Explanation
Why a CAD design lives in your repository
CAD mode reads your repository's own Python and files, and keeps no copy of a design anywhere else.
CAD mode treats the files in your repository as the design. The Python that makes the geometry is yours, the parameters are yours, and git is the design's history. Turret keeps no copy of a design in a database, a registry or a service.
What a design is
A design package is a folder with a design.toml in it. That file names the Python function that
builds the geometry, and it declares the design's parts and parameters. The function is ordinary
Python that you or the session write and commit like any other code.
What Turret provides
Turret provides three things.
The first is a Python environment. Turret installs a single pinned set of CAD libraries, once per machine. A design that builds on a supported machine builds on the next, and the repository never sets up an environment of its own.
The second is the build. When the session builds a design, Turret runs the generator in that
environment. It writes each part's STEP and STL files, plus a manifest, into the package's
build/ folder. Every tool that follows reads that folder and nothing else.
The third is a set of tools for looking at the result. The session can draw the latest build from any angle and cut a section through it. It reads exact sizes from the STEP files. You see the same build in the viewer.
Why nothing else is stored
A stored copy of a build can fall out of date. Reading the folder means the viewer, the pictures and the measurements always describe the build on disk. Nothing has to be registered first, and no separate program has to be running.
It also keeps the design portable. Cloning the repository on another machine gives you the design. Building it there gives you the same files.
What CAD mode leaves to you
CAD mode stops at geometry files. It does not plate a part, slice it or send anything to a printer. You take the STL files to your slicer.
A check that belongs to a single design is a script in the repository. The session runs it with the same Python environment, like any other script.
See Modes for what CAD mode adds to a session. See Your first design in CAD mode to try it.