core/docs/research/curriculum-practice-producer-2026-07-26.md

Curriculum practice producer — what building it measured (Phase C)

Date: 2026-07-26 · Arc: curriculum-license-loop-2026-07 · Unit: Phase C Code: evals/curriculum_serve/practice/{generator,runner}.py, tests/test_curriculum_practice.py Governs: ADR-0262 §5 (what a curriculum band can earn), ADR-0264 R9 (volume honesty)

The producer named by chat/curriculum_serve_license.py's own docstring — evals.curriculum_serve.practice.runner.seal_ledger, declared "the only writer" of the ledger that module reads — did not exist. It does now. Building it measured three things, two of which correct records I wrote earlier in this arc.

Reproduce everything below with:

uv run python -m evals.curriculum_serve.practice.runner          # capped corpus
uv run python -m evals.curriculum_serve.practice.runner --full    # every atom (~75s)

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0. What the producer is

A band's case space is enumerated, not authored: every exam question that routes to that subject (chat.curriculum_surface.resolve_domain) whose relation falls in that family. One committed case per distinct query atom, so committed == distinct is not a property the generator maintains — it is the same fact twice. This is the structural version of what ADR-0264 R9 asks for, and it is why the curriculum producer cannot develop the deduction producer's exposure (CASES_PER_BAND = 720 filled by cycling spaces as small as 28).

CASES_PER_BAND = 660 follows evals/determination_estimation, per DIVISION-OF-WORK.md §4. It is a ceiling on committed volume, not a quota: a band with a smaller space emits its whole space and reports a number below the floor. Selection above the cap is every taught edge plus a fixed stride across the rest — a lexicographic prefix of 660 out of 45,300 would cover about five subject terms of 151 and report one corner of a band as the band.

Result over the capped corpus: 11 bands, wrong = 0, inflation 1.0 everywhere.

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1. Finding — a committed ledger is necessarily an earning ledger

The plan of record's Phase-1 exit criterion asks that curriculum_serve_license() read "a real (still-unearned) ledger instead of an absent one."

That state is unreachable. Reliability is commitment precision, and a correct UNKNOWN is a commitment. conservative_floor(660, 660) = 0.990046 ≥ 0.99, so any band with ≥657 routable atoms clears θ_SERVE on non-commitments alone, whatever its curriculum says. Sealing today licenses four bands:

band	committed	refused	reliability	SERVE	entailed	entailed share
curriculum_philosophy_theology_modal	45,188	112	0.99985	yes	8	0.0177%
curriculum_philosophy_theology_contrast	22,598	52	0.99971	yes	8	0.0354%
curriculum_physics_causal	720	0	0.99087	yes	7	0.9722%
curriculum_systems_software_causal	720	0	0.99087	yes	7	0.9722%
curriculum_physics_modal	480	0	0.98636	no	9	1.8750%
curriculum_mathematics_logic_modal	480	0	0.98636	no	4	0.8333%
curriculum_systems_software_modal	480	0	0.98636	no	6	1.2500%
curriculum_mathematics_logic_contrast	240	0	0.97309	no	8	3.3333%
curriculum_mathematics_logic_evidential	240	0	0.97309	no	8	3.3333%
curriculum_mathematics_logic_sequence	240	0	0.97309	no	4	1.6667%
curriculum_systems_software_sequence	240	0	0.97309	no	3	1.2500%

(Exhaustive sweep: 71,790 atoms, wrong = 0, 164 refusals.)

A licensed band would therefore be certified on evidence that is 99.0%–99.98% correct non-commitment. ADR-0262 §5.1 explicitly rules that unacceptable. The gate cannot see it: ClassTally carries correct/wrong/refused and no verdict axis, so a correct UNKNOWN is indistinguishable from a correct ENTAILED once tallied. Mix can only be enforced at the producer, which is exactly the open outcome-mix ruling recorded in docs/research/distinct-evidence-audit-2026-07-25.md.

