dotnet-backend-expert

dotnet-backend-expert is an agent for Claude Code from FortiumPartners/ensemble. It costs 30 tokens per session (2,386 once invoked), scanned A, original, MIT.

A .NET backend specialist for ASP.NET Core APIs, Wolverine CQRS, MartenDB, event sourcing, and C# development. CQRS separates commands that change data from queries that read it.

In plain words
What is it for?
It is for building APIs, command and query handlers, message workflows, event-sourced data models, dependency injection, and automated tests in C#.
Why use it?
It provides focused guidance for designing and implementing backend services with these .NET technologies and patterns.

Agent for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the ensemble-dotnet plugin — 1 agent shipped together

Good fit It is for building APIs, command and query handlers, message workflows, event-sourced…

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Install with agentmods
npx agentmods add agents/fortiumpartners/ensemble/dotnet-backend-expert
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.

Clone the repo
git clone --depth 1 https://github.com/FortiumPartners/ensemble

Made for: Claude Code.

Or install ensemble-dotnet, the plugin that ships this one along with the rest of its 1 agent.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for dotnet-backend-expert

README.md
[![agentmods](https://agentmods.dev/badge/agents/fortiumpartners/ensemble/dotnet-backend-expert.svg)](https://agentmods.dev/agents/fortiumpartners/ensemble/dotnet-backend-expert)
Your own site
<a href="https://agentmods.dev/agents/fortiumpartners/ensemble/dotnet-backend-expert"><img src="https://agentmods.dev/badge/agents/fortiumpartners/ensemble/dotnet-backend-expert.svg" alt="Measured on agentmods" height="20"></a>
Per session 30 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,386 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.
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 $0.00030 $0.02386
Opus 5 $0.00015 $0.01193
Sonnet 5 $0.00006 $0.00477
Haiku 4.5 $0.00003 $0.00239

Measured 3d ago against content hash 29ff4f01d309, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

dotnet-backend-expert 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 3d ago.

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.

packages/dotnet/agents/dotnet-backend-expert.md · 263 lines

How it starts

The opening of the file, as written. The whole thing — 263 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Mission

Expert .NET backend developer specialising in ASP.NET Core Web API, Minimal API, Wolverine CQRS/message bus, MartenDB document storage and event sourcing, and idiomatic C# patterns. Loads the dotnet-framework skill from packages/blazor/skills/dotnet-framework/SKILL.md at task start for fast-lookup of patterns and conventions, escalating to REFERENCE.md for advanced scenarios.

Core Strengths:

  • ASP.NET Core: Controller-based and Minimal API design with OpenAPI, versioning, and middleware
  • Wolverine CQRS: Command/query handlers, message routing, sagas, and outbox patterns
  • MartenDB: Document storage, event sourcing, projections, and snapshots on PostgreSQL
  • C# Patterns: Records, pattern matching, nullable reference types, async/await, and LINQ
  • Dependency Injection: Built-in DI container, scoped lifetimes, and Scrutor conventions
  • EF Core: Code-first migrations, owned entities, and query optimisation (when MartenDB is not used)
  • Testing: xUnit, Moq/NSubstitute, integration tests with WebApplicationFactory and Testcontainers

Boundaries

Handles:

  • ASP.NET Core controller-based and Minimal API design
  • Wolverine command handlers, query handlers, message routing, and sagas
  • MartenDB document storage, event sourcing streams, projections, and snapshots
  • Entity Framework Core code-first schema management (when not using MartenDB)
  • C# domain modelling: aggregate roots, value objects, domain events
  • Dependency injection configuration, middleware, filters, and health checks
  • Authentication and authorisation (JWT Bearer, ASP.NET Core Identity, policy-based)
  • Input validation (FluentValidation, data annotations)
  • xUnit unit and integration testing with WebApplicationFactory and Testcontainers
  • OpenAPI/Swagger documentation and versioning (Asp.Versioning, Scalar)
  • Background services (IHostedService, Quartz.NET, Wolverine scheduled messages)
  • Performance: response compression, output caching, connection pooling, async I/O

Read the full file on GitHub · 263 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. 3d ago First seen · 263 lines · 30 tokens per session scan A 29ff4f01d309

Subscribe to this mod's changes

dotnet-backend-expert is an agent published in the GitHub repository FortiumPartners/ensemble (11 stars, last pushed 1mo ago), licensed MIT. It adds 30 tokens to every session and 2,386 once invoked, about $0.0002 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 2026-09-03.

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