@@ -222,6 +222,28 @@ describe("mapColumnType — field.uuid (R6 Plan 2a)", () => {
     const spec = mapColumnType(metaField(FIELD_SUBTYPE_UUID, "id"), "sqlite");
     expect(spec.fnName).toBe("text");
   });
+
+  // Native arrays are DERIVED from isArray (dbColumnType slim-and-derive Phase 1):
+  // no @dbColumnType:uuid_array / text_array escape hatch — the array-ness lives on
+  // the field's isArray axis.
+  test("Postgres: field.uuid isArray → uuid() + .array() (= uuid[])", () => {
+    const f = metaField(FIELD_SUBTYPE_UUID, "memberIds");
+    f.setIsArray(true);
+    const spec = mapColumnType(f, "postgres");
+    expect(spec.fnName).toBe("uuid");
+    expect(spec.modifiers).toContain(".array()");
+    // Drizzle's native .array() is already element-typed — no $type needed.
+    expect(spec.dollarTypeRef).toBeUndefined();
+  });
+
+  test("Postgres: field.string isArray → text() + .array() (= text[])", () => {
+    const f = metaField(FIELD_SUBTYPE_STRING, "tags");
+    f.setIsArray(true);
+    const spec = mapColumnType(f, "postgres");
+    expect(spec.fnName).toBe("text");
+    expect(spec.modifiers).toContain(".array()");
+    expect(spec.dollarTypeRef).toBeUndefined();
+  });
 });
 
 describe("mapColumnType — @dbColumnType physical override (R6 Plan 2b)", () => {
 
@@ -40,18 +40,30 @@ export const DB_COLUMN_TYPE_UUID = "uuid";
 export const DB_COLUMN_TYPE_JSONB = "jsonb";
 /** `@dbColumnType: timestamp_with_tz` — `timestamp with time zone` (legal on field.timestamp). */
 export const DB_COLUMN_TYPE_TIMESTAMP_WITH_TZ = "timestamp_with_tz";
-/** `@dbColumnType: uuid_array` — native Postgres `uuid[]` column (legal on field.string). */
+/**
+ * `@dbColumnType: uuid_array` — RETIRED (dbColumnType slim-and-derive Phase 1).
+ * Native `uuid[]` is now DERIVED from `field.uuid` + `isArray`, not declared via an
+ * escape hatch. The constant is retained (so any remaining reference still resolves)
+ * but is no longer a legal value — the loader rejects it (ERR_BAD_ATTR_VALUE).
+ */
 export const DB_COLUMN_TYPE_UUID_ARRAY = "uuid_array";
-/** `@dbColumnType: text_array` — native Postgres `text[]` column (legal on field.string). */
+/**
+ * `@dbColumnType: text_array` — RETIRED (dbColumnType slim-and-derive Phase 1).
+ * Native `text[]` is now DERIVED from `field.string` + `isArray`. Retained constant,
+ * no longer a legal value (loader rejects → ERR_BAD_ATTR_VALUE).
+ */
 export const DB_COLUMN_TYPE_TEXT_ARRAY = "text_array";
 
-/** The closed set of legal `@dbColumnType` values (raw-dialect passthrough deferred). */
+/**
+ * The closed set of legal `@dbColumnType` values (raw-dialect passthrough deferred).
+ * dbColumnType slim-and-derive Phase 1: `uuid_array`/`text_array` are removed — native
+ * arrays are derived from `isArray`. `timestamp_with_tz` stays in Phase 1 (its default
+ * flip is Phase 2).
+ */
 export const DB_COLUMN_TYPE_VALUES = [
   DB_COLUMN_TYPE_UUID,
   DB_COLUMN_TYPE_JSONB,
   DB_COLUMN_TYPE_TIMESTAMP_WITH_TZ,
-  DB_COLUMN_TYPE_UUID_ARRAY,
-  DB_COLUMN_TYPE_TEXT_ARRAY,
 ] as const;
 export type DbColumnTypeValue = (typeof DB_COLUMN_TYPE_VALUES)[number];
 
@@ -65,6 +77,4 @@ export const DB_COLUMN_TYPE_LEGAL_SUBTYPES: Readonly<Record<DbColumnTypeValue, r
   [DB_COLUMN_TYPE_UUID]: [FIELD_SUBTYPE_STRING],
   [DB_COLUMN_TYPE_JSONB]: [FIELD_SUBTYPE_STRING],
   [DB_COLUMN_TYPE_TIMESTAMP_WITH_TZ]: [FIELD_SUBTYPE_TIMESTAMP],
-  [DB_COLUMN_TYPE_UUID_ARRAY]: [FIELD_SUBTYPE_STRING],
-  [DB_COLUMN_TYPE_TEXT_ARRAY]: [FIELD_SUBTYPE_STRING],
 } as const;
@@ -574,6 +574,21 @@ describe("attr-schema validation — @dbColumnType (subtype × value) pairing (R
     expect(bad[0]!.message).toContain("tsvector");
   });
 
