RECON: cold-start verification audit - 9/9 capsules verify, layer 1 adjudicated, first tamper test

papers/ERRATA_replications_2026_09_01.md

@@ -0,0 +1,86 @@
+# ERRATA — the CPU-only replication install line cannot work as written
+
+Fathom Lab · 2026-09-01 · Companion to `papers/RECON_cold_start_verification_2026_09_01.md`.
+
+This file records a **factually wrong command** found during a cold-start audit. It corrects
+nothing in place: `REPLICATE_legibility.md` and `REPLICATIONS.md` are history and are left
+exactly as published. This is the correction, in a new file, as the record requires.
+
+Nothing else in either document is contradicted here. The corpus-audit target in
+`REPLICATIONS.md` reproduced; the divergences found in it are recorded in the RECON, not here,
+because they are stale content rather than commands that cannot run.
+
+---
+
+## The wrong line
+
+`papers/disjoint-worlds/REPLICATE_legibility.md`, under **Run it**, publishes:
+
+```bash
+git clone https://github.com/fathom-lab/styxx && cd styxx/papers/disjoint-worlds
+pip install numpy scipy
+python run_b37.py          # the 12-pair legibility matrix
+```
+
+**Followed literally in a clean virtualenv, this stops before it computes anything.** Observed,
+in order, as each missing package was supplied:
+
+```
+ModuleNotFoundError: No module named 'torch'
+    run_b37.py:24  ->  run_g0clear.py:21
+
+ModuleNotFoundError: No module named 'transformers'
+    run_b37.py:27  ->  run_b31v2.py:25
+```
+
+The same two failures block `run_b45.py`, the row `REPLICATIONS.md` advertises as
+"CPU-only, ~4 s — the single easiest check in this repo".
+
+`styxx` itself is also required — `run_b37.py:130` does `from styxx.protocol import Experiment` —
+and the published line does not install it either.
+
+## The command that works
+
+Verified on Windows 11, Python 3.12.10, no GPU, in a virtualenv that began with nothing but pip:
+
+```bash
+git clone https://github.com/fathom-lab/styxx && cd styxx/papers/disjoint-worlds
+pip install numpy scipy styxx torch transformers
+python run_b45.py          # island frame geometry, ~3 s
+python run_b37.py          # the 12-pair legibility matrix
+```
+
+On this machine `pip install torch` resolves to a CPU build without extra flags. Where it does
+not, `pip install torch --index-url https://download.pytorch.org/whl/cpu` installs the CPU wheel
+(observed: `torch-2.14.0+cpu`) and adds no GPU requirement.
+
+With that install, `run_b45.py` completed in **3 s**, exit 0, verdict
+`SHARED_FRAME_CONFIRMED_GEOMETRICALLY__island_rotated_away`, reproducing every scientific field
+of the committed `b45_result.json` exactly — `median_clique_affinity_k20` 0.848,
+`clique_affinity_minus_null_p95_k20` 0.7914, `seeds_qwen_below_clique_k20` 5. The only differing
+field is `prereg_commit`, which records the commit of the tree it ran in.
+
+## Two things the corrected command does not fix
+
+**The heading remains misleading, and the fix is in the code rather than the docs.** The page is
+titled "one command, no GPU, no model downloads", and the computation genuinely is CPU-only and
+downloads no models. But torch and transformers are pulled in purely by module-scope imports in
+files these scripts borrow one constant from: `run_g0clear.py` imports torch for a GPU extraction
+path, and `run_b31v2.py` imports `transformers.AutoConfig`. **None of the six CPU scripts —
+`run_b37`, `run_b40`, `run_b41`, `run_b42`, `run_b45`, `run_b46` — references torch at all.**
+Substituting a stand-in `torch` that raises on any real use, `run_b45.py` still completed
+correctly, which establishes that the dependency is an import-graph artifact and not a
+computational one. Documenting the heavier install is the honest short-term correction; moving
+`CONCEPTS` and `fit_mlp` behind lazy imports would let the published one-liner become true.
+
+**Running the advertised command overwrites the receipt it is checked against.** `run_b37.py`
+and `run_b45.py` write `b37_result.json` and `b45_result.json` into their own directory — the
+filenames of the committed canonical receipts. In a single clone the baseline is destroyed by the
+act of replication. Until that changes, copy the committed receipts elsewhere first, or run in a
+throwaway copy of the tree. This audit did the latter; the committed tree was confirmed unmodified
+afterwards.
+
+---
+
+*Found by running the published instructions on a machine that had never run this code, and
+getting three import errors before the first number.*