diff --git a/packages/spacecat-shared-data-access/src/models/plg-onboarding/plg-onboarding.model.js b/packages/spacecat-shared-data-access/src/models/plg-onboarding/plg-onboarding.model.js
index 4e7676dd0..797900854 100644
--- a/packages/spacecat-shared-data-access/src/models/plg-onboarding/plg-onboarding.model.js
+++ b/packages/spacecat-shared-data-access/src/models/plg-onboarding/plg-onboarding.model.js
@@ -24,7 +24,9 @@ class PlgOnboarding extends BaseModel {
 
   static IMS_ORG_ID_PATTERN = /^[a-z0-9]{24}@AdobeOrg$/i;
 
-  static DOMAIN_PATTERN = /^[a-z0-9]([a-z0-9-]*[a-z0-9])?(\.[a-z0-9]([a-z0-9-]*[a-z0-9])?)*$/;
+  // Matches plain hostnames and subpath domains (e.g. nba.com, nba.com/kings).
+  // Rejects schemes (https://), IPv4 addresses, and query strings/fragments.
+  static DOMAIN_PATTERN = /^(?!\d+(\.\d+){3})[a-z0-9][a-z0-9-]*(\.[a-z0-9][a-z0-9-]*)*(\/[a-z0-9._~-]*)*$/;
 
   static STATUSES = {
     PRE_ONBOARDING: 'PRE_ONBOARDING',
diff --git a/packages/spacecat-shared-data-access/src/models/plg-onboarding/plg-onboarding.schema.js b/packages/spacecat-shared-data-access/src/models/plg-onboarding/plg-onboarding.schema.js
index 5233a4f6b..c76d47f44 100644
--- a/packages/spacecat-shared-data-access/src/models/plg-onboarding/plg-onboarding.schema.js
+++ b/packages/spacecat-shared-data-access/src/models/plg-onboarding/plg-onboarding.schema.js
@@ -28,7 +28,7 @@ const schema = new SchemaBuilder(PlgOnboarding, PlgOnboardingCollection)
     type: 'string',
     required: true,
     readOnly: true,
-    validate: (value) => PlgOnboarding.DOMAIN_PATTERN.test(value) && value.length <= 253,
+    validate: (value) => PlgOnboarding.DOMAIN_PATTERN.test(value) && value.split('/')[0].length <= 253,
   })
   .addAttribute('baseURL', {
     type: 'string',
diff --git a/packages/spacecat-shared-data-access/test/unit/models/plg-onboarding/plg-onboarding.model.test.js b/packages/spacecat-shared-data-access/test/unit/models/plg-onboarding/plg-onboarding.model.test.js
index 39d4e817d..31445aa02 100644
--- a/packages/spacecat-shared-data-access/test/unit/models/plg-onboarding/plg-onboarding.model.test.js
+++ b/packages/spacecat-shared-data-access/test/unit/models/plg-onboarding/plg-onboarding.model.test.js
@@ -79,6 +79,45 @@ describe('PlgOnboardingModel', () => {
     });
   });
 
+  describe('DOMAIN_PATTERN', () => {
+    const { DOMAIN_PATTERN } = PlgOnboarding;
+
+    describe('valid values', () => {
+      [
+        'nba.com',
+        'www.nba.com',
+        'sub.domain.example.com',
+        'nba.com/kings',
+        'nba.com/us/kings',
+        'example.com/path/with-hyphens',
+        'example.com/path.with.dots',
+        'example.io/a/b/c',
+      ].forEach((value) => {
+        it(`accepts "${value}"`, () => {
+          expect(DOMAIN_PATTERN.test(value)).to.be.true;
+        });
+      });
+    });
+
+    describe('invalid values', () => {
+      [
+        ['empty string', ''],
+        ['scheme prefix', 'https://nba.com'],
+        ['scheme prefix http', 'http://nba.com'],
+        ['IPv4 address', '127.0.0.1'],
+        ['IPv4 address 8.8.8.8', '8.8.8.8'],
+        ['query string', 'nba.com?foo=bar'],
+        ['fragment', 'nba.com#section'],
+        ['path with query string', 'nba.com/kings?q=1'],
+        ['path with fragment', 'nba.com/kings#top'],
+      ].forEach(([label, value]) => {
+        it(`rejects ${label}: "${value}"`, () => {
+          expect(DOMAIN_PATTERN.test(value)).to.be.false;
+        });
+      });
+    });
+  });
+
   describe('REVIEW_DECISIONS', () => {
     it('defines all expected review decisions', () => {
       expect(PlgOnboarding.REVIEW_DECISIONS).to.deep.equal({
diff --git a/packages/spacecat-shared-data-access/test/unit/models/plg-onboarding/plg-onboarding.schema.test.js b/packages/spacecat-shared-data-access/test/unit/models/plg-onboarding/plg-onboarding.schema.test.js
index 9eabd2617..34cbc48b0 100644
--- a/packages/spacecat-shared-data-access/test/unit/models/plg-onboarding/plg-onboarding.schema.test.js
+++ b/packages/spacecat-shared-data-access/test/unit/models/plg-onboarding/plg-onboarding.schema.test.js
@@ -14,6 +14,66 @@ import { expect } from 'chai';
 import plgOnboardingSchema from '../../../../src/models/plg-onboarding/plg-onboarding.schema.js';
 
 describe('PlgOnboarding Schema', () => {
+  describe('domain attribute', () => {
+    let domainAttr;
+
+    before(() => {
+      const attributes = plgOnboardingSchema.getAttributes();
+      domainAttr = attributes.domain;
+    });
+
+    it('is a required read-only string', () => {
+      expect(domainAttr.type).to.equal('string');
+      expect(domainAttr.required).to.be.true;
+      expect(domainAttr.readOnly).to.be.true;
+    });
+
+    it('has a validate function', () => {
+      expect(domainAttr.validate).to.be.a('function');
+    });
+
+    describe('valid values', () => {
+      [
+        'nba.com',
+        'www.nba.com',
+        'nba.com/kings',
+        'nba.com/us/kings',
+        'example.com/path-with-hyphens',
+      ].forEach((value) => {
+        it(`accepts "${value}"`, () => {
+          expect(domainAttr.validate(value)).to.be.true;
+        });
+      });
+    });
+
+    describe('invalid values', () => {
+      [
+        ['empty string', ''],
+        ['scheme prefix', 'https://nba.com'],
+        ['IPv4 address', '127.0.0.1'],
+        ['query string', 'nba.com?q=1'],
+        ['fragment', 'nba.com#top'],
+        ['hostname over 253 chars', `${'a'.repeat(250)}.com`],
+      ].forEach(([label, value]) => {
+        it(`rejects ${label}`, () => {
+          expect(domainAttr.validate(value)).to.be.false;
+        });
+      });
+    });
+
+    it('allows a subpath domain whose hostname is exactly 253 chars', () => {
+      const hostname = `${'a'.repeat(249)}.com`;
+      expect(hostname.length).to.equal(253);
+      expect(domainAttr.validate(`${hostname}/path`)).to.be.true;
+    });
+
+    it('rejects when only the hostname exceeds 253 chars (path does not inflate count)', () => {
+      const hostname = `${'a'.repeat(250)}.com`;
+      expect(hostname.length).to.equal(254);
+      expect(domainAttr.validate(`${hostname}/path`)).to.be.false;
+    });
+  });
+
   describe('reviews attribute', () => {
     let reviewsAttr;