diff --git a/portal-frontend/src/app/case-detail/case-detail/case-detail.html b/portal-frontend/src/app/case-detail/case-detail/case-detail.html
index 4add799..b0eaec3 100644
--- a/portal-frontend/src/app/case-detail/case-detail/case-detail.html
+++ b/portal-frontend/src/app/case-detail/case-detail/case-detail.html
@@ -73,7 +73,15 @@
 
   <section>
     <h3>Acties</h3>
-    <app-case-actions [actions]="d.actions" (savedRequested)="reload()" />
+    @if (banner(); as message) {
+      <p class="banner" data-testid="ownership-banner">{{ message }}</p>
+    }
+    <app-case-actions
+      [actions]="d.actions"
+      (savedRequested)="reload()"
+      (takeOwnershipRequested)="onTakeOwnership($event)"
+      (releaseOwnershipRequested)="onReleaseOwnership($event)"
+    />
   </section>
 } @else {
   <p>Laden...</p>
diff --git a/portal-frontend/src/app/case-detail/case-detail/case-detail.spec.ts b/portal-frontend/src/app/case-detail/case-detail/case-detail.spec.ts
index 659a26e..162ea27 100644
--- a/portal-frontend/src/app/case-detail/case-detail/case-detail.spec.ts
+++ b/portal-frontend/src/app/case-detail/case-detail/case-detail.spec.ts
@@ -1,7 +1,8 @@
+import { HttpErrorResponse } from '@angular/common/http';
 import { ComponentFixture, TestBed } from '@angular/core/testing';
-import { ActivatedRoute, convertToParamMap } from '@angular/router';
-import { of } from 'rxjs';
-import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { ActivatedRoute, Router, convertToParamMap, provideRouter } from '@angular/router';
+import { of, throwError } from 'rxjs';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
 
 import { CaseDetailService } from '../case-detail.service';
 import { CaseDetail } from '../case-detail.types';
@@ -9,7 +10,7 @@ import { CaseDetailPage } from './case-detail';
 
 const legacyDetail: CaseDetail = {
   origin: 'Legacy',
-  legacyAanvraagId: 1001,
+  legacyAanvraagId: 1002,
   registrationApplicationId: null,
   surname: 'de Vries',
   initials: 'A.',
@@ -26,54 +27,162 @@ const legacyDetail: CaseDetail = {
   processStatus: null,
   lastModifiedAt: null,
   actions: {
-    editApplicantDetails: { mode: 'writeThrough', href: '/api/worklist/legacy/1001/details' },
-    recordAssessment: { mode: 'redirect', href: '/legacy/aanvraag/1001/beoordeling' },
-    takeOwnership: { mode: 'transition', href: '/api/worklist/legacy/1001/take-ownership' },
+    editApplicantDetails: { mode: 'writeThrough', href: '/api/worklist/legacy/1002/details' },
+    recordAssessment: { mode: 'redirect', href: '/legacy/aanvraag/1002/beoordeling' },
+    takeOwnership: { mode: 'transition', href: '/api/worklist/legacy/1002/take-ownership' },
   },
   seams: { aanvrager: 'legacy-backend', procestijdlijn: null },
 };
 
-function configure(routeConfigPath: string, paramMap: Record<string, string>, getLegacyDetail: unknown, getOwnedDetail: unknown) {
-  return TestBed.configureTestingModule({
-    imports: [CaseDetailPage],
-    providers: [
-      { provide: CaseDetailService, useValue: { getLegacyDetail, getOwnedDetail } },
-      {
-        provide: ActivatedRoute,
-        useValue: {
-          paramMap: of(convertToParamMap(paramMap)),
-          snapshot: { routeConfig: { path: routeConfigPath } },
+const ownedDetail: CaseDetail = {
+  ...legacyDetail,
+  origin: 'Owned',
+  legacyAanvraagId: null,
+  registrationApplicationId: '00000000-0000-0000-0000-000000000002',
+  actions: {
+    editApplicantDetails: { mode: 'owned', href: '/api/worklist/owned/00000000-0000-0000-0000-000000000002/details' },
+    recordAssessment: { mode: 'owned', href: '/api/worklist/owned/00000000-0000-0000-0000-000000000002/assessment' },
+    releaseOwnership: { mode: 'transition', href: '/api/worklist/owned/00000000-0000-0000-0000-000000000002/ownership' },
+  },
+  seams: { aanvrager: 'owned', procestijdlijn: 'case-framework-timeline' },
+};
+
+function configure(routeConfigPath: string, paramMap: Record<string, string>, serviceOverrides: Record<string, unknown> = {}) {
+  const service = {
+    getLegacyDetail: vi.fn().mockReturnValue(of(legacyDetail)),
+    getOwnedDetail: vi.fn().mockReturnValue(of(ownedDetail)),
+    updateDetails: vi.fn(),
+    recordAssessment: vi.fn(),
+    takeOwnership: vi.fn(),
+    releaseOwnership: vi.fn(),
+    ...serviceOverrides,
+  };
+  return {
+    service,
+    ready: TestBed.configureTestingModule({
+      imports: [CaseDetailPage],
+      providers: [
+        provideRouter([]),
+        { provide: CaseDetailService, useValue: service },
+        {
+          provide: ActivatedRoute,
+          useValue: {
+            paramMap: of(convertToParamMap(paramMap)),
+            snapshot: { routeConfig: { path: routeConfigPath } },
+          },
         },
-      },
-    ],
-  }).compileComponents();
+      ],
+    }).compileComponents(),
+  };
 }
 
