core/docs/handoff/generalization-2026-07/BRIEF-S-sonnet-low-tier.md

Handoff Brief — Tier S (Sonnet 5, LOW risk)

Read first: docs/plans/generalization-arc-2026-07-24.md §6 (constraint set is binding) and the Tier-O brief's constraints block — they apply verbatim.

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STATE AT THE OPUS → SONNET CHECKPOINT (updated 2026-07-24)

Tier O is complete. Four units, all committed, all with local gates green:

unit	branch @ commit	what
O1	feat/existential-band @ e84c0e84	Band v6-EX existentials (ADR-0261) + a wrong-answer fix in Band v1b
O2	feat/curriculum-serve-physics @ 44e78aa4	curriculum-grounded serving (ADR-0262), physics lane 32/32 wrong=0
O3	same branch @ 0a17c496	ratified-ledger bridge (ADR-0263)
O4	same branch @ 353a52b8	math Phase 4.1 measured status — null result, documented

Branch stack (each on the previous): main → feat/verb-predicate-band (PR #111, Shay's, still open) → feat/existential-band → feat/curriculum-serve-physics.

⛔ BLOCKER — pushes to core-labs/core are failing server-side

The Forgejo repo has a corrupt object: refs/heads/feat/verb-predicate-band (= PR #111 head, e41a3e2a) points at a zero-length object file on the server. Symptoms:

remote: error: object file .../objects/e4/1a3e2a...  is empty
remote: fatal: bad object refs/heads/feat/verb-predicate-band
! [remote rejected] <your-branch> (missing necessary objects)

This blocks every push to the repo, not just the Opus branches — the server fails its own connectivity check before accepting any ref. Reads (git fetch, ls-remote, MCP) still work. Nothing local is damaged: the identical content exists locally as d181ae30.

Repair needs filesystem access on the Forgejo VM (remove the empty object, then reset or delete refs/heads/feat/verb-predicate-band and refs/pull/111/head, git fsck). This is Shay's call — do not delete or force-push someone else's PR branch. Until it is fixed, work locally and commit; push when the server is repaired.

Corrections to the plan's ground truth (verified — act on these)

1. There is no biology domain-chain corpus. evals/foundational_biology_ood is a fluency lane (its own contract says so) and no biology_chains_*.jsonl exists. The subjects with ratified chains AND mounted packs are physics, mathematics_logic, systems_software, philosophy_theology. Pick the second subject from those, or author biology's chains first.
2. Phase 4.1 (seeding-sentence injection) was already built before this arc and converts 0 cases; the frozen-500 baseline re-measured today is correct=5 wrong=0 refused=495. See docs/research/math-reader-phase-4-1-status-2026-07-24.md. Phase 4 should be re-pointed at the reader arc's own live recommendation (increment-2 case-first on cases 0000/0001/0148/0082).
3. No curriculum band can earn a SERVE license from present data. A band needs n≥657 with a real outcome mix; physics teaches 7 causal + 9 modal relations, so at most 16 questions in the whole subject can ever come back ENTAILED. A balanced band needs ≈219 taught relations per subject × family. Phase 2's blocker is ratified curriculum volume, not machinery (ADR-0262 §5.1). Every curriculum answer is served DISCLOSED until that changes — which is the license working, not a workaround.

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You own (independent items, any order unless noted)

1. S1 — ratification packet for deduction_serving_enabled. Evidence collation only — the flip is Shay's decision, never yours. Contents: the 25-band sealed ledger stats (chat/data/deduction_serve_ledger.json, all 25 at 720/720 wrong=0), serve-lane results (evals/deduction_serve/report.json, 166/166 across six splits), byte-identical-when-off proof (cite ADR-0256 + tests/test_deduction_surface.py flag tests), blast radius (the deduction branch in chat/runtime.py), and rollback (flip back, zero residue). Add a second section for curriculum_serving_enabled (ADR-0262): same shape, noting explicitly that every curriculum band is unearned, so the flip enables a disclosed capability. One markdown doc in docs/research/.

2. S2 — lane re-pins + the public_demo drift. The Phase-0.1 findings doc exists (docs/research/lane-drift-investigation-2026-07-24.md). Correct the standing note: public_demo is NOT a timing flake here. It reproduces deterministically. Measured this session:

   • pinned: 7d8ba0db… (last set at commit 7f6c497a, long before this arc)
   • content with the register-axis fix reverted: c6596e11…
   • content today: da7fad65… (3 identical runs, incl. on the base commit)

   So there are two drifts: one predating PR #110 (unexplained — find it before re-pinning) and one caused by PR #110's register-axis fix (expected, intended). all_passed stays true throughout; only the demo payload digest moved. Do the archaeology, then re-pin surgically — never --update (it rewrites every lane and silently drops erroring lanes' pins). Three arcs now depend on that rule.

3. S3 — vocab-trigger instrument. Implement the measurable test specified in docs/handoffs/COMPREHENSION-READER-AUDIT.md (§measurable-test): refusal histogram split mechanism-vs-coverage + admissions-per-lexicon-batch counter. Two ready-made feeds now exist: the curriculum path's untaught_vocabulary / out_of_curriculum refusals (chat/curriculum_surface.py) are literally coverage-class refusals, and the deduction bands' typed refusals are mostly mechanism-class. Do not invent policy — the spec decides, you implement.

4. S4 — HITL proposal-queue CLI. A core CLI surface listing + reviewing pending proposals from the existing sinks (teaching/proposals/, contemplation/idle sinks). Read + review-state transitions only; NO ratification automation, NO corpus mutation, NO flag flips.

5. S5 — housekeeping.

   • Add tests/test_register_substantive_consumption.py's e2e tests to the curated smoke suite (a red test outside every gate is a silent red — the lesson from the #96 regression).
   • Capability-index entries for the new lanes (curriculum_serve_v1, the v2_exist split).
   • Promotion sweep: ds-mem-0020 was promoted declined→unknown by v6-EX (already done); check nothing else in the older splits is now decidable.
   • Memory/doc updates; dead-code removal only when unambiguous.

6. S6 (new) — quantify the curriculum-volume ask. From ADR-0262 §5.1: produce a short doc stating, per served subject × relation family, how many ratified chains exist and how many a balanced 657-case band would need. Evidence only — authoring or ratifying curriculum content is Shay's.

Constraints: identical to Tier O (worktrees, fresh venv, pre-push gate, compare-URL PRs, Shay merges, wrong=0, flags stay off, no timelines). When any item's scope turns out larger than described here — stop and flag it in the PR/handoff notes rather than improvising.

Arc close: all Tier-S PRs pushed; memory updated; note whether the Phase-5 articulation trigger (multi-step decided content exists) has fired. Evidence for it now exists on both sides: the deduction bands produce multi-premise decided chains, and the curriculum path produces answers that state how much curriculum they were decided from.