this pack for .NET backend work: ASP.NET Core APIs, service layers, auth flows, background processing, data access, and server-side delivery patterns that live in the C# ecosystem.

Defer first-pass route choice and lane selection to ../../reference/routing-matrix.md.

This is the general .NET backend pack for the repo. Use the overlay in reference/aspnet-core.md to tune decisions for controllers, minimal APIs, middleware pipelines, and hosted-service behavior while preserving the same quality bar for contracts, validation, documentation, and runtime clarity.

Setup posture

• Prefer modernizing, refining, or extending an existing project in place.
• Treat scaffold, create, init, or new flows as greenfield-only and explicit-request-only. Defer to .opencode/reference/project-setup-policy.md.

Core focus

• Design API contracts that are stable across controllers, minimal APIs, filters, and client integrations.
• Keep validation, model binding, and error responses explicit so failures are predictable.
• Choose authentication and authorization flows deliberately: cookies, JWTs, OAuth2, policy-based auth, claims, or service credentials.
• Treat async I/O, hosted services, queue consumers, and cancellation as part of the service design.
• Keep OpenAPI, health signals, and failure semantics visible at the backend edge.

Shared .NET backend standards

• Keep endpoints thin and move orchestration plus business rules into services that are not coupled to transport or EF internals.
• Decide deliberately between controllers and minimal APIs based on surface area, reuse, and clarity.
• Use request models, validation rules, and ProblemDetails-style errors so contracts stay consistent under change.
• Keep dependency-injection lifetimes explicit and make background work, retries, and scheduled execution easy to trace.
• Honor CancellationToken, timeouts, and graceful shutdown expectations on I/O-heavy paths.
• Document shared APIs with OpenAPI and keep auth policies, claims, and role checks close to the endpoint surface.

Default workflow

1. Inspect the current endpoint style, DI setup, and hosting model.
2. Choose the ASP.NET Core overlay in reference/aspnet-core.md.
3. Define contracts, validation, auth flow, background behavior, and cancellation boundaries before widening the implementation.
4. Implement endpoints, services, and docs together so runtime behavior stays legible.
5. Run review-work after substantial backend changes.

Collaboration in this repo

• Use Explore before editing so the new work matches local endpoint, middleware, and service patterns.
• Use Librarian or Context7 when framework APIs, auth configuration, or hosting behavior need a source-of-truth check.
• Pair with architecture-integration when the hard part is really service boundaries, contracts, or client coordination.

Overlays

• reference/aspnet-core.md for controllers, minimal APIs, middleware pipelines, endpoint filters, EF-adjacent services, and hosted background work.

Guardrails

• Do not leak EF entities, request objects, or framework-specific state through the whole service layer.
• Do not ignore cancellation, retry, and graceful shutdown semantics on long-running paths.
• Do not let DI lifetime mistakes turn background or request behavior into production-only bugs.