D-GRAMMAR-WHEN-1: binding a grammatical WHEN through DT64 (lab)

.claude/board/entries/2026-11-03-d-grammar-when-1.md

@@ -0,0 +1,36 @@
+# D-GRAMMAR-WHEN-1: binding a grammatical WHEN through DT64 (2026-11-03)
+
+**Status:** measured, lab only. Probe `crates/grammar-constraints-probe` (`src/when.rs`, `tests/when.rs`, `examples/when_cost.rs`); report `.claude/probes/2026-11-03-d-grammar-when-1/REPORT.md`. No production change, no ClassId, no `F###`.
+
+## Measured
+
+- **The #1947 head hop is gather-shaped.**
+  - #1947 used `Pred::EqU32Via`, which reads `foreign[fk[i]]`.
+  - ADMISSION B: "a position derived from another relational column or table is not admissible as a read address … Execution remains co-addressed."
+  - The 2026-10-16 banner bans reads at a position taken from another lane's value.
+  - Its sibling `EqU32ViaLane` is marked VIOLATION (D-ASM-11A).
+  - No ruling admits `EqU32Via`; EXO-140 is still OPEN.
+- **DT64 can state the dependent's own conditions, but not the head frame.**
+  - The only hop-shaped leaf is an opaque `Sym`, and `admit` checks witness equality only.
+  - `validate` never checks WHEN lanes against the class basis (pinned by a test).
+  - No read-only "returns" DO exists.
+  - R2IL `prepare` still refuses any WHEN (`GuardNotExecutable`); its integration suite passes 52/52.
+- **A co-addressed form ("the join is the layout") makes the WHEN row-local in today's SetExpr.**
+  - The head's frame is written as a lane at the dependent's own coordinate, so the WHEN needs no `Sym`, and the two guards keep distinct witnesses.
+  - The query needs no `EqU32Via`: 10 ops, about 0.41–0.47 µs for both methods over 40 tokens, against 0.56–0.57 µs via the hop.
+  - The cross-row read moves into the producer, which does it once and counted (35 lookups).
+- **Lab composer (approach C): admit → check description vs witness → lower description ∧ shared WHERE into ONE program.**
+  - Both forms match an independent oracle and the gold.
+  - 11 negative controls behave as predicted (incl. a re-sealed same-size layout, from Codex review); 9 source disables go red.
+
+## Open (owner)
+
+- **EXO-140:** classify `EqU32Via`. Proposed, nonbinding: gather-class, not admitted on the query path.
+- **EXO-46 / D-RMAP-1:** admit, or refuse, a witnessed sequential producer for co-addressed relation lanes.
+- **D-DT64-6:** three open questions.
+  - A verified description identity in place of an opaque `Sym`.
+  - Checking guard lanes in `validate`.
+  - A read-only DO.
+- **Frame lexicon:** an owner, a revision and a language scope (`LanguageId` exists).
+- **Role identity:** CE64 `Orientation` (one code: `Core`+7) vs `DativeFunction` (a set of 8 incl. Judicantis). The 7 shared functions are offset by one.
+- **Candidate promotion:** a selection policy, plus the hydration / Rubicon gate.

.claude/board/entries/README.md

@@ -25,11 +25,12 @@ index row, (3) no duplicate entry id. Checks 1 and 2 are deliberately
 opposite directions; the stranding this convention prevents shows up in
 exactly one of them, never both.
 
-566 entries, 2026-08-06 .. 2026-11-03.
+567 entries, 2026-08-06 .. 2026-11-03.
 
 | date | entry id | finding | file |
 |---|---|---|---|
 | 2026-11-03 | `D-XLOG-META-WIRE-P0` |  | [2026-11-03-d-xlog-meta-wire-p0.md](2026-11-03-d-xlog-meta-wire-p0.md) |
+| 2026-11-03 | `D-GRAMMAR-WHEN-1` |  | [2026-11-03-d-grammar-when-1.md](2026-11-03-d-grammar-when-1.md) |
 | 2026-11-03 | `D-GRAMMAR-CONSTRAINTS-0` |  | [2026-11-03-d-grammar-constraints-0.md](2026-11-03-d-grammar-constraints-0.md) |
 | 2026-11-03 | `D-GLOBAL-WHERE` |  | [2026-11-03-d-global-where-p0.md](2026-11-03-d-global-where-p0.md) |
 | 2026-11-03 | `D-DR-FOLD-MAP` |  | [2026-11-03-d-dr-fold-map.md](2026-11-03-d-dr-fold-map.md) |

.claude/probes/2026-11-03-d-grammar-constraints/REPORT.md

@@ -1,5 +1,15 @@
 # D-GRAMMAR-CONSTRAINTS-0 — grammatical constraints × RelAlg × CE64/DT64
 
+> **⊘ CORRECTION (D-GRAMMAR-WHEN-1, 2026-11-03).** This report says the head hop
+> `Pred::EqU32Via` "executes; call sites EXO-140-unclassified". That is true but
+> understated. ADMISSION B (`entries/2026-10-20-six-decisions.md:26-34`) says "a
+> position derived from another relational column or table is not admissible as
+> a read address", and the 2026-10-16 banner calls a read "at a position taken
+> from another lane's values" a violation. `EqU32Via` reads `foreign[fk[i]]`, so
+> it is gather-shaped, and no ruling admits it. The results below stand as LAB.
+> The co-addressed alternative, and the owner decisions it raises, are in
+> `.claude/probes/2026-11-03-d-grammar-when-1/REPORT.md`.
+
 **Date:** 2026-11-03. **Status:** RESEARCH + LAB PROBE.
 - Probe: `crates/grammar-constraints-probe`. It has its own workspace and is
   excluded from the root workspace.