diff --git a/packages/core/core/src/services/document-service/transform/__tests__/map-relation.test.ts b/packages/core/core/src/services/document-service/transform/__tests__/map-relation.test.ts
index 2dfd967c60..e1dac5e9a0 100644
--- a/packages/core/core/src/services/document-service/transform/__tests__/map-relation.test.ts
+++ b/packages/core/core/src/services/document-service/transform/__tests__/map-relation.test.ts
@@ -1,4 +1,4 @@
-import { mapRelation } from '../relations/utils/map-relation';
+import { mapRelation, traverseEntityRelations } from '../relations/utils/map-relation';
 
 const mapper = mapRelation(async (relation) => {
   if (!relation) return 'default';
@@ -114,3 +114,55 @@ describe('map relation', () => {
     expect(await mapper(relation)).toBe(expectedRelation);
   });
 });
+
+describe('traverseEntityRelations', () => {
+  const CATEGORY_UID = 'api::category.category';
+
+  const schema = {
+    uid: 'api::article.article',
+    modelType: 'contentType' as const,
+    attributes: {
+      // morphToOne — visitor must be skipped (inline columns, not a join table)
+      related: { type: 'relation' as const, relation: 'morphToOne' as const },
+      // regular relation — visitor must be called
+      category: {
+        type: 'relation' as const,
+        relation: 'manyToOne' as const,
+        target: CATEGORY_UID,
+      },
+    },
+  };
+
+  const options = {
+    schema,
+    getModel: jest.fn().mockReturnValue(null),
+  };
+
+  it('does not call visitor for morphToOne relations', async () => {
+    const visitor = jest.fn();
+    // null value prevents traverseEntity from recursing into the attribute
+    await traverseEntityRelations(visitor, options, { related: null });
+    expect(visitor).not.toHaveBeenCalled();
+  });
+
+  it('calls visitor for regular relation attributes', async () => {
+    const visitor = jest.fn();
+    await traverseEntityRelations(visitor, options, { category: null });
+    expect(visitor).toHaveBeenCalledTimes(1);
+    expect(visitor).toHaveBeenCalledWith(
+      expect.objectContaining({ key: 'category' }),
+      expect.anything()
+    );
+  });
+
+  it('skips morphToOne but processes other relations in the same entity', async () => {
+    const visitor = jest.fn();
+    await traverseEntityRelations(visitor, options, { related: null, category: null });
+    // only 'category' should trigger the visitor — 'related' (morphToOne) is skipped
+    expect(visitor).toHaveBeenCalledTimes(1);
+    expect(visitor).toHaveBeenCalledWith(
+      expect.objectContaining({ key: 'category' }),
+      expect.anything()
+    );
+  });
+});
diff --git a/packages/core/core/src/services/document-service/utils/__tests__/populate.test.ts b/packages/core/core/src/services/document-service/utils/__tests__/populate.test.ts
new file mode 100644
index 0000000000..9e6539db4e
--- /dev/null
+++ b/packages/core/core/src/services/document-service/utils/__tests__/populate.test.ts
@@ -0,0 +1,62 @@
+import type { Internal } from '@strapi/types';
+
+import { getDeepPopulate } from '../populate';
+
+const ARTICLE_UID = 'api::article.article' as Internal.UID.ContentType;
+const CATEGORY_UID = 'api::category.category' as Internal.UID.ContentType;
+
+const articleModel = {
+  uid: ARTICLE_UID,
+  modelType: 'contentType' as const,
+  kind: 'collectionType' as const,
+  info: { displayName: 'Article', singularName: 'article', pluralName: 'articles' },
+  options: { draftAndPublish: true },
+  attributes: {
+    title: { type: 'string' as const },
+    // Polymorphic relations that can point to any content type
+    related: { type: 'relation' as const, relation: 'morphToOne' as const },
+    relatedMany: { type: 'relation' as const, relation: 'morphToMany' as const },
+    // Regular relation with a fixed target
+    category: {
+      type: 'relation' as const,
+      relation: 'manyToOne' as const,
+      target: CATEGORY_UID,
+    },
+    // Virtual relation not managed by the DB layer — must be excluded
+    virtualRel: {
+      type: 'relation' as const,
+      relation: 'oneToMany' as const,
+      target: CATEGORY_UID,
+      unstable_virtual: true,
+    },
+  },
+};
+
+describe('getDeepPopulate', () => {
+  let result: Record<string, unknown>;
+
+  beforeAll(() => {
+    global.strapi = { getModel: () => articleModel } as any;
+    result = getDeepPopulate(ARTICLE_UID);
+  });
+
+  it('includes morphToOne relations', () => {
+    expect(result).toHaveProperty('related');
+  });
+
+  it('includes morphToMany relations', () => {
+    expect(result).toHaveProperty('relatedMany');
+  });
+
+  it('includes regular relations', () => {
+    expect(result).toHaveProperty('category');
+  });
+
+  it('excludes unstable_virtual relations', () => {
+    expect(result).not.toHaveProperty('virtualRel');
+  });
+
+  it('does not include scalar attributes', () => {
+    expect(result).not.toHaveProperty('title');
+  });
+});
diff --git a/packages/core/database/src/query/helpers/populate/__tests__/apply-morph-to-one.test.ts b/packages/core/database/src/query/helpers/populate/__tests__/apply-morph-to-one.test.ts
new file mode 100644
index 0000000000..7d56de5b30
--- /dev/null
+++ b/packages/core/database/src/query/helpers/populate/__tests__/apply-morph-to-one.test.ts
@@ -0,0 +1,129 @@
+import applyPopulate from '../apply';
+
+/**
+ * Tests for the morphToOne populate helper in apply.ts.
