Show HN: BRep Geometric CAD Kernel and Parametric Code CAD

I'm pretty excited to show off something I've been working on for the past few months. A free, open-source geometric kernel that allows humans/LLMs to write code (in this case, a DSL called Firmament) and generate 3D models of CAD parts, to finally provide an alternative to OpenCascade.

To get some questions out of the way. - Full STEP import/export support for AP242, AP203 and AP214 are still experimental at the time, but everything produced by Aetheris should open in any CAD app with STEP support. - Support for single edge/planar fillets/chamfers right now, should be more than sufficient for most CNC/3D printing use cases. - Fillets: https://github.com/yuechen-li-dev/Aetheris/blob/master/testd... - Chamfers: https://github.com/yuechen-li-dev/Aetheris/blob/master/testd... - Supports dimensional/GD&T annotation via STEP 242's semantic PMI. - Kernel is written entirely in C#, with bindings for Go, Rust, Python, and TypeScript available.

If you just want to vibe-CAD, clone the repo, run it locally and ask Codex/Claude to build a part for you using Aetheris with the Firmament DSL. You can check the results in Fusion 360/FreeCAD or any other package you use. For features that are not implemented, GPT 5.6 Codex and Claude 5 usually can implement their own algorithms fairly easily via the KernelSDK.

Otherwise, you can go through the Firmament language fixtures and try building some of the samples via the CLI. A VSCode extension and browser viewer is included for convenience.

https://github.com/yuechen-li-dev/Aetheris/tree/master/fixtu...

Happy to answer any technical questions and talk about the architecture. Please report any weird bugs you find though.