diff --git a/_primitives/_rust/Cargo.lock b/_primitives/_rust/Cargo.lock
index bf44e3d..1a6b205 100644
--- a/_primitives/_rust/Cargo.lock
+++ b/_primitives/_rust/Cargo.lock
@@ -1978,6 +1978,7 @@ dependencies = [
  "anyhow",
  "chrono",
  "clap",
+ "kei-entity-store",
  "rusqlite",
  "serde",
  "serde_json",
diff --git a/_primitives/_rust/kei-crossdomain/Cargo.toml b/_primitives/_rust/kei-crossdomain/Cargo.toml
index 88e5194..56b1c67 100644
--- a/_primitives/_rust/kei-crossdomain/Cargo.toml
+++ b/_primitives/_rust/kei-crossdomain/Cargo.toml
@@ -14,6 +14,7 @@ name = "kei_crossdomain"
 path = "src/lib.rs"
 
 [dependencies]
+kei-entity-store = { path = "../kei-entity-store" }
 rusqlite = { version = "0.31", features = ["bundled"] }
 clap = { version = "4", features = ["derive"] }
 serde = { version = "1", features = ["derive"] }
diff --git a/_primitives/_rust/kei-crossdomain/src/schema.rs b/_primitives/_rust/kei-crossdomain/src/schema.rs
index 796874f..056e939 100644
--- a/_primitives/_rust/kei-crossdomain/src/schema.rs
+++ b/_primitives/_rust/kei-crossdomain/src/schema.rs
@@ -1,7 +1,42 @@
+//! kei-crossdomain EntitySchema — declarative spec consumed by
+//! `kei_entity_store::Store` for migrations + user_version pragma.
+//!
+//! **Architectural note (2026-04-23 migration to Layer-A engine):**
+//! kei-crossdomain is an edges-only graph store — URIs (`domain://path`)
+//! are the only identifiers; there is no primary "node" entity row. The
+//! engine's `EntitySchema` contract requires exactly one `IntegerPk`
+//! field, so we declare a minimal synthetic `cross_nodes` table purely
+//! to satisfy the DDL contract. No code writes to this table; every
+//! query still runs against `cross_edges`.
+//!
+//! **Why `edge_table: None` instead of `Some("cross_edges")` + TextPair:**
+//! the engine's TextPair edge DDL is `(src_path, dst_path, edge_type)`
+//! with `PRIMARY KEY(src_path, dst_path, edge_type)` — **incompatible**
+//! with the existing `cross_edges` schema, which carries five extra
+//! columns (`id INTEGER PRIMARY KEY`, `weight`, `evidence`, `metadata`,
+//! `created_at`) and uses column names `from_uri` / `to_uri`. Adopting
+//! engine's TextPair would destroy the `CrossEdge` type, the
+//! `link()` rowid return, and backward compatibility with existing
+//! on-disk DBs. Instead we follow the kei-task pattern: ride the engine
+//! for connection lifecycle + `PRAGMA user_version` + migration
+//! orchestration, keep the rich edge DDL in `custom_migrations`.
+//!
+//! Constructive path (not pursued here, would require destructive
+//! rewrite): extend `kei-entity-store` with a richer TextPair variant
+//! that preserves extra columns via schema fields, OR migrate
+//! kei-crossdomain callers to drop the id/weight/evidence/metadata
+//! fields. Both are multi-file changes outside this crate's scope.
+
+use kei_entity_store::schema::{EdgeKeyKind, EntitySchema, FieldDef};
 use rusqlite::{Connection, Result};
 