+ *
+ * Key behaviour under test:
+ *  - The populated result row includes a `__type` field (or a custom typeField from morphColumn)
+ *    that carries the target content-type UID.
+ *  - When a result row has no morph target (null id / type columns) the attribute is set to null.
+ */
+
+// fromRow is the only piece of transform we need to isolate — mock it so tests
+// don't depend on field/scalar serialisation internals.
+jest.mock('../../transform', () => ({
+  fromRow: jest.fn((_meta: unknown, row: unknown) => {
+    if (row == null) return null;
+    return row; // pass-through for test purposes
+  }),
+}));
+
+const TARGET_TYPE = 'api::category.category';
+const SOURCE_UID = 'api::article.article';
+const ATTRIBUTE_NAME = 'related';
+
+const buildMorphAttribute = (typeField?: string) => ({
+  type: 'relation' as const,
+  relation: 'morphToOne' as const,
+  morphColumn: {
+    idColumn: { name: 'related_id', referencedColumn: 'id' },
+    typeColumn: { name: 'related_type' },
+    ...(typeField ? { typeField } : {}),
+  },
+});
+
+const buildCtx = (targetRows: Record<string, unknown>[], typeField?: string) => {
+  const mockQb = {
+    alias: 't',
+    init: jest.fn().mockReturnThis(),
+    addSelect: jest.fn().mockReturnThis(),
+    where: jest.fn().mockReturnThis(),
+    execute: jest.fn().mockResolvedValue(targetRows),
+  };
+
+  const db = {
+    metadata: {
+      get: jest.fn((type: string) => {
+        if (type === SOURCE_UID) {
+          return {
+            attributes: {
+              [ATTRIBUTE_NAME]: buildMorphAttribute(typeField),
+            },
+          };
+        }
+        // target type meta — only needs to exist (fromRow is mocked)
+        return { columnToAttribute: {}, attributes: {} };
+      }),
+    },
+    entityManager: {
+      createQueryBuilder: jest.fn().mockReturnValue(mockQb),
+    },
+  };
+
+  const ctx = {
+    db,
+    uid: SOURCE_UID,
+    qb: { state: { filters: {} } },
+  };
+
+  return { ctx, mockQb };
+};
+
+describe('morphToOne populate', () => {
+  it('includes __type in the populated result', async () => {
+    const targetRow = { id: 10, name: 'Category A' };
+    const { ctx } = buildCtx([targetRow]);
+
+    const results: Record<string, unknown>[] = [
+      { id: 1, related_id: 10, related_type: TARGET_TYPE },
+    ];
+
+    await applyPopulate(results, { [ATTRIBUTE_NAME]: {} }, ctx as any);
+
+    expect(results[0][ATTRIBUTE_NAME]).toEqual({
+      __type: TARGET_TYPE,
+      ...targetRow,
+    });
+  });
+
+  it('uses a custom typeField from morphColumn when provided', async () => {
+    const targetRow = { id: 10, name: 'Category A' };
+    const { ctx } = buildCtx([targetRow], 'contentType');
+
+    const results: Record<string, unknown>[] = [
+      { id: 1, related_id: 10, related_type: TARGET_TYPE },
+    ];
+
+    await applyPopulate(results, { [ATTRIBUTE_NAME]: {} }, ctx as any);
+
+    expect(results[0][ATTRIBUTE_NAME]).toEqual({
+      contentType: TARGET_TYPE,
+      ...targetRow,
+    });
+  });
+
+  it('sets the attribute to null when the morph columns are empty', async () => {
+    const { ctx } = buildCtx([]);
+
+    const results: Record<string, unknown>[] = [{ id: 2, related_id: null, related_type: null }];
+
+    await applyPopulate(results, { [ATTRIBUTE_NAME]: {} }, ctx as any);
+
+    expect(results[0][ATTRIBUTE_NAME]).toBeNull();
+  });
+
+  it('handles mixed results — some with targets, some without', async () => {
+    const targetRow = { id: 10, name: 'Category A' };
+    const { ctx } = buildCtx([targetRow]);
+
+    const results: Record<string, unknown>[] = [
+      { id: 1, related_id: 10, related_type: TARGET_TYPE },
+      { id: 2, related_id: null, related_type: null },
+    ];
+
+    await applyPopulate(results, { [ATTRIBUTE_NAME]: {} }, ctx as any);
+
+    expect(results[0][ATTRIBUTE_NAME]).toEqual({ __type: TARGET_TYPE, ...targetRow });
+    expect(results[1][ATTRIBUTE_NAME]).toBeNull();
+  });
+});