Merge pull request 'Grammar unification — plan of record (CORE cannot read its own writing: 0/280)' (#128) from docs/grammar-unification-plan into main

Reviewed-on: #128

docs/plans/grammar-unification-2026-07-26.md

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+# Grammar Unification — Plan of Record
+
+**Date:** 2026-07-26 · **Status:** ACTIVE · **Base:** main @ `9696443a`
+(post ADR-0264 ratification, PR #127)
+
+> **One sentence:** CORE cannot read its own writing — measured 0/280 — and this
+> arc makes reading and writing share one grammar so that every construction
+> taught works in both directions, with round-trip as the falsifiable gate.
+
+---
+
+## 0. Why this arc, and why now
+
+The curriculum-license-loop arc closed on the finding that the outcome-mix
+ruling is the binding constraint for *curriculum* serving. That finding stands.
+It is not, however, the binding constraint on **delivered capability**, and the
+measurements in §1 say what is.
+
+Six ADR-scoped deduction bands (v1, v1b, v2-EN, v3-MEM, v4-CM, v5-VP, v6-EX) are
+ratified, flag-ON, and `wrong=0`. They are reachable only through
+`looks_like_deductive_argument`, which is *sentence-initial "therefore"*:
+
+```
+"If it rains then the ground is wet. It rains. Therefore the ground is wet."
+  → Given: if it rains then the ground is wet; it rains.
+    Your premises entail: the ground is wet.                    DECIDED
+
+"It rains. So the ground is wet, right?"
+  → Pack-resident tokens — pack-grounded (en_core_cognition_v1):
+    ground (relation.ground; predicate.support)…                TOKEN DUMP
+
+"All men are mortal and Socrates is a man, so he must be mortal."
+  → Pack-resident tokens — pack-grounded (en_core_quantitative_v1):
+    all (quantitative.universal.total…)                         TOKEN DUMP
+```
+
+Each band widened what CORE can **decide**. None widened what a person can
+**ask**. Deepening the room behind the keyhole is not progress in delivered
+capability, and the keyhole is a *reading* problem.
+
+This arc is scoped to the reading/writing seam. It does **not** author content,
+does **not** move a flag, and does **not** touch the decision layer.
+
+---
+
+## 1. Measured baseline
+
+Every number below was measured on `main` @ `9696443a` by reading source and
+running probes, not inferred from docs. Reproduction scripts land in Phase 1.
+
+### 1.1 The writer that serves is eight format strings
+
+`generate/semantic_templates.py::render_semantic` — the function
+`core/cognition/pipeline.py` actually calls — is a dict of **8** format strings
+keyed on `IntentTag`, plus a predicate-display dict. No morphology, no
+agreement, no tense, no negation, no pluralization, no clause joining.
+
+Best-case live output:
+
+> **Q:** Explain knowledge.
+> **A:** Knowledge is what a person knows from truth and evidence. Furthermore,
+> it belongs to cognition.knowledge. In turn, it requires evidence.
+
+One fact per sentence, uniform subject-predicate-object, connectives from a
+fixed bucket, and an internal dotted path (`cognition.knowledge`) leaking into
+prose.
+
+### 1.2 The good realizer exists and never serves
+
+`generate/templates.py::render_step` (232 lines) has real linguistics —
+quantifier agreement, mass vs count nouns, irregular morphology, tense/aspect,
+and via `realize_target` it joins clauses with *and / or / that / which*.
+
+It is called from exactly three places, **all `evals/*/runner.py`**.
+`core/cognition/pipeline.py` calls `realize_semantic`, never `realize_target`.
