Door B listed `inbox.iterdir()` and kept only top-level files. A file in a
subdirectory was neither ingested nor refused: it appeared in none of the
result's buckets, so a nested drop produced a bundle that was silently short
of what was dropped and no count said so. That broke the K1b identity for any
inbox with folders in it. Operator decision 2026-09-06.
- `walk_inbox` is the ONE walk rule, shared with `tools/okf_corpus_run.py`:
the denominator N is now counted over exactly the set of files the door
ingests, rather than over a second listing that happened to agree.
- Sorted on the whole relative path, not the basename, so the order is a
function of the tree; that is what keeps rebuild-from-scratch byte-equal to
an incremental update.
- A concept's `source_file` is the path relative to the inbox root,
`/`-separated. The concept NAME still comes from the basename, so two
folders holding one basename hit the existing §3 collision refusal instead
of one silently claiming the other's concept.
- Dot-directories and a bundle directory inside the inbox are skipped with a
CODE, in a new `InboxResult.skipped`. Recursion makes the door's own output
reachable as its own input; a silent skip would be the same
absence-without-a-denominator defect one level down.
- `--path-prefix` reduces per component and rejoins with `/`, so the caller
driving a nested corpus can carry the relative directory. Reducing the whole
string folded the separator into a `-` and flattened `sub/sub2`.
`tests/test_inbox_flow.py::test_subdirectories_are_not_walked` asserted the
opposite and is superseded in place, with the reason written down.
Measured on the K2 corpus (flat, N=43): 39/43 merged, 4 coded, K1b holds. The
bundle digest is
`1472e98aec8643c5beee540f4c42b5e437bd26e7c61d69a91bcff799f06a6d13` over 1108
files -- byte-identical to a run of the same corpus at 190086f WITHOUT this
change (`diff -r` exit 0), so recursion costs a flat inbox nothing. It differs
from the stored 2026-09-03 artifact by one line in `index.md`
(`- [Corpus run history](log.md)`), which 95eb271 added 15 hours after that
bundle was built.
Suite 1113 passed, `ruff` clean, `mypy --strict src/ tools/` clean.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
