improvise-x1ns (found by ChatGPT Codex on PR #90, live on main at ce895ff).
`encoded_width` computed `has_missing` and used it in the numeric arm only, while
`build_categorical` maps every absent cell to MISSING_CAT and includes it in
`distinct(&mapped)`. A forced category with N distinct present values and one
record lacking that coordinate promised N features and materialised N+1.
That under-reports in the direction that costs. The preflight runs before
`preprocess`; the exact check on `feature_names.len()` runs after, so it bounds
the error message and not the allocation the preflight exists to prevent. gp.md
§14 claimed drift was "bounded in both directions by the exact check" — wrong,
and wrong against the argument two paragraphs above it in the same section. That
sentence is corrected rather than softened; the previous wave read this shape and
reasoned it away with it.
The clamp stays outside the addition, so an entirely-missing column — which
`preprocess` skips — is still counted as one and the fix moves only its own case.
improvise-e8no is DECLINED, on evidence rather than on appetite. `formula.pest`'s
only coordinate predicate is `is_expr`, a single-value equality: no IN, no
ordering over items, and a coordinate reaches an `Expr` only through IS. So the
predicates a tree may state about a category are exactly its items, one at a
time, and one-hot is the only encoding whose splits are spellable — the width is
the size of the vocabulary, not an implementation's appetite. Ordinal encoding is
already the classified refusal `Artefact::NumericCategory`, and hashing has no
document name at all. The pre-zv8t "fit that succeeded" therefore either never
split on the column, in which case Label is exactly equivalent and in budget, or
was refused at storage time: no fit is lost that was both storable and used the
column. Asserted by a_split_on_a_numeric_category_read_as_a_number_cannot_be_stored,
which is also the first coverage NumericCategory has had.
Both refusal messages said "a category with a distinct value per record becomes
one column per record", which diagnoses the runaway shape and not e8no's. They
now say a category becomes one column per distinct item, whether its items read
as numbers or not — that clause being the whole of what zv8t changed.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FC2jVn8Au7E9JPkw6bwXXH
Edward Langley
e045f9871b