Why the Critter Stack
The Best .NET Tooling for Event-Driven Architectures
The Critter Stack is a suite of open source .NET libraries or frameworks that give you a complete, low-ceremony platform for building server-side applications with Event Sourcing, CQRS, Document Database features, and asynchronous messaging.
How the Pieces Fit Together
Marten
Document Database & Event Store
Use PostgreSQL as a fully-featured document database and event store. The most complete Event Sourcing solution on .NET - projections, snapshots, multi-tenancy, and more.
Documentation ➔
Wolverine
Command Bus & Message Bus
A next-generation mediator, command bus, message bus, and alternative HTTP endpoint framework for .NET. Handles both in-process commands and distributed messaging with minimal ceremony and maximum reliability. Strong integration for EF Core and many database engines and message broker technologies
Documentation ➔
Polecat
Event Store on SQL Server
Bringing the Critter Stack experience to SQL Server 2025. Event store and document database for teams that need or prefer SQL Server.
Documentation ➔
Fisher
Event Store on SQLite
The full Critter Stack experience on SQLite. Event store and document database that lives inside your own process - no database server to install or provision.
Documentation ➔
Weasel
Schema Management
Database schema management for PostgreSQL, SQL Server, and SQLite. Handles migrations and schema diffing for Critter Stack applications.
Documentation ➔
Alba
Integration Testing
Fast and expressive integration testing for ASP.NET Core applications.
Documentation ➔
Bobcat
Integration Testing & Specifications
Author, supervise, and run integration tests in .NET. Executable specifications that read as requirements, with big suites split across worker processes and flakiness reported honestly.
Documentation ➔
JasperFx
Shared Libraries
Common utilities and infrastructure shared across the Critter Stack ecosystem.
Documentation ➔The Critter Stack libraries are designed to work together seamlessly, but each can also be used independently. Start with what you need and adopt more as your system grows.
Why Teams Choose the Critter Stack
Proven in Production
The Critter Stack is battle-hardened software used in production by teams in finance, healthcare, logistics, IoT, and more. These are not experimental tools - they are mature, well-documented, and actively maintained.
Best-in-Class for Event Sourcing & CQRS
Marten is the most full-featured Event Sourcing library on .NET with Polecat bringing the same model to SQL Server and Fisher to embedded SQLite. Combined with Wolverine's command and message handling, the Critter Stack gives you the most complete CQRS and Event Sourcing platform available.
Low Friction Development
The Critter Stack is designed for minimal ceremony. Write code that fits in your head - clean handlers, simple configuration, and conventions that let you focus on business logic instead of infrastructure plumbing.
Optimized for AI-Assisted Development
The Critter Stack's low-ceremony, convention-based approach makes it exceptionally well-suited for AI-assisted coding workflows. AI tools can generate correct, idiomatic Critter Stack code because the patterns are clean and predictable.
Testable by Design
Every layer of the Critter Stack is built for testability. Alba provides fast HTTP integration testing, Bobcat turns large integration suites into executable specifications you can trust, Wolverine handlers are pure functions that are trivial to unit test, and the architecture naturally supports test-driven development.
Observable & Resilient
Built-in OpenTelemetry instrumentation, comprehensive logging, health checks, and CritterWatch for production monitoring. Wolverine provides durable messaging with automatic retries, dead letter queues, and transactional outbox support.
Getting Started
Explore the Documentation
Start with the Marten and Wolverine docs to understand the core tools.
View documentation ➔Try the Sample Projects
See working examples that demonstrate Event Sourcing, CQRS, and messaging patterns in action.
View on GitHub ➔Talk to Us
Have questions? Need help evaluating whether the Critter Stack is right for your project? Get in touch - we are happy to help.
Get in touch ➔Need Help Getting Started?
JasperFx Software offers consulting, support plans, and workshops to help your team succeed with the Critter Stack.