First Phase 5 lane. Tests whether the deterministic realizer
produces grammatical English across all 13 C01-C13 constructions
when the (subject, predicate, object) vocabulary is outside the
en_core_cognition_v1 seed pack. Four OOD domains: nature, tech,
domestic (public), chemistry (holdouts).
Public 117/117 (100%) and holdouts 39/39 (100%) — every
construction passes on every domain. Realizer fluency is
mechanistic and pack-independent; the Phase 5 capability story
rests on a sound structural bet.
Known v1 gaps (designed around to isolate the structural
claim): G1 irregular past tense (realizer applies -ed
unconditionally), G2 plural agreement under quantifiers (no
pluralisation of subjects under "all"/"some"), G3 rubric-side
punctuation strictness in shared _check_word_order. All three
are documented in gaps.md with bounded follow-on lanes.
Scoring is delegated to evals.grammatical_coverage.runner so the
rubric stays consistent. Cases generated by
scripts/generate_english_fluency_ood.py for reproducibility.
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