 describe('CaseDetailPage', () => {
   let fixture: ComponentFixture<CaseDetailPage>;
 
   it('given a legacy/:id route, fetches via getLegacyDetail and renders the case', async () => {
-    const getLegacyDetail = vi.fn().mockReturnValue(of(legacyDetail));
-    const getOwnedDetail = vi.fn();
-    await configure('legacy/:id', { id: '1001' }, getLegacyDetail, getOwnedDetail);
+    const { service, ready } = configure('legacy/:id', { id: '1002' });
+    await ready;
 
     fixture = TestBed.createComponent(CaseDetailPage);
     fixture.detectChanges();
 
-    expect(getLegacyDetail).toHaveBeenCalledWith('1001');
-    expect(getOwnedDetail).not.toHaveBeenCalled();
+    expect(service.getLegacyDetail).toHaveBeenCalledWith('1002');
+    expect(service.getOwnedDetail).not.toHaveBeenCalled();
     expect(fixture.nativeElement.textContent).toContain('de Vries');
   });
 
   it('given an owned/:id route, fetches via getOwnedDetail', async () => {
-    const getLegacyDetail = vi.fn();
-    const getOwnedDetail = vi.fn().mockReturnValue(of({ ...legacyDetail, origin: 'Owned', legacyAanvraagId: null, registrationApplicationId: 'abc' }));
-    await configure('owned/:id', { id: 'abc' }, getLegacyDetail, getOwnedDetail);
+    const { service, ready } = configure('owned/:id', { id: '00000000-0000-0000-0000-000000000002' });
+    await ready;
 
     fixture = TestBed.createComponent(CaseDetailPage);
     fixture.detectChanges();
 
-    expect(getOwnedDetail).toHaveBeenCalledWith('abc');
-    expect(getLegacyDetail).not.toHaveBeenCalled();
+    expect(service.getOwnedDetail).toHaveBeenCalledWith('00000000-0000-0000-0000-000000000002');
+    expect(service.getLegacyDetail).not.toHaveBeenCalled();
+  });
+
+  describe('take ownership', () => {
+    afterEach(() => vi.restoreAllMocks());
+
+    it('does nothing when the user declines the confirm dialog', async () => {
+      vi.spyOn(window, 'confirm').mockReturnValue(false);
+      const { service, ready } = configure('legacy/:id', { id: '1002' });
+      await ready;
+      fixture = TestBed.createComponent(CaseDetailPage);
+      fixture.detectChanges();
+
+      fixture.nativeElement.querySelector('[data-testid="take-ownership-button"]').click();
+
+      expect(service.takeOwnership).not.toHaveBeenCalled();
+    });
+
+    it('on confirm, calls takeOwnership and navigates to the new owned detail', async () => {
+      vi.spyOn(window, 'confirm').mockReturnValue(true);
+      const { service, ready } = configure('legacy/:id', { id: '1002' }, {
+        takeOwnership: vi.fn().mockReturnValue(of({ registrationApplicationId: '00000000-0000-0000-0000-000000000002' })),
+      });
+      await ready;
+      fixture = TestBed.createComponent(CaseDetailPage);
+      fixture.detectChanges();
+      const navigate = vi.spyOn(TestBed.inject(Router), 'navigate');
+
+      fixture.nativeElement.querySelector('[data-testid="take-ownership-button"]').click();
+
+      expect(service.takeOwnership).toHaveBeenCalledWith('/api/worklist/legacy/1002/take-ownership');
+      expect(navigate).toHaveBeenCalledWith(['owned', '00000000-0000-0000-0000-000000000002']);
+    });
+
+    it('on a 422 InvariantViolationResponse, shows a banner instead of navigating', async () => {
+      vi.spyOn(window, 'confirm').mockReturnValue(true);
+      const { ready } = configure('legacy/:id', { id: '1002' }, {
+        takeOwnership: vi
+          .fn()
+          .mockReturnValue(throwError(() => new HttpErrorResponse({ status: 422, error: { invariant: 'Bsn.ElevenProof', message: 'BSN fails the eleven-proof.' } }))),
+      });
+      await ready;
+      fixture = TestBed.createComponent(CaseDetailPage);
+      fixture.detectChanges();
+
+      fixture.nativeElement.querySelector('[data-testid="take-ownership-button"]').click();
+      fixture.detectChanges();
+
+      const banner = fixture.nativeElement.querySelector('[data-testid="ownership-banner"]');
+      expect(banner?.textContent).toContain('Bsn.ElevenProof');
+      expect(banner?.textContent).toContain('BSN fails the eleven-proof.');
+    });
+  });
+
+  describe('release ownership', () => {
+    it('calls releaseOwnership and navigates to the worklist on success', async () => {
+      const { service, ready } = configure('owned/:id', { id: '00000000-0000-0000-0000-000000000002' }, {
+        releaseOwnership: vi.fn().mockReturnValue(of(undefined)),
+      });
+      await ready;
+      fixture = TestBed.createComponent(CaseDetailPage);
+      fixture.detectChanges();
+      const navigate = vi.spyOn(TestBed.inject(Router), 'navigate');
+
+      fixture.nativeElement.querySelector('[data-testid="release-ownership-button"]').click();
+
+      expect(service.releaseOwnership).toHaveBeenCalledWith('/api/worklist/owned/00000000-0000-0000-0000-000000000002/ownership');
+      expect(navigate).toHaveBeenCalledWith(['/']);
+    });
+
+    it('on a 409 MessageResponse, shows the server message as a banner', async () => {
+      const { ready } = configure('owned/:id', { id: '00000000-0000-0000-0000-000000000002' }, {
+        releaseOwnership: vi
+          .fn()
+          .mockReturnValue(throwError(() => new HttpErrorResponse({ status: 409, error: { message: 'Domain writes exist since adoption.' } }))),
+      });
+      await ready;
+      fixture = TestBed.createComponent(CaseDetailPage);
+      fixture.detectChanges();
+
+      fixture.nativeElement.querySelector('[data-testid="release-ownership-button"]').click();
+      fixture.detectChanges();
+
+      expect(fixture.nativeElement.querySelector('[data-testid="ownership-banner"]')?.textContent).toContain('Domain writes exist since adoption.');
+    });
   });
 });
diff --git a/portal-frontend/src/app/case-detail/case-detail/case-detail.ts b/portal-frontend/src/app/case-detail/case-detail/case-detail.ts
index a1c532d..cf09f5d 100644
--- a/portal-frontend/src/app/case-detail/case-detail/case-detail.ts
+++ b/portal-frontend/src/app/case-detail/case-detail/case-detail.ts
@@ -1,10 +1,12 @@
+import { HttpErrorResponse } from '@angular/common/http';
 import { KeyValuePipe } from '@angular/common';
 import { Component, inject, signal } from '@angular/core';
-import { ActivatedRoute } from '@angular/router';
+import { ActivatedRoute, Router } from '@angular/router';
 
