How it is checked

How the interface stays stable, what tests stand behind it, and what it does not do yet.

A stable interface

Everything public is under include/dxfio; dxfio/dxfio.hpp brings in all of it. The reader’s machinery stays in source.
Failures come back in std::expected; what was mended or left out, in a list of issues. Nothing throws.
Every public declaration carries a comment, and every header compiles on its own.
A snapshot of the public headers is checked in. The dxfio_api test fails on any change to it, so a change to the interface is always a deliberate one.

155 drawings AutoCAD 2026 wrote, for each release, read without an issue, and what dxfio saves back reads to the same document: every group and value, in its order.
What dxfio writes, to each release, is opened by AutoCAD’s console and passes its audit.
The tests cover every line, function, region and branch; the coverage build fails below that.
libFuzzer targets feed broken input to the reader, the tags and the text escapes.

No type yet for CAMERA, FIELD, GEODATA or SUN: they are kept whole and written back, with no fields of their own.
Saving to R12 leaves out paper space viewports; AutoCAD keeps them with ACAD MVIEW extended data.
MTEXT saved to R12 wraps no line to its width; only its own line breaks start a new TEXT.