docs(mailbox): MailboxSoA becomes per-mailbox thoughtspace; BindSpace-singleton→SoA migration spec

Document the dissolution of the shared Arc<BindSpace> singleton into
per-mailbox MailboxSoA<N> ephemeral thoughtspace (the BindSpace surrogate,
NOT a per-mailbox copy of a singleton):

- plan: bindspace-singleton-to-mailbox-soa-v1 — singleton inventory
  (driver.rs:56 / serve.rs:29 / engine_bridge.rs), column-by-column
  migration map (drop the 64 KB Vsa16kF32 cycle plane; own
  edges/qualia/meta/entity_type; reference content via CAM-PQ; keep
  ontology a shared Arc), cradle-to-grave lifecycle, 5 gated steps,
  preserved invariants (E-CE64-MB-4 ownership=compile-time no-alias,
  E-BATON-1, I-VSA-IDENTITIES, I-LEGACY-API-FEATURE-GATED), 4 open questions
- EPIPHANIES: E-MAILBOX-IS-BINDSPACE design ruling
- INTEGRATION_PLANS + STATUS_BOARD: D-MBX-1..5 deliverables (Queued, gated
  on D-CE64-MB-1-impl + PR-NDARRAY-MIRI-COMPLETE)
- mailbox_soa.rs: module doc-note pointing to the migration plan

Design/spec only; no behavioral code change.

https://claude.ai/code/session_017GFLBnDy23AWBqvkbHHC41

Author: claude

.claude/board/EPIPHANIES.md

@@ -1,3 +1,21 @@
+## 2026-05-27 — E-MAILBOX-IS-BINDSPACE — the singleton `Arc<BindSpace>` dissolves *onto* mailboxes: `MailboxSoA<N>` *becomes* the per-mailbox ephemeral thoughtspace (BindSpace surrogate), it is NOT copied per mailbox
+
+**Status:** CONJECTURE / design-ruling (migration spec authored this session; NOT yet implemented). Extends `E-BATON-1` + `E-CE64-MB-4` downward into the column layout. Plan: `.claude/plans/bindspace-singleton-to-mailbox-soa-v1.md`.
+
+**The correction:** the ask began as *"MailboxSoA has an individual **copy** of the BindSpace."* That is still a singleton (N synchronized copies = the aliasing problem `E-CE64-MB-4` kills). The ruling: **there is no global address space to copy.** `MailboxSoA<N>` *is* the BindSpace for the life of one think-arc — each mailbox **owns** its per-row SoA columns (born in the mailbox, die with it), and the shared singleton `Arc<BindSpace>` is **dissolved**, not sharded.
+
+**Current singleton (to migrate):** `crates/cognitive-shader-driver` — `ShaderDriver.bindspace: Arc<BindSpace>` (`driver.rs:56`); one `Arc::new(BindSpace::zeros(4096))` in `bin/serve.rs:29`; per-row read/write surface in `engine_bridge.rs`. `BindSpace` (`bindspace.rs:234`) carries a **64 KB/row `Vsa16kF32` `cycle` plane** (`FLOATS_PER_VSA=16384`) — 256 MB across the 4096-row singleton.
+
+**Column migration (full map in the plan §3):** `cycle` `Vsa16kF32` plane → **DROP** (ephemeral local compute, never a column — `E-BATON-1`); `content/topic/angle` dense planes → **reference** (CAM-PQ code ≤6 B), not own (`I-VSA-IDENTITIES`); `edges`(`CausalEdge64`)/`qualia`(i4-16D)/`meta`(u32)/`entity_type`(u16) → **own** in `MailboxSoA`; `temporal`/`expert` → fold into `CausalEdge64`/mailbox identity (OQ-2); **`ontology: Arc<OntologyRegistry>` STAYS shared** (cold Zone-2, read-only). Per-row hot footprint drops ~71.6 KB → ~24–30 B.
+
+**Why it's safe:** mailbox *moves* batons in (`apply_edges`) and *moves* emissions out (`CollapseGateEmission`), so the borrow checker proves no shared-mutable aliasing of the thoughtspace — the guarantee the `Arc<BindSpace>`+`CollapseGate` "read-only by convention" only enforced by discipline becomes a **compile error** (`E-CE64-MB-4`).
+
+**Gated staging (plan §6):** S1 add columns behind `mailbox-thoughtspace` feature → S2 move `engine_bridge` surface onto mailbox rows → S3 driver holds a sea-star of mailboxes (kill the 4096 singleton in `serve.rs`) → S4 death→SPO+Lance tombstone-witness → S5 delete `BindSpace`+`cycle` plane. Gated on `D-CE64-MB-1-impl` (par-tile) + `PR-NDARRAY-MIRI-COMPLETE`; S5 blocked on the CLAUDE.md "The Click" / `Vsa16kF32` doctrinal update (OQ-4, already flagged in `surreal/RECONCILIATION`).
+
+**Cross-ref:** `E-BATON-1`, `E-CE64-MB-4`, `E-LADDER-SERVES-MAILBOX` (§6 tombstone-witness), `I-VSA-IDENTITIES`, `I-LEGACY-API-FEATURE-GATED` (feature-gate the v1 accessors during S1–S4), `causaledge64-mailbox-rename-soa-v1` (§5 MailboxSoA), `cognitive-substrate-convergence-v1` (D-CSV-7 shipped accumulator).
+
+---
+
 ## 2026-05-27 — E-CONTRACT-NO-SERIALIZE-2 — correction to E-CONTRACT-NO-SERIALIZE (below): the audit event never leaves the inside; "serialize at the membrane" was the wrong half — audit is not membrane traffic at all
 
 **Status:** FINDING (sharpens the entry directly below; user correction via the question "why should the audit event go outside?"). The §1 half of the prior entry — *contracts compile types, never serialize; build-time serde codegen is fine* — stands. This entry replaces its "outer membrane's job" framing (board is append-only, so the prior entry is left intact and corrected here).

