core/docs/research/increment-2-caseband-plan-2026-07-19.md

Increment-2 Plan — CASE-FIRST first-conversion band (DESIGN-FIRST, for ruling)

Status: DESIGN-FIRST — ruling before any build (usual terms). Date: 2026-07-19 Base: forgejo/main @ 854ce023 (worktree core-wt-inc2, branch feat/reader-inc2-caseband). Context: increment 1 shipped the #78 foundations (PR #79), band-solve=0. Per the fragmentation finding (taxonomy not at bedrock; statements are per-sentence multi-capability), increment 2 is case-first: target specific closest cases, build their exact end-to-end needs, convert them with a correct-for-the-right-reason proof. This is the increment that crosses zero on the reader side.

§1 Target cases — the 0148 / 0001 cluster (0000 deferred)

Case	exp	decomposition
0148	1500	first-day = 2 × second-day; second-day = 500 (in "If"); total = 1000+500
0001	480	Hooper = 2 × (two other harbors combined); each other = 80 → combined 160; total = 320+160

0000 deferred (fast-follow): needs chained compare ("…who has twice…as Spencer") + compound-subject summation ("how many do Aria and Emily have") + question-arithmetic ("twice the total") — three extra capabilities beyond the cluster spine.

§2 The spine is PROVEN to work (grounding, not assumption)

Canonical rewrites — each target's compare statement rewritten to the plain "A has N times as many X as B" form and its seed moved to a statement — both solve wrong=0 today:

• 0148 canonical → 1500 ✓ · 0001 canonical → 480 ✓ · a fresh forward-compare+total → 20 ✓

So forward multiplicative compare + statement-seed + summation all work (compare compiler merged #77, #78 substrate, 2b summation). The gap is exactly the surface forms below — nothing in the solver.

§3 The gap increment 2 builds (the isolated delta)

1. Conditional-seed-in-question — parse If <REF> <has|is|have> <N> [each], <question> and seed REF = N (or REF = N × count for "each") from the question clause. Shared by all three cluster cases. (The reader has extract_conditional_op_question_candidates; increment 2 extends/verifies it for the seed-a-reference form.)
2. Compare reference-form extensions (the per-case differ):
   • 0001: than accepted alongside as; aggregate reference "the two other harbors combined" (an explicit sum of the two seeded peers) + "each" distribution.
   • 0148: mass-noun temporal entities ("the number of people counted on the first/second day") + the "<A> was twice the total number counted on <B>" copula-compare frame.
3. (already works) summation over registers for these two cases (verified in §2).

§4 wrong=0 drivers (positively determined, fail-closed — the review focus)

Each new surface is a wrong=0 driver; each must bind correctly or refuse:

• Conditional-seed binding — If <REF> has <N> must seed the named REF, never a nearest/other entity. Ambiguous or unmatched reference → refuse (no guessed binding).
• Aggregate reference ("the two other harbors combined") — must sum exactly the two seeded peers, never more/fewer; if the peer count isn't unambiguous, refuse.
• "each" distribution — "80 each" × (peer count) must use the count the text grounds; ambiguous → refuse.
• than surface — admit only where it is provably the multiplicative-comparison surface (factor + explicit reference present), same frame gate as as; otherwise refuse.
• Compare direction itself is already covered (#78 allowlist + the compiler's inverse-refusal); no new direction driver is introduced (the seeds make these FORWARD compares).

§5 Done-when (band model)

1. band-solve ≥ 1 wrong=0 (target both 0148 + 0001) — the first real reader conversions of the arc; AND
2. correct-for-the-right-reason proof for each conversion (the 3-part standard): every statement injects the semantically correct graph element; the question reads to the right target/op; end-to-end == gold — NOT answer-matches; AND
3. full-500 wrong=0; mis-injection sweep clean (any new mis-injection → fix-to-refuse, not a conversion); refusal histogram stable-or-explained; smoke green.

§6 Measurement / discipline

Develop-on-tune / measure-once. Funnel re-run after each surface. Haircut factor reported with the triple. The mis-injection sweep (per the #79 caution) runs again — the new surfaces widen admission, so verify no statement mis-injects. Single measure run at the end.

§7 Out of scope

0000 (chained + compound-summation + question-arithmetic); multi-compound (highest-leverage but its own increment); currency / rate / percent / fraction / simultaneous; q:complex (the ~48% ceiling, pending the scheduled decomposition). q:difference stays deferred + fail-closed (locked by test_adr_0250_q_difference_failclosed.py).

§8 Open questions for the ruling

• Q1 — target both 0148 + 0001 (two reference forms), or just one for the very first conversion and the other as fast-follow? (Plan: both — they share the spine + conditional-seed; the reference forms are small and independent. Recommend both, but one is a clean minimum.)
• Q2 — conditional-seed-in-question: extend the existing extract_conditional_op_question_candidates, or a dedicated narrow extractor? (Plan: verify the existing path first; add narrow only if it can't bind a seeded reference fail-closed.)
• Q3 — aggregate "the two other harbors combined": model as an explicit 2-peer sum bound to the "each" count, or refuse aggregates in increment 2 and drop 0001 to a later increment? (Plan: attempt the 2-peer sum fail-closed; if it can't be made unambiguous, 0148 alone is the first conversion.)