Real-draft testing on the HML bibliography surfaced inconsistent
preposition capitalization in headline-style titles: the formatter
was sometimes lowercasing "among", "beyond", "within", "into", etc.
and sometimes capitalizing them, violating CMOS 8.159. The behavior
was nondeterministic across similar entries — smoking-gun evidence
of GPT-5 judgment drift on a rule the existing prompt only
implicitly covered via rule 6's "headline-style capitalization".
Rule 29 makes the carve-out explicit and instructs the model to
apply CMOS 8.159 independently of the source's casing, with:
- a substantial but illustrative preposition list including "as"
(which CMOS 8.159 calls out as always lowercased)
- an explicit scope restriction to PREPOSITIONS, with subordinating
conjunctions (If, That, Because, Although, Unless, etc.)
capitalized
- a CMOS 8.161 carve-out for hyphenated compounds: the first
element is always capitalized (so "In-School" stays, not
"in-School")
- a first/last-word exception covering "last word of the main
title immediately before a subtitle colon", which the model
was treating as mid-title
Verified on the 134-entry HML draft: ~17 entries now produce more
CMOS-correct forms, and two consecutive re-runs show no new rule-
29-related regressions. Observed GPT-5 drift on orthogonal axes
(multi-author inversion, inner-quote style, periodical
italicization) washed out across re-runs, consistent with the
~5% single-run variance documented in project memory.
Rule count: 28 -> 29. No linter version bump required.
