gdsfactory is a Python library and Typer CLI (entry point `gf`) for parametric semiconductor layout generation. In production use it programmatically designs photonic integrated circuits (waveguides, ring resonators, MZIs, grating couplers, AWGs, tapers, spirals), electrical/analog structures (pads, vias, inductors, heaters), MEMS actuators, quantum/superconducting devices, and foundry process-control test structures, emitting GDS/OASIS/STL/Gerber/NumPy output. It is built on kfactory's KLayout-backed geometry kernel and ships a 300+ parametric cell library organized as thin wrapper modules (`gdsfactory/components/`) delegating to implementations in `gdsfactory/component_functions/`, with deterministic cell naming and caching via `@cell` decorators. Architecturally it is a library plus CLI, not a service: core abstractions are the `Component`, `Port`, `CrossSection` (with path extrusion and transitions), and a `Pdk` registry that resolves components, cross-sections, and layers by name/spec. A routing subsystem provides Manhattan bundle routing, A* obstacle-aware routing, Dubins all-angle paths, auto-taper insertion, and fiber-array/pad fan-out. A YAML instances/placements/routes/ports DSL (`read.from_yaml`) supports schematic-driven place-and-route, and export modules cover GDS/OASIS, SVG, STL 3D, and Gerber X2. Verification tooling includes a KLayout-based generic DRC/LVS rule deck plus git-diff GDS regression testing. The repo is hybrid with a strong research flavor — it embeds published-device geometry (cited DOIs), process control monitors, DOE packing utilities, and an ASV benchmark suite — but its dominant character is application software. It is under very active maintenance (v10.0.0rc1, frequent releases, ~70 test modules, hundreds of YAML regression golden files, hypothesis property tests). Principal craft risks are the duplicated `components`/`component_functions` trees, API churn across major versions (complete netlist rewrite, ports-in-µm migration, kfactory major bumps), and sample/notebook artifacts (`samples/fixme/`, debug prints, skipped tests) that indicate some drift around an otherwise disciplined core.