# Pre-registration engineering checks

No new brain trajectory or conditioning result existed during these repairs.
Only the new, unregistered AM code was changed; all prior models remained
read-only. The new experiment root was provisioned empty and owned by the
existing project user before preparation.

The first server-only unit test run had 74 tests: 73 passed, one failed
(`test_static25_repeat_and_single_validation`, copied-input SHA mismatch).
The local machine had not reproduced that failure. A direct synthetic probe
established the cause, rather than changing a tolerance or expected result:

- A temporary NPZ was overwritten with different, same-size (556-byte) data.
- Its device, inode, length, mtime_ns and ctime_ns were identical before/after.
- The fresh SHA changed from
  `38219e908f1b500423c9fe1a70b6070103f878903c5f005c79e387fca8b449c4` to
  `fa45373dd04bf5f9d574a5329d42f8259c99c70aa69b077673aaef8c95bf0a02`.
- The timestamp-keyed digest cache returned the former SHA for the latter
  bytes. Both timestamps were `1790749632756475909` in the observed probe.

The new comparator was corrected to read fresh bytes for SHA verification and
to include content hashes in static cache identity. A deliberate same-stat,
same-length rewrite test guards this issue. No waiting/sleep workaround, relaxed
hash equality, modified old data, or scientific rerun is used to hide it.

This note is a human-readable preparation record, not a saved raw unit-test
transcript. The subsequent complete server test transcript is recorded during
formal preparation and must pass without skipped Torch compatibility tests.