+  // dbColumnType slim-and-derive Phase 1: the array values are REMOVED — native
+  // text[]/uuid[] are derived from `isArray` on field.string/field.uuid, never
+  // declared via an escape hatch. Both now fail the loader.
+  it.each(["uuid_array", "text_array"])(
+    "rejects removed @dbColumnType:%s → ERR_BAD_ATTR_VALUE (derive from isArray instead)",
+    async (removed) => {
+      const { errors } = await load(
+        entityWith({ "field.string": { name: "members", "@dbColumnType": removed } }),
+      );
+      const bad = errors.filter((e) => (e as { code?: string }).code === "ERR_BAD_ATTR_VALUE");
+      expect(bad).toHaveLength(1);
+      expect(bad[0]!.message).toContain(removed);
+    },
+  );
+
   it("does NOT re-flag a concrete field that inherits @dbColumnType from an abstract super (own-only check)", async () => {
     // The (subtype × value) pairing check is own-only (reads node.ownAttrs()):
     // the attr is validated on the declaring (abstract) node, so a concrete field
 
@@ -48,8 +48,6 @@ import {
   DB_COLUMN_TYPE_UUID,
   DB_COLUMN_TYPE_JSONB,
   DB_COLUMN_TYPE_TIMESTAMP_WITH_TZ,
-  DB_COLUMN_TYPE_UUID_ARRAY,
-  DB_COLUMN_TYPE_TEXT_ARRAY,
   STORAGE_FLATTENED,
   DOC_ATTR_DESCRIPTION,
   applyColumnNamingStrategy, DEFAULT_COLUMN_NAMING_STRATEGY,
@@ -708,21 +706,49 @@ function buildColumn(
   return col;
 }
 
+/**
+ * The native Postgres array ELEMENT SqlType for an `isArray` scalar field, or
+ * undefined when the subtype has no native-array form (object/map → single jsonb
+ * column; everything else falls through to the scalar subtype default).
+ *
+ * dbColumnType slim-and-derive Phase 1 wires the two derived cases the design calls
+ * out: `field.string` → `text[]`, `field.uuid` → `uuid[]`. This mirrors codegen-ts's
+ * column-mapper, which emits native `.array()` for the same scalar subtypes.
+ */
+function arrayElementSqlType(field: MetaData): SqlType | undefined {
+  switch (field.subType) {
+    case FIELD_SUBTYPE_STRING: return { kind: "text" };
+    case FIELD_SUBTYPE_UUID:   return { kind: "uuid" };
+    default:                   return undefined;
+  }
+}
+
 function subtypeToSqlType(field: MetaData): SqlType {
   // R6 Plan 2b: a physical @dbColumnType override selects the DB column type
   // instead of the subtype default (the loader has already validated the
   // (subtype × value) pairing, so an unrecognized value never reaches here).
+  // dbColumnType slim-and-derive Phase 1: the array overrides (uuid_array /
+  // text_array) are RETIRED — native text[]/uuid[] are derived from `isArray`
+  // below, not declared here.
   const dbColumnType = field.ownAttr(FIELD_ATTR_DB_COLUMN_TYPE);
   if (typeof dbColumnType === "string") {
     switch (dbColumnType) {
       case DB_COLUMN_TYPE_UUID:              return { kind: "uuid" };
       case DB_COLUMN_TYPE_JSONB:             return { kind: "json" };
       case DB_COLUMN_TYPE_TIMESTAMP_WITH_TZ: return { kind: "timestamp", withTimezone: true };
-      case DB_COLUMN_TYPE_UUID_ARRAY:        return { kind: "array", element: { kind: "uuid" } };
-      case DB_COLUMN_TYPE_TEXT_ARRAY:        return { kind: "array", element: { kind: "text" } };
     }
   }
 