+This was deliberate — `core/cognition/surface_resolution.py` records that the
+`realize_semantic` path "was granted supremacy by the Shadow Coherence Gate" —
+but the consequence is that **`english_fluency_ood` 117/117 + 39/39 scores a
+function that never speaks.**
+
+### 1.3 Linguistic knowledge is duplicated 35-vs-9 ways, Jaccard 0.083
+
+| | word-tables | distinct words |
+|---|---|---|
+| reading path (9 files) | **35** | 202 |
+| writing path (6 files) | **9** | 359 |
+| shared | — | **43** of 518 union (**Jaccard 0.083**) |
+
+Tables that should agree and do not:
+
+| linguistic fact | copies | status |
+|---|---|---|
+| irregular plurals | **3** (`member.py` 29, `reader.py` 8, `templates.py` 25) | **all three diverge** |
+| quantifier tokens | **5** across both paths | **3-way divergence** |
+| connective tokens | **4** (`english`, `member`, `verb`, `cond_member`) | 3 identical, `english` adds `therefore` |
+| sentential-negation prefix | 2 (`english`, `member`) | identical |
+| negation-bearing tokens | 2 | diverge by `'not'` |
+| predicate display | 2 (`semantic_templates`, `templates`) | identical, 26 entries |
+| copula forms | 2 | same content, different type (frozenset vs tuple) |
+
+Demonstrated consequences of the plural divergence:
+
+- CORE **reads** `wolves / knives / leaves / thieves / halves / loaves / elves /
+  cacti / fungi / dice / aircraft / offspring` and **cannot write** them —
+  `pluralize("cactus") → "cactuses"`, `pluralize("die") → "dies"`.
+- CORE **writes** `criterion→criteria, phenomenon→phenomena, analysis→analyses,
+  hypothesis→hypotheses, axis→axes, basis→bases, thesis→theses` and the reader's
+  table knows **none** of those plurals.
+
+Note this duplication is **not only** read-vs-write: two of the three plural
+tables are both on the reading side, and four connective tables are all on the
+reading side. The six deduction bands were built as successive independent
+tiers, each re-encoding English from scratch.
+
+### 1.4 A demonstrated grammar defect: 9 of 26 predicates mis-agree
+
+`_inflect_predicate(display, plural_subject=True)` against a hand-written
+English oracle:
+
+```
+plural-subject agreement over _PREDICATE_DISPLAY: 17/26 correct, 9 WRONG
+
+  belongs_to             'belongs to'              -> 'belongs to'              want 'belong to'
+  causes                 'causes'                  -> 'caus'                    want 'cause'
+  contrasts_with         'contrasts with'          -> 'contrasts with'          want 'contrast with'
+  has_steps              'has the following steps' -> 'has the following step'   want 'have the following steps'
+  is_caused_by           'is caused by'            -> 'is caused by'            want 'are caused by'
+  is_defined_as          'is defined as'           -> 'is defined a'            want 'are defined as'
+  is_distinguished_from  'is distinguished from'   -> 'is distinguished from'   want 'are distinguished from'
+  is_grounded_in         'is grounded in'          -> 'is grounded in'          want 'are grounded in'
+  is_verified_as         'is verified as'          -> 'is verified a'           want 'are verified as'
+```
+
+Live example: `render_step(ASSERT, "wolf", "is_defined_as", "mammal",
+quantifier="all")` → **`"all wolves is defined a mammal"`**.
+
+Two root causes, both single-point:
+
+1. **`base_form()` is written for single verbs and applied to whole humanized
+   predicate phrases.** It strips the last character-class of the final word:
+   `"is defined as" → "is defined a"`, `"has the following steps" → "has the
+   following step"`, `"causes" → "caus"`.
+2. **The `copular` flag is computed in `_inflect_predicate` and consulted only
+   on the negated-singular branch.** The plural branch
+   (`case (_, _, False, True)`) ignores it, so `is/has/belongs` never becomes
+   `are/have/belong`.
+
+Singular is clean: 0 of 26 differ. **This defect reaches zero served turns
+today** because `render_step` is eval-only (§1.2). It matters because the
+fluency suite scores this function, and because Phase 4 would wire it into
+serving.
