Cosmos OS for Rider

JetBrains Rider plugin for Cosmos gen3, the NativeAOT-based C# kernel framework. Create, build, run and debug a kernel without leaving the IDE.

Features

Available from the Cosmos menu, the Cosmos tool window and the Run/Debug toolbar:

• New kernel project from the cosmos new template
• Build the kernel and run it in QEMU through cosmos run
• Debug with GDB: C# breakpoints, stepping, call stack, variables, watches and evaluation
• Live kernel diagnostics while debugging: threads, GC and memory (with a page map)
• Edit project properties: kernel features, QEMU machine, devices (network card, keyboard, mouse, audio), disks and port forwards
• Run the Cosmos kernel test suites (in the Cosmos repository)
• Check and install the toolchain (.NET 10 SDK, Cosmos CLI, QEMU, GDB)
• Clean build outputs

Requirements

• JetBrains Rider 2025.3+
• .NET SDK 10.0+
• Cosmos.Tools CLI, QEMU, and GDB (gdb-multiarch for ARM64)

Missing tools can be installed from the plugin.

Installation

Install the plugin, then set up the toolchain:

dotnet tool install -g Cosmos.Tools
cosmos install
cosmos check

On Windows, run CosmosSetup-<version>-windows.exe from the releases page instead.

Running and debugging

Opening a Cosmos project adds a Cosmos Kernel run configuration, so the toolbar's Run and Debug buttons boot the kernel in QEMU. Run streams the serial console into the Run tool window; Debug attaches GDB to QEMU's gdbstub:

• Breakpoints are Rider's own C# breakpoints, set in the gutter as usual (conditions are passed to GDB as GDB expressions).
• Variables, Watches and Evaluate use GDB expressions; the NativeAOT pretty-printers render strings and arrays when GDB has Python.
• The debug session gets Kernel Threads, Kernel GC and Kernel Memory tabs, read over QEMU's QMP socket without pausing the guest.

Stop ends QEMU and GDB together. QEMU's devices, memory and disks come from Project Properties.

Testing

In the Cosmos repository, the tool window's Tests tab lists the suites under tests/Kernels. Run them on x64 or arm64 (results land in the test runner tree), or debug a suite's kernel under GDB. Cosmos Kernel Tests run configurations can also be created by hand.

Building from source

./gradlew runIde        # sandbox Rider with the plugin loaded
./gradlew buildPlugin   # build/distributions/*.zip
./gradlew test          # unit tests

DebuggerSmokeTest boots a real kernel under QEMU and GDB; it runs when COSMOS_SMOKE_ROOT points at a nativeaot-patcher checkout with the Timer test kernel built.

Documentation

User Guide — installation, kernel startup, filesystem, network, graphics and debugging.

Also available for VS Code.

License

MIT