Research language from Microsoft. Related to P. Github. Deprecated and now moved to Coyote.
From the Github repo:
The P# framework provides:
- An actor-based programming model for building event-driven asynchronous applications. The unit of concurrency in P# is an asynchronous communicating state-machine, which is basically an actor that can create new machines, send and receive events, and transition to different states. Using P# machines, you can express your design and code at a higher level that is a natural fit for many cloud services.
- An efficient, lightweight runtime that is build on top of the Task Parallel Library (TPL). This runtime can be used to deploy a P# program in production. The P# runtime is very flexible and can work with any communication and storage layer.
- The capability to easily write safety and liveness specifications (similar to TLA+) programmatically in C#.
- A systematic testing engine that can control the P# program schedule, as well as all declared sources of nondeterminism (e.g. failures and timeouts), and systematically explore the actual executable code to discover bugs (e.g. crashes or specification violations). If a bug is found, the P# testing engine will report a deterministic reproducible trace that can be replayed using the Visual Studio Debugger.
Tags:
clr
language
event
Last modified 26 January 2026