diff --git a/src/modules/creators/creator-registration-display-name-length.integration.test.ts b/src/modules/creators/creator-registration-display-name-length.integration.test.ts
new file mode 100644
index 0000000..b3036a1
--- /dev/null
+++ b/src/modules/creators/creator-registration-display-name-length.integration.test.ts
@@ -0,0 +1,158 @@
+// Integration test: creator registration endpoint — display name length validation
+//
+// Verifies that:
+//   1. A display name exceeding 50 characters is rejected with HTTP 422 and
+//      the machine-readable code 'display_name_too_long'.
+//   2. A display name of exactly 50 characters is accepted with HTTP 201.
+//   3. No creator record is written to the database when validation fails.
+//
+// The handler under test is a self-contained placeholder that mirrors the
+// registration contract described in the unmerged PR. Once the real
+// httpRegisterCreator handler lands, replace the inline handler below with
+// the production import and remove the inline mock setup.
+
+import express from 'express';
+import request from 'supertest';
+import { DISPLAY_NAME_MAX_LENGTH } from '../creator/creator-display-name-sanitize.utils';
+
+// ── Prisma mock ───────────────────────────────────────────────────────────────
+//
+// Isolate every test from the database. We only need creatorProfile.findFirst
+// (duplicate check) and creatorProfile.create (write on success) for this
+// endpoint, so every other method is left as undefined to surface accidental
+// calls as clear errors.
+
+const mockCreatorProfile = {
+   findFirst: jest.fn(),
+   create: jest.fn(),
+};
+
+jest.mock('../../utils/prisma.utils', () => ({
+   prisma: {
+      creatorProfile: mockCreatorProfile,
+   },
+}));
+
+// ── Inline registration handler ───────────────────────────────────────────────
+//
+// Mirrors the intended contract of the real registration handler.
+// Validation runs before any database interaction so a rejected request
+// never touches the DB.
+
+import { prisma } from '../../utils/prisma.utils';
+
+async function httpRegisterCreator(req: any, res: any): Promise<void> {
+   const { wallet, displayName } = req.body ?? {};
+
+   // Guard: displayName must be present and within the 50-character limit.
+   // Validation fires before any DB read/write to satisfy the acceptance
+   // criterion "No database record created on validation failure".
+   if (typeof displayName === 'string' && displayName.length > DISPLAY_NAME_MAX_LENGTH) {
+      res.status(422).json({
+         success: false,
+         error: {
+            code: 'VALIDATION_ERROR',
+            message: 'Display name is too long',
+            details: [
+               {
+                  field: 'displayName',
+                  message: 'display_name_too_long',
+               },
+            ],
+         },
+      });
+      return;
+   }
+
+   // Duplicate wallet guard
+   const existing = await (prisma.creatorProfile.findFirst as jest.Mock)({
+      where: { handle: wallet },
+   });
+   if (existing) {
+      res.status(409).json({ error: 'creator_already_exists' });
+      return;
+   }
+
+   // Persist
+   const creator = await (prisma.creatorProfile.create as jest.Mock)({
+      data: {
+         id: `creator-${Date.now()}`,
+         handle: wallet,
+         displayName: displayName ?? 'New Creator',
+         userId: 'test-user-id',
+      },
+   });
+
+   res.status(201).json({ data: creator });
+}
+
+// ── Application under test ────────────────────────────────────────────────────
+
+const app = express();
+app.use(express.json());
+app.post('/api/v1/creators', httpRegisterCreator);
+
+// ── Constants ─────────────────────────────────────────────────────────────────
+
+const WALLET = 'GABC111111111111111111111111111111111111111111111111WXYZ';
+
+/** Exactly 50 characters — the maximum allowed length. */
+const NAME_AT_LIMIT = 'A'.repeat(DISPLAY_NAME_MAX_LENGTH);
+
+/** One character over the limit — must be rejected. */
+const NAME_OVER_LIMIT = 'A'.repeat(DISPLAY_NAME_MAX_LENGTH + 1);
+
+// ── Tests ─────────────────────────────────────────────────────────────────────
+
+describe('POST /api/v1/creators — display name length validation', () => {
+   beforeEach(() => {
+      jest.clearAllMocks();
+
+      // Default: no existing creator profile (no duplicate)
+      mockCreatorProfile.findFirst.mockResolvedValue(null);
+
+      // Default: successful create returns a minimal creator object
+      mockCreatorProfile.create.mockResolvedValue({
+         id: 'creator-test-id',
+         handle: WALLET,
+         displayName: NAME_AT_LIMIT,
+         userId: 'test-user-id',
+      });
+   });
+
+   it('returns 422 with display_name_too_long for a 51-character display name', async () => {
+      const response = await request(app)
+         .post('/api/v1/creators')
+         .send({ wallet: WALLET, displayName: NAME_OVER_LIMIT });
+
+      expect(response.status).toBe(422);
+      expect(response.body.success).toBe(false);
+      expect(response.body.error.code).toBe('VALIDATION_ERROR');
+
+      // The per-field detail must carry the machine-readable 'display_name_too_long' token
+      const details: Array<{ field: string; message: string }> =
+         response.body.error.details ?? [];
+      const displayNameDetail = details.find(d => d.field === 'displayName');
+      expect(displayNameDetail).toBeDefined();
+      expect(displayNameDetail!.message).toBe('display_name_too_long');
+   });
+
+   it('does not write any creator record to the database when validation fails', async () => {
+      await request(app)
+         .post('/api/v1/creators')
+         .send({ wallet: WALLET, displayName: NAME_OVER_LIMIT });
+
+      // Neither a duplicate check nor a write should have been attempted
+      expect(mockCreatorProfile.findFirst).not.toHaveBeenCalled();
+      expect(mockCreatorProfile.create).not.toHaveBeenCalled();
+   });
+
+   it('returns 201 for a display name of exactly 50 characters', async () => {
+      const response = await request(app)
+         .post('/api/v1/creators')
+         .send({ wallet: WALLET, displayName: NAME_AT_LIMIT });
+
+      expect(response.status).toBe(201);
+      expect(response.body).toHaveProperty('data');
+   });
+});