clean-architecture-dotnet

clean-architecture-dotnet is a skill for Claude Code, Codex from SebastienDegodez/copilot-instructions. It costs 50 tokens per session (4,628 once invoked), scanned A, original, Apache-2.0.

A guide to Clean Architecture in .NET, a way of organizing applications into separate layers for business rules, application actions, external systems, and APIs. It emphasizes keeping dependencies directed toward the core business code.

In plain words
What is it for?
Use it when separating domain, application, infrastructure, and API code; choosing between simple commands and queries or more complex CQRS and domain-driven patterns; and reviewing project references.
Why use it?
It helps prevent business logic from leaking into controllers or infrastructure and avoids circular project dependencies.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it when separating domain, application, infrastructure, and API code; choosing between simple commands and queries or more complex CQRS and domain-driven patterns; and reviewing project references.

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Install with agentmods
npx agentmods add skills/sebastiendegodez/copilot-instructions/clean-architecture-dotnet
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add SebastienDegodez/copilot-instructions --skill clean-architecture-dotnet
Clone the repo
git clone --depth 1 https://github.com/SebastienDegodez/copilot-instructions

Made for: Claude Code, Codex.

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README.md
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Per session 50 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,628 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00050 $0.04628
Opus 5 $0.00025 $0.02314
Sonnet 5 $0.00010 $0.00926
Haiku 4.5 $0.00005 $0.00463

Measured 10d ago against content hash 5ca6cb7bf77b, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

clean-architecture-dotnet scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 10d ago.

The scan reads SKILL.md. This mod also ships 2 executable files (scripts/init-project.ps1, scripts/init-project.sh), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/csharp-clean-architecture-development/skills/clean-architecture-dotnet/SKILL.md · 393 lines

How it starts

The opening of the file, as written. The whole thing — 393 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Clean Architecture in .NET

Overview

Clean Architecture organizes code into independent layers (Domain → Application → Infrastructure → API).

The Iron Law: Violating layer boundaries is a failure. If API references Application or Domain references Infrastructure, delete the change and start over.

Concrete violations that break the Iron Law:

  • using MyApp.Infrastructure; in a Domain class — Infrastructure must never flow inward.
  • using MyApp.Application; in an API endpoint file — API must only interact via ICommandBus / IQueryBus or an injected use case interface.
  • new AppDbContext() inside a Controller — bypasses both Infrastructure and Application layers.
  • HttpClient injected directly into a Domain or Application class — HTTP belongs in Infrastructure behind an interface.

Fix: move the dependency to the correct outer layer and expose it through an interface pointing inward.

When to Use

  • Business logic is leaking into Controllers or Repositories
  • Circular dependencies occur between projects
  • Need to isolate core business rules from external frameworks (EF Core, APIs)
  • Autonomy is required: sealed Domain objects, strongly-typed IDs

When NOT to add CQRS or DDD:

  • The feature is pure CRUD with no business rules, no invariants, and no domain events → use a CQS Application service (see Pattern A below)
  • A query only reads data with no domain logic → inject the repository or a read service directly in the Application handler; no IQueryBus required
  • You have fewer than 3 use cases with no cross-cutting concerns (logging pipeline, validation pipeline) → a CQRS bus adds ceremony without value

CQS vs CQRS vs DDD — Complexity Threshold

These three patterns are independent tools. Choose based on what the codebase actually needs.

Pattern Rule Add it when… Skip it when…
CQS (always) Every handler/method is either a command (void) or a query (returns value) — never both Always — zero exceptions Never skip
CQRS + Bus (optional) Separate ICommandBus / IQueryBus routing commands and queries through a pipeline Cross-cutting concerns (validation, logging pipelines), large teams writing many use cases, read/write model asymmetry Simple CRUD; < 3 use cases; no cross-cutting pipeline needed
DDD (optional) Aggregates, factory methods, value objects, domain events Domain has invariants (rules that must be enforced on every state change), state machines, rich business logic Entities are pure data (no if/throw to protect state); CRUD-only feature

Read the full file on GitHub · 393 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 10d ago First seen · 393 lines · 50 tokens per session scan A 5ca6cb7bf77b

Subscribe to this mod's changes

clean-architecture-dotnet is a skill published in the GitHub repository SebastienDegodez/copilot-instructions (193 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 50 tokens to every session and 4,628 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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