-pub fn create_schema(conn: &Connection) -> Result<()> {
-    conn.execute_batch(r#"
+/// Synthetic primary table — exists solely to satisfy the engine's
+/// `IntegerPk` requirement. Not used by any verb or caller.
+static FIELDS: &[FieldDef] = &[FieldDef::pk("id")];
+
+/// Byte-identical to the pre-migration `cross_edges` DDL (plus the
+/// three indexes that used to live in the same `execute_batch`).
+const DDL_CROSS_EDGES: &str = r#"
     CREATE TABLE IF NOT EXISTS cross_edges (
         id         INTEGER PRIMARY KEY,
         from_uri   TEXT NOT NULL,
@@ -16,6 +51,32 @@ pub fn create_schema(conn: &Connection) -> Result<()> {
     CREATE INDEX IF NOT EXISTS idx_ce_from ON cross_edges(from_uri);
     CREATE INDEX IF NOT EXISTS idx_ce_to   ON cross_edges(to_uri);
     CREATE INDEX IF NOT EXISTS idx_ce_type ON cross_edges(edge_type);
-    "#)?;
+"#;
+
+pub static CROSSDOMAIN_SCHEMA: EntitySchema = EntitySchema {
+    name: "crossdomain",
+    table: "cross_nodes",
+    fields: FIELDS,
+    // Empty verb set: every kei-crossdomain op is bespoke (TextPair with
+    // extra columns — engine verbs can't dispatch them). Link/unlink/
+    // query/BFS/auto-link/stats all live in `edges.rs`, `bfs.rs`,
+    // `auto_link.rs`.
+    enabled_verbs: &[],
+    fts_columns: None,
+    // `None`: engine skips edge DDL. `cross_edges` is created via
+    // `custom_migrations` with byte-identical legacy DDL.
+    edge_table: None,
+    // Documentation hint only (inert while `edge_table = None`).
+    edge_key_kind: EdgeKeyKind::TextPair,
+    archived_field: None,
+    custom_migrations: &[DDL_CROSS_EDGES],
+};
+
+/// Kept for backward compatibility with any external caller that
+/// imported `schema::create_schema` directly. New code should open via
+/// `Store::open` / `Store::open_memory`, which invokes the engine's
+/// migration runner with `CROSSDOMAIN_SCHEMA`.
+pub fn create_schema(conn: &Connection) -> Result<()> {
+    conn.execute_batch(DDL_CROSS_EDGES)?;
     Ok(())
 }
diff --git a/_primitives/_rust/kei-crossdomain/src/store.rs b/_primitives/_rust/kei-crossdomain/src/store.rs
index af862a3..251e552 100644
--- a/_primitives/_rust/kei-crossdomain/src/store.rs
+++ b/_primitives/_rust/kei-crossdomain/src/store.rs
@@ -1,28 +1,38 @@
-use crate::schema::create_schema;
-use anyhow::{Context, Result};
+//! Crossdomain store — thin shim over `kei_entity_store::Store`.
+//!
+//! Layer-A convergence (2026-04-23): connection lifecycle + migrations +
+//! `PRAGMA user_version` stamping now ride the shared engine via
+//! `CROSSDOMAIN_SCHEMA`. Public surface preserved byte-for-byte so
+//! `edges.rs`, `bfs.rs`, `auto_link.rs`, and integration tests compile
+//! unchanged.
+//!
+//! Generic CRUD verbs are NOT wired here — kei-crossdomain is an
+//! edges-only store with bespoke TextPair+extras columns; see
+//! `schema.rs` for the architectural note on why engine's `link`/`rank`
+//! verbs cannot serve this crate without a destructive schema rewrite.
+
+use crate::schema::CROSSDOMAIN_SCHEMA;
+use anyhow::Result;
+use kei_entity_store::Store as EntityStore;
 use rusqlite::Connection;
 use std::path::Path;
 
 pub struct Store {
-    conn: Connection,
+    inner: EntityStore,
 }
 
 impl Store {
     pub fn open(path: &Path) -> Result<Self> {
-        if let Some(parent) = path.parent() {
-            let _ = std::fs::create_dir_all(parent);
-        }
-        let conn = Connection::open(path).context("open sqlite")?;
-        conn.pragma_update(None, "journal_mode", "WAL").ok();
-        create_schema(&conn)?;
-        Ok(Self { conn })
+        let inner = EntityStore::open(path, &CROSSDOMAIN_SCHEMA)?;
+        Ok(Self { inner })
     }
 
     pub fn open_memory() -> Result<Self> {
-        let conn = Connection::open_in_memory()?;
-        create_schema(&conn)?;
-        Ok(Self { conn })
+        let inner = EntityStore::open_memory(&CROSSDOMAIN_SCHEMA)?;
+        Ok(Self { inner })
     }
 
-    pub fn conn(&self) -> &Connection { &self.conn }
+    pub fn conn(&self) -> &Connection {
+        self.inner.conn()
+    }
 }