contract: signed Register128 readings (32×i4, 16×i8) with a per-family law

.claude/board/LATEST_STATE.md

@@ -1,3 +1,7 @@
+## 2026-10-08 — Register128 signed readings on branch `ccr-b2e415d9-4jfvyk-register-readings` (unmerged)
+
+- Contract delta (additive): `hotplug::SlabReading::{RegisterI4x32(law), RegisterI8x16(law)}` (tags 2..=7, `to_tag`), `Activation::{with_register_laws, register_law_for}`, `ResolvedReading::bind_signed_register(&activation, rails)`, `ActivationDrift::{NotSignedRegister, NoRegisterLawFor, RegisterLawMismatch}`; `register128::{RegisterCarving, RegisterLaw, SignedRegisterLanes, SignedRegisterRefusal}`; `atoms::I4x32::{from_bytes, as_bytes}`. No layout change. Entry: `entries/2026-10-08-register128-signed-readings.md`.
+
 ## 2026-10-08 — HHTL / NARS / Moore value tenants on branch `ccr-b2e415d9-4jfvyk-tenants` (unmerged)
 
 - Contract delta (additive): `ValueTenant::{Nars16x8 = 18, MoorePalettePairs = 19, MooreNars16 = 20}` at row [284,332), in `ValueSchema::Full` only; new module `contract::moore_tenant::{MooreSlot, MooreNars16, DirectionReading, DirectionRefusal, MooreRefusal, MooreTenantView, MooreTenantMut}`. BoardAggregates reservation re-based to 21. Entry: `entries/2026-10-08-hhtl-nars-moore-value-tenants.md`.

.claude/board/entries/2026-10-08-register128-signed-readings.md

@@ -0,0 +1,78 @@
+# 2026-10-08 — Register128 signed readings (32×i4, 16×i8) with a per-family law
+
+**Status:** CURRENT-CONTRACT, TEST-PINNED. Branch
+`ccr-b2e415d9-4jfvyk-register-readings`, commits `14831543` and `96304b88`
+(law authority, after Codex P2 on #1410).
+
+## What landed
+
+The carrier is unchanged: the `Register0` / `Register1` rails (16 B each), no
+classid in the payload, no layout change.
+
+- **Carving and recorded law, declared by the slab.**
+  `SlabReading::RegisterI4x32(law)` (32 × i4, dim `2k` = low nibble of byte
+  `k`, the `atoms::I4x32` layout) and `SlabReading::RegisterI8x16(law)` (16 ×
+  i8, dim `k` = byte `k`). Envelope tags 2..=7 (`to_tag` inverts `from_tag`).
+  The law is the one the writer actually wrote with.
+- **Concept law, declared by the authority.** `Activation::with_register_laws`
+  / `register_law_for` (fail-closed: `NoRegisterLawFor`).
+- **Binding checks agreement.** `ResolvedReading::bind_signed_register(&activation,
+  rails)` takes no law; it refuses `RegisterLawMismatch` when the slab's law and
+  the concept's differ. A writer and a reader of one population therefore hold
+  the same law. The returned `SignedRegisterLanes` carry concept, rails, carving
+  and law. `RegisterLaw::{RelativeOffset, AxisPosition, Support}`.
+- **Checked on every access.** `read_i4x32` / `read_i8x16` / `write_i4x32` /
+  `write_i8x16` take the law the caller expects and refuse, in order, an absent
+  rail, a different carving, a different law. An i4 outside `-8..=7` is refused,
+  never saturated. A refused write leaves the row unchanged.
+- **Separation from the unsigned reading.** `bind_register128` (4 × u32 words)
+  is unchanged and refuses the signed carvings; `bind_signed_register` refuses
+  `Register128`, `Facet96` and undeclared slabs.
+- **EpistemicState5 has no law here.** It stays on CE64 bits 59..63.
+
+## Inventory of the 24×i4 families on `main` (2026-10-08)
+
+| family | on `main` | law it would bind |
+|---|---|---|
+| Temporal / anaphora | `CausalWitness` tenant 14, Facet96 read as G24N4 (24 i4 window pointers). EXPERIMENTAL. The only resident 24×i4 lane. | `RelativeOffset` |
+| Evidence (Tarski) | Probe only: `probe_four_plane_causal_medium.rs` (G24N4 as support/falsifier). | `Support` |
+| Taxonomy axes | Fixture only: `entries/2026-10-04-coresearch-evidence-stance-dependence.md` (Mammal: `terrestrial`, `placental`). | `AxisPosition` |
+| Episodic basin | `EpisodicBasin` tenant 15: 32 B of references, not i4. | none (not a signed family) |
+| 32×i4 carrier | `atoms::I4x32`; now also the i4 carving's layout. | — |
+| 16×i8 | `ndarray` SIMD `I8x16` only. | — |
+
+`CausalWitness` is NOT moved onto a register by this change: it is a Facet96
+lane with its own classid, and re-homing it is a separate decision.
+
+## Tests and disable runs
+
+Hotplug: `signed_rails_need_a_signed_carving_and_an_agreeing_law`; tag test now
+accepts 2 and 3. Register128: round trip of every i4 value in every dim with the
+nibble layout pinned; i8 dim-k-is-byte-k; the same bytes differ under the two
+carvings; law mismatch (all 3×3 pairs, both carvings) refused and writes
+nothing; carving mismatch refused; out-of-range i4 in the last dim refused
+before writing; writes stay inside their rail.
+
+| disable | caught by |
+|---|---|
+| law check removed | `a_different_law_is_refused_and_writes_nothing` |
+| carving check removed | `a_different_carving_is_refused` |
+| rail check removed | `signed_writes_stay_inside_their_rail` |
+| i4 range check removed | `an_out_of_range_i4_is_refused_before_writing` |
+| binding accepts `Register128` as i4 | `signed_rails_need_a_signed_carving_and_an_agreeing_law` |
+| binding swaps the carvings | same |
+| binding skips the schema check | same |
+| law mismatch check removed | `signed_rails_need_a_signed_carving_and_an_agreeing_law` |
+| concept law ignored (slab law used) | same |
+| `to_tag` shifts the I8x16 tags | `an_unsupported_physical_reading_fails_closed` |
+| `from_tag` drops the law | same |
+
+## OPEN
+
+- No OGAR authority populates `with_register_laws` yet (`lance-graph-ogar`
+  builds its `Activation` without laws), so in production every concept still
+  refuses to bind signed registers. That is fail-closed, not a gap in the check.
+- Lane or reading per family is undecided until measured: 32×i4 vs 16×i8 on
+  KJV anaphora and the mammal fixture. The rule "outside the local window →
+  basin edge" is not changed by `RelativeOffset` under `I8x16`.
+- No production writer or reader.

.claude/board/entries/README.md

@@ -25,10 +25,11 @@ 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.
 
-270 entries, 2026-08-06 .. 2026-10-08.
+271 entries, 2026-08-06 .. 2026-10-08.
 
 | date | entry id | finding | file |
 |---|---|---|---|
+| 2026-10-08 | `register128-signed-readings` |  | [2026-10-08-register128-signed-readings.md](2026-10-08-register128-signed-readings.md) |
 | 2026-10-08 | `rbac-nested-scope-path` |  | [2026-10-08-rbac-nested-scope-path.md](2026-10-08-rbac-nested-scope-path.md) |
 | 2026-10-08 | `rbac-membership-scope` |  | [2026-10-08-rbac-membership-scope.md](2026-10-08-rbac-membership-scope.md) |
 | 2026-10-08 | `rbac-hotplug-socket` |  | [2026-10-08-rbac-hotplug-socket.md](2026-10-08-rbac-hotplug-socket.md) |