+import { InvariantViolationResponse, MessageResponse } from '../../shared/api-error.types';
 import { CaseActions } from '../case-actions/case-actions';
 import { CaseDetailService } from '../case-detail.service';
-import { CaseDetail, toApplicantDetailsRequest } from '../case-detail.types';
+import { ActionLink, CaseDetail, toApplicantDetailsRequest } from '../case-detail.types';
 import { EditApplicantDetails } from '../edit-applicant-details/edit-applicant-details';
 
 @Component({
@@ -15,9 +17,11 @@ import { EditApplicantDetails } from '../edit-applicant-details/edit-applicant-d
 })
 export class CaseDetailPage {
   private readonly route = inject(ActivatedRoute);
+  private readonly router = inject(Router);
   private readonly caseDetailService = inject(CaseDetailService);
 
   readonly detail = signal<CaseDetail | null>(null);
+  readonly banner = signal<string | null>(null);
   readonly toApplicantDetailsRequest = toApplicantDetailsRequest;
 
   constructor() {
@@ -38,4 +42,35 @@ export class CaseDetailPage {
         : this.caseDetailService.getOwnedDetail(current.registrationApplicationId!);
     source$.subscribe((updated) => this.detail.set(updated));
   }
+
+  // Matches the placeholder's own confirm() dialog before this one-way,
+  // per-case migration step (ADR-003).
+  onTakeOwnership(link: ActionLink): void {
+    if (!confirm('Dit dossier in eigen beheer nemen?')) return;
+    this.banner.set(null);
+    this.caseDetailService.takeOwnership(link.href).subscribe({
+      next: (result) => this.router.navigate(['owned', result.registrationApplicationId]),
+      error: (error: HttpErrorResponse) => this.banner.set(this.describeError(error)),
+    });
+  }
+
+  onReleaseOwnership(link: ActionLink): void {
+    this.banner.set(null);
+    this.caseDetailService.releaseOwnership(link.href).subscribe({
+      next: () => this.router.navigate(['/']),
+      error: (error: HttpErrorResponse) => this.banner.set(this.describeError(error)),
+    });
+  }
+
+  private describeError(error: HttpErrorResponse): string {
+    if (error.status === 422) {
+      const body = error.error as InvariantViolationResponse;
+      return `${body.invariant}: ${body.message}`;
+    }
+    if (error.status === 409) {
+      const body = error.error as MessageResponse;
+      return body.message;
+    }
+    return 'Onbekende fout.';
+  }
 }