+
+### 1.5 The fluency instrument is decorative
+
+`evals/deterministic_fluency` reports **1.00 on all six predicates**. Control
+test (the absence test — a green measurement that would look identical with the
+mechanism removed):
+
+| candidate surface | passes all 5 content predicates? |
+|---|---|
+| `"Truth is what corresponds to reality, and knowledge is belief grounded in it."` | yes |
+| `"colorless green ideas sleep furiously."` | yes |
+| `"wet ground rains the is."` | **yes** |
+| `"is is is is."` | **yes** |
+| `"banana does the."` | **yes** |
+
+It checks terminal punctuation, presence of a verb-ish token, and two
+anti-shape regexes. **It cannot distinguish English from word salad.**
+
+And the suite cannot see §1.4 either. Across all **280** cases in
+`english_fluency_ood` + `grammatical_coverage`:
+
+- 40 use a quantifier — only `all` and `some`
+- **0** use any copular predicate
+- **0** exercise the quantifier × copular combination that breaks
+
+`english_fluency_ood`'s own `accept_surfaces` include `"river flows valley"` and
+`"wind shapes dune"` — token-ordered, not English. The 100% is real against the
+lane's contract and says nothing about fluency.
+
+### 1.6 The headline: round-trip is 0/280, and all six readers refuse
+
+Feed each of the 280 writer-produced surfaces to `meaning_graph.comprehend`:
+
+```
+surfaces written by CORE : 280
+reader COMPREHENDED      : 0/280 = 0.0%
+reader REFUSED           : 280/280 = 100.0%
+refusal reasons          : {'no_template_match': 280}
+```
+
+Control (proves the harness works): the reader comprehends 31/166 = 18.7% of the
+`deduction_serve` corpus, and `comprehend("Socrates is a man.")` returns
+2 entities + `member(socrates, man)`.
+
+Six readers × four writer outputs, including CORE's own **live served**
+surfaces — **24 refusals, 0 comprehensions**:
+
+| writer output | comprehend | english | member | cond_member | verb | exist |
+|---|---|---|---|---|---|---|
+| `Molecule binds enzyme.` (writer's own accept_surface) | no_template_match | no_conclusion | out_of_band | out_of_band | no_conclusion | no_conclusion |
+| `all wolves is defined a mammal` | no_template_match | empty | empty | empty | empty | empty |
+| `Knowledge is what a person knows from truth and evidence.` (**live**) | no_template_match | no_conclusion | mixed_structure | out_of_band | mixed_structure | mixed_structure |
+| `Wisdom is a good use of knowledge. Furthermore, it belongs to cognition.wisdom.` (**live**) | reserved_word_in_np | membership_shape | out_of_band | out_of_band | out_of_band | out_of_band |
+
+### 1.7 A ratified band serves malformed English today
+
+This was found while designing Phase 1's projection, and it is the most
+consequential item in §1 because it is **user-visible on a ratified, flag-ON
+band**.
+
+`generate/proof_chain/render.py`:
+
+```python
+_CATEGORICAL_PHRASE = {
+    "A": "all {s} are {p}",     # plural syntax…
+    "E": "no {s} are {p}",
+    "I": "some {s} are {p}",
+    "O": "some {s} are not {p}",
+}
+```
+
+…but `{s}` / `{p}` are filled with the **singularized entity ids** the
+MeaningGraph reader produces (`_chunk_class` → `_singularize`). There is no
+re-pluralization step, because the reader and the renderer are on opposite sides
+of the seam described in §1.3. Result, live through `deduction_grounded_surface`:
+
+```
+in : All dogs are mammals. All mammals are animals. Therefore all dogs are animals.
+out: Given: all dog are mammal; all mammal are animal. That's valid — all dog are animal follows.
+
+in : No dogs are cats. All cats are animals. Therefore no dogs are animals.
+out: Given: no dog are cat; all cat are animal. That doesn't follow — …
+
+in : All wolves are mammals. All mammals are animals. Therefore all wolves are animals.
+out: Given: all wolve are mammal; … — all wolve are animal follows.
+```
+
+Scope, measured two ways:
+
+- **Synthetically: every plural noun**, regular or irregular. `all dog are
+  mammal`, `all cat are mammal`, `all student are mammal`, `all child are
+  mammal`, `all man are mammal`.
+- **In the ratified corpus: 4 of 47** cases that serve a categorical clause —
+  `ds-v1-0023`, `ds-v1-0024`, `ds-v1-0026`, `ds-v1-0028`, all band v1. The corpus
+  under-represents the defect only because band routing sends most arguments to
+  renderers that echo the user's original text.
+
+**`wrong=0` is not threatened.** Every verdict above is correct; this is purely a
+surface defect. Two distinct causes compound in it:
+
+1. **No re-pluralization at render time** — affects *all* nouns. This is the
+   dominant cause.