.claude/v3/soa_layout/tenants.md

@@ -57,7 +57,7 @@ Offsets are FULL-ROW; subtract 32 for slab-relative.
 | 14 | CausalWitness | U8 × 16 | 16 B | [204,220) | CausalWitness facet lane — 16 B content-blind V3 4+12 facet read as **G24N4** (24 signed i4 loci, a lane shape name, never a `CascadeShape` variant); each nibble is a context pointer (signed ±8 window offset), not a strength. Slots 16..24 reserved-zero. **Status: EXPERIMENTAL — not in the operator-locked §3 catalogue** (per its own doc-comment) |
 | 15 | EpisodicBasin | U8 × 32 | 32 B | [220,252) | **D-ACR-6 rail** — a promoted basin as REFERENCES: `subject` u16 · `member_count` u16 · `self_code` 12 B (Cam96 centroid) · `version_from`/`version_to` u64. Members are reached by following `(subject, [from,to))` into the triple stream, never inlined — the fat-concept guard `§3a` names. Width is NOT stored (recomputable through the references) |
 | 16 | Register0 | U8 × 16 | 16 B | [252,268) | **D-LXC-29** 128-bit working register, NO classid in the payload; read as `Register128` only when the slab declares `SlabReading::Register128` (`ResolvedReading::bind_register128` refuses otherwise). All-zero = empty accumulator |
-| 17 | Register1 | U8 × 16 | 16 B | [268,284) | Second independent `Register128` rail, same contract as Register0 |
+| 17 | Register1 | U8 × 16 | 16 B | [268,284) | Second independent `Register128` rail, same contract as Register0. Both rails can instead be declared signed: `SlabReading::RegisterI4x32(law)` / `RegisterI8x16(law)`, bound by `bind_signed_register`, which requires the slab's recorded `RegisterLaw` to equal the concept's (2026-10-08) |
 | 18 | Nars16x8 | U16 × 8 (LE) | 16 B | [284,300) | One `u16` per Moore slot (`NW,N,NE,W,E,SW,S,SE`). Layout RATIFIED; the `u16` reading is CANDIDATE and NOT declared by this tenant. Never shares bytes or a reading with MooreNars16 |
 | 19 | MoorePalettePairs | U8 × 16 | 16 B | [300,316) | One Palette256 `(u8:u8)` pair per Moore slot: byte `2i` = first operand, `2i+1` = second, addressing a 256×256 law as `(first << 8) \| second` (the #1336 `PairAddress` orientation). Two separate bytes, never one widened `u16` |
 | 20 | MooreNars16 | U16 × 8 (LE) | 16 B | [316,332) | One `MooreNars16` per Moore slot: `Pearl3 \| Energy4 \| Plasticity3 \| Polarity1 \| Epi5` (bits 0..2, 3..6, 7..9, 10, 11..15). Direction = `(slot, polarity)`, never the S/P/O sign triple (`DirectionReading::require_sign_triple` refuses it); one witness for all eight lanes, held by the owner, not in these bytes (`MooreTenantMut::lift_ce64` refuses mixed W). Epi5 24..31 reserved. Layout RATIFIED, semantics CANDIDATE |

crates/lance-graph-contract/src/atoms.rs

@@ -79,6 +79,19 @@ impl I4x32 {
     /// The all-zero style vector (every lane neutral).
     pub const ZERO: Self = Self { bytes: [0u8; 16] };
 
+    /// Wrap 16 already-packed bytes. No conversion: dim `2k` is the low
+    /// nibble of byte `k`, dim `2k+1` the high nibble.
+    #[must_use]
+    pub const fn from_bytes(bytes: [u8; 16]) -> Self {
+        Self { bytes }
+    }
+
+    /// The 16 packed bytes, in the layout [`from_bytes`](Self::from_bytes) takes.
+    #[must_use]
+    pub const fn as_bytes(&self) -> &[u8; 16] {
+        &self.bytes
+    }
+
     /// Pack 32 signed dims into the i4 CAM carrier, saturating to `[−8, 7]`.
     ///
     /// The carrier is a **sparse, deterministic 32×CAM address** (128-bit) — the non-zero