The image codec's tests are pinned against data produced by the reference implementation, not by the Dart code. That is the whole point: a Dart encoder and a Dart decoder that agree with each other prove nothing, because they would agree just as happily on a wrong wire format. These scripts produce the data the Dart side is checked against.

They are committed here so test/services/golden/ is reproducible. Nothing in the app runs them.

script	produces	used by
`export_golden.py`	`golden/aeic_cdf_ft32.bin`, `golden/vectors/*.gv`	`rans_coder_test.dart`, `entropy_tables_test.dart`
`record_entropy_io.py`	`golden/e2e/*.aeicrec`, `golden/e2e/manifest.json`	`image_codec_e2e_test.dart`

What they need

Neither script is self-contained. Both drive the real AEIC model, so they need the research checkout that is not part of this repository:

the AEIC source (github.com/LuizScarlet/AEIC) with the two local patches: pybind11 bumped to v2.13.6 (2.10.4 silently returns stride-0 arrays under NumPy 2), and .contiguous() on z_hat in both compress() and decompress() (the encoder and decoder otherwise land in different memory layouts, and the ~2.8e-7 drift that causes desynchronises the rANS decoder on roughly one image in 26, with no error raised)
the AEIC_SE_ft32.pkl checkpoint
the compiled C++ rANS extension (src/cpp, CMake) — the golden bitstreams are produced by it, which is what makes them worth comparing against
PyTorch, onnxruntime, NumPy 2

Running them

cd <aeic-research-checkout>
AEIC_DEVICE=cpu python export_golden.py           # tables + symbol vectors
AEIC_DEVICE=cpu python record_entropy_io.py       # ONNX I/O recordings

Then copy the output into test/services/golden/.

If you change the wire format

Regenerate. The fixtures encode the chunk framing and the metadata byte layout, so a format change makes them stale in a way the tests will report as a codec bug — which is the correct behaviour, but only if you know to look here.