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AI Coding Agent Skill

Compono ships an official agent skill — guidance an AI coding agent (like Claude Code) reads before writing, modifying, reviewing, or troubleshooting Compono-based tests in your project. It's developer tooling, not a runtime package: nothing here runs inside your test process, and it has no effect on dotnet build/dotnet test.

What it does

An agent without this skill knows Compono only from pretraining, and will likely reach for AutoFixture-shaped habits that don't apply — [Frozen] semantics, customization override, reflection-based construction. The skill teaches the agent Compono's actual model: source-generated composition, [Composable]'s narrow scope, registration/rule precedence, [Shared], deterministic seeding, the real CMP0001-CMP0012 diagnostic set, and the package-specific surface of Compono.XunitV3/ Compono.NSubstitute/Compono.Bogus — only recommending an integration's API when that package is actually referenced in your project.

It also carries guardrails: it won't suggest reflection-based workarounds, won't silently substitute AutoFixture, and won't add [Composable] speculatively. And it stays out of the way for ordinary, non-Compono .NET test work — it only activates on genuine Compono-related tasks.

Install

The canonical source is the skills/ directory of this repository. Add it to a project via npx skills (works with Claude Code and other npx skills-compatible agent hosts):

npx skills add LayeredCraft/compono

or, targeting the skills/ directory explicitly:

npx skills add https://github.com/LayeredCraft/compono/tree/main/skills

This installs the compono skill into your project's agent-skill directory (e.g. .claude/skills/compono for Claude Code). No NuGet package, no .csproj change, no dotnet command — this is entirely separate from installing the Compono/Compono.XunitV3/ Compono.NSubstitute/Compono.Bogus packages themselves (see Installation for those).

Update

npx skills update compono

npx skills ships a dedicated update command for refreshing an already-installed skill (-g/--global or -p/--project to scope it, if you have the same skill installed at both levels) — use that rather than re-running add. There's no separate version pin to manage for this skill; an update always pulls whatever is currently on this repository's default branch.

Which agents support it

Any agent host compatible with the npx skills/skills.sh convention — the skill is plain Markdown (a SKILL.md plus references/), with no Claude-specific mechanics baked in. It's developed and verified primarily against Claude Code.

Relationship to the NuGet packages

The skill and the packages are independent, and neither requires the other:

  • Installing the skill doesn't add any package reference to your project, and doesn't require Compono to already be in use — an agent with the skill installed can also help you adopt Compono in a project that doesn't have it yet, if you ask.
  • Installing the packages without the skill works fine — the skill only changes how well an AI agent assists you; Compono itself doesn't know or care whether it's installed.
  • The skill's guidance is checked against this repository's actual shipped API on every change — it should never describe an API that doesn't exist, or a roadmap item as if it were current.

See ADR-0035 for the design decision behind the skill's structure.