+2. **The reader's plural table is 8 entries** where the v3-MEM band's is 29, so
+   `wolves → wolve`, `knives → knive`, `leaves → leave`, `lives → live`,
+   `halves → halve`, `loaves → loave`, `thieves → thieve`, `elves → elve`
+   — **8 silently wrong singulars**, and 4 more (`cacti`, `dice`, `fungi`,
+   `oxen`) that refuse outright. **CORE's two readers disagree on 12 of 20
+   plurals.**
+
+The wrong singulars do *not* break soundness, because `_singularize` is a
+deterministic function applied uniformly to premises and conclusion, so the
+lowering stays a consistent bijection. They are label defects — and they are the
+reason cause (2) must be fixed with a *shared* table rather than by patching one
+side.
+
+### 1.8 The models are not type-compatible
+
+A literal `read(write(g)) == g` is not expressible today:
+
+- `MeaningGraph` = `Entity(entity_id, name, span, kind)` +
+  `Relation(predicate, arguments: tuple[str, ...], span, negated)` — n-ary
+  predicate/argument structure with source spans.
+- `PropositionGraph` = `GraphNode(node_id, subject, predicate, obj,
+  source_intent, language, root, morphology_id)` +
+  `GraphEdge(source, target, relation)` — fixed SPO triples with discourse edges.
+
+Round-trip therefore needs a **defined projection**, not identity. Choosing that
+projection is Phase 1's first design decision, and §6 records why this matters
+for direction.
+
+---
+
+## 2. Goal, non-goals, and the thesis check
+
+**Goal.** One grammar, used in both directions, so that a construction taught
+once works for reading and for writing, and so that surface diversity becomes
+*verifiable* rather than risky.
+
+**Non-goals — stated so success is not silently redefined:**
+
+- **Not "prettier prose."** Fluidity is a function of construction-inventory
+  size, which is content work. This arc builds the mechanism that makes growing
+  the inventory safe and measurable.
+- **Not an LLM, sampler, or paraphraser.** No stochastic generation enters the
+  truth path. See the thesis check below.
+- **Not curriculum content.** Scripture/theology content is separately deferred
+  (word-for-word verification + a faith-domain evidentiary regime are both
+  undesigned).
+- **Not a graph-model merge.** §1.8 says that may be needed; §6 makes it a
+  measured decision for a *later* arc behind an ADR, not a silent expansion of
+  this one.
+
+**Thesis check — "decoding, not generating."** Every ADR must pass this. A
+bidirectional grammar is a *decoder run in reverse*: writing selects among
+surface forms that the decoder provably maps back to the same graph. Nothing is
+sampled, nothing is invented, and every emitted variant carries a proof of
+meaning-preservation. Diversity comes from *enumerating verified forms*, not
+from generating candidates and hoping. `chat/register_variation.py` already
+implements exactly the deterministic seeded selector this needs (uniform,
+replay-stable, `variant_id` in the audit stream).
+
+---
+
+## 3. The central design decision: the instrument *is* the fix
+
+An honest fluency measurement cannot be built out of heuristic predicates — §1.5
+is what that attempt already produced, and any new heuristic set will be gameable
+the same way. **You cannot measure grammaticality without a grammar.**
+
+Therefore the instrument and the remedy are one artifact:
+
+- A grammar that **parses** is a measurement (word salad fails to parse).
+- The same grammar used to **generate** is the remedy.
+- **Round-trip** forces one artifact to do both, and is falsifiable without a
+  judge, an embedding, or a gold aesthetic.
+
+**Necessary, not sufficient — stated up front.** Round-trip measures *mutual
+intelligibility*, not English quality. `"river flows valley"` may round-trip
+perfectly while remaining un-English, because both sides can share an
+impoverished construction. So the lane needs two corpora and both are load-bearing:
+
+- a **positive** corpus (round-trip must succeed), and
+- a **negative** corpus of word salad (round-trip must fail, 100%).
+
+If the lane ever reports high scores on both, the lane is broken. That
+bidirectional requirement is what keeps this instrument from becoming the next
+§1.5.
