next.BREP.io

next.BREP.io is a unified mechanical and electronics CAD platform built from the ground up in Rust, on its own B-rep kernel. Constrained sketches, parametric features, assemblies and electronics workbenches share one document, the .BREP.json file, and one undo stack. The same source builds the browser app and native Linux and Windows desktop binaries. Models are true B-rep solids with analytic and NURBS surfaces, not meshes; STEP and IGES import and export exactly, and STL or OBJ meshes come in through automatic reconstruction into analytic faces.

The mechanical side covers sketching, extrude, revolve, sweep, loft, fillet, chamfer, holes, shell and Booleans, parametric history with named expressions, sheet metal with flat-pattern DXF and SVG export, and assemblies with constraints, interference checks and STEP import. The electronics side covers schematic and wiring diagrams, board layout with design rules, symbol and pad editors, an autorouter, wire harnesses with cut lengths and their own BOM lines, and a fabrication archive. Placement is pose: moving a footprint on the board moves the part in the 3D assembly, and a wire drawn on the diagram becomes a real harness in the model. It reads KiCad 9 symbol and footprint libraries with their 3D models.

The native MCP server, brep-mcp, runs the real CAD application headlessly and serves it as a Model Context Protocol server over stdio or streamable HTTP. An agent opens models, creates and edits features, inspects geometry, exports files and captures screenshots, with no window and no person at the machine. The server lists six tools (run_script, script_result, script_halt, screenshot, input and files); everything else is a function a program calls, generated from the application's own registries, about 300 tools in total. Files stay local: in the browser, documents live in IndexedDB and are never uploaded.