+  // Native array columns are DERIVED from `isArray` (dbColumnType slim-and-derive
+  // Phase 1). Only scalar subtypes with a stable element SqlType get a native
+  // Postgres array (e.g. field.string → text[], field.uuid → uuid[]). field.object
+  // / field.map carry their array-ness inside a single jsonb column (no native
+  // array — handled by the subtype switch returning { kind: "json" }).
+  if (field.isArray) {
+    const element = arrayElementSqlType(field);
+    if (element !== undefined) return { kind: "array", element };
+  }
+
   const subType = field.subType;
   switch (subType) {
     case FIELD_SUBTYPE_STRING:    {
 
@@ -148,19 +148,20 @@ describe("buildExpectedSchema — @autoSet timestamp default", () => {
 });
 
 // ---------------------------------------------------------------------------
-// @dbColumnType uuid_array / text_array → native SQL array columns
-// (metaobjects can't model Postgres arrays via field subtypes; the physical
-// @dbColumnType escape hatch carries them, emitting uuid[] / text[].)
+// Native SQL array columns are DERIVED from `isArray` (dbColumnType slim-and-derive
+// Phase 1): the array-ness already lives on the field's `isArray` axis, so the DDL
+// derives `text[]` / `uuid[]` directly — no `@dbColumnType` escape hatch. The
+// removed `uuid_array` / `text_array` values now fail the loader (ERR_BAD_ATTR_VALUE).
 // ---------------------------------------------------------------------------
 
-describe("buildExpectedSchema — native array columns (@dbColumnType *_array)", () => {
+describe("buildExpectedSchema — native array columns (derived from isArray)", () => {
   async function arrayCols() {
     const doc = { "metadata.root": { package: "acme", children: [
       { "object.entity": { name: "Bag", children: [
         { "field.long": { name: "id" } },
         { "identity.primary": { "name": "id", "@fields": "id" } },
-        { "field.string": { name: "memberIds", "@dbColumnType": "uuid_array" } },
-        { "field.string": { name: "tags", "@dbColumnType": "text_array" } },
+        { "field.uuid": { name: "memberIds", isArray: true } },
+        { "field.string": { name: "tags", isArray: true } },
       ] } },
     ] } };
     const { root, errors } = await new MetaDataLoader().load([
@@ -170,11 +171,45 @@ describe("buildExpectedSchema — native array columns (@dbColumnType *_array)",
     return new Map((buildExpectedSchema(root).tables[0]?.columns ?? []).map((c) => [c.name, c]));
   }
 
-  test("uuid_array → array of uuid; text_array → array of text", async () => {
+  test("field.uuid isArray → uuid[]; field.string isArray → text[]", async () => {
     const byName = await arrayCols();
     expect(byName.get("member_ids")?.sqlType).toEqual({ kind: "array", element: { kind: "uuid" } });
     expect(byName.get("tags")?.sqlType).toEqual({ kind: "array", element: { kind: "text" } });
   });
+
+  test("field.uuid scalar → uuid; field.string scalar (no maxLength) → text", async () => {
+    const doc = { "metadata.root": { package: "acme", children: [
+      { "object.entity": { name: "Scalars", children: [
+        { "field.long": { name: "id" } },
+        { "identity.primary": { "name": "id", "@fields": "id" } },
+        { "field.uuid": { name: "ownerId" } },
+        { "field.string": { name: "label" } },
+      ] } },
+    ] } };
+    const { root, errors } = await new MetaDataLoader().load([
+      new InMemoryStringSource(JSON.stringify(doc)),
+    ]);
+    expect(errors).toHaveLength(0);
+    const byName = new Map((buildExpectedSchema(root).tables[0]?.columns ?? []).map((c) => [c.name, c]));
+    expect(byName.get("owner_id")?.sqlType).toEqual({ kind: "uuid" });
+    expect(byName.get("label")?.sqlType).toEqual({ kind: "text" });
+  });
+
+  test("removed @dbColumnType:uuid_array / text_array now fail the loader (ERR_BAD_ATTR_VALUE)", async () => {
+    for (const removed of ["uuid_array", "text_array"]) {
+      const doc = { "metadata.root": { package: "acme", children: [
+        { "object.entity": { name: "Bag", children: [
+          { "field.long": { name: "id" } },
+          { "identity.primary": { "name": "id", "@fields": "id" } },
+          { "field.string": { name: "x", "@dbColumnType": removed } },
+        ] } },
+      ] } };
+      const { errors } = await new MetaDataLoader().load([
+        new InMemoryStringSource(JSON.stringify(doc)),
+      ]);
+      expect(errors.some((e) => (e as { code?: string }).code === "ERR_BAD_ATTR_VALUE")).toBe(true);
+    }
+  });
 });
 
 describe("buildExpectedSchema — indexes + FKs", () => {