Astra vs. Fable 5.1 on real ML tasks -- tradeoffs, strengths, shortcomings [P]

I ran a side-by-side ML text-processing and model-training workflow using Fable 5.1 vs. Astra (both on xhigh), and the results could not have been more different. Warning, long post. TL;DR -- Astra codes more agentically, Fable more coherently. Fable writes better and follows directions better. Astra's final outcome was slightly better, and its scientific rigor/reproducibility was noticeably stronger. Both models improved their F1/Accuracy by 0.02-04 after human feedback on their approach, demonstrating that neither have mastered the AI/ML text processsing, vectorization, and model training process completely. Astra is a better coder, writing a stricter evaluation protocol (70/15/15 train/val/test vs. Fable's basic 80/20) that selected its model using a held-out validation set vs. Fable's simpler test F1-based selection. It also debugged more deeply, as both models hit a gensim 4.4 compiled-kernel bug: Fable tried to figure it out, failed, and just hid the stderr notices on affected runs (though told me it had done so), while Astra root-caused it aggressively, then fixed the environment by downgrading gensim alongiside compatible NumPy/SciPy dependencies. Astra wrote hardened training-run.py code the forced the uv venv it rebuilt without changing my default one, SHA-256'd the corpus to ensure reproducibility on later runs, output a split manifest and run-summary.json, and rendered a headless browser for QA with screenshots (not sure this was necessary, but impressive overkill all around). Fable's builder script was ephemeral, living only in tmp, and less intense overall. Astra deployed subagents more effectively, making use of my pre-built notebook-reviewer and citation-checker agents, the former of which caught a real bug via review (sentence-final word-loss tokenization defect) and fixed it, retaining a regression test in the process. Fable overlooked this issue because, for some reason, it did not call the subagents I had available (which is surprising, usually i