.claude/board/INTEGRATION_PLANS.md

@@ -1,3 +1,12 @@
+## 2026-05-27 — bindspace-singleton-to-mailbox-soa-v1 (dissolve the shared `Arc<BindSpace>` into per-mailbox `MailboxSoA<N>` ephemeral thoughtspace)
+
+**Status:** PROPOSAL / design (migration spec; NOT yet implemented). **Plan file:** `.claude/plans/bindspace-singleton-to-mailbox-soa-v1.md`. **Epiphany:** `E-MAILBOX-IS-BINDSPACE`.
+**Scope:** `MailboxSoA<N>` *becomes* the per-mailbox, mailbox-owned, ephemeral "thoughtspace" — the BindSpace surrogate. The singleton `ShaderDriver.bindspace: Arc<BindSpace>` (`cognitive-shader-driver/src/driver.rs:56`; one `BindSpace::zeros(4096)` in `bin/serve.rs:29`) is **dissolved**, not copied. Column map: drop the 64 KB `Vsa16kF32` `cycle` plane; own `edges`/`qualia`/`meta`/`entity_type` in the mailbox; reference content via CAM-PQ; keep `ontology` a shared `Arc`.
+**Deliverables:** D-MBX-1 add migrated columns to `MailboxSoA<N>` (feature-gated) · D-MBX-2 move `engine_bridge` per-row surface onto mailbox rows · D-MBX-3 driver holds sea-star of mailboxes (kill the singleton) · D-MBX-4 death→SPO+Lance tombstone-witness · D-MBX-5 delete `BindSpace`+`cycle` plane.
+**Gates:** `D-CE64-MB-1-impl` (par-tile) + `PR-NDARRAY-MIRI-COMPLETE` first; D-MBX-5 blocked on the CLAUDE.md "The Click"/`Vsa16kF32` doctrinal update (OQ-4).
+**Invariants:** `E-CE64-MB-4` (ownership = compile-time no-alias) · `E-BATON-1` (LE baton is the only cross-boundary state) · `I-VSA-IDENTITIES` (reference content, don't copy planes) · `I-LEGACY-API-FEATURE-GATED` (feature-gate v1 `BindSpace` accessors during S1–S4) · no double-mailbox (sync inner / ractor outer).
+
+---
 ## 2026-05-27 — odoo-savant-reasoners-v1 (lance-graph side of the Odoo richness harvest: 2 new OGIT families + Layer-2 axioms + StyleCluster wiring + 5 Reasoner impls)
 
 **Status:** PROPOSAL (picks up the cross-repo handover boundary in `.claude/odoo/SAVANTS.md` §"lance-graph handover boundary"). woa-rs defined the 25-Savant roster + delegation tuples; lance-graph implements (a) Reasoner impls, (b) 2 new families + Layer-2 alignment axioms for the `None` classes, (c) StyleCluster wiring.

.claude/board/STATUS_BOARD.md

@@ -514,6 +514,20 @@ hot/cold/feedback loop onto our contract types + SoA floor
 
 ---
 
+## bindspace-singleton-to-mailbox-soa-v1 — dissolve `Arc<BindSpace>` into per-mailbox `MailboxSoA<N>`
+
+Plan path: `.claude/plans/bindspace-singleton-to-mailbox-soa-v1.md`. Epiphany `E-MAILBOX-IS-BINDSPACE`. Migration of the shared singleton address space into mailbox-owned ephemeral thoughtspace (LE-contract SoA columns); drops the 64 KB `Vsa16kF32` `cycle` plane.
+
+| D-id | Title | Crate(s) | ~LOC | Risk | Status | PR / Evidence |
+|---|---|---|---|---|---|---|
+| D-MBX-1 | add migrated columns (`edges`/`qualia`/`meta`/`entity_type`) to `MailboxSoA<N>` behind `mailbox-thoughtspace` feature | cognitive-shader-driver | 120 | MED | **Queued** | gated on D-CE64-MB-1-impl + PR-NDARRAY-MIRI-COMPLETE |
+| D-MBX-2 | move `engine_bridge` per-row read/write surface onto mailbox rows; `cycle` plane becomes a transient local | cognitive-shader-driver | 180 | MED | **Queued** | blocked on D-MBX-1 + OQ-1 (content-ref shape) |
+| D-MBX-3 | `ShaderDriver` holds a sea-star of mailboxes; kill the `BindSpace::zeros(4096)` singleton in `serve.rs` | cognitive-shader-driver | 160 | HIGH | **Queued** | blocked on D-MBX-2 + OQ-2 (temporal/expert fold) |
+| D-MBX-4 | death → SPO-G quad + Lance tombstone-witness (link-integrity back-pointer) | cognitive-shader-driver + Lance | 200 | HIGH | **Queued** | blocked on D-MBX-3 + Zone-2 persistence |
+| D-MBX-5 | delete `BindSpace` singleton + `Vsa16kF32` `cycle` plane; remove feature gate | cognitive-shader-driver | 80 | MED | **Queued** | blocked on D-MBX-4 + OQ-4 (CLAUDE.md "The Click" doctrinal update) |
+
+---
+
 ## Update protocol
 
 When a deliverable ships: