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Kestrun — PowerShell brains. Kestrel speed.

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Kestrun is a hybrid web framework that combines the speed of ASP.NET Core (Kestrel) with the flexibility of PowerShell

Build APIs, automation endpoints, and dynamic services using both C# and PowerShell in a single, integrated environment

Rich Documentation and Tutorial

Full documentation and tutorial for Kestrun is available online at docs.kestrun.dev. You can find guides, API references, and usage examples to help you get started and explore advanced features.

Core Capabilities

• 🚀 Fast, cross-platform web server Powered by ASP.NET Core (Kestrel) with full access to advanced HTTP/2, header compression, and TLS options.

• 🐚 Native PowerShell integration Routes can be backed by PowerShell scripts with isolated, pooled runspaces and dynamic $Context.Request / $Context.Response variables.

• 🧠 Multi-language route execution Register endpoints backed by PowerShell, C# (Roslyn scripting), VB.NET (Roslyn scripting), or native C# handlers. (F# / Python / JavaScript exist as language identifiers, but scripting for them is not enabled yet.)

• 🔐 Authentication built-ins JWT bearer, API keys, Basic, Windows/Negotiate, and client certificate authentication.

• 📘 OpenAPI + interactive docs Generate OpenAPI (v3.0 / v3.1 / v3.2) and serve docs UIs (Swagger UI / ReDoc / Scalar / RapiDoc / Elements).

• 🤖 MCP server Expose route discovery, OpenAPI inspection, runtime inspection, request validation, and gated safe route invocation to MCP-compatible clients with Kestrun.Mcp.

• 🔁 Realtime Server-Sent Events (SSE) and SignalR support.

• 🌍 Localization Request-based culture resolution with PowerShell .psd1 or JSON string tables, per-key fallback across culture hierarchies, and seamless integration with PowerShell routes and Razor pages.

• 🛡️ Middleware & extensibility Add middleware for antiforgery, CORS, compression, caching, sessions, status code pages, exception handling, static files, gRPC, and more.

• ⚡ Task Scheduling & Background Jobs Cron-based scheduling (Cronos) with PowerShell, C#, and VB.NET jobs.

Requirements

For Building:

• .NET 8 SDK AND .NET 10 SDK (solution multi-targets net8.0 + net10.0; net9.0 available via -Frameworks parameter)
• PowerShell 7.4+ (7.4 / 7.5 run on .NET 8; 7.6 runs on .NET 10)

Invoke-Build and Pester PowerShell modules:

Install-PSResource -Name 'InvokeBuild','Pester' -Scope CurrentUser

For Runtime (Run Only):

If you're only running Kestrun apps (not building from source), install the ASP.NET Core Runtime matching the PowerShell version you are using:

PowerShell Version	Install (Run-only)	Rationale
7.4 / 7.5	.NET 8 ASP.NET Core Runtime	Bundles Microsoft.NETCore.App + Microsoft.AspNetCore.App 8.x
7.6 (rc)	.NET 10 ASP.NET Core Runtime	Runtime aligning with PS 7.6 build

Installing the .NET SDK already gives you the corresponding runtimes. For run-only scenarios the ASP.NET Core Runtime alone is sufficient (it includes the base .NET runtime).

Download PowerShell from the official PowerShell Releases.

Verify installation

# List SDKs (expect 8.x and 9.x if building from source)
dotnet --list-sdks

# List runtimes (look for Microsoft.NETCore.App and Microsoft.AspNetCore.App)
dotnet --list-runtimes | Where-Object { $_ -match 'Microsoft.(AspNetCore|NETCore).App' }

Expected (abbreviated):

Microsoft.NETCore.App 8.0.x
Microsoft.AspNetCore.App 8.0.x
Microsoft.NETCore.App 9.0.x
Microsoft.AspNetCore.App 9.0.x
Microsoft.NETCore.App 10.0.x
Microsoft.AspNetCore.App 10.0.x

If something is missing, install the matching ASP.NET Core Runtime from the download links above.

Build & Run

Clone the repository:

git clone https://github.com/Kestrun/Kestrun.git
cd Kestrun

Build the core project and sync the PowerShell module:

Invoke-Build Restore
Invoke-Build Build

Build the MCP host explicitly when you want the stdio server:

Invoke-Build Build-KestrunMcp

For MCP setup and client configuration, see docs/guides/mcp.md.

• 🛠️ CI/CD ready

  • Build- and run-time configurable
  • Works in containerized / headless environments
  • Supports Dev/Prod fallback module path detection

• 🛡️ Optional Add-ons Add via fluent extensions:

  • AddAntiforgery() middleware
  • AddStaticFiles(), AddDefaultFiles(), AddFileServer()
  • AddCors(policy) or AddCorsAllowAll()
  • AddSignalR<T>() for real-time hubs
  • AddAuthentication() with multiple schemes (Windows, Basic, JWT, Certificate, etc.)
  • Ready for Swagger, gRPC, custom middleware hooks

• ⚡ Task Scheduling & Background Jobs

  • Cron-based scheduling: Full cron expression support via Cronos
  • Multi-language job support: Schedule PowerShell, C#, and VB.NET scripts as background jobs
  • Job management: Start, stop, and monitor scheduled tasks with detailed logging

MCP Server

Kestrun includes a standalone stdio MCP host project at src/CSharp/Kestrun.Mcp/. It lets MCP-compatible clients connect to a local Kestrun script and use tools for:

• route discovery
• route metadata lookup
• generated OpenAPI retrieval
• runtime inspection
• request validation
• gated safe route invocation

Use the dedicated build task:

Invoke-Build Build-KestrunMcp

Typical local workflow:

1. Point Kestrun.Mcp at a PowerShell script that starts a Kestrun host.
2. Call kestrun.inspect_runtime to confirm the listener is up.
3. Call kestrun.list_routes or kestrun.get_route to inspect the live route table.
4. Call kestrun.get_openapi to retrieve the generated OpenAPI document as JSON.
5. Call kestrun.validate_request to explain likely 404, 406, or 415 outcomes before sending a request.
6. Call kestrun.invoke_route only for routes explicitly allowlisted with --allow-invoke.