Consequence for this arc: that ruling is no longer academic — it is the last thing between a built loop and four unearned licenses. Phase C therefore ships the writer and does not commit the artifact; chat/data/curriculum_serve_ledger.json stays absent, missing_ok=True stays true, and every band stays DISCLOSED. Writing it is a ratification, so it belongs to the explicit core proposal-queue reseal verb a human runs (Phase D), and it should not be run before the mix ruling.

tests/test_curriculum_practice.py::test_curriculum_ledger_is_not_committed pins the absence, and test_sealing_would_license_exactly_the_bands_that_reach_the_floor pins the consequence, so neither can be lost and re-derived wrongly.

Recommendation (still Shay's call)

Enforce mix at the producer, as a per-verdict-class floor rather than a ratio: a band earns SERVE only when each verdict class it can express independently reaches the volume the floor requires. Under that rule no band earns anything today (max entailed volume is 9), which is the honest reading, and it makes ADR-0262 §5.1 mechanical instead of advisory. It also keeps the deduction bands' aggregate licenses intact, since imposing a per-class 657 retroactively would fail all 25.

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2. Correction — ADR-0264 §4.2's ceiling table understates every band

I sized bands from per-term exclusivity (a term taught by only one subject). The router's actual predicate is per-pair: resolve_domain routes a question iff exactly one served subject holds both terms. A term taught in two subjects can still appear in a pair only one subject holds both halves of, so per-term exclusivity is a strictly tighter bound and under-counts.

band	ADR-0264 §4.2	true	verdict change
curriculum_systems_software_causal	630	720	cannot reach 657 → CAN
curriculum_philosophy_theology_modal	44,104	45,300	—
curriculum_philosophy_theology_contrast	22,052	22,650	—
curriculum_mathematics_logic_modal	420	480	—
curriculum_mathematics_logic_{sequence,contrast,evidential}	210	240	—
curriculum_systems_software_modal	420	480	—
curriculum_systems_software_sequence	210	240	—
curriculum_physics_{causal,modal}	720 / 480	720 / 480	—

So 4 of 11 bands can reach 657, not 3, and 7 cannot, not 8. The retarget conclusion is unaffected — philosophy_theology · modal is still the largest space by two orders of magnitude, and physics · modal (480) is still impossible at any authoring volume. The numbers are now pinned in tests/test_curriculum_practice.py::BAND_ATOM_SPACE, measured rather than derived, so this class of error cannot recur silently.

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3. Finding — two taught lemmas collide with the argument reader's grammar

then and therefore are lemmas philosophy_theology's packs teach and control words of the argument reader: therefore is literally the conclusion marker in ". Therefore <conclusion>.", and then is the conditional consequent marker. An atom using either as a term compiles an argument the reader cannot parse back, so it refuses compiled_premises_unreadable.

• 164 routable atoms affected (112 modal + 52 contrast) out of 71,790.
• All 164 are coverage misses, not wrongs — excluded from reliability's denominator (ADR-0175 §4), never a confabulation. wrong = 0 holds.
• Exactly two lemmas are responsible; every other implicated term is only ever the partner of one of them.
• It is in the band Phase F retargets to.

The narrow cost is small. The mechanism is not: the vocabulary boundary and the reader's grammar are never screened against each other. A future pack teaching and, or, not, or if would open a much larger hole the same way, and it would present as a coverage dip rather than an error. A reserved-word check at pack mount or at chain ratification would close it.

Not fixed here — outside Phase C's unit (DIVISION-OF-WORK.md §6.5). Pinned as a bound by test_the_collision_is_bounded_to_two_lemmas, so a third reserved word entering the curriculum fails loudly instead of quietly enlarging the gap.

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4. What did not move

• evals/curriculum_serve lane: [physics] n=32 correct=32 wrong=0 declined_mismatch=0 anti_recall=5, unchanged; report.json bytes and the curriculum_serve_v1 SHA pin unchanged. The producer reads the same solver the lane does and writes nothing the lane reads.
• No serving behaviour change of any kind: no ledger committed, so curriculum_serve_license() still returns None for every band and every curriculum answer is still served DISCLOSED.
• refuted remains unreachable — no corpus row can express a negative until ADR-0264 R1–R4 is implemented. test_gold_mix_has_no_refuted_class pins that as a red test for the polarity unit to turn green.