+
+---
+
+## 4. Phases
+
+Each phase is independently valuable, independently landable, and has a
+falsifiable exit test.
+
+**Serving-risk classification — corrected 2026-07-26 after §1.7.** An earlier
+draft of this plan asserted "Phases 1–3 cannot change serving behaviour." That
+was **wrong**, and the error is worth recording because it is the same shape as
+the mistakes this arc exists to fix: I classified a table as off-serving without
+asking which callers reach it. `generate/meaning_graph/reader.py::_IRREGULAR_PLURALS`
+**is** on the serving path — `comprehend` → `to_syllogism` → band v1b →
+`deduction_grounded_surface`. Unifying it changes entity ids, which moves
+trace hashes and served surfaces.
+
+The corrected rule for this arc: **a table is off-serving only when every caller
+is proven to be eval-only.** Phase 2 is therefore split by that test, not by
+topic.
+
+| phase | changes served output? | gate |
+|---|---|---|
+| 1 — instrument | no (new files only) | local smoke/deductive |
+| 2A — off-serving tables | no (callers proven eval-only) | byte-identical lane SHAs |
+| 2B — serving tables + render fix | **yes** | **explicit authorization** |
+| 3 — agreement defect | no (`render_step` is eval-only) | 26/26 oracle |
+| 4 — which realizer serves | **yes** | **explicit authorization** |
+| 5 — round-trip + diversity | **yes** | **explicit authorization** |
+
+### Phase 1 — Build the instrument, record the baseline
+
+*Touches:* new `evals/grammar_roundtrip/`, new `generate/grammar/` (smallest
+shared construction inventory), reproduction scripts for every §1 number.
+*Serving risk:* none (new files + eval lane only).
+
+Deliver:
+
+1. `evals/grammar_roundtrip/` lane reporting, over a positive corpus:
+   `write_rate`, `read_rate`, `graph_match_rate` under the chosen projection.
+2. Over a **negative** corpus (hand-written word salad + programmatically
+   shuffled tokens from positive cases): `reject_rate`.
+3. The chosen `MeaningGraph`↔`PropositionGraph` projection, written down with
+   what it deliberately discards.
+4. Reproduction scripts for §1.3–§1.7 so every number in this plan is re-runnable.
+
+**Exit criteria (all required):**
+
+| criterion | measure |
+|---|---|
+| baseline recorded | `read_rate` on the 280-case corpus, expected ≈ 0.0% |
+| word salad rejected | `reject_rate` = **1.00** on the negative corpus |
+| lane is non-vacuous | mutating the reader to accept-everything drives `reject_rate` → 0 (**must go red**) |
+| no behaviour change | smoke **621**, deductive **349**, 11/11 lane SHA pins unchanged |
+
+**Failure / stop condition:** if the negative corpus cannot be rejected without
+also rejecting the positive corpus, the grammar formulation is wrong. **Stop and
+reassess — do not tune a threshold to split them.**
+
+### Phase 2A — One source of linguistic truth, off-serving only
+
+*Touches:* the word-tables in §1.3 whose every caller is proven eval-only, plus
+new single-owner modules. *Serving risk:* none, and proven by byte-identity.
+
+Deliver:
+
+1. One module owning each linguistic fact: plurals, quantifiers, connectives,
+   copulas, negation-bearing tokens, predicate display.
+2. The **identical** duplicate groups collapsed — 3 connective tables, 2
+   `_SENTENTIAL_NOT`, 2 predicate-display tables — with byte-identical lane
+   hashes as the proof of zero behaviour change.
+3. Each divergence among off-serving tables resolved by an explicit recorded
+   decision (not by picking the larger table), with a test pinning the answer.
+4. A structural test asserting no module defines a second copy — same discipline
+   as `tests/test_volume_honesty.py`, which must fail if a duplicate is
+   reintroduced.
+5. **A caller-provenance test**: for every table the new module owns, assert
+   whether it is serving-reachable. This is the check whose absence produced the
+   error corrected above, so it belongs in the tree, not in a reviewer's head.