Practical examples shipped in this branch:

• docs/_includes/examples/pwsh/24.1-Mcp-Hello.ps1 for route discovery, runtime inspection, and safe GET /hello invocation
• docs/_includes/examples/pwsh/24.2-Mcp-OpenAPI.ps1 for route schema inspection, OpenAPI retrieval, request validation, and safe POST /items/{id} invocation

Then configure your MCP client to launch Kestrun.Mcp with a target script and optional --allow-invoke route globs. See the full guide: docs/guides/mcp.md.

Deployment & Extensibility

This section summarizes extension capabilities (see earlier sections for build & run instructions).

Using the PowerShell Module

Import the module (from source):

Import-Module ./src/PowerShell/Kestrun/Kestrun.psm1

Service Packaging Quick Start (Service/Daemon)

For full production deployment guidance, see Production Deployment (Service/Daemon).

Create a Service.psd1 descriptor:

New-KrServiceDescriptor `
  -Path .\MyServiceApp\Service.psd1 `
  -Name 'my-service' `
  -Description 'Production Kestrun service' `
  -Version 1.2.0 `
  -EntryPoint '.\Service.ps1' `
  -ServiceLogPath '.\logs\service.log' `
  -PreservePaths @('config/production.json') `
  -ApplicationDataFolders @('data/', 'logs/')

Package a single script (auto-generates Service.psd1):

New-KrServicePackage `
  -ScriptPath .\Service.ps1 `
  -Name 'my-service' `
  -Description 'Production Kestrun service' `
  -Version 1.2.0 `
  -OutputPath .\my-service-1.2.0.krpack

Running Tests

Using Invoke-Build (Recommended)

The project includes an Invoke-Build script that automatically handles both C# (xUnit) and PowerShell (Pester) tests:

Invoke-Build Test

Manual Test Execution

C# Tests

Invoke-Build Test-xUnit

PowerShell Tests

Invoke-Build Test-Pester

Documentation and Tutorial

Kestrun docs are built with Just-the-Docs. All new documentation must be compatible (front matter, parent, nav_order, etc.).

See docs/ for structure.

Project Structure

• src/CSharp/ — C# core libraries and web server
  • Kestrun.Mcp — stdio MCP host for route, OpenAPI, runtime, and safe invocation tools
  • Kestrun/Authentication — authentication handlers and schemes
  • Kestrun/Certificates — certificate management utilities
  • Kestrun/Hosting — host configuration and extensions
  • Kestrun/Languages — multi-language scripting support (C#, VB.NET, etc.)
  • Kestrun/Logging — Serilog integration and logging helpers
  • Kestrun/Middleware — custom middleware components
  • Kestrun/Models — request/response classes and data models
  • Kestrun/Razor — Razor Pages integration with PowerShell
  • Kestrun/Scheduling — task scheduling and background job support
  • Kestrun/Scripting — script execution and validation
  • Kestrun/Security — security utilities and helpers
  • Kestrun/SharedState — thread-safe global state management
  • Kestrun/Utilities — shared utility functions
• src/PowerShell/ — PowerShell module and scripts
• examples/ — Example projects and demonstrations
  • CSharp/Authentication — authentication examples
  • CSharp/Certificates — certificate usage examples
  • CSharp/HtmlTemplate — HTML templating examples
  • CSharp/MultiRoutes — multi-route examples
  • CSharp/RazorSample — Razor Pages examples
  • CSharp/Scheduling — task scheduling examples
  • CSharp/SharedState — shared state examples
  • PowerShell/ — PowerShell examples
    • BikeRentalShop/Synchronized/ — package-ready rental API using a shared in-memory state object with serialized write/persist operations
    • BikeRentalShop/Concurrent/ — package-ready rental API using a fully concurrent dictionary-backed in-memory database
  • Files/ — test files and resources

The two bike rental PowerShell samples intentionally show different state models under docs/_includes/examples/pwsh/BikeRentalShop/. Use Synchronized when you want a simpler shared-state pattern around a familiar PowerShell object graph, and Concurrent when you want the in-memory database itself to be keyed with concurrent dictionaries end to end.

• tests/ — Test projects (C#, PowerShell)
• docs/ — Documentation files (Just-the-Docs)
• Utility/ — Build and maintenance scripts
• .github/ — GitHub Actions workflows
• Lint/ — Code analysis rules

Contributing

Contributions of all sizes are welcome — from docs improvements to new feature modules. See CONTRIBUTING.md and the online guide at https://docs.kestrun.dev/contributing.

License

Licensed under the MIT License. See LICENSE.

Acknowledgements

Documentation

• Just-the-Docs for documentation

Code Quality

• ReportGenerator for code coverage reporting
• codefactor for code quality analysis
• coveralls for code coverage tracking

AI Assistance

• ChatGPT for conversational AI support
• Copilot for AI-powered code suggestions

Collaboration and Version Control

• GitHub for version control and collaboration
• NuGet for package management
• PowerShell Gallery for PowerShell modules

Scripting and Automation

• PowerShell for scripting and automation
• .NET for the underlying framework
• Pester for PowerShell testing

Logging and Serialization

• PoShLog — inspiration and portions of code for logging (MIT License)
• powershell-yaml — adapted tests and implementation code for YAML serialization (Apache-2.0 License)

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