diff --git a/packages/runtime/src/http-dispatcher.test.ts b/packages/runtime/src/http-dispatcher.test.ts
index cca5e5ec2c..9e8cb5a7fc 100644
--- a/packages/runtime/src/http-dispatcher.test.ts
+++ b/packages/runtime/src/http-dispatcher.test.ts
@@ -1119,6 +1119,103 @@ describe('HttpDispatcher', () => {
             expect(updatePackage).toHaveBeenCalledWith({ packageId: 'a.b', patch: { description: 'hi' } });
         });
 
+        it('POST /packages creates a new package (201) after checking the id is free', async () => {
+            const installPackage = vi
+                .fn()
+                .mockReturnValue({ manifest: { id: 'com.acme.new', name: 'New', version: '0.1.0' } });
+            const mockRegistry = {
+                getPackage: vi.fn().mockReturnValue(undefined),
+                installPackage,
+                getAllPackages: vi.fn().mockReturnValue([]),
+            };
+            (kernel as any).getService = vi.fn().mockImplementation((name: string) => {
+                if (name === 'objectql') return Promise.resolve({ registry: mockRegistry });
+                return null; // no protocol service → fall back to registry.installPackage
+            });
+
+            const result = await dispatcher.handlePackages(
+                '',
+                'POST',
+                { manifest: { id: 'com.acme.new', name: 'New', version: '0.1.0', type: 'app' } },
+                {},
+                { request: {} },
+            );
+            expect(result.response?.status).toBe(201);
+            expect(mockRegistry.getPackage).toHaveBeenCalledWith('com.acme.new');
+            expect(installPackage).toHaveBeenCalled();
+        });
+
+        it('POST /packages rejects a duplicate id with 409 instead of silently overwriting', async () => {
+            const installPackage = vi.fn();
+            const mockRegistry = {
+                getPackage: vi.fn().mockReturnValue({ manifest: { id: 'com.acme.crm', name: 'Existing' } }),
+                installPackage,
+                getAllPackages: vi.fn().mockReturnValue([]),
+            };
+            (kernel as any).getService = vi.fn().mockImplementation((name: string) => {
+                if (name === 'objectql') return Promise.resolve({ registry: mockRegistry });
+                return null;
+            });
+
+            const result = await dispatcher.handlePackages(
+                '',
+                'POST',
+                { manifest: { id: 'com.acme.crm', name: 'Clobber', version: '9.9.9' } },
+                {},
+                { request: {} },
+            );
+            expect(result.response?.status).toBe(409);
+            // The existing manifest must NOT be overwritten.
+            expect(installPackage).not.toHaveBeenCalled();
+        });
+
+        it('POST /packages?overwrite=true allows intentional overwrite of an existing id', async () => {
+            const installPackage = vi
+                .fn()
+                .mockReturnValue({ manifest: { id: 'com.acme.crm', name: 'Upgraded', version: '2.0.0' } });
+            const mockRegistry = {
+                getPackage: vi.fn().mockReturnValue({ manifest: { id: 'com.acme.crm' } }),
+                installPackage,
+                getAllPackages: vi.fn().mockReturnValue([]),
+            };
+            (kernel as any).getService = vi.fn().mockImplementation((name: string) => {
+                if (name === 'objectql') return Promise.resolve({ registry: mockRegistry });
+                return null;
+            });
+
+            const result = await dispatcher.handlePackages(
+                '',
+                'POST',
+                { manifest: { id: 'com.acme.crm', name: 'Upgraded', version: '2.0.0' } },
+                { overwrite: 'true' },
+                { request: {} },
+            );
+            expect(result.response?.status).toBe(201);
+            expect(installPackage).toHaveBeenCalled();
+        });
+
+        it('POST /packages rejects a missing id with 400', async () => {
+            const mockRegistry = {
+                getPackage: vi.fn(),
+                installPackage: vi.fn(),
+                getAllPackages: vi.fn().mockReturnValue([]),
+            };
+            (kernel as any).getService = vi.fn().mockImplementation((name: string) => {
+                if (name === 'objectql') return Promise.resolve({ registry: mockRegistry });
+                return null;
+            });
+
+            const result = await dispatcher.handlePackages(
+                '',
+                'POST',
+                { manifest: { name: 'No Id' } },
+                {},
+                { request: {} },
+            );
+            expect(result.response?.status).toBe(400);
+            expect(mockRegistry.installPackage).not.toHaveBeenCalled();
+        });
+
         it('PATCH /packages/:id rejects an empty patch with 400', async () => {
             (kernel as any).getService = vi.fn().mockImplementation((name: string) => {
                 if (name === 'objectql') return Promise.resolve({ registry: { getAllPackages: vi.fn().mockReturnValue([]) } });
@@ -1409,7 +1506,11 @@ describe('HttpDispatcher', () => {
                 package: { manifest: { id: 'app.demo' }, status: 'installed' },
                 message: 'Installed package: app.demo',
             });
-            const mockRegistry = { installPackage: vi.fn(), getAllPackages: vi.fn().mockReturnValue([]) };
+            const mockRegistry = {
+                installPackage: vi.fn(),
+                getPackage: vi.fn().mockReturnValue(undefined),
+                getAllPackages: vi.fn().mockReturnValue([]),
+            };
             (kernel as any).getService = vi.fn().mockImplementation((name: string) => {
                 if (name === 'protocol') return Promise.resolve({ installPackage });
                 if (name === 'objectql') return Promise.resolve({ registry: mockRegistry });
@@ -1429,6 +1530,7 @@ describe('HttpDispatcher', () => {
         it('falls back to registry.installPackage when the protocol lacks the method', async () => {
             const mockRegistry = {
                 installPackage: vi.fn().mockReturnValue({ manifest: { id: 'app.fb' }, status: 'installed' }),
+                getPackage: vi.fn().mockReturnValue(undefined),
                 getAllPackages: vi.fn().mockReturnValue([]),
             };
             (kernel as any).getService = vi.fn().mockImplementation((name: string) => {
diff --git a/packages/runtime/src/http-dispatcher.ts b/packages/runtime/src/http-dispatcher.ts
index 61ed2137b6..60549d1516 100644
--- a/packages/runtime/src/http-dispatcher.ts
+++ b/packages/runtime/src/http-dispatcher.ts
@@ -2316,6 +2316,25 @@ export class HttpDispatcher {
             // registry write only when the protocol service/method is unavailable.
             if (parts.length === 0 && m === 'POST') {
                 const manifest = body.manifest || body;
+                const pkgId = typeof manifest?.id === 'string' ? manifest.id.trim() : '';
+                // A package id is mandatory — without one the install cannot be keyed.
+                if (!pkgId) {
+                    return { handled: true, response: this.error('Package id is required', 400) };
+                }
+                // Duplicate-detection: POST /packages CREATES a package. If one with
+                // this id already exists, silently overwriting it destroys the existing
+                // manifest (name/version/…) with no warning — a data-loss footgun
+                // surfaced in Studio package-create dogfooding. Reject with 409 Conflict
+                // instead. Intentional upgrade / re-install flows opt back in with
+                // `overwrite: true` (body) or `?overwrite=true`.
+                const overwrite =
+                    body?.overwrite === true || query?.overwrite === 'true' || query?.overwrite === true;
+                if (!overwrite && registry.getPackage(pkgId)) {
+                    return {
+                        handled: true,
+                        response: this.error(`Package '${pkgId}' already exists`, 409),
+                    };
+                }
                 let pkg: any;
                 const protocolSvc: any = await this.resolveService('protocol').catch(() => null);
                 if (protocolSvc && typeof protocolSvc.installPackage === 'function') {