+
+**Exit criteria:**
+
+| criterion | measure |
+|---|---|
+| duplication removed | one table per fact; structural test green and mutation-red |
+| identical collapses are inert | 11/11 lane SHA pins **byte-identical** |
+| divergences decided, not averaged | each has a recorded decision + pinning test |
+| agreement | Jaccard → 1.00 for facts that should agree (from 0.083 overall) |
+| serving reachability is known | caller-provenance test covers every owned table |
+
+**Failure / stop condition:** if collapsing an "identical" pair moves a lane
+hash, the tables were not actually identical — stop, treat it as a divergence
+requiring a decision, and move it to Phase 2B.
+
+### Phase 2B — Serving-path tables and the categorical render defect — **authorization gate**
+
+*Touches:* `generate/meaning_graph/reader.py::_IRREGULAR_PLURALS`,
+`generate/proof_chain/render.py::_CATEGORICAL_PHRASE`, the band readers' tables.
+**Changes served surfaces and trace hashes.** Depends on 2A's shared pluralizer.
+
+Deliver:
+
+1. Re-pluralization at categorical render time, fixing `all dog are mammal` →
+   `all dogs are mammals` (§1.7 cause 1 — affects *all* nouns).
+2. The reader's 8-entry plural table replaced by 2A's shared table, fixing the
+   8 silently-wrong singulars and the 12-of-20 reader-vs-reader disagreement
+   (§1.7 cause 2).
+3. Updated lane SHA pins — **surgical single-line edits only**, never
+   `--update` — with the old and new hash recorded per lane.
+
+**Exit criteria:**
+
+| criterion | measure |
+|---|---|
+| surfaces well-formed | 0 malformed categorical surfaces; `ds-v1-0023/0024/0026/0028` render plurals |
+| readers agree | reader-vs-reader singularization agreement **20/20** (from 8/20) |
+| soundness preserved | `wrong=0` holds; deduction lane verdicts **unchanged case-for-case** |
+| hash movement is intended | every moved pin explained; no pin changed that shouldn't move |
+
+**Why gated:** this changes what users see. Fixing a defect is still a serving
+change, and serving changes are Shay's call.
+
+### Phase 3 — Fix the 9-of-26 agreement defect
+
+*Touches:* `generate/morphology.py::base_form`, `generate/templates.py::_inflect_predicate`,
+new eval cases. Depends on Phase 2A (unified tables) and Phase 1 (instrument).
+*Serving risk:* none (`render_step` is eval-only).
+
+Deliver:
+
+1. `base_form` no longer applied to multi-word phrases — phrase-head handling.
+2. The `copular` flag consulted on the plural branch.
+3. Eval cases covering **quantifier × copular**, which is 0 of 280 today.
+
+**Exit criteria:**
+
+| criterion | measure |
+|---|---|
+| agreement correct | **26/26** against the oracle (from 17/26) |
+| the gap is closed for good | new cases exercise quantifier × copular; reverting either fix goes red |
+| no regression | `english_fluency_ood` 117/117 + 39/39 holds; smoke/deductive unchanged |
+
+### Phase 4 — Resolve `realize_semantic` vs `realize_target` — **authorization gate**
+
+*Touches:* `core/cognition/pipeline.py` or the eval lanes. **First phase that can
+change served output.** Requires explicit authorization before merge.
+
+The current state is untenable in one specific way: 149 green fluency cases
+score a function that never serves. Exactly one of these must become true:
+
+- **(a)** `realize_target` earns the serving path, gated on the Phase 1
+  round-trip instrument and a `wrong=0` hold; or
+- **(b)** the lanes scoring it are retired/re-pointed, and the claim
+  "realizer fluency is mechanistic" is restated as a claim about eval-only code.
+
+**Exit criterion:** no eval lane scores a non-serving function. Whichever branch
+is taken is recorded with its reasoning.
+
+**Why this is gated:** (a) changes what users see and would move surface hashes.
+It is a serving change and belongs to Shay, not to this plan.
+
+### Phase 5 — Raise round-trip, then earn diversity
+
+*Depends on:* Phases 1–3 plus 2B, and on the Phase 1 baseline being non-zero-able.
+*Scope: deliberately unestimated* — see §5.
+
+Deliver:
+
+1. Construction inventory grown until `read_rate` clears a floor, with the floor
+   ratcheted (never lowered to accommodate a regression).
+2. **N > 1** verified surface forms per graph, each proven to round-trip to the
+   same graph.
+3. Deterministic seeded selection among verified variants, reusing
+   `chat/register_variation.py`'s existing selector, with `variant_id` in the
+   audit stream.
+
+**Exit criteria:**
+
+| criterion | measure |
+|---|---|
+| round-trip improved | `read_rate` clears a ratcheted floor, well above the ≈0% baseline |
+| diversity is real | mean verified variants per graph > 1, measured |
+| diversity is safe | 100% of emitted variants round-trip to the source graph — **zero exceptions** |
+| truth path untouched | `wrong=0` holds; variant selection provably cannot alter a verdict |
+
+---
+
+## 5. What is deliberately not estimated
+
+Phase 5's size cannot be estimated before Phase 1 produces real numbers, and
+pretending otherwise is how the last arc acquired an unreachable exit criterion.
+Phases 1–3 are bounded and specified. **Phase 5 is scoped only after Phase 3
+reports.**
+
+I also do not claim Phases 1–4 produce human-like prose. They produce: a
+measurement that cannot be faked, a single source of linguistic truth, a fixed
+agreement defect, and an honest answer about which realizer serves. That is the
+foundation the diversity work needs — and it is worth landing even if Phase 5 is
+later judged infeasible.
+
+---
+
+## 6. The decision rule for afterwards
+
+The point of the instrument is that the *next* direction is chosen by a number,
+not by argument. After Phase 3, `read_rate` is re-measured on the unified
+grammar. That number forks the road:
+
+- **`read_rate` rises materially from unification alone** ⇒ the two grammars were
+  closer than they looked, the surface layer was the barrier, and Phase 5
+  (diversity) is the right next arc.
+- **`read_rate` stays near zero after unification** ⇒ the barrier is **§1.8**:
+  `MeaningGraph` and `PropositionGraph` are genuinely different models, and no
+  amount of table-sharing bridges them. The next arc is then a **graph-model**
+  decision, which is large, touches the decision layer, and **must go to an ADR
+  before any code**. It is explicitly *not* an extension of this plan.
+
+Either way we will know which, and why, from a measured quantity — which is the
+thing the previous arc could not do until after it had built the machinery.
+
+**One reading of the evidence is worth pre-committing to now:** §1.6's uniform
+`no_template_match` across all 280, combined with §1.8's type mismatch, makes
+the second fork more likely than the first. If that is where we land, Phases 1–3
+are still exactly the right work — they are what makes the graph-model question
+answerable instead of speculative — but the arc should be expected to *end* at
+the ADR rather than at fluid prose.
+
+---
+
+## 7. Verification protocol
+
+Per `AGENTS.md`, unchanged from prior arcs:
+
+- Every phase, in-worktree on canonical CPython 3.12.13 with `uv sync --locked`,
+  before push: `uv run core test --suite smoke -q` then `--suite deductive -q`.
+  Baselines: **smoke 621 / deductive 349**.
+- Every new gate must **fail under mutation**. A pin that cannot fail is
+  worthless — this arc exists because three such pins were found (§1.5, the Rust
+  parity lane, and the fluency suite's blind spot).
+- Phase 2A additionally requires **byte-identical** 11/11 lane SHA pins.
+  Never `scripts/verify_lane_shas.py --update`; surgical single-line edits only.
+- One PR per phase, branch + worktree each, Forgejo compare URL,
+  `[Verification]:` line. No merge automation — PRs sit until authorized.
+- Phase 4 additionally requires explicit serving-change authorization.
+
+## 8. Standing traps carried into this arc
+
+- **`then` / `therefore` are taught `philosophy_theology` lemmas AND the argument
+  reader's control words.** The vocabulary boundary is never screened against the
+  reader's grammar. A unified grammar makes this screenable for the first time —
+  and makes forgetting to screen it a single-point failure. Add the screen in
+  Phase 2A.
+- Corpus-mutating tests must never write committed files: the `full` suite
+  injects `-n auto`, so writes race.
+- Never "fix" a hash drift or a ledger inventory to make a test pass.
+- `PYO3_PYTHON=/opt/homebrew/bin/python3.12` is required for